We all know that feeling after a big meal, when your body begs you to curl up on the couch and absolutely refuses to do anything but digest. This is a phenomenon called postprandial sleep (more fondly referred to as the food coma) and I would bet that most of us have fallen victim to it at least once or twice in our lives.
But have you ever considered, as you lie on the couch completely immobilized, why exactly this happens? If you have—or you’re curious about it now—you’ve come to the right place. Researchers have been studying postprandial sleep and there’s some new information out there on why and how this post-meal drowsiness happens to us.
Did you know that animals can get food comas too?
A recent study from the Scripps Research Institute measured the feeding and sleep behaviors of fruit flies and found that just like humans, fruit flies like to nap after they eat too. Researchers observed that the animals often sleep for about 20-40 minutes after a meal and then wake up and continue on with their normal activity.
After introducing us to the idea of a fruit fly power nap (which we think is pretty amazing) these researchers seized the opportunity to really test out the science of food comas. This is a subject that hasn’t been studied much in the past because of the many human factors that create high variability in our energy levels and activity.
Post meal sleepiness affects specific parts of our brains.
Using genetic tools to turn on and off different parts of the brain, the scientists were able to identify specific brain circuits and neurons (brain cells) involved in the food coma experience. In the past, these same areas of the brain have been been linked to behavior that controls meal size and frequency. And as it turns out, food comas are positively correlated to the amount of food consumed, but volume is definitely not the only contributing factor.
Certain foods cause sleepiness—but probably not the ones you think.
The same researchers decided to test out a long-standing theory that certain foods make us particularly sleepy. They did this by feeding the flies different meals consisting of protein, salt, or sugar and then observing their brain activity and behavior. Results suggested that only salt and protein caused post-meal sleepiness and that, somewhat surprisingly, sugar did not.
So for those of us that were blaming our food coma on that extra slice of pie, we might need to rethink our theory just a little bit.
So, your best bet at preventing a food coma is eating a balanced plant-based diet, as it is unlikely to cause you to overload on protein. At the same time, plant proteins are more easily digested and processed by the body!
Food affects our brain and our brains control our food coma.
Observing brain activity after different types of meals, scientists found that some circuits were specifically influenced by the consumption of meals high in protein. Interestingly, other pathways were particularly sensitive to the animal’s internal clock, detecting reduced food-coma activity in the early evening.
This tells us that food comas are much more complex than just eating too much and needing to lie down. And while they are associated with the amount of food we eat, it seems that the type of food we eat and the way our body and brain are affected by those foods are also to blame.
So, in summary, what causes a food coma?
1. What you ate
“Refined foods, foods that have a lot of sugar, and refined carbohydrates can cause glucose levels to go up and then quickly go down,” says Raphael Kellman, M.D., a physician of integrative and functional medicine, author of The Microbiome Breakthrough and founder of the Kellman Wellness Center. “That’s when you go in the ‘food coma’ state and feel very out of it, lethargic, lightheaded, foggy, and like you can’t think straight.”
2. The size of your meal
This comes down to the hormones your body releases: ghrelin makes you feel hungry and leptin tells you that you’re full. “If you eat too quickly, your body might not have a chance to catch up with you,” says Dr. Firshein. “So by the time leptin kicks in, you’ve already consumed too much and your gut is too full. That’s when you experience that bloating.”
3. Thyroid issues
“When the thyroid is low, you’re very vulnerable to the ups and downs of glucose because you’re already not producing enough energy,” says Dr. Kellman. “If you have a healthy adrenal gland and thyroid, your body can adjust and adapt to bring glucose back up to maintain your energy levels, allowing you to withstand those occasional glucose swings.”
If your microbiome, a.k.a the environment where our microorganisms live, isn’t healthy, it can interfere with the absorption of foods, says Dr. Kellman, while a stronger microbiome can mitigate a surge of sugar or a hormonal swing.
“Many people have reactions to foods that they aren’t aware of which may increase fatigue,” says Dr. Firshein. “Not every allergic reaction has to be specifically related to a rash.”
6. Nutrient deficiencies
“You may be lacking nutrients, vitamins (like B12), iron or fiber— all of which may make you crave more food,” says Dr. Firshein.
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