Feeling Tired After Eating? Learn Why It Happens

Understanding Postprandial Somnolence or “Food Coma”

Feeling sleepy after eating is a common phenomenon. The medical term for it is postprandial somnolence. It is commonly called a post-lunch dip, 3 PM slump, or food coma.

Research shows that several factors cause post-meal tiredness and sleepiness, including what you eat, how much you eat, and when you eat. Other factors that contribute to post-lunch sleepiness include a dip in the natural circadian rhythm (the body’s internal clock), increased blood supply to the gut to aid digestion, fluctuations in your blood sugar level, and hormonal changes.

In most people, post-meal drowsiness is harmless and can be managed with lifestyle changes. However, if post-meal fatigue and sleepiness interfere with your daily life, you should talk to your healthcare provider. These symptoms occasionally signal underlying health conditions that should be diagnosed and treated.

Physiological Reasons for Post-Meal Sleepiness

Vigilance Signals

Scientists have hypothesized that animals, including humans, are hard-wired to remain awake and alert when they’re hungry so that they can find food. These “vigilance signals” decrease after eating, leading to a dip in energy and feelings of fatigue.

Digestion and Blood Circulation

One theory about why eating makes you feel tired and sleepy is that blood flow gets redirected to your gastrointestinal tract after meals to help you digest food. As a result, there is a fall in blood supply to the brain, which triggers feelings of sleepiness and fatigue.

Insulin and Blood Sugar Levels

Blood sugar levels rise after meals. This triggers insulin hormone to move sugar from the bloodstream into cells for energy, which can lead to a sugar crash with low energy and fatigue.

Tryptophan and Serotonin Production

Studies suggest that you can feel sleepy and tired after eating because of elevated serotonin levels. Serotonin is a natural chemical in the brain that regulates mood, appetite, and sleep cycles. It is also a chemical precursor for melatonin, the main hormone involved in regulating sleep.

Certain protein-rich foods that contain the essential amino acid tryptophan are more likely to make you sleepy after meals because the body uses tryptophan to make serotonin.

Dietary Factors Contributing to Feeling Sleepy After Eating

Food Choices

What foods you eat can impact how fatigued or sleepy you feel after meals. Studies have shown that people who eat diets high in processed meats and fast foods experience more post-meal drowsiness compared to people who eat healthy, balanced meals consisting of fruits, vegetables, dairy, fiber-rich foods, and healthy fats.

Research also suggests heavy fat, carbohydrate, or protein intake at mealtimes can disrupt the body’s natural circadian rhythm (sleep-wake cycle), resulting in daytime sleepiness after meals.

Consuming meals containing the following foods can cause a post-lunch dip:

Foods high in melatonin, such as tart cherries, eggs, mushrooms, tomatoes, oats, and pistachios
Foods rich in tryptophan, such as soybeans, certain cheeses (cheddar and Parmesan), chia seeds, squash seeds, pumpkin seeds, chicken, lamb, lobster, and turkey
High-fat and fried foods such as chicken nuggets, French fries, onion rings, and buttery confectionery products
Sugary foods and beverages that provide an initial energy boost, but in the absence of other nutrients like fiber and protein, lead to high blood sugar followed by a sugar crash.
Carbohydrates such as rice, pasta, white bread, and desserts (cakes and cookies) cause changes in blood glucose levels. This is especially true for high glycemic index foods, which are carbohydrates with low fiber content. They are digested more quickly, resulting in a rapid increase in blood sugar levels, followed by a subsequent sugar crash.
Alcohol consumption with meals can cause drowsiness, sluggishness, and fatigue.
Caffeine can reduce fatigue and increase alertness during the day but can mess with sleep patterns at night, resulting in sleep deprivation. This can result in daytime sleepiness and make you feel sleepy after meals.

Meal Size

Eating a big meal can be a strong trigger for post-meal sluggishness and drowsiness. Scientists postulate this happens because:

More blood is redirected to the overloaded digestive tract to help digest a large meal, especially high-protein, high-carbohydrate, or high-fat foods.
Large meals result in the release of hormones that cause tiredness.
Sleep helps with digestion, and post-meal sleepiness occurs to support nutrient absorption in the gut.

Feeling sleepy after a large meal is more likely to occur if you typically eat smaller meals, because your body is not used to the extra energy demands of digesting a big, calorie-dense meal.

Note: Not eating enough or frequently throughout the day can also cause low blood sugar and a dip in energy levels.

Meal Timings

Research suggests eating too frequently can result in post-meal sleepiness. It takes the body 30-40 hours to digest food. If you put more food in your digestive tract while your body is still digesting food that’s already there, it can lead to postprandial fatigue and sleepiness.

Additionally, eating rich or heavy meals in the early afternoon can cause more tiredness and drowsiness than usual. This is a time of day when your body experiences a dip in alertness due to the natural circadian rhythm (the body’s internal clock).

Interestingly, researchers studying daytime sleepiness after meals have found that people who skip breakfast can find it challenging to maintain alertness after lunch. They believe this happens because skipping breakfast places a heavier burden on the body post-lunch, causing more blood to be redirected to the gut. This results in decreased blood circulation in the brain, which causes tiredness and sleepiness.

Is Feeling Sleepy After Eating a Cause for Concern?

Feeling sleepy after eating is not a cause for concern in most people. It is a common occurrence, especially after a heavy meal that is rich in any one macronutrient (carbohydrates, proteins, or fats). Eating balanced meals and getting a good night’s sleep can help manage post-meal drowsiness and prevent an afternoon lull in most healthy adults.

When to Consult a Doctor

You should consult a doctor if you’ve tried eating smaller, more balanced meals at regular mealtimes and getting enough sleep at night and you still continue to feel fatigued and drowsy after meals. Also talk to your doctor if your post-meal lethargy and tiredness are severe enough to interfere with your work or life.

Connection to Health Conditions

Your healthcare provider will obtain a history, perform a physical exam, and order tests to find the cause of your fatigue and sleepiness. Certain medical conditions, such as food allergies and intolerances, nutrient deficiencies, anemia, diabetes, celiac disease, and sleep apnea, can cause unexplained or excessive tiredness and daytime sleepiness.

Tips to Prevent Post-Meal Fatigue

Eat Well-Balanced Meals

Not all foods affect energy levels equally after eating. Your goal should be to eat well-balanced meals that provide 10-35% of your daily calories from proteins, 45-65% from carbohydrates, and 20-35% from healthy fats.

These percentages can vary depending on a person's goals. For example, if the goal is to lose weight, you should reduce the carbohydrate content in your diet while increasing protein and healthy fat.

Many foods are energy-boosting and can prevent a post-lunch slump. Some of the best foods for sustained energy include fatty fish, whole grains like brown rice, beans, leafy green vegetables, oatmeal, a nut butter like peanut butter, and chia seeds.

Choosing plant-based whole foods that contain dietary fiber can also help to control post-meal fatigue by stabilizing blood glucose levels. High-fiber foods also support digestion, keep you feeling energized, and help you maintain a healthy weight.

Another strategy that can help prevent a food coma is to eat smaller meals throughout the day rather than one or two big meals, especially at lunchtime. This makes it easier for your body to digest food and provides short bursts of energy throughout the day versus making you feel tired after eating a heavy meal.

Drink Enough Water

Drinking plenty of water and staying well hydrated throughout the day (including before, during, and after meals) aids digestion. Research has also shown that dehydration can cause fatigue. A good rule of thumb is to divide your body weight in pounds by two and drink that many ounces of water daily.

Get a Good Night’s Sleep

You’re more likely to get sleepy after eating if you’re already sleep-deprived. Not getting enough shut-eye can put your circadian cycle out of rhythm, which can affect energy levels and cause sleepiness post-meals.

Most adults need 7-9 hours of sleep every night. But the quality of sleep matters as much as the quantity.

Stick to a regular bedtime and make sure your bedroom is cool, dark, and quiet. Switch off all electronics 1-2 hours before bedtime. Avoid drinking alcohol or consuming caffeine for at least 3-4 hours before bedtime. These simple measures can prevent sleep disturbances and promote restful sleep.

Do Light Physical Activity After Meals

Exercise promotes healthy digestion and gets blood flowing to your gut, which stabilizes blood glucose levels and keeps your energy up after meals. Try taking a short 10-15 minute walk after lunch for a natural burst of energy.

Consider Bright Light Therapy

Studies show that phototherapy (also called bright light therapy) can help prevent a post-meal slump in energy levels. Try placing a bright lamp on your desk at work to see if it helps you stay more alert after eating.

Frequently Asked Questions

Should I Be Worried If I Fall Asleep After Eating?

If you find yourself falling asleep after eating or find it difficult to stay awake during the day, consult your healthcare provider. You may have an underlying medical condition that should be diagnosed and treated. For example, people with a sleep disorder called narcolepsy feel very sleepy throughout the day, even when they are well-rested.

Do Diabetics Feel Sleepy After Eating?

People with diabetes can feel sleepy after eating. People with diabetes have high blood glucose levels, which lead to excessive thirst and frequent urination. This can cause dehydration, low energy, and post-meal tiredness. However, it is worth noting that many people who don’t have diabetes experience sleepiness and sluggishness following meals.