What it is |Causes | Prevention | When to seek help |
People often use the term “food coma” to describe the feeling of sleepiness or decreased energy levels after eating. However, the medical term for this response is postprandial somnolence.
Researchers do not fully understand exactly what causes postprandial somnolence. It may occur as a natural biological reaction to the body digesting food, or there may be other reasons why the person feels sleepy.
This article discusses the possible causes of postprandial somnolence, how people who often feel sleepy after food can cope with feeling tired, and when to contact a doctor about the symptoms.
What is postprandial somnolence?
Postprandial somnolence, which many describe colloquially as a food coma, refers to the sense of fatigue, sleepiness, or decreased energy levels that can occur shortly after eating a meal. Postprandial means after eating, while somnolence means sleepiness.
People with postprandial somnolence may experience the following symptoms after eating:
drowsiness or sleepiness
low energy levels
lack of focus or concentration
The symptoms may last for a couple of hours Trusted Source or more.
What causes a food coma?
There are different theories about what causes food comas, ranging from the types of food that a person eats during a meal to shifts in the circadian rhythm. The circadian rhythm is the body’s internal clock, which regulates sleep patterns. Below, we look at some of the most popular theories about postprandial somnolence and the science behind them.
The type of food
Meals that are rich in carbohydrates can help the body absorb tryptophan, which is an amino acid that the body uses to create serotonin. Serotonin is a hormone that helps regulate sleep, digestion, and mood, which may account for that common post-meal feeling of happiness, sleepiness, and satiety.
Protein-rich foods also contain tryptophan, so eating meals that are rich in protein and carbohydrates may be more likely to induce feelings of sleepiness after eating.
A 2021 study of Chinese truck drivers found that those who primarily ate vegetables and staple foods, such as grains, dairy, and eggs, were less likely to exhibit dangerous driving techniques than truck drivers who mostly ate meat and fish, which are high in protein. The researchers suggest that this could be due to the underlying differences in fatigue after eating.
Foods that are high in tryptophan include:
lean poultry, such as chicken and turkey
nuts and seeds
Foods that are high in carbohydrates include:
refined or highly processed foods, such as white bread, pastries, and sodas
starchy foods, such as pasta, potatoes, and rice
grains, including oats and quinoa
The size of the meal
Research into the sleep patterns of fruit flies found that sleep was much more likely after a large meal than after a small meal, especially if that meal was high in protein or salt.
The bigger the meal, the longer it takes for the digestive system to absorb all the nutrients. Blood sugar will also rise, which can lead to a dip in energy levels shortly afterward.
A 2019 study into the diets of 52 Brazilian truck drivers supports this theory. The researchers found that those who ate a “prudent” meal were less likely to feel sleepy after eating than those who had large meals.
The time of day
Eating a large lunch often makes people feel sleepy in the afternoon. The reason for this may be that the effort it takes to digest a large meal also coincides with the body’s natural slump in energy.
This energy slump is due to the circadian rhythms of wakefulness, which take a dip between 2 p.m. and 5 p.m.Trusted Source in the afternoon before an evening boost. This natural fall in wakefulness may combine with the body’s tendency to feel sleepy after a large meal.
In a small 2018 Source involving people who skipped breakfast, the participants experienced a sudden dip in blood flow to the brain soon after eating lunch, causing increased levels of daytime sleepiness.
After a meal, the body needs to focus on digesting the food, so more blood moves to the digestive system and away from the brain. This change in circulation may trigger feelings of lightheadedness, dizziness, or sleepiness soon after eating.
Ancient, primitive instinct
Finally, some Source believe that feeling sleepy after a meal is an instinctive human trait that our cave-dwelling, hunting, and foraging ancestors handed down. It is possible that humans are programmed to be vigilant in times of hunger to help them locate food and to relax and sleep once they have found and eaten the food.
How to prevent a food coma
There is no treatment for postprandial somnolence, but a person can take steps to increase their feelings of alertness after eating, especially during the daytime.
People can try the following to help prevent tiredness after a meal:
Going for a walk outside after eating: Light helps Source alertness and mental function during the post-lunch dip, while physical activity is great for overall health.
Eating smaller portions more often: Smaller but more frequent meals will help keep energy levels stable, avoiding bigger dips.
Taking an afternoon nap: Source has shown that a quick doze after lunch may improve cognitive performance for the rest of the afternoon.
Balancing meals: Going easy on carb- or protein-heavy meals in the afternoon and bulking up the vegetable portion of a meal may help prevent energy dips.
Getting more sleep at night: Sticking to a sleep schedule and getting enough hours of quality sleep each night may help decrease fatigue during the day.
Keeping a food diary: Keeping a note of which foods are more likely to cause sleepiness may help people avoid them during the day or eliminate them from their diet.
When to contact a doctor
Various underlying conditions may cause excessive tiredness and fatigue. Among these are:
blood diseases, such as anemia
autoimmune conditions, such as celiac disease
complex, long term illnesses, such as chronic fatigue syndrome and long COVID
mental health conditions, such as depression
metabolic diseases, such as diabetes
infections, such as glandular fever
thyroid conditions, such as hypothyroidism
sleep problems, such as sleep apnea
People who experience overwhelming fatigue that does not improve with sleep or rest should discuss their symptoms with a doctor.
Postprandial somnolence may occur due to the body’s attempts to digest certain types of food or larger-than-usual portion sizes. Alternatively, it may be an ancient human trait that is ingrained into people’s ancestral DNA.
Whatever the reason behind a food coma, people can take simple steps to avoid feelings of lethargy and sleepiness after meals. These include reducing portion sizes, eating a nutritious, well-balanced diet, and getting more exercise and sleep.
People who continue to experience fatigue during the day should speak with a doctor to identify any underlying conditions.