I’ve written about what to eat. I’ve written about what not to eat. I’ve even discussed the benefits of occasionally eating things you “shouldn’t eat.” I’ve written about skipping breakfast, eating a big lunch, and skipping entire days of meals altogether. I’ve discussed sleeping low (carb) and punctuating a low-carb diet with occasional high-carb refeeds. But I haven’t written very much about when to eat.
I won’t tell you when to eat. There are many paths. You must find the one that takes you to your goal. But there are some physiological “truths” that impact how we process food depending on what’s happening in our lives which seem to apply to all humans. I’ll discuss several ways to think about meal timing, and then you can decide which concepts make sense for you and your life.
Eating shortly before or after a workout will improve the metabolic response to the meal.
Conventional Primal wisdom says that you can’t out-exercise a bad diet. Is it true?
Kinda. Nothing, except god-tier genetics, will protect you against a diet of exclusively deep-fried food. Even if you were to maintain good body comp, I’d hate to see how you looked on the inside.
But that doesn’t erase the fact that training alters the metabolic effects of a meal and the fate of the nutrients comprising it.
Research has found that a bout of full-body resistance training done prior to a meal offers more protection against postprandial lipemia than a bout of aerobic training, despite the former burning fewer calories than the latter.
Resistance training also sensitizes skeletal muscle to insulin (so you need less insulin to do the same job and can burn more fat as a result) and increases glycogen storage (so glucose fills muscle glycogen stores rather than contributes to energy overload and eventual fat gain). It increases muscle protein synthesis, creating an “anabolic window” for dietary protein to contribute to muscle gain.
Anything works, though. Moderate to high intensity aerobic activity creates a glycogen debt that must be filled, so the body oxidizes fat to allow glucose entry into glycogen stores. Low intensity aerobic activity doesn’t create a glycogen debt but does burn fat (and trains your body to burn fat more efficiently).
In my experience, full body resistance training using compound movements creates a “black hole” effect. I get incredibly hungry, and no matter what I eat, nothing changes. I even find that after a lifting session, eating more carbs, sugar, and even wheat or alcohol have very few negative effects, almost like lifting makes me more resilient over all.
Don’t become wedded to your workouts, though. Don’t fear eating outside of a post- or pre-workout window. The anabolic window opened through exercise lasts for hours, not minutes. Many studies show that exercising today improves the postprandial metabolic response tomorrow. But any type of activity, even just a walk, before or after a meal can really improve how you respond to it.
Eating right before bed truncates the sleep-induced fasting state.
Everyone reading this blog for more than a few months has picked up on the notion that fasting from time to time is beneficial. Whether it’s skipping a meal or three, going without food for a little while upregulates autophagy, increases fat burning, and exerts potentially anti-aging effects.
Sleep is a freebie for the fasting—curious. It’s built in. You have dinner in the early evening and hang out for a few hours. You brush your teeth, take a bath, and relax before bed. Once you’re in bed, you read a good book or engage in something slightly more physical and enjoyable before you actually fall asleep. And then you sleep. Growth hormone spikes, fat burning skyrockets, cellular repair occurs, brain pruning engages. You wake up and, at some point, eat. That’s at least 8-12 hours (and probably more) of quality fasting time—without even trying.
If you eat dinner late at night, you lose valuable fasting time.
One recent study even found that skipping dinner or having it in the early evening reduces hunger, increases fat burning, and improves metabolic flexibility (the ability to switch between fat and sugar burning). They didn’t follow the subjects long enough to detect weight loss, but a similar setup led to increased fat loss in rats.
However, if you’re a nighttime snacker, meaning you wake up in the middle of the night hungry and end up eating, pushing dinner back before bed or having a snack after dinner can help you avoid it.
If you do eat dinner later, push breakfast back a bit. What we’re ultimately after is that 10-12 hour block of not eating anything. I’ve already laid out exactly why skipping or delaying breakfast is not only safe for most people, it’s downright beneficial and often promotes weight loss.
Eating with the light may provide a boost to health.
There isn’t just one central clock running things. There are hundreds of biological clocks associated with nearly every tissue, muscle, and organ—the “majority of the cells in the body“—and they all respond to circadian entrainment stimuli. Foremost among the entrainers is light. At the right times (day), bright light gets the clocks moving.
Eating is another powerful entrainer of the circadian rhythm, with larger meals having the biggest entrainment effects. Insulin sensitivity follows a circadian rhythm, and it’s different for muscle and adipose tissue. Muscle insulin sensitivity is high in the morning and declines as the day progresses. Adipose tissue insulin sensitivity is lowest in the morning and increases as the day progresses. This is most pronounced in women, by the way.
This is why you have something called “afternoon diabetes,” where insulin sensitivity has degraded to the point of glucose intolerance by lunchtime. It’s why eating at regular times improves insulin sensitivity and lipid profiles—your mealtimes are attuned to the biological clocks determining your metabolism.
Bill Lagakos has written extensively about the utility of eating with your circadian rhythm and boils it down to this:
- Eat with the sunrise, focusing on protein and carbs (to take advantage of high insulin sensitivity and pair two major circadian entrainers—light and a large meal).
- Eat progressively smaller meals throughout the day. Breakfast like a king, lunch like a prince, dinner like a pauper (or not at all; if you want to skip a meal, skip dinner).
- More protein and carbs in the earlier part of the day, more fat and low-carb veggies at night to take advantage of the diurnal variation in adipose tissue/muscle insulin sensitivity.
I’m pretty lucky. As an insulin-sensitive dude to begin with, I can get away with any type of eating schedule. Always have, probably always will. If that wasn’t the case and I had problems with insulin resistance, I’d probably try something close to what Bill discusses.
Find a schedule and stick to it.
Once you figure out what seems to work, stick with it. Skip meals if you like, but try to eat at roughly the same time each day. This conditions your body to expect food (and get hungry at the right time, not before), and it improves the metabolic response to eating.
In a recent study, the authors actually tested the effect of breaking your eating habits by separating overweight women into habitual breakfast skippers and habitual breakfast eaters and then having them either skip breakfast or eat breakfast.
Habitual breakfast eaters who skipped breakfast experienced way more hunger at lunch, had worse blood lipids, and higher insulin levels. They had worse blood lipids and their insulin skyrocketed. Habitual breakfast skippers who skipped breakfast experienced none of these deleterious effects.
Meanwhile, habitual breakfast eaters who ate breakfast were more satiated at lunch. They had better blood lipids and normal insulin levels. Habitual breakfast skippers who ate breakfast were still hungry at lunch. Eating breakfast didn’t inhibit their regular lunch-time appetites.
Other research has found that maintaining a regular eating schedule improves insulin sensitivity, increases energy expenditure, and improves fasting lipids. Overall, sticking to an (rough, not draconian) eating schedule results in the best metabolic effects.
What’s it all mean?
Whatever you want.
Humans are flexible beings by nature. We adapt. We roll with the punches. We thrive on a wide variety of foods and eating schedules, even if we seem to do best on a consistent schedule—whatever that may be.
As always, my message is one of freedom. You make the choice when to eat. You decide. I provide some of the information you might not have considered, and you do whatever you want with it.
What do you think, folks? Do you worry about meal timing, or do you just go with the flow? Noticed any differences?
Thanks for reading, all. Take care!
About the Author
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.
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