If you ever want to nap after a meal, you've found that food coma feeling—a state of extreme fatigue or lethargy that can last for several hours. The technical term is postprandial somnolence, a condition that can occur after eating a large meal. There are several theories about the causes of food coma and what you can do to prevent it from occurring.

What Is Postprandial Somnolence?

If after Thanksgiving dinner, you find yourself hitting the couch and spending the rest of the evening lounging in a semi-vegetative state, you've most likely experienced the effects of postprandial somnolence.

This phenomenon is known as a food coma, but is it real? Yes, it turns out that food comas are an actual condition studied by scientists.

While the cause of after-meal sluggishness is debatable, there is no confusion about the symptoms: laziness and heaviness, usually accompanied by bloating and a feeling of tightness in the belly.

Symptoms of a Food Coma

Common symptoms of a food coma include:

• Lethargy
• Sleepiness
• Feeling full

Food Coma Causes

There are different theories about the causes of postprandial somnolence. Researchers have studied the condition for years and can't agree on why the condition occurs.

Eating Foods With Tryptophan

Have you ever experienced a food coma after Thanksgiving dinner? Health experts attribute this post-meal slump to the high levels of L-tryptophan (commonly called "tryptophan") in turkey. Tryptophan is an amino acid in particular meat and dairy products.

When this 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 with elevated serotonin levels.

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 bodily functions like heart rate, 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.

High-Fat or High-Calorie Meals

Some researchers have questioned both the tryptophan theory and the link between blood flow changes and food coma. Instead, they propose that eating a meal high in fat and low in carbohydrates can cause post-meal sleepiness.

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

Increase in Cytokines

Interleukin-1 (IL-1) family cytokines are signaling molecules in the inflammatory response and other processes. Researchers believe these particular cytokines are responsible for increased post-meal fatigue.

When people take medications to reduce inflammatory responses, postprandial somnolence is less common and intense. Cytokines can increase the perception of fatigue by affecting the central nervous system.

Coping With a Food Coma

If you experience a food coma, rest and relax to aid digestion. Alternatively, take a walk to help balance blood sugar and help reduce fatigue. If you've eaten a high-fat meal, however, digestion will be slowed and this may cause nausea and even vomiting, so stick to light exercise like a walk or easy bike ride.

Food comas last a different amount of time for everyone and depend on factors like how much you've eaten, general fatigue levels, sleep habits, alcohol consumption, and digestion rate.

Food Coma Prevention

Avoid landing on the couch for hours after your next indulgent meal by following a few guidelines.

Eat Smaller Meals That Include Liquids

Large meals are more likely to induce post-meal fatigue. Most experts agree that solid foods may cause that familiar post-meal sleepiness. Consume a smaller meal and make part of it liquid (with soup or a smoothie) if you want to stay alert after lunch or dinner.

Get Enough Sleep 

Make sure you are well-rested before eating if you plan on driving after your meal. One study of drivers who got behind the wheel after eating a big lunch found that a larger meal worsened inherent sleepiness.

Additionally, lack of sleep may increase the likelihood of reaching for high-calorie and fat foods, and post-meal fatigue.

Consume Balanced Meals

Even though they disagree on the mechanism in action, researchers 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 carbohydrates with a small amount of healthy fat, you may be less likely to fall victim to ​a food coma.

Choosing a variety of foods as part of balanced meals, including fruits, vegetables, whole grains, healthy fats, and protein sources will ensure you get the vitamins and minerals to boost energy and prevent fatigue. These include iron, B vitamins, magnesium, potassium, carnitine, and more.

Control Your Portions

Keeping portion sizes in control should help keep food coma at bay. A single portion of meat or fish is just three to four ounces. A single portion of starchy carbohydrates is one cup, or about the size of your fist. A single serving of fat is usually one to two tablespoons.

The bigger the meal, the more insulin will be released, which scientists believe can cause drowsiness. Insulin impacts certain neurotransmitters in the sleep/wake cycle, nervous system, and endocrine syndrome. This includes dampening the production of one neurotransmitter called orexin that helps keep you feeling alert.

Get Active Post-Meal

Increase circulation and stimulate your muscles after a big meal with a short walk or activity session. Activity can invigorate your body to keep fatigue symptoms at bay. Getting active in general can increase your energy levels and help with digestion.

A Word From Verywell

While feeling extremely tired after a meal isn't comfortable, an occasional episode of postprandial somnolence isn't likely to cause harm. In fact, a food coma may remind you to stick to smaller, less fatty meals. So rest after your big meal if you need to. Then use reasonable food practices most of the time to keep your body healthy, active, and alert.