The Primal Blueprint is generally considered a low-carb way of eating, especially in contrast to the Standard American Diet and the like. We’re not anti-carb. My Big-Ass Salad is a huge bowl of carbs from vegetables, after all. We’re selective about the sources of our carbs and generally mindful about how many we take in.
Given that, readers always want to know the “right” way to incorporate carbs. Which carb sources? How many? When? How often?
The Primal Blueprint Food Pyramid and Carb Curve provide answers to the first two questions. The latter two… well, those are more complicated.
I’ve written about these topics many times, but the questions keep on coming. Today I’m going to try to condense the main points into one post. I’ll touch on some issues you’ve raised in the comments of recent posts, too.
In truth, I keep getting questions because there are so few definitive answers about the optimal way to incorporate carbs in your diet. Underlying hormonal and metabolic health, activity level, and lifestyle variables to make it impossible to make across-the-board recommendations. Few studies address these issues, and those that do always use standard high-carb diets in their manipulations.
The best I can do is explain the logic behind different strategies and encourage you to experiment. As with so many things, it might take time to discover which strategies work best for you.
Carb Timing, Carb Cycling, and Carb Refeeds, Oh My!
Let’s get some terminology out of the way.
- Carb timing refers to when you eat your carbs. Usually this means when during the day, morning versus night, but it can also mean relative to exercise or other activities.
- The term carb cycling encompasses various strategies in which you rotate periods of higher- and lower-carb eating. A common carb cycling schedule is eating low-carb for five or six days, then higher-carb for a day or two. Some people eat low-carb for a period of, say, six to eight weeks, then higher-carb for a week or two. Women may also vary their carb intake around their menstrual cycles.
- Carb refeeds can be synonymous with carb cycling—the higher-carb days are called “refeed” or “carb-up” days. Carb refeeds can also be less systematic than carb cycling. For example, you might throw in a couple high-carb days because your weight loss has plateaued, or you’re doing some particularly strenuous exercise.
It should go without saying that when I say “carbs,” I mean nutrient-dense, whole-food sources of carbohydrate. I’m talking about sweet potatoes and other root vegetables, in-season fruit, nuts, high-fat dairy, perhaps wild rice and occasional legumes if they work for you. There’s obviously no situation in which I’d tell you to throw back a couple donuts with a soda chaser and call it a refeed.
Why Should You Carb Cycle or Refeed?
The main reason to periodically increase your carbs is to boost your leptin levels. Leptin is an important metabolic hormone that is secreted by adipose cells. Leptin also rises after eating, especially carbohydrates but also protein and maybe fat to a lesser degree.
Leptin’s main job is to signal how much energy is available. When leptin levels fall, the brain understands that we are low on energy. This leads to hunger and energy conservation. Chronically low leptin can interfere with fertility, thyroid and adrenal function, skeletal integrity, and cardiovascular health.
Carb refeeds can “reset” leptin levels. Among other benefits, these bursts of leptin improve insulin sensitivity and may help with weight loss. Sustained caloric deficits lead to decreased metabolic rate—part of the energy conservation adaptation. Refeeds will boost metabolic rate, especially if you also eat more calories along with carbs, and reduce hunger. Plus, occasionally eating higher-carb meals offers a welcome break from constant restriction.
Some signs you might benefit carb cycling/refeeds are:
- Excessive hunger
- Irregular menstrual cycles
- Mood disturbances or depression
- Low body fat
- Sleep disturbances
- Weight-loss plateau
- Better adherence to dietary goals with occasional “breaks”
In each of these cases, adding carbs is only one of several dietary strategies you might try. Also consider whether you are eating enough calories, and protein, to meet your needs, and whether you are minding your Ps and Qs when it comes to sleep practices and stress reduction.
People who might not need carb refeeds:
- Carry significant body fat or are insulin resistant
- Find it easier to adhere to dietary goals when they abstain from higher-carb foods/meals
- Use low-carb eating regimens therapeutically (e.g., under medical guidance for epilepsy, cognitive decline, or type 1 diabetes)
This should be obvious, but you also don’t need refeeds if you’re not restricting carbohydrates. What does that mean, though? Anyone who is eating a ketogenic diet is clearly restricting carbs. Beyond that, there is a lot of gray area. An extreme endurance athlete eating 150 or even 200 grams of carb per day could be considered low-carb, and hence they might benefit from cycling in more carbs occasionally. Your best bet is to rely on subjective markers of how you feel.
How to Incorporate Carb Cycling or Refeeds
This depends on your goal. If you’re feeling good without carb refeeds, you probably don’t need them. In that case, you might throw in high-carb meals intuitively or when a special occasion offers the opportunity.
Otherwise, you can be more systematic about it. I’d start small and increase as needed. One meal every other week could suffice. You might find you do better with one high-carb day per week, or one meal every three or four days. It’s not uncommon for women to feel better with a slightly higher carb intake than men, but it’s still highly individual.
For weight-loss stalls, consider eating at maintenance calories for a week or two along with including more carbs than normal. This signals to your body that you are no longer in an energy shortage, so it is safe to reverse some of those energy conserving adaptations.
Premenopausal women can try increasing carbs four to five days post-ovulation (around days 19 and 20 of their cycle) and on the first day or two of their period. Women’s bodies are especially attuned to energy shortages, so these periodic boosts in leptin, timed to coincide with greater demand, can be beneficial.
There are no hard rules about how much to increase your carbs. A good place to start is doubling your normal carb intake and adjusting from there. I’d also recommend dialing back your fat intake with higher-carb meals. Triglycerides prevent leptin from crossing the blood-brain barrier.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071301/‘>2 This effect might be especially pronounced in people who have poor glucose control to start with. In one small study, carb timing didn’t matter for participants who were metabolically healthy. For those with impaired glucose tolerance, eating carbs at night led to unfavorable changes on several makers of glucose tolerance compared to eating their carbs in the morning.https://pubmed.ncbi.nlm.nih.gov/26741119/‘>4 The sleep low group also lost fat but not lean mass. Using the same protocol, researchers showed that after only a week of sleeping low, the men improved their performance on a 20k cycling time trial, whereas the control group showed no improvement.https://academic.oup.com/ajcn/article/85/2/426/4649589‘>6 I’d say if you want to try this, you probably don’t need a lot of carbs—maybe half a small sweet potato with dinner, a piece of fruit, or a tablespoon of honey in a mug of herbal tea.
Cortisol Levels Respond to Carb Intake
Here’s the argument: Cortisol naturally rises in the morning as part of the sleep-wake cycle. One of cortisol’s effects is to mobilize stored energy from fat. Insulin opposes the action of cortisol and inhibits the release of fat from adipose tissue. If you eat carbs in the morning, you increase insulin. Therefore, you counteract the desirable high cortisol levels that characterize a healthy circadian rhythm. You also interfere with fat burning.
It makes sense, but the data doesn’t clearly support it. Studies in healthy menhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC3033415/‘>8 fail to show a marked decrease in cortisol levels following carbohydrate consumption. In fact, when the men in that first study consumed carbs, protein, and fat in isolation, cortisol levels were highest in the carb-only condition. Likewise, when researchers in another study fed women high-protein or high-carb meals, the high-carb meals resulted in higher, not lower, cortisol levels among women with abdominal obesity (the kind linked to metabolic syndrome), but not peripheral obesity.https://link.springer.com/article/10.1007/s00394-013-0497-7‘>10
There may be a benefit to eating more of your total calories in the morning, but that’s not about carbs per se.
Morning Carbs May Cause Cravings
This is anecdotal, but I’ve had many people tell me that if they start their day with a high-carb breakfast, even complex carbs, they feel hungrier and more snacky all day. If this is you, by all means listen to your body and avoid carbs in the morning.
Reasons to Consume Carbs around Exercise
There are a couple good reasons to target your carbs around exercise. One is their ergogenic effect—that is, their ability to enhance performance. Now, you know I’m a staunch advocate for becoming a fat-burning beast. I think it should be every athlete’s goal to burn as much fat as possible at all levels of intensity. Heck, I even have a book, Primal Endurance, that is all about helping endurance athletes minimize their reliance on carbs.
Still, there’s no denying that carbs can help you tap into top-end speed and power. I’ve always made room for the strategic use of carbs in training, and especially in racing. Train low, race high is a viable strategy for athletes at all levels. For athletes who are engaged in prolonged high-intensity efforts (not my preference), carbs may well be necessary to deliver their desired performance. Hardcore CrossFitters, for example, usually do better when they use carbs around exercise.
Taking in some carbs before or during intense exercise isn’t the same as eating 200 grams of carbs and sitting on the couch. During exercise, those carbs are utilized quickly for energy. Exercise actually increases the ability of cells to take up glucose from the bloodstream, thanks to a glucose transporter in muscle cells called GLUT4 that doesn’t rely on insulin.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6019055/‘>12 The carbs you eat then will preferentially go to topping off glycogen.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6019055/‘>14 And contrary to what that swole dude at the gym might have told you, you don’t need to throw down post-workout carbs to build lean muscle. You should worry more about getting adequate protein in your diet than about how many carbs you’re eating.https://pubmed.ncbi.nlm.nih.gov/10805507/‘>16
On the other hand, proponents of eating carbs and fat together will tell you that eating fat alongside carbs is desirable because fat blunts the glycemic response. However, the empirical data here are inconsistent and, frankly, confusing. I’m not hanging my hat on this effect.
What’s clearly true is that carbs + fat = delicious. It’s easier to overeat the combo of the two than to overeat either one by itself. In that sense, you might want to watch your consumption of mixed meals if you’re trying to lose weight. At least be mindful of the total caloric load.
When it comes to both carb cycling and carb timing, there is no one-size-fits-most strategy. As with most things we talk about here, you’re going to have to experiment to see what works for you. Hopefully this post has given you some ideas. To summarize the main points:
I think there is fairly decent evidence that carb cycling and/or carb refeeds may benefit you if you typically eat a low-carb diet, especially if it’s also calorie (energy) restricted. You don’t have to, though, especially if you’re feeling good.
Personally, I’m a bigger fan of listening to my body and allowing my carb intake to vary according to my circumstances and intuition rather than adhering to a particular schedule. Your mileage may vary. Premenopausal women in particular may do well to consider being more intentional about it. If you’re going to try incorporating carb cycling, the exact strategy you should try depends on what you hope to accomplish.
As for carb timing, morning versus night, I’m not convinced that it matters a whole lot for most people. If you have chronically low cortisol, or your daily cortisol rhythm is out of alignment, you might do well to consume most of your carbs later in the day. If you’re struggling with insulin resistance, try eating breakfast and including some carbs. For sleep issues, experiment with adding some carbs in the few hours before bedtime.
If you’re using carb cycling or carb timing strategies in the service of a longer term goal—losing weight, sleeping better, improving glucose tolerance—pick a strategy and stick to it for at least a few weeks if not months unless it’s clearly not working for you. If your first experiment doesn’t work, you can always try tweaking the timing, types, and/or amount of carbs you’re eating. Be patient.
For some people, carb cycling or carb timing turns out to be the key to resolving a persistent health issue. For others, they have more of a fine-tuning effect. Still for others, they make no obvious difference.
Are they worth trying? Absolutely, if you want. I’m definitely sold on targeting your carbs around exercise; that’s a clear yes in my book. Even then, though, I like to mix up my fueling to challenge my body. Sometimes I eat right after a workout, sometimes I wait. Sometimes I go out fasted, other times I eat beforehand. That’s how I roll.
How do you roll? Are you gung-ho about a particular carb strategy? Has changing up the timing of your carb intake led to any profound shifts in your health? If yes, I want to hear about it in the comments.
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If you have your own success story and would like to share it with me and the Mark’s Daily Apple community please contact me here. I’ll continue to publish these as long as they keep coming in. Thank you for reading!
Folks, I have been grateful for every story that has come my way over the years. It’s an incredible privilege being on the receiving end of your reflections and evolutions, and they are why I’ve kept at it all these years—knowing the message and information have made a difference in people’s lives. I appreciate every single one. This success story comes from Registered Dietician, Primal Health Coach, and cancer survivor Martha Tettenborn. She takes us through her journey from learning to advise a low-fat, high-carb lifestyle to beating cancer using Primal principles. Enjoy! —Mark
It has become my passion to share the power of nutritional interventions for improving health overall, but especially in the treatment of cancer. I have come to this from personal experience…
I studied at University in the early 1980’s to become a dietitian, because I had an overwhelming interest in nutrition and wanted to be in a helping profession. At that time, the cholesterol and saturated fat theory of heart disease and overall health was considered cutting edge science and we were fully indoctrinated into the low-fat approach to almost all health issues. The only exception was using a high calorie, high protein approach to under-nutrition (such as with failure-to-thrive or cancer patients), and in that situation, we recommended using sugar or honey, butter or cream, and other added fats and simple carbs to increase the caloric density of foods.
I have been a Registered Dietitian for over 30 years, basing my practice for most of that time on the standard paradigm of low fat foods, heavily carb-based meals, fruits and vegetables, lower fat meats. Personally, our family spent many years eating no red meats, using turkey “bacon,” ground chicken and other processed foods, but avoiding beef and pork – and feeling virtuous while doing that.
Professionally, I have spent the last 20 years working in geriatrics, contracting my services to long term care facilities. I care for many residents with the end stage consequences of the Standard American (and Canadian) Diet – diabetes, strokes and of course, dementia, both vascular and Alzheimer’s. It is rare that a resident has simple osteoarthritis or other simple wearing out of old age. Most of them are younger and slowly dying for years with the chronic “diseases of civilization.”
About 10 years ago, I started down the path of alternative nutrition, starting with Seth Robert’s ideas, called the Shangri La Diet, using flavourless oil shots to impact on appetite control in the brain. I was successful in losing about 18 lbs that had been quite stubborn prior to that time. Shortly after that, I found Mark’s Daily Apple and the concept of the Primal Diet, eating an Ancestral pattern that suited our physiology. It resonated so strongly with me that this was correct, although it went against all of my training. The strength of the science won me over; however, I spent hours on the MDA forums, reading scientific discussions, success stories, recipe and meal planning ideas and journals from the MDA community.
About 3 years ago, I decided that I wanted to take my interest in low-carb, high-fat (LCHF) and start up a private practice. In order to update my knowledge, I completed the Primal Health Coach certification – an excellently presented and in-depth course. As an RD and member of a Registered Health Profession, with a regulatory college, I had to establish a private practice that met with the regulatory guidelines of my
profession, so I started Primal RD in July 2017. Because of my counter-conventional approach, I have had no support from local doctors and getting my practice going in my small Ontario community has been slow.
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Last summer, I discovered the presence of a large ovarian cyst in my abdomen and had it surgically removed in late September. The cyst was a simple fluid-filled balloon, but huge, holding 1.5 litres of fluid (over 50 oz – 6 cups!). Despite nobody expecting it, it turned out to be Stage 1 high grade serous carcinoma – ovarian cancer. It had been intentionally ruptured to make laparoscopic removal possible, so that was considered a “spill” and a second surgery for hysterectomy and chemotherapy were highly recommended.
I was 58 years old and in stellar health prior to this diagnosis. In fact, a great deal of my self-identity was wrapped up in being “super-healthy” and this sudden change to “cancer patient” was a huge crisis for me. However, as a naturally optimistic and curious person, I headed down the rabbit hole of research to determine what I could do for myself to impact on my health journey and return myself to my formerly stellar good health.
What I discovered was startling. That cancer is no longer considered by some to be a genetic disease, but rather a disease of disordered metabolism. That this information was first discovered and described by Otto Warburg in the 1920’s, for which he received a Nobel Prize. That this scientific information was then lost by virtue of it being of German origin, and the Germans lost the Second World War. And that this critical understanding of the metabolic nature of cancer has only been brought back to light in the past 10 years through the work of dedicated researchers who are working outside of the medical establishment.
Cancer, although it is thought of as a genetic disease, and that it is thought of as many different diseases, has one almost universal underlying common characteristic. Almost all cancers have damaged and malfunctioning mitochondria, the fuel-processing organelles that create the energy for all cellular life. Instead, they produce energy by the ancient process of fermentation in the cytoplasm of the cell, an inefficient process that is entirely dependent on glucose or glutamine for substrate. Cancer cells have no ability to burn fatty acids or ketone bodies. That’s their Achilles heel.
By using a ketogenic diet throughout my chemotherapy, I was able to deprive any remaining cancer cells from having access to elevated circulating insulin or glucose. And by producing ketones through the diet and through fasting for 72 hours each chemo administration, I was able to starve the cancer cells of their preferred fuel, while putting my body further into ketosis, thus supplying my healthy cells with adequate fuel. My healthy cells down-regulated their metabolism in response to the fasting, going into “stealth mode” and escaping notice by the chemo drugs (essentially poisons aimed at fast-metabolizing cells). This turned out to be powerfully protective in preventing most side effects. I had no nausea, emesis (vomiting0, gastrointestinal damage, nerve damage, tingling or neuropathy, no joint or muscle pains. I did experience hair loss and bone marrow suppression, the 2nd week effects of the chemo, but these were moderate, not requiring any additional medication. Overall, I sailed through chemo with a few “low energy” days, but mostly it was life as normal, just with no hair. This was decidedly NOT the expected course for this type of chemo.
A friend said to me when I was starting down the cancer path that it appeared that everything in my life to this point (becoming a low carb dietitian, the PHC certification, and my passion for researching health) had prepared me for this day – that I would be the “Keto Cancer Dietitian.” The idea stuck, and a passion for sharing what I had learned about how powerful nutrition can be in the cancer journey was born.
As I went through chemo, I started blogging about my experiences and my journey so that others could read my story and gain hope and understand the power that we each have to impact on our own health, even in the face of daunting obstacles like a cancer diagnosis. I write about my experiences at my website, Powerful Beyond Measure, at www.marthatettenborn.com.
I feel very blessed for so many reasons. Firstly, that I had found the low carb Primal way of eating and had a solid basis of good health prior to starting this cancer journey. Secondly, that I had the knowledge and skills to research the metabolic nature of cancer and implement specific nutritional interventions (namely ketogenic diet and therapeutic fasting) for impacting on the chemotherapy experience. And thirdly, that I am now able to share that knowledge with others so that we can change the cancer and cancer treatment experience for the better. I was not a helpless “victim” of cancer and I was not fighting a war against my cancer. I was an empowered and effective partner in my own healthcare, positively impacting my response to conventional treatment.
That’s what I wish to share with others.
Mark has been so generous to share his knowledge with the goal of changing lives and that’s what I hope to do as well, from the perspective of a Registered Dietitian, a Primal Health Coach, a lifelong “healthy eater” and a cancer
survivor thriver. I’m just at the beginning of that journey.
Martha Tettenborn, RD
Owen Sound, Ontario, Canada
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Even after publishing several books and hundreds of articles that draw upon the science of ketosis and low-carb living, I keep researching, thinking, revisiting, and discussing the underpinnings of ketosis. My writing partner, Brad Kearns, and I maintain a running dialogue on all things keto. The latest conversation revolved around two very common questions or “problems” that keep coming up in the ketogenic community: why am I getting low ketone readings?
It’s a fair question. Why do some people on a keto diet register high ketones while others eating the same way register low numbers?
I won’t offer definitive answers fit to etch into stone. I will offer my exploration of the research, some educated speculation, and actionable advice you can ruminate on. And by all means get back to me with your take on the questions and my explorations, please. Dialogue is essential to understanding.
What Level of Ketones Indicates Ketosis?
The generally accepted range that indicates ketosis is 0.5-3 mmol/L. I hesitate to define a prescriptive range, though, because so many factors affect readings – what you ate for your most recent meal, how long ago you exercised, and even the instrument you used to test can affect readings.
Why do some people on ketogenic diets produce low ketone readings when they test?
There are several potential explanations for low ketone readings. Some are hypotheses, some are based on your individual biology. A few possible explanations for low ketone readings include:
- You have developed fat-burning efficiency
- Keto-adapted people may be able to burn free fatty acids
- Genetic predisposition to low ketones
- Recent exercise
- Total caloric intake
- Use of exogenous ketones
Let’s dig deeper.
You have developed fat-burning efficiency
One theory is that some keto-adapted people are so efficient at producing and burning ketones that they don’t leave any extra to spill into the urine and breath. They make only as many as they can use and their cells gobble up almost every ketone they produce. Under this argument, low ketone numbers on a ketogenic diet are a reliable sign of full ketone adaptation.
This sounds plausible, but I haven’t seen any empirical evidence that it’s the case.
Keto-adapted People May Be Able to Burn Free Fatty Acids in the Bloodstream
Another theory is that the keto-adapted have built so much fat-burning metabolic machinery in their muscles that they can burn free fatty acids directly and don’t require much additional fuel from ketones. They make enough ketones to fuel the brain, since our brain can’t run on fatty acids directly, but your muscles no longer require as many. Many people who have been in long term ketosis can get by quite nicely on 20-30 net grams of carbs a day and might only show .4 or .7 millimolar ketones on a blood test, but they have plenty of energy from burning free fatty acids and maintain muscle mass on relatively fewer calories than when they were dependent on carbs.
The evidence is inconclusive, but a few indications point to increased ability to extract energy directly from fat as a possibility.
Keto pioneers Stephen Phinney and Jeff Volek found that keto dieters blew higher readings early on in the diet when they were still burning ketones in the muscle. As they grew adapted to free fatty acids as a source of fuel and produced ketones primarily for the brain, ketone levels dropped. It was totally normal. If anything, they were more fat- and keto-adapted at lower ketone readings.
Consider the energy requirements of the brain. Whether it’s running on glucose (most of the population) or mostly on ketones, the brain is a steady state organ that never spikes energy demand. It’s a slow-burn 24/7 at nearly the same output whether you are sleeping, exercising hard, or concentrating hard. While the brain has a substantial caloric requirement (at roughly 2% of our body weight, it uses 20% of our resting metabolic rate), you don’t need a ton of glucose or ketones at any one time to power your brain gracefully all day long. That’s why people can “get away” with lower ketone production and still reap the benefits we expect from eating this way.
Genetic Predisposition to Low Ketones
There’s almost certainly a genetic component to ketone production, too. Take the Inuit, who were rarely in ketosis despite traditionally eating a very low-carb diet.1 It takes several days of deep fasting for them to produce measurable ketones. Yet, they are adept at burning free fatty acids, almost as if they “skip” keto-adaptation and proceed directly to burning fat. Other variants that affect ketone production have yet to be discovered, but they’re out there.
Recent Exercise or Otherwise Increased Energy Demand
If you test your ketones before and after you exercise, you may be surprised to find that your numbers are quite different after you’ve worked out. Remember, ketones are an energy source, not a stamp of accomplishment. Ketones are consumed when there is an energy demand in your body. It doesn’t mean you messed up your diet. Quite the opposite – it simply means your body used the energy source available at the time. Once ketone bodies are in low supply, your body will burn fat to make more, and that’s a win.
Why do Some People on Long-term Keto Diets Still Get High Ketone Readings?
A few of the previous theories assume that you develop an increased ability to burn fat after you have been in ketosis for a while. But there are people who, after being in ketosis for a long period of time, still get high ketone readings when they test. What gives?
Total caloric intake is a factor in ketone levels
A major factor not often mentioned in whether someone on a keto diet registers high or low ketones is overall calorie intake. How much food are you eating?
Ketones are generated when the amount of dietary fat available to be burned exceeds the supply of oxaloacetate (provided by protein or carbohydrates). It’s not that the body thinks, “This woman needs some ketones, stat.” It’s more like, “I’ve got too much acetyl-COA from all this fat, and I can’t find any oxaloacetate. Time to ask for ketones!” If you’re the type to use keto to justify chugging olive oil, you’ll generate lots of ketones simply because your fat intake is outpacing the supply of oxaloacetate. Keto athletes eating tons of calories will probably produce more ketones simply because they’re eating so much fat.
If you’ve attained “caloric efficiency” and are eating fewer calories overall, you’ll generate fewer ketones but still experience all of the benefits of being in ketosis.
Use of exogenous ketones result in high ketone readings
Another factor is the use of exogenous ketones. Realistically, you could take your ketone readings, then take keto salts or keto esters, then take your readings again and see a bump. That is what they’re for.
Don’t Get Caught Up in the Numbers
Above all else, focus on how you feel.
- Can you go without a meal and maintain steady, even energy and concentration?
- Are you losing body fat, or are you happy with your body composition?
- Are you thinking more clearly?
- Has the keto flu come and gone?
- Are aerobic activities easier than ever?
If you’re experiencing the benefits of ketosis, there’s no need to fret over some numbers on a device. The numbers can’t negate your real world experience.
The post Why Am I Getting Low Ketone Readings on a Ketogenic Diet? appeared first on Mark’s Daily Apple.
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A little planning and motivation will help you start a low-carb, keto, or Primal lifestyle, and under normal circumstances, keeping your carbs on the low side is easy. But let’s not create the illusion that it is easy all the time. From time to time, you may get stressed and eat mindlessly. Or, your aunt drops off her blue-ribbon cake that you’ve loved since you were in preschool, and you give in, just this once. Or, you had a jam-packed day and all you can muster to make for dinner is that package of gluten-free noodles in the back of your pantry. The next thing you know, you’ve eaten enough carbs for a week, and you wonder how you’ll get back into ketosis after a carb binge.
The short answer is, yes you will recover from a carb binge. Yes, you will get back into ketosis. As far as how long it will take to get back into ketosis – that depends on numerous factors, that we’ll dive into here. The important thing to remember is, you did not obliterate your goals with one misstep. Especially after you’ve spent some amount of time in ketosis, your body will allow for fluctuations in carb consumption here and there. That’s called metabolic flexibility, which we’ll go into shortly.
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Can You Have a Cheat Day on Keto or a Primal Diet?
Admittedly, I’m not a fan of calling them “cheat days,” for a few reasons:
- “Cheating” implies that you did something wrong and should feel guilty about it.
- Earmarking “cheat days” sends the message that you can eat whatever you want that day with abandon. You’d be surprised how much you can backpedal on your goals in a 24-hour period.
I prefer to frame higher carb meals or snacks as carb cycling or carb refeeding, which is an intentional higher carb meal to enhance your results; or, frame them as treats, which are planned. That way, the extra carbs are enjoyable, planned in advance, and come with limitations so you don’t go overboard. And, there’s no guilt involved.
So, can you have high-carb days on keto? If you are in ketosis and have a sudden surge in sugar or carbs, your body will burn glucose instead of producing ketones. In order to get back into ketosis, you have to use up the glucose you just consumed, and the glycogen your body just stored.
The concern is whether the transition back into ketosis will be as difficult as you remember from those first days cutting carbs. If you have been in and out of ketosis for a while, you may slip back into ketosis fairly easily because you’ve developed metabolic flexibility. If you’re just starting, you may go through some of the discomfort of transitioning between fueling with sugar vs. fueling with ketones. Your body “remembers” though, and most likely, it will not last as long or be as severe. This article contains some things you can do if you experience “low-carb flu.”
What Happens to Your Body After a Carb Binge?
So, you decided to give in. First, don’t beat yourself up. It happens. What does your metabolism do with the surge of insulin and carbs? Even a few quick forkfuls can shift you from small doses of quality carbs wisely spread throughout the day to possibly 100 or more grams of pure sugar in one sitting. It’s likely you’ll experience some effects, but you can get past it.
First off, the good news. There’s no carb police coming to take away your keto card. Nor is there any other permanent fate awaiting you. You’ll go about your day a live, generally functional human being. There is no truly long-term risk elevation for that matter. Nonetheless, you’ll likely experience a fair amount of regret for cheating on keto.
- Your Pancreas Kicks Into Overdrive. Within a few minutes, your pancreas starts pumping out a flood of insulin to try to sop up all the excess glucose that’s suddenly rushing through your bloodstream. Remember, while glucose is muscle fuel when it’s in the muscles, it’s toxic sludge when it stays in your bloodstream. Your body knows that and does everything it can to get it out of there. Perhaps you’re feeling flushed, a little high, spastic, anxious, or nauseous depending on how much you ate, how big you are, what your normal carb load is, and how acutely you tend to “feel” the effects of sugar and other substances. Ironically, if you were insulin resistant, you might not even notice these sensations.
- Excess glucose converts into body fat. The gush of insulin now creates a see-saw effect. If your glycogen stores have room, some of the sugar goes into muscles. If there’s no more room, the excess goes into fat cells, where it is stored as fat. In reaction to this quasi-emergency that your brain perceives as a life-threatening stress, the body steps up its efforts to achieve homeostasis by releasing both epinephrine (adrenaline) and cortisol from your adrenals. Your heart starts racing, and you’re starting to feel uncomfortable, maybe even sweating. And we’re still likely within the first hour after you finished off that cake!
- Sugar crash. After a bit more time passes, burnout settles in? That’s called a sugar crash – when all the glucose is gone from the bloodstream and you start to feel sluggish, off-kilter, like the internal circuits are all fried after sparking in a heap of now smoldering wires.
- Your immune system slows down. The havoc that sugar rush set off – the swing of glucose and insulin, the cortisol and adrenaline – they’ve sent your immune system into a tailspin. Researchhttp://jcem.endojournals.org/cgi/content/abstract/85/8/2970?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=1&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&volume=85&firstpage=2970&resourcetype=HWCIT‘>2 on the body. Your blood even thickens as a response to the stressors. A hefty dose of sugar can compromise the immune system
One of the more common questions we get in the Keto Reset Facebook community is, “How do I break through a weight-loss plateau?”
Stalls are frustrating. You’re cruising along on your Primal or Primal + keto diet, and then wham—you hit a wall. It’s all a totally normal and expected part of the weight loss process. Weight loss is never linear. There are always downs, ups, and flat spots.
In fact, if you’ve been losing weight for a while, and then you stall out for a week or two, I wouldn’t even consider that a plateau necessarily. Your body might keep losing weight on its own if you give it time and don’t stress about it. Still, I get it, you’re eager to kick-start the weight loss again.
One strategy that gets tossed around is trying a carb refeed or “carb up.” Carb refeeds are touted as plateau busters and also, more generally, as a strategy to support weight loss. In today’s post, I’ll explain the logic behind this idea and explain why it might be effective, especially for women following a generally low-carb approach.
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What Is a Carb Refeed?
Let’s get some terminology out of the way. Strategically adding carbs to a low-carb diet is variously called a “carb refeed,” “carb up,” or “carb cycle.” These terms don’t have standardized definitions. In general, carb cycling usually refers to eating low carb for a certain number of days, then higher carb for a certain number of days, and repeating.
“Carb refeed” and “carb up” can mean the same thing, or they can mean adding carbs more intuitively when you feel like you need them.
Carb cycling strategies have long been used to promote leanness, especially by physique and other athletes trying to achieve low body fat percentages. In this context, carb cycling involves specific protocols, usually 5-6 days of very low carb eating combined with 1-2 days of higher carb eating. They may include exercise and fasting regimens, too.
The carb cycling protocols used for getting super lean aren’t the same as what we’ll be talking about for general weight loss and breaking out of a stall. For one thing, they usually involve more carbs than you probably need. We’ll get to that later. Also, although some of the mechanisms are probably the same, they focus specifically on depleting and refilling glycogen stores. For our purposes, that’s not so important.
How Do Carb Refeeds Work?
First let me say that the evidence for carb cycling strategies, especially with regard to weight loss and plateaus, is mostly anecdotal. There is pretty good data to support the pieces, but the whole picture has not been rigorously tested.
So what do we think is happening? There are a few (not mutually exclusive) hypotheses here:
- Carb refeeds work by boosting leptin
- Carb refeeds work by relieving the stress of dieting
- Dieting is hard, and carb refeeds help us stick to them
Carb Refeeds Work by Boosting Leptin
Leptin is sometimes called the “satiation hormone,” but it’s probably more accurate to think of it as a starvation sensor.1 Its main role is to tell the brain whether we have sufficient energy on board, either in fat cells, which secrete leptin, or because we have recently eaten (especially carbs).
It’s well established that leptin levels drop both when we lose body fat and when we eat in a caloric deficit2 for even a short period. Remember, from an evolutionary perspective, weight loss signals that we are in a time of food insecurity and stress. Low leptin signals to the hypothalamus that we might be facing an energy shortage. In turn, the hypothalamus kicks on the processes collectively known as adaptive thermogenesis,3 or energy conservation. These include down-regulating thyroid activity and slowing metabolic rate, decreasing energy expenditure, and increasing hunger and appetite.
Premenopausal women’s bodies are especially sensitive to anything that sets off the “Danger! Starvation possible!” alarms. (Postmenopausal women are generally more resilient.) Leptin is a key player in that system. It is also involved in the regulation of insulin sensitivity and glucose metabolism, the female reproductive and immune systems, and skeletal and cardiovascular health. Basically, leptin is really important if we want to feel good and achieve optimal hormonal balance.
Leptin levels rise in response to eating carbohydrates specifically.4 Thus, one rationale behind carb refeeds is that by boosting leptin, we can reset the system. Basically, it tells the brain, “Hey, it’s cool, we have food around. It’s safe to let go of some of this body fat.”
Carb Refeeds Work by Relieving the Stress of Dieting
A related hypothesis is that dieting is physiologically stressful on the body. After periods of energy restriction, we see a decrease in thyroid hormones and an increase in cortisol (which may be related to falling leptin). These are part of the adaptive response that aims to restore energy balance. Carb refeeds alleviate the stress of being in a constant state of energy restriction.
Dieting Is Hard, and Carb Refeeds Help Us Stick to Them
One of the main reasons dieting hard is because of hormonal changes (ahem, leptin5) that increase hunger and appetite. Besides feeling unpleasant, this leads many dieters to eat more than they realize, undermining fat loss. Multiple studies also suggest that low leptin levels increase reward-seeking behavior. Basically, food becomes more appealing and harder to resist.
Low leptin is also related to depression6, anxiety, and perceived stress, all of which can make it harder to stick to your diet goals.
For all these reasons, periodically boosting your leptin via carb refeeds should make dieting feel less challenging. Beyond that, there’s also the psychological factor of knowing that you don’t have to strictly adhere to a diet indefinitely. Although it might seem counterintuitive, research confirms 78that giving yourself planned breaks can help relive the doldrums of dieting and actually increase your adherence in the long term.
Who Should and Should Not Consider Incorporating Carb Refeeds
There’s no evidence that carb refeeds are necessary or optimal if weight loss is your goal. Like so many things, this is going to be an n=1 situation. They might help, hurt, or be neutral depending on the individual.
First and foremost, if it ain’t broke, don’t fix it. If your current diet is working just fine, you feel great, and you’re losing weight, you don’t need carb refeeds. (By the way, if you’re impatient because you’re losing slowly, I haven’t seen any evidence that they will speed up weight loss.)
Likewise, they generally aren’t recommended for people who still carry a significant amount of body fat. There’s no real guidance as to what constitutes “significant amount,” unfortunately. As a rule, though, leaner individuals are more likely to benefit from the hit of leptin because they have less adipose tissue to produce it on a day-to-day basis.
DO: Reasons to experiment with carb refeeds include:
- You’re experiencing a weight loss plateau. This means several weeks of no change in weight or body measurements despite nothing else changing. This isn’t a guaranteed strategy, of course. There are lots of reasons weight loss can stall, not all of them related to leptin or diet adherence. It’s certainly worth a try, though.
- You’ve been low-carb and/or calorie restricted for a while, and you’re experiencing other signs of hormone dysregulation. These include menstrual irregularity and sleep9 disruptions, among others. Depending on how severe your symptoms, you might need more than the occasional carb refeed. For mild symptoms, an occasional refeed might help.
- You’re sick of dieting. Mixing it up with carb refeeds (which are not the same as “cheat days”) can relieve the dieting fatigue.
DON’T: Other instances when carb refeeds are not advised are:
- For people who are using low-carb or keto therapeutically, such as for epilepsy or Parkinson’s, unless advised by their health care practitioners.
- For people who are extremely insulin resistant.
How to Implement Carb Refeeds
No matter what strategy you use, you want to refeed with nutrient-dense, Primal-aligned foods. We’re talking sweet potatoes, potatoes, beets, baked goods made with almond or coconut flour if you want, in-season fruit, quinoa, maybe legumes if they work for you. If you want to eat some rice (sushi!), no judgement here.
Primal carb refeeds aren’t just an excuse to “cheat” (a term that I hate). You’ll see carb cycling protocols that allow, even advocate, eating copious amounts of junk food (another term I don’t love) on refeed days. Since our goal here is metabolic health and hormone balance, stick to the same Primal foods that support those goals, just with more carbs.
How Many Carbs Should I Add?
If you look at the literature on carb cycling, you’ll find various opinions. Depending on who you ask, it can be upwards of 300+ grams per day. Again, though, these come mostly from protocols aimed at physique and other athletes, and these high carb recommendations are for men who are already quite lean. It’s not clear how they apply to the average woman looking to kickstart their weight loss.
As usual, it’s also hard to find research on people who follow a low-carb Primal or paleo approach. In this oft-cited study,10 for example, the control diet was a mainly liquid diet supplemented with orange juice, yogurt, and cream that came in at an average of 224 grams of carbs per day. In the carb overfeeding condition, which was shown to boost leptin, the average daily carb intake was 394 grams—way more than the average Primal eater probably consumes.
In the absence of solid research-based recommendations, you’ll have to experiment. A good place to start is bumping up to twice your normal daily intake by adding nutrient-dense carbs to one or two of your meals, and increasing as necessary. If you want to be scientific about it, log your food and also keep track of metrics like weight, sleep, and energy. Play around with the frequency of carb-ups, as well as the amount of carb you add, and see what works best.
Should You Increase Carbs, Calories, or Both?
Technically, carb refeeds don’t have to involve more calories. Some protocols state that you should reduce fat on carb-up days so that your total caloric intake stays the same. Others specifically recommend adding carbs and increasing calories by a fixed amount.
Unfortunately, we don’t have enough studies to break down the separate effects of carbs and calories here. In theory, both should signal to the body that energy is available, but carb intake uniquely boosts leptin. Once again, experiment to see what works for you. To start, I’d recommend allowing your calories to increase on refeed days. You might dial back your fat a little, but I wouldn’t overthink it, especially if you’re already low-carb or keto. Adding 50 or 75 grams of carbs is 200 to 300 calories. That might be less than your typical caloric deficit. Even if you add more, it’s unlikely to negatively effect weight loss if we’re talking occasional refeeds.
I know that many dieters are afraid to increase their calories for fear of “undoing” their progress. That fear seems to be unfounded. Multiple studies confirm that intermittent dieting—mixing periods of caloric restriction with eating around your maintenance calories—is no worse11 for losing weight than continuous calorie restriction. It may even be advantageous12 for weight loss, and fat loss specifically.
How Often Should I Refeed?
In terms of how often to refeed, you have some options:
- Add in carbs whenever you plateau
- Carb cycling on a schedule
- Carb cycling around your menstrual cycle
- Eating carbs intuitively
Add in Carbs Whenever You Plateau
If you’re actively trying to lose weight, one option is to wait until you hit a plateau—at least a couple weeks when the scale stops moving—then add a day or two of higher-carb Primal meals to see if that moves the needle.
Carb Cycling on a Schedule
As I said up top, some carb cycling strategies involve fixed periods of lower- and higher-carb eating. Often this looks like eating low-carb during the week and then doing one or two higher-carb days on the weekend. This is more convenience than science though. There’s no reason you can’t do 9/1 or 12/2 or any other pattern that works for you. You don’t even need to take a whole day. Some people just do one high-carb meal per week and feel great.
Obviously this strategy is more of a lifestyle than an acute tool for breaking through a weight-loss plateau. This is for people who don’t do well with continuous dieting or who find it easier to stick to their goals when they have planned deviations. It is akin to the idea of a cyclical ketogenic diet, although you don’t have to be keto to use carb cycling.
Carb Cycling Around Your Menstrual Cycle
Another carb cycling strategy is timing carbs strategically around your menstrual cycle.
This strategy isn’t specifically geared at weight loss but rather supporting the whole hormonal system, but it potentially allows you to kill two birds with one stone. There are different approaches here, but a common one is increasing carbs 4 to 5 days post-ovulation (around days 19 and 20 of your cycle) and on the first couple days of your period. These are times when your leptin levels naturally dip, so you could possibly benefit from the boost. Some women prefer instead to add carbs around ovulation, days 13 to 15. Again, see what works be for you.
Eating Carbs Intuitively
Finally, you can wait until your body starts calling out for carbs and respond appropriately. In my opinion, intuitive eating is one of the goals of a Primal diet and lifestyle. When we improve hormone balance and tap into how good it feels to nourish ourselves with nutrient-dense foods, we should be able to trust when our inner voice says, “Hey, I could use some starchy vegetables here!”
Eating carbs intuitively isn’t the same responding to sugar cravings or eating something off plan just because it “sounds good.” I think we can all recognize the difference between listening to our bodies and eating purely for pleasure. (You’re more than welcome to do that too, but it’s not what we’re talking about here.)
Intuitive carb refeeds are probably going to work best for people who have been on the Primal train for a while and who generally feel pretty in tune with their bodies. Women who are dealing with chronic health issues or hormone imbalances might need something more structured.
Note that this is a different question than carb timing, which Mark covered recently. Carb timing is about when to eat your carbs during the day.
Don’t Be Afraid to Experiment
I’m a big fan of experimenting with your diet. There is so much bioindividuality, it’s impossible to find a one-size-fits-all approach. The best strategy for you is the one that hits that sweet spot where you to feel your best and also enjoy how you eat.
Moreover, I’m going to go out on a limb and say if you’ve been low-carb for so long that you’re afraid to consider eating even nutrient-dense, Primal-aligned carb-y foods like sweet potatoes, you should challenge yourself to try a carb refeed and see what happens. I’m not talking about people who know they feel better eating very-low-carb and simply don’t have the desire to switch it up. I’m talking about people who have a mental block around the very idea of carbs. We don’t want people to get “stuck” in a low-carb paradigm to the point where they feel unable to enjoy otherwise nutritious foods just because they have more carbs than, say, broccoli.
Finally, although their are good reasons to try carb refeeds if your current low-carb diet isn’t working the way you want, it’s only one of many things you might try. In particular, if you haven’t also gotten your sleep and stress in order, make those priorities as well. Carb refeeds can only do so much if you don’t have a solid foundation of healthy habits in place.
Tell us: Have you had success implementing a carb cycling approach? What works for you? What are your favorite foods to use to increase carb intake?
Related posts from Mark’s Daily Apple
The post Carb Refeeds for Women: Do They Help With Fat Loss? appeared first on Mark’s Daily Apple.
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Beyond the great debate about how many carbs we should be eating, there is another question you might be wondering about: When is the best time of day to eat carbs?
Today we’re going to dig into the data and see if we can get some answers. Before we do, though, I want to make something clear. The types and amounts of food you are eating are much more important than nutrient timing when it comes to health, body composition, and even athletic performance.
Before worrying about nutrient timing, you should:
- Eliminate the “big three”—grains, excess sugars, and offensive vegetable and seed oils
- Consume an appropriate amount of food for your goals and activity level—neither too much nor too little
- Ensure that you are getting enough micronutrients via diverse, nutrient-dense foods, plus supplementation when necessary
I’d also say that macronutrients—the relative amounts of carbs, protein, and fat you’re eating—comes before nutrient timing in the hierarchy of “likely to matter.” A Keto Reset is probably going to impact your health and body composition more than changing the timing of your carb intake.
Still, I know many of you are self-experimenters and optimizers. You like to explore ways to squeeze a little more “edge” out of your diet and lifestyle. For some of you, nutrient timing might be the key to resolving a nagging issue that hasn’t been fixed by diet and lifestyle changes. If this is something you’re curious about, read on.
The Best Time to Eat Carbs: Why Would Carb Timing Matter?
The growing field of “chrononutrition” investigates how food timing affects overall health. I’m sure you know that many bodily systems operate according to biological clocks. Sleep, immune system activity, and body temperature are all governed by circadian (~24-hour) clocks, for example. Disruption to our normal biological clocks negatively impacts health.
Metabolism operates according to circadian rhythms, too. On a basic level, we are meant to sleep when it’s dark, move and eat when it’s light. Insulin sensitivity and beta cell activity (the cells in the pancreas that produce insulin) are highest in the morning. Research shows that glucose tolerance—the body’s ability to clear glucose from the bloodstream after a meal—goes down if your sleep is poor or under conditions of circadian misalignment. There also seems to be a link between eating later at night, weight gain, impaired fat oxidation, and other negative health outcomes.
Taken together, this has led some researchers to suggest that we should eat most of our food earlier in the day to entrain, or align, our circadian rhythms. Doing so, they argue, could improve glycemic control (glucose regulation) and insulin sensitivity. It might also regulate appetite hormones and cortisol, and have downstream effects on body composition.
Carb Timing for Glycemic Control and Insulin Sensitivity
A number of studies seem to suggest that eating later is associated with impaired glucose tolerance and/or insulin sensitivity. On the other hand, both may be improved with early time restricted feeding (eTRF). This is where you eat in a compressed window, say 8 or 10 hours, and that window is shifted toward the morning. A typical eTRF schedule might entail eating all one’s food between 8 a.m. and 4 p.m.
Most of these studies focus on food timing generally, not nutrient timing per se. For example, in this study, men with type 2 diabetes ate all their calories in a 9-hour window. In one phase, they ate from 8 a.m. to 5 p.m. (eTRF). In the other, they ate from 12 p.m. to 9 p.m. Both schedules improved glucose tolerance, but only eTRF decreased fasting glucose.
A handful of studies do specifically look at carb timing:
- Healthy volunteers kept three-day food diaries. Those who ate relatively more of their food, and more carbs specifically, in the morning were also more insulin sensitive than late eaters. (Eating more fat in the evening was also correlated with poorer insulin sensitivity. It’s not clear how much these effects were driven by total caloric intake.)
- In another interesting study, researchers assigned men to eat two different diets for four weeks. They either ate most of their carbs before 1:30 p.m. and most of their fat after, or vice versa, in a cross-over design. For men who started out normal glucose control, carb timing didn’t matter. However, among men with high fasting glucose or impaired glucose tolerance, eating carbs at night led to unfavorable changes on several makers of glucose tolerance.
- In contrast, in this study, men followed a hypocaloric diet for eight weeks. Participants who were assigned to eat most of their carbs at lunch instead of dinner ended up with higher fasting glucose and insulin, and poorer insulin resistance.
Does type of carb matter?
Maybe. Researchers compared low-GI (glycemic index) and high-GI meals with most of the calories loaded into either the morning or the evening. Participants had the highest postprandial glucose (glucose after a meal) and insulin in the high-GI + evening eating condition. It didn’t matter when participants ate low-GI carbs. (Participants also consumed 302 grams of carbohydrate per day. Diets consisted of bran cereal, low-fat fruit yogurt, “fruit loaf,” and a Mars bar, among other things. It’s not clear exactly how these findings apply to Primal eaters.)
Conclusion: More research is needed in this area, but the available evidence points to morning carb consumption being favorable for glycemic control, perhaps especially among people who already struggle in this area.
Carb timing for athletes
As you know, I’m a big fan of athletes using fat for fuel. It’s an efficient, cleaner burning, more abundant source of energy. Once you become fat-adapted, it’s amazing what you can do as a fat-burner. As I detail in Primal Endurance, low-carb and keto diets work tremendously well for endurance athletes and even for hard-core strength athletes.
That said, there is no denying the ergogenic effect of carbs – carbs’ effect on stamina, physical performance and recovery. When you’re fat-adapted and running mainly on fat (and maybe ketones), adding some carbs to the mix can be like rocket fuel. I’m a fan of the “train low, race high” strategy for endurance athletes. Conduct most of your training using a low-carb approach, but add carbs strategically for your highest-intensity training sessions and races. You don’t need a lot, maybe 60-100 grams per hour.
Targeted Carbs: Should You Eat Carbs Before a Workout?
One strategy I’ve talked about before is targeting your carb intake around workouts. There are two rationales here. One is the aforementioned ergogenic effect — giving your workouts a boost. The second is that when you exercise, a glucose transporter in muscle cells called GLUT4 moves to the surface of the cell. This facilitates the transport of glucose into the cells without insulin.
Intense exercise also depletes glycogen, so there is a window after exercise in which ingested carbs are more likely to go to replenish glycogen. This is what I mean when I talk about the “glycogen suitcases being open” after exercise.
Thus, it makes sense to time your carb intake around exercise, especially hard and/or long bouts. In the keto world, this strategy is called “targeted keto.” The same principle applies for low-carb-but-not-keto folks. It’s not because you need the carbs for workouts—most of us do just fine without any special carb loading—but that’s when the body is most ready to use or store them.
Does Eating Carbs in the Evening Help You Build Muscle?
In the world of muscle gains, there are a handful of approaches that involve backloading carbs into the evening following a workout. Bill Lagakos does an excellent job unpacking them in a two part blog series here and here. Briefly, the logic behind carb backloading is that you don’t want to eat carbs when you’re more insulin sensitive in the morning because they’ll get stored as fat (oversimplifying here). Instead, wait until later in the day when insulin sensitivity decreases, then use exercise to push carbs into muscle instead of fat.
There’s no real evidence that this works, beyond anecdotal evidence from people who enjoy eating carbs at night. If you have body fat to lose, I think the evidence favors shifting calories and carbs toward the morning.
For the average person looking to gain strength and functional fitness, carb timing is not a great concern. For fitness competitors or people trying to push their physical limits, it might start to matter.
If you’re looking to gain lean muscle, you might find that ingesting a small amount of carbohydrate—25 to 30 grams—before hitting the gym can be beneficial. Contrary to popular belief, however, post-workout carbs do not seem to enhance muscle synthesis or recovery to a meaningful degree, especially not when protein needs are covered.
Bottom line: Carb timing isn’t important for muscle building except maybe for elite competitors and high-performers.
Timing Carbs for Weight Loss: What Does the Science Say?
In recent years, some people have claimed that eating carbs at night actually supports weight loss. In fact, this is one of the rationales offered for the aforementioned carb backloading. However, the studies they typically cite as evidence for this assertion have methodological problems that I can’t overlook.
Those studies are also at odds with a larger number of studies linking weight loss to eating more of your calories earlier in the day. Mechanistically, eating late delays the onset of the overnight fast, interfering with fat-burning and potentially with switching on ketosis. Eating later can also be associated with eating more, period.
Unfortunately for the purposes of this post, studies that look at meal timing and weight loss don’t examine nutrient timing, with one exception. In this study, researchers compared two diets, one prioritizing carbs at lunch and protein at dinner, and the other vice versa. Participants lost equal amounts of fat on each, but the group who ate most of their carbs at dinner also lost more lean tissue—not what you want! (This was also the study that showed poorer glycemic control with lunchtime carbs, in contrast to most other studies.)
Bottom line: When it comes to weight loss, there’s not enough data to convince me that carb timing seems very important.
Carbs Before Bed and Sleep Quality
Theoretically, carb intake at night could positively affect sleep by increasing tryptophan production, which is a precursor of serotonin, which in turn promotes sleep. It makes sense. No empirical research directly supports this hypothesis, though. Still, experts recommend you try adding some carbs at night if you’re struggling with sleep, especially on a low-carb diet.
There are plenty of studies looking at the relationship between macronutrients and sleep. However, they look at dietary composition as a whole, not nutrient timing. A single small study found that eating a high-GI meal four hours before bed improved sleep onset, compared to a lower-GI meal, and also compared to eating that same high-GI meal eaten one hour before bed. That’s all we have data-wise, besides anecdotes.
Conclusion: Anecdotal evidence aside, there’s no proof that timing carbs at night help your sleep. It probably doesn’t hurt to try.
So Where Does This Leave Us?
Well first, it leaves us asking for more studies that systematically investigate carb timing. I specifically want to see more studies looking at carb timing in a low-carb population. As usual, the studies I cited here involved a standard high-carb paradigm. If you read the reports and see what researchers are feeding their participants… well, let’s just say you Primal folks wouldn’t volunteer for these studies.
This always leaves me wondering how well any of these findings apply to us fat-adapted folks. We can’t know for sure.
Let’s summarize the findings we have, though. First, for entraining your circadian rhythm, improving glycemic control, and losing weight, the available data altogether point to the benefits of eating more of your carbs earlier in the day.
You might wonder how this fits with intermittent fasting. First of all, I.F., doesn’t have to mean skipping breakfast. Many people skip breakfast largely out of convenience. If it works for you, great. Nothing I’ve said suggests that it’s bad for you. That said, if you’re still struggling with glucose tolerance, or you have a few stubborn pounds of body fat you’d like to lose, loading more of your calories and carbs earlier in the day seems to be a worthwhile experiment, as I’ve said before.
It makes sense to target carbs around exercise, but it’s generally not necessary for athletic performance. Most weekend warriors can get by just fine without any special carb timing strategy. People looking to gain muscle may want to ingest a small amount of pre-workout carbs, and endurance athletes should be open to using carbs around heavy training and races. I still think becoming fat-adapted should be every athlete’s first priority.
Finally, maybe experiment with some extra nighttime carbs if you’re a low-carb eater whose sleep is suffering.
But Don’t Sweat It
Nothing I’ve seen suggests that carb timing is more important than the amount and quality of food you eat. Once you dial in those higher-priority goals, by all means go ahead and try being more intentional about your carb timing if you want.
It might make a difference if you’re at the top of your performance game looking to squeeze out a few more drops, or if you have lingering health issues. Otherwise, I’d consider it just another variable you can experiment with if you want, but don’t sweat it if you have bigger things to worry about.
More related posts from Mark’s Daily Apple
Challet, E. (2019). The circadian regulation of food intake. Nature Reviews Endocrinology, 15(7), 393–405.
Oda, H. (2015). Chrononutrition. Journal of Nutritional Science and Vitaminology, 61 Suppl, S92-94.
Oike, H., Oishi, K., & Kobori, M. (2014). Nutrients, Clock Genes, and Chrononutrition. Current Nutrition Reports, 3(3), 204–212.
Qian, J., Dalla Man, C., Morris, C. J., Cobelli, C., & Scheer, F. A. J. L. (2018). Differential effects of the circadian system and circadian misalignment on insulin sensitivity and insulin secretion in humans. Diabetes, Obesity and Metabolism, 20(10), 2481–2485.
Wefers, J., van Moorsel, D., Hansen, J., Connell, N. J., Havekes, B., Hoeks, J., van Marken Lichtenbelt, W. D., Duez, H., Phielix, E., Kalsbeek, A., Boekschoten, M. V., Hooiveld, G. J., Hesselink, M. K. C., Kersten, S., Staels, B., Scheer, F. A. J. L., & Schrauwen, P. (2018). Circadian misalignment induces fatty acid metabolism gene profiles and compromises insulin sensitivity in human skeletal muscle. Proceedings of the National Academy of Sciences of the United States of America, 115(30), 7789–7794.
Zilberter, T., & Zilberter, E. Y. (2014). Breakfast: To Skip or Not to Skip? Frontiers in Public Health, 2. Retrieved from https://www.frontiersin.org/articles/10.3389/fpubh.2014.00059/full.
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For today’s edition of Dear Mark, I’m answering three questions taken from last week’s post on the power of pairing low-carb with fasting. First, do I have any advice for a woman who’s struggling to see results eating one meal a day? Second, how does low-carb interact with the different types of glucose tests you can take? And third, what are my thoughts on carb limits when fasting? Is lower always better? Is there a carb threshold after which fasting stops working so well?
I have been dappling in low carb for nearly year and in the last 2-3 months I have been playing around with OMAD. My question is, I eat ’till I’m full ,which is about 12-18 grams of carbs, never over 100g protein and around 100g fat, sitting at 1000-1400 calories—but I’m not losing weight. Over 3 months I’ve lost about 6kg and I have about 30kg to lose. Do I keep going? I’m enjoying it but I get frustrated about the lack of weight loss (I’ve lost a dress size).
The majority of women don’t do well on one meal a day. Consider the average office worker struggling to lose weight. They do coffee for breakfast and maybe have a salad with no meat (and few calories) for lunch, struggle mightily not to eat five stale donuts at 3p.m. in the break room, only to cave at night and eat a sack of potato chips and take out while streaming some show.
My point is not that these people would do better if only they ate a solid meal for dinner rather than chips and snacks and Netflix. Nor is it that this problem only afflicts women and never men. Plenty of men do it, too, and have bad results. But it shows more quickly in women, who by nature of their reproductive physiology are simply more vulnerable to nutritional insults than men—on average. I explain the reasons this happens in this post on fasting for women. Long story short, because reproduction is far more costly and demanding on a woman’s body than a man’s (conception, pregnancy, nursing); woman are more finely attuned to caloric restriction and fasting. My point is that fasting for most of the day, every day, doesn’t work well for most women—it becomes a constant stressor, driving unhealthy cravings to which you eventually succumb.
It sounds like OMAD might not be working for you. Just one dress size (which is a better barometer than weight) in 3 months? Yeah, it might be time to try something else.
Was low carb with more frequent meals working?
I’ve seen a lot of men burn out on OMAD, too. Throw in some sleep disturbances, a heavy training schedule, work-related stress, cooking for the family, bills, and whatever other stressors modern life throws our way, and OMAD can be counterproductive.
For one thing, your calorie intake is way too low. One thousand calories is way too low; 1400 calories is really pushing it. Perpetually starving yourself for 22 hours a day and then trying to cram a big meal in that doesn’t even provide enough calories or nutrients just doesn’t work for most people. I can imagine your leptin is low, your caloric expenditure dampened, your thyroid function inhibited.
Here’s what you might try.
Do OMAD with 1000-1400 calories once a week. Twice max. Eat normal—two to three meals—the rest of the days. This way you pulse your fasting and OMAD’ing. You eat normal amounts of calories for five days a week and then drop them down low twice a week, giving your body a message of relative abundance punctuated with short bouts of scarcity.
I think that’ll work better for you. Write back with your results.
If you are low carb and need to do a glucose blood test and an A1C test: What is the best fasting times then? Just the night before or for 24 hours?
If you fast longer, shouldn’t the glucose reading be lower?
It really depends on what kind of test you take.
If you’re doing a fasting blood glucose test, fasting will probably lower it.
If you’re doing a postprandial blood glucose test, fasting will probably raise it. You’re asking your body to suddenly go from burning fat to processing 75 grams of pure glucose. The fat-based metabolism triggers transient insulin resistance, which inhibits your ability to process the glucose efficiently. Your postprandial reading will thus be higher than is “real.”
If you’re doing an HbA1c test, fasting won’t affect it. HbA1c is the “average” blood sugar over three months or so; a single meal will have no impact.
I totally agree with the science of this relationship. Mark, at what intake level of carbs are you considering this relationship no longer synergistic? Anything over 100 grams or should the carb intake be kept lower to have the greatest fat-burning / weight-loss effect?
The bulk of the synergy lies in the ease with which you can maintain the fast. Low-carb/fat-based metabolisms simply make it easier to slip into and remain in the fat-based metabolism of the fasting state. If you can easily fast, easily slip back into ketosis and maintain the fast while eating an otherwise moderate or high-carb diet, have at it. That isn’t as common as the opposite, drawing on my experience talking to hundreds of people about this.
However, some people get the best weight-loss effect by combining intermittent fasting, heavy weight training, and periodic/timed carb feeds. The trick is to time your carbs around your workouts, and eat no more than you’ve actually expended through glycogen depletion. That means you’re still in a fat-based metabolism because the carbs you do eat are going toward glycogen repletion rather than being burned for energy, so they never actually inhibit the burning of body fat.
If you’re doing CrossFit WODs that hit every muscle and leave you panting on the ground (or the equivalent), you could probably get away with 100-200 grams right after without any issues. It really depends, of course. More muscle, larger glycogen sinks. Some people just slip right back into ketosis more easily. Others have a life history that may inhibit this. But that 100-ish carbs after a “hard” training session that you feel should be a good target for most people.
You should keep fat low and protein high in these carb-heavy meals. What you want is to refill that glycogen and hit the protein hard.
That’s it for today, folks. Take care. Be sure to ask any followups or additional questions down below. Thanks for reading!
The post Dear Mark: OMAD for Women, Low-Carb Glucose Testing, and Carb Limit When Fasting appeared first on Mark’s Daily Apple.
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Is it just a case of overlapping interests? Is it because when you stumble upon one big lie perpetrated by the experts—that cutting carbs will give you heart disease and leave your brain starving for energy/you must eat 6-8 small meals a day or else risk “starvation mode” and “slow metabolism”—you start questioning all the other advice they give?
It might be some of that. But a big reason why intermittent fasting and low-carb eating tend to converge is that they are synergistic. Doing one makes the other work better, and vice versa.
What are the benefits? What are the synergies?
Fasting is easier when you’re low-carb. Low-carb is easier when you fast.
Low-carb is easier when you fast.
Fasting is easier when you’re low-carb.
The two inputs support each other. Rather than a vicious cycle, it’s a virtuous one. Fasting promotes fat-adaptation by upregulating fat-burning mitochondria, spurring the creation of new mitochondria, and reducing your reliance on sugar. Fat-adaptation makes going low-carb easier, because you’re really good at burning body fat and don’t get so many sugar cravings. Going low-carb makes you even better at burning fat and builds even more mitochondria, which is a prerequisite for fasting for extended periods of time.
If low-carb is going to work, you have to do it. If fasting is going to work, you have to fast. Anything that makes those easier is going to be good for your health. That’s where it all starts.
You’ll burn more fat.
A 2013 study compared low-fat dieters on an alternate day fasting schedule with low-carb dieters on an alternate day fasting schedule. Both groups lost weight and improved metabolic health markers, but the low-carbers lost more body fat.
A more recent study putting low-carbers on a fasting schedule for six months saw their body fat drop, lean mass remain stable, and fasting insulin decrease. However, there was no control group and the low-carb diet was still 30% carbs. I think you’d see better results if you dropped those carbs down even lower.
You’ll lose less muscle.
One common criticism lobbed at intermittent fasting enthusiasts is that it has the potential to cause muscle loss. This is a valid point. If you are insufficiently fat-adapted, your glucose requirements will remain elevated when fasting, and you may break down muscle tissue for the amino acids to convert to glucose.
Luckily, ketones spare muscle tissue by reducing your need for glucose. It turns out that a fair number of tissues that would otherwise run on glucose can run on ketones. Being in a ketogenic or low-carb fat-burning state before you fast accentuates this effect. It’s no wonder that the studies mentioned in the last section found that weight loss via low-carb dieting and fasting was entirely from body fat.
Bump up the muscle-sparing effect even more by lifting heavy things (even during the fast).
You’ll forget to eat.
A major reason low-carb and keto diets work so well for weight loss is that they increase satiety and inadvertently reduce calories. Whereas your average calorie-counter is painstakingly tracking everything he or she eats and expends just to wrangle a few pounds lost, the low-carb dieter often just eats to satiety and lets the weight loss happen.
The average low-carber will fast without even thinking about it. They fast because they simply aren’t hungry and forget to eat. Someone on a higher-carb “regular” diet often must summon superhuman willpower to fast. They fast in spite of being ravenous and can think of nothing else but eating.
Forgetting to eat is a much easier way to fast than willing yourself to do it.
You’ll avoid harmful postprandial blood sugar spikes.
Eating a high-carb meal after fasting for two days will spike your postprandial blood sugar. Eating a low-carb meal after fasting for two days will likely not. Why?
Consider the problem of the long-term low-carber trying to pass a glucose tolerance test. It’s common for long-term low-carbers to “fail” glucose tolerance tests because they’re trying to handle 75 grams of pure glucose with a fat-based metabolism. The body is set up to burn fat and you suddenly introduce a bunch of glucose. It’s hard to do, and most people will fail that—even if they’re healthy.
When you’re coming off a fast, you’re burning fat. You may not have the glucose intolerance of a long-term low-carber, but you are running on fat, and that’s going to raise the chance of exaggerated postprandial blood sugar numbers.
If you do want to eat carbs after a fast, the best way to mitigate this issue is to break the fast with a hard workout and then eat the carbs. You’ll “simulate” glucose tolerance by clearing out glycogen and providing open storage depots for the incoming carbohydrates.
Or you could just be a low-carber to begin with and avoid the problem altogether.
You’re less likely to overdo the re-feeds.
Fasting is a great way to induce caloric deficits and thus lose weight. That’s pretty much why it works so well, as an artificial boundary to control our eating and snacking habits. However, people can tend to go a little wild on the re-feeds. They haven’t eaten all day, so of course they’re going to pig out when they break the fast and eat all sorts of foods they wouldn’t otherwise eat—and eat way more calories than they would have, thereby counteracting all the good they did not eating.
If you’re sticking to low-carb or keto principles, the re-feed is safer. You’re less likely to overeat, because low-carb is so satiating. You’re less likely to eat junk, because the “rules” of the diet eliminate most of the offending foods like chips, sweets, and fried carbohydrates.
Your insulin will normalize.
When insulin is elevated, fat is locked away in our adipose tissue, making it very difficult to burn fat. Hyperinsulinemia, or chronically elevated insulin, also increases the risk of cancer and Alzheimer’s disease, and elevated insulin levels are linked to atherosclerosis.
Intermittent fasting is a potent antidote to hyperinsulinemia. This recent study found that, despite causing similar reductions in body weight, alternate day fasting led to greater improvements in insulin and insulin resistance than regular caloric restriction.
Low-carb eating is also a potent antidote to hyperinsulinemia. As it turns out, avoiding carbohydrates reduces one’s insulin load.
I’m no enemy of insulin. It serves many valuable purposes, and we wouldn’t be alive without it. But too much insulin at the wrong time causes undeniable problems—and combining IF with low-carb can normalize it.
So, should you avoid fasting if you’re not low-carb?
Fasting while low-carb isn’t the only way to do it. Many people have great success combining high-carb dieting with fasting, provided they also lift weights. One popular (and effective) method is to go high-carb, low-fat on training days, with the workout coming at the tail end of the fast and the first meal coming after the workout. Then on rest days, you break the fast with low-carb, high-fat meals. The training stimulus increases insulin sensitivity and gives all those carbs a place to go (your muscle glycogen stores).
But combining low-carb and intermittent fasting really does increase and accentuate the benefits of both practices.
Thanks for reading, everyone. I’d love to hear about your experiences with intermittent fasting and low-carb eating. Do you find that the two go hand in hand, or have you also had success fasting with a higher-carb diet?
Klempel MC, Kroeger CM, Varady KA. Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet. Metab Clin Exp. 2013;62(1):137-43.
Kalam F, Gabel K, Cienfuegos S, et al. Alternate day fasting combined with a low-carbohydrate diet for weight loss, weight maintenance, and metabolic disease risk reduction. Obes Sci Pract. 2019;5(6):531-539.
Mujaj B, Bos D, Kavousi M, et al. Serum insulin levels are associated with vulnerable plaque components in the carotid artery: the Rotterdam Study. Eur J Endocrinol. 2020;
Gabel K, Kroeger CM, Trepanowski JF, et al. Differential Effects of Alternate-Day Fasting Versus Daily Calorie Restriction on Insulin Resistance. Obesity (Silver Spring). 2019;27(9):1443-1450.
The post Benefits of Pairing Low-Carb Eating with Intermittent Fasting for Health and Weight Loss appeared first on Mark’s Daily Apple.
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