Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...Tell Me More
The relationship between stress and carbohydrates is confusing, with seemingly contradictory arguments bouncing around the online health sphere.
There are those who say high-carb diets cause stress, and that eating more fat and fewer carbs is the solution.
There are those who say high-fat diets increase stress and eating carbs ameliorates it.
Who’s right? They can’t both be right, can they?
You’d be surprised.
Let’s dig into four common carb questions and assertions.
This is well-established. You have a terrible day at the office, your kids have appointments twenty miles apart within fifteen minutes of each other, the traffic is backed up to your driveway, you’re late for work, the dog needs a walk, you haven’t even thought about what to make for dinner, you slept four hours last night—it adds up. People deal with a lot. And in that moment, a carbohydrate-based snack really does seem to take the edge off.
Across millions of years of hominid evolution, the human stress response developed in the context of real-world, short-term, and infrequent but intense stressors: battles, hunts, freak injuries, dangerous animal encounters, interpersonal conflicts. These were situations that demanded heightened senses, available fuel, and a rapid heart rate to deliver everything to the tissues that needed to move and act. It makes perfect sense for your body to pump out adrenaline to increase fat burning and glucose in the blood—you need that fuel to deal with the situation. It also makes sense for your body to follow that up with a blast of cortisol, which makes you crave high-carb junk food to replace the fuel you utilized. The problem is that our modern stressors are too frequent, they aren’t physically demanding, we aren’t utilizing the fuel we mobilize, and we have no real need for the carb cravings that come after.
What happens when we eat too many carbs that we never actually needed?
We get fat. Cellular energy supply becomes overloaded, impairing our mitochondria’s ability to process energy efficiently. This degrades metabolic flexibility—the ability to switch between different fuel sources—preventing us from burning the fat on our bodies in between meals. We become reliant on those carbs, and when we don’t get them fast enough, our bodies perceive that as a major stressor.
So while giving in to carb cravings can reduce stress in the short-term, it sets us up for longer-term, more chronic stress.
It can be.
A primary goal of cortisol is to increase glucose availability. It does this through multiple avenues. One I just mentioned is to increase carb cravings. Another is to make you insulin resistant, thereby preventing insulin from sucking up blood glucose. Gluconeogenesis—the creation of glucose from amino acids and other substrates—is another.
If you’re a sugar-burner, stressful situations will increase carb cravings, induce gluconeogenesis, and may even make you insulin resistant. If you’re fat-adapted, the story shifts.
A fat-adapted person will have ketones and fatty acids available to provide energy in between meals. A fat-adapted person will have ketones and fatty acids available to provide energy in stressful situations. A fat-adapted person will be able to utilize those ketones and fatty acids during stressful situations—their mitochondria will literally be primed to utilize those fuels, not just glucose. A fat-adapted person is less likely to perceive carbohydrate shortages as stress shortages because they’ve got all this other fuel available to burn.
This adaptation doesn’t happen overnight. If your diet is low-carb or keto, but your body is still reliant on sugar, you will perceive reduced carb availability as a stressor. That’s one of the hallmarks of the keto flu, and it’s one reason why some people have extended keto flu—their bodies are still expecting and demanding glucose.
Some people never get over the carb cravings; they never fully adapt. This is the subset of the population that doesn’t function or perform well on a long-term ketogenic diet. The cause is unknown, at least for now (I suspect it has to do with recent ancestry and genetic proclivities), but what matters is that these people exist. For them, a long-term keto or very low carb diet approach will probably always be stressful. But even in these folks, spending some time in ketosis—through short term low-carb eating, intermittent fasting, or even extended low-level endurance activity that primarily burns fat—is a good idea that will reduce stress and improve overall resilience.
Exercise is stressful to begin with. But then you adapt to the stress and overcome it—and end up stronger, fitter, and faster than before. Without the stress, working out doesn’t work. A legitimate method for increasing your work capacity is to train-low (carb), race-high (carb). Athletes have been doing this for decades—training in a low-carb state to get better at performing without ample muscle glycogen, then going into a race with full glycogen reserves and the ability to perform without glycogen. Exercising in that low-glycogen state is stressful, but that’s the whole point. It makes them better, stronger, faster, and it conserves glycogen for when they really need it.
If you consistently perform glucose-intensive high-intensity anaerobic activity for extended periods of time—CrossFit style WODs done 3-5 times per week, for example—you will run up a glucose debt and should replenish some of the carbohydrates you expend or risk cortisol spikes. Fat-adaptation can improve your tolerance of anaerobic activity in a low-glucose state, but there’s a breaking point, a physiological limit.
Eat the carbs you earn. This is a subtle point I don’t often see made. The reverse is widely understood—don’t eat the carbs you don’t earn—because millions of obese and overweight people do that every day. It’s a big reason why we’re so overweight. But if you fail to eat the carbs you earn through intense, protracted physical activity, you’re creating an undeniable glycogen deficiency that your body may perceive as a stressor. It may turn out that fully fat- and keto-adapted athletes can perform intense medium-to-long-term activities at high levels, and there’s some indication that this is the case, but for the time being it appears that eating the carbs you earn can stave off the stress.
There’s a glimmer of truth here. Allow me to explain.
Women are inherently more sensitive to caloric fluctuations than men…on average. The reason is sheer biology. Human evolution is concerned with fertility and reproduction. Can you produce, foster, and support viable offspring? Awesome. Natural selection deems you fit.
To fulfill their biological role, men have to produce sperm. They can do so almost indefinitely. They don’t run out; they just make more. If a batch is damaged due to poor lifestyle or dietary choices, there’s more on the way. After a man gets someone pregnant, his biological involvement with the growing baby is done. What or when he eats has no impact on the survival of the growing baby.
To fulfill theirs, women have a finite number of eggs, or “chances.” Once an egg is gone, there’s no replacing it.
And so the body seeks to inculcate the egg from environmental insults.
When you are preparing to get pregnant, your body needs extra nutrients to build up a reserve and “prime the pump.”
When you are pregnant, the growing baby needs a reliable and constant stream of nutrients for almost a year.
After you’ve given birth, the growing newborn needs breastmilk. To make that milk requires additional calories and extra doses of specific nutrients. Modern technology allows us to skip nursing and go straight to the bottle, but your body doesn’t “know” that.
It all points to women being more finely attuned to caloric deficits. For example, women’s levels of ghrelin, the hunger hormone, are quicker to rise after meals. Even if you’re never going to have kids, your body is still wired to protect against these caloric fluctuations.
Where do carbs come in?
One’s carbohydrate consumption is uniquely hewed to our sense of caloric sufficiency. If carbs are plentiful, your body perceives that as a signal of environmental plenty: the weather is good, the plants are producing, the trees are bearing fruit, the men are bringing back lots of honey. Life is good. It’s the perfect time to get pregnant. Above all other macronutrients, carbohydrate consumption increases the short-term expression of leptin, a satiety hormone that signals the presence of incoming calories, caloric sufficiency, and environmental plenty.
There’s also the issue of extreme satiety. Low-carb diets often become low-calorie diets without you even trying. That’s why they work so well for fat loss, by inadvertently reducing the amount of food you eat and increasing satiety. But for some women, especially those at or approaching their ideal weight, going too low in calories can increase stress.
Are you unable to access your own body fat in between meals for energy? Then you’ll be a ball of stress unless you can get those Jolly Ranchers unwrapped quickly enough. It’ll be a constant battle. And yeah, if you keep pumping yourself full of carbs to keep your blood glucose topped off, you’ll keep stress at bay—but you’ll always be teetering on that precipice.
Are you exercising? Then you should strike a balance between gaining the adaptive benefits of training in a low-carbohydrate state and eating the carbs you earn.
Are you a woman? Then you’re probably more sensitive to diet-induced stress and may benefit from occasional carbohydrate refeeds. You should watch out for excessive satiety on ketogenic diets, which is great for fat loss but can lead to stress issues down the line if calories get too low.
The relationship between carbohydrates and stress isn’t exactly straightforward, but it is navigable. Hopefully after today you have a better idea of where you stand in the relationship.
What’s been your experience with stress and carbohydrates? Has your tolerance for stress gone up or down since going low-carb or keto? Thanks for stopping in today.
Mcallister MJ, Webb HE, Tidwell DK, et al. Exogenous Carbohydrate Reduces Cortisol Response from Combined Mental and Physical Stress. Int J Sports Med. 2016;37(14):1159-1165.
Dirlewanger M, Di vetta V, Guenat E, et al. Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects. Int J Obes Relat Metab Disord. 2000;24(11):1413-8.