What Is a Food Coma?

Learn Causes and Prevention Tips for Postprandial Somnolence

Taking a cat nap
PeopleImages.com / Getty Images

Food coma, or postprandial somnolence, is a condition that can occur after eating a large meal. It is usually described as a feeling of extreme fatigue or lethargy that can last for several hours. There are several different theories about the causes of food coma and what you can do to prevent the condition from occurring.

What Is a Food Coma?

We've all had the familiar feeling following a big meal.

After scraping the last forkful of food into your mouth, you hit the couch, get comfy, grab the remote, and spend the rest of the afternoon or evening lounging in a semi-vegetative state—unable to do much more than change the channel on the television. You've heard that this is called a "food coma," but is a food coma a real thing?

Yes. "Food coma," also known as postprandial somnolence or postprandial sleepiness, is a real condition that is studied by real scientists. While the cause of after-meal sluggishness is up for debate, there is no confusion about the symptoms: laziness and heaviness, usually accompanied by bloating and a feeling of tightness in the belly.

What Causes Food Coma?

There are different theories about the causes of postprandial somnolence. Researchers have studied the condition for years, but don't necessarily agree on why the condition occurs. These are some of the popular theories.

  • Eating foods with tryptophan. Have you ever experienced food coma after Thanksgiving dinner? Many health experts attribute the post-meal slump to the high levels of L-tryptophan (commonly called "tryptophan") in turkey.

    Tryptophan is an amino acid found in certain meat and dairy products. When the amino acid is consumed along with carbohydrate-rich foods (like mashed potatoes and stuffing), it easily enters the brain and boosts serotonin levels. Serotonin is a neurotransmitter that decreases arousal, so you're likely to feel more relaxed and even lazy when serotonin levels are elevated.

    Tryptophan and serotonin also play a key role in the production of melatonin in the body. Melatonin is a hormone that helps the body prepare for sleep.
  • Changes in blood flow to the brain. Some health experts say that postprandial somnolence is caused by a slight shift in blood flow away from the brain to the digestive organs. Eating activates your parasympathetic nervous system (PNS).

    The PNS regulates certain functions in your body like slowing the heart rate and regulating blood pressure and digestion. The PNS is triggered when the stomach expands from eating a big meal. As a result of PNS signals, blood flow is directed more to the working digestive organs and less to the brain. This slight blood flow diversion may cause you to feel sleepy and tired.
  • Consumption of high-fat or high calorie meals. Some research studies have questioned both the tryptophan theory and the link between blood flow changes and food coma. Instead, these researchers propose that eating a meal that is high in fat and low in carbohydrates can cause post-meal sleepiness.

    In one small study, researchers found higher levels of cholecystokinin (CCK) after their test subjects ate a fatty, low carb meal. They suggest a link between the release of CCK (a hormone that suppresses hunger) and the onset of sleepiness because higher levels of CCK has been shown to induce sleep in rats.

    Other researchers have proposed that a complex combination of satiety signals is sent to important sleep centers in your brain after eating a solid meal that is high in fat and/or high in calories. The signals decrease arousal and hunger signals in the brain and increase sleepiness.

    Ways to Prevent a Food Coma

    If you want to avoid landing on the couch for hours after your next indulgent meal, there are a few guidelines you can follow. Most involve using basic common sense.

    • Eat smaller meals that include liquids. Researchers have found that large meals are more likely to induce food coma. In addition, most researchers agree that solid meals are more likely to induce that familiar feeling of after-meal sleepiness. If you want to stay alert after lunch or dinner, it might help to consume a smaller meal and make part of it liquid. Enjoy soup and a small sandwich, or a smoothie with a hard-boiled egg.
    • Get enough sleep. If you plan to drive after a big meal, make sure you are well rested prior to eating. One study of drivers who got behind the wheel after eating a big lunch found that a larger meal made inherent sleepiness worse. That means that if the driver was already sleepy, eating the big meal made it much worse.
    • Balance macronutrients. Even though they disagree on the mechanism in action, researchers seem to agree that fatty meals are more likely to make you sleepy in the hours after eating. If you build balanced meals around a moderate intake of protein and carbohydrate with a small amount of healthy fat, then you may be less likely to fall victim to food coma.

      And keeping portion sizes in control is always smart. A single portion of meat or fish is just three to four ounces. And a single portion size of starchy carbohydrates is just one cup, or about the size of your fist. A single serving of fat is usually one to two tablespoons.
    • Get active after your meal. Increase circulation and stimulate your muscles after a big meal with a short walk or activity session. At the very least, it will help you feel better about the number of calories consumed. But it might also help to invigorate your body to keep food coma symptoms at bay.

    A Word From Verywell

    Eating a very large fatty meal is usually not a smart idea. We like to promote moderation, but we also know how easy it is to indulge on special occasions like Thanksgiving or a special birthday celebration.

    We’ve all been there. While food coma isn't comfortable, an occasional episode of postprandial somnolence isn't likely to cause harm. In fact, it may remind us to use smarter eating habits at the next meal. So rest after your big meal if you need to, but then remember to use moderate food practices most of the time to keep your body healthy, active and alert.

    Sources:

    Anita S Wells,N.W Read,K Uvnas-Moberg,P Alster . Influences of Fat and Carbohydrate on Postprandial Sleepiness, Mood, and Hormones. Physiology & Behavior. May, 1997.

    Browning KN, Travagli RA. Central Nervous System Control of Gastrointestinal Motility and Secretion and Modulation of Gastrointestinal Functions. Comprehensive Physiology. 2014;4(4):1339-1368.

    Kimberly A. Bazar,A.Joon Yun,Patrick Y. Lee . Debunking a myth: neurohormonal and vagal modulation of sleep centers, not redistribution of blood flow, may account for postprandial somnolence . Medical Hypotheses. Volume 63, Issue 5, 2004, Pages 778-782.

    Sang Woo Kim,Byung In Lee. Metabolic state, neurohormones, and vagal stimulation, not increased serotonin, orchestrate postprandial drowsiness. Bioscience Hypotheses. Volume 2, Issue 6, 2009, Pages 422-427.

    B.Y. Silber,J.A.J. Schmitt Effects of tryptophan loading on human cognition, mood, and sleep. Neuroscience & Biobehavioral Reviews. February 2010.

    Continue Reading