Why do I feel tired after eating?

Last updated on April 1st, 2025 at 08:44 am

Reasons for tiredness after eating

We’ve all felt tired after eating, and it is usually nothing to worry about. However, for some, it can be a sign of something underlying.

Some reasons why you could be tired after a meal:

Diet: Different foods affect the body differently; some can make you sleepier than others. An example of this is foods high in the amino acid tryptophan.

These foods promote the production of serotonin in the body, which helps regulate sleep and increases sleepiness. Foods high in tryptophan include fish, eggs, peanuts, and cheese. Here are the top 10 foods highest in tryptophan per 100 grams:

These values vary slightly depending on preparation and source, but these foods are consistently among the highest in tryptophan per 100 grams.

Other sleep-inducing foods are those high in melatonin, such as cherries, almonds and bananas. These foods help to promote relaxation and are sleep-inducing.

Meal portions: Studies suggest that people are more likely to feel tired after a large calorie-dense meal; more research is needed to understand why this is (1).

Sleeping habits: If you do not get enough sleep, you are more likely to feel tired after eating due to increased sleep drive (2).

Stress: When we are stressed, it can influence how much we eat. Many people choose higher-calorie and fatty foods, which can contribute to fatigue and drowsiness after eating.

The science behind sleepiness after eating

Postprandial somnolence, commonly known as feeling sleepy after a meal, is influenced by many factors, including:

Brain activity: After a meal, certain brain functions decrease, which can contribute to fatigue (3). As we get ready for bed, specific brain cells that promote sleep become more active.

Chemicals called neurotransmitters help by reducing the activity of wakefulness signals. Examples include GABA, which helps with sleep, muscle relaxation, and calmness.

Norepinephrine and orexin keep the brain alert when we are awake. Other neurotransmitters, like acetylcholine, histamine, adrenaline, cortisol, and serotonin, also play a role in balancing sleep and wakefulness (4).

Circadian rhythms: The body’s internal clock affects how food is metabolised at different times of the day. Eating large meals, significantly those high in carbohydrates, during periods when the body is naturally more inclined to rest (such as late evening) can exacerbate feelings of sleepiness (5).

Additionally, studies on time-restricted eating, where food intake is limited to specific windows during the day, have shown that aligning mealtimes with the body’s natural circadian rhythms can influence sleep patterns and energy levels (5).

Sleep drive:  Sleep drive is regulated by the build-up of the brain chemical adenosine, which peaks right before going to sleep. The longer a person stays awake and eats, the more adenosine builds, increasing sleepiness (6).

Hormones:  The hormones amylin, glucagon, and cholecystokinin are released after eating and can increase satiety and fatigue.

Cytokines: After a meal, the body releases cytokines like IL-1β and TNF-α. These proteins help promote sleepiness by affecting brain regions that regulate sleep.

These cytokines also influence metabolism, serotonin levels, and the gut-brain connection, leading to fatigue.

High-fat or carbohydrate-heavy meals trigger a stronger inflammatory response, making post-meal drowsiness more likely.

Blood circulation: During digestion, increased blood flow to the gastrointestinal tract may lead to reduced blood flow to other areas, including the brain, potentially contributing to feelings of fatigue.

How types of food affect sleepiness

• Sugary foods: Foods high in sugar can lead to fluctuations in energy levels. A study found that tiredness and reduced alertness occurred one hour after sugar consumption (7).
• High-carbohydrate foods: Foods with a high glycaemic index are more likely to cause fatigue after eating as they raise blood sugar quickly and cause a crash. Examples of these foods include potatoes, white bread and white rice.
• Tryptophan foods: When tryptophan is consumed, the body converts it into serotonin, then melatonin, which can both make you tired. Poultry such as chicken and turkey contain high amounts of tryptophan.
• High-fat foods: Foods high in saturated fats, such as deep-fried foods, cheese, butter, and pork, have been associated with increased post-meal fatigue (8).
• Melatonin foods: Melatonin is a sleep regulating hormone, which the body naturally produces in response to darkness. Foods can also contain melatonin, which can contribute to sleepiness after eating. Foods high in melatonin include rice, salmon, wheat, and eggs.

Learn More: The Best Foods to Help You Sleep

Is it normal to feel tired after eating?

Yes, most people feel tired after eating. Others may not feel tired at all; for example, people with Attention Deficit Hyperactivity Disorder (ADHD) may not experience post-meal energy dips. However, persistent tiredness after eating can be a sign of an underlying condition.

Conditions related to tiredness

If your tiredness after eating is frequent and accompanied by other symptoms, it can indicate an underlying condition. From sleep disorders to deficiencies, here are some related factors:

Obstructive Sleep Apnoea (OSA): Sleep Apnoea is a condition that causes airway blockages during sleep, causing breathing to stop and start. One of the main symptoms of OSA is daytime sleepiness due to broken sleep.

OSA is a common sleep disorder that affects millions of people worldwide and is easily managed through treatment and lifestyle adaptations.

Some of the changes mentioned above can also help the condition; for example, studies have found that eating earlier can improve sleep quality and reduce the number of apnoea events (9).

The gold-standard treatment method for OSA is CPAP therapy, which consists of a machine and mask that provide continuous airflow to keep the airway open.

Diabetes: High or low blood sugar can make you feel tired due to the difficulty regulating blood sugar. Lifestyle choices such as diet, physical activity and stress can all impact blood sugar levels and lead to drowsiness.

Deficiencies: Certain nutrient deficiencies, such as iron deficiency, can increase the risk of restless leg syndrome (RLS) and affect sleep quality and fatigue.

Food intolerances: Tiredness can be a food allergy symptom as the body uses energy to combat the allergy.

It can also be the body’s response to food sensitivity, such as Irritable Bowel Syndrome (IBS) and Irritable Bowel Disease (IBD).

Treatment and management of these conditions can help increase energy levels so that you can feel your best during the day.

Ways to stop feeling tired after eating

1. Eat balanced meals: Choose well-balanced meals with proteins, fats, and complex carbohydrates to help maintain stable blood sugar levels and prevent energy crashes.
2. Try not to overeat: Overeating can make you feel more tired. Prioritising lighter and more frequent meals rather than larger calorie-dense meals will help to maintain your energy levels.
3. Physical activity: Exercise can help you feel alert during the day, minimising the risk of sleepiness. Research has found that exercise improves attention and memory, benefitting day-to-day functioning (10). Exercising in the morning has a similar effect on the body as taking a shower, helping to wake you up as it elevates your body temperature, signalling the brain to remain alert. However, you should avoid exercising too close to bedtime, as it can make it harder to fall asleep (11).
4. Prioritise sleep: Getting enough sleep is vital. If you think you could have a sleep disorder, you should get tested for it. Sleep Apnoea is one of the most common disorders and can be easily tested for from the comfort of your own home.

Summary

Sleepiness after eating is often nothing to worry about, but if it’s persistent and affecting daily functioning, contact your healthcare provider.

We are experts in Sleep Apnoea, from diagnosis to treatment and advice. If you need any guidance or support, please contact us.

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References

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2. Reyner LA, Wells SJ, Mortlock V, Horne JA. ‘Post-lunch’ sleepiness during prolonged, monotonous driving – effects of meal size. (2012). Available at: https://pubmed.ncbi.nlm.nih.gov/22155490/. Accessed: 04.02.2025.
3. Yang B, Zhang H, Jiang T, Yu S. (20230. Natural brain state change with E/I balance shifting toward inhibition is associated with vigilance impairment. Available at: https://pubmed.ncbi.nlm.nih.gov/37822500/. Accessed: 04.02.2025.
4. National Institute of Neurological Disorders and Stroke. (2024). Brain Basics: Understanding Sleep. Available at:  https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep. Accessed: 04.02.2025.
5. Yoshitake R, Park I, Ogata H, Omi N. Meal Timing and Sleeping Energy Metabolism. (2023). Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9919906. Accessed: 04.02.2025.
6. Reichert CF, Deboer T, Landolt HP. (2022). Adenosine, caffeine, and sleep-wake regulation: state of the science and perspectives. Available at: https://pubmed.ncbi.nlm.nih.gov/35575450/. Accessed: 04.02.2025.
7. Mantantzis K, Schlaghecken F, Sünram-Lea S, A.Maylor E. (2019). Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0149763418309175. Accessed: 04.02.2025.
8. Makowski MS, Shanafelt TD, Hausel A, Bohman BD, Roberts R, Trockel MT. (2019). Associations Between Dietary Patterns and Sleep-Related Impairment in a Cohort of Community Physicians: A Cross-sectional Study. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC8669895/. Accessed: 04.02.2025.
9. Lopes T, Borba M, Lopes R, Fisberg R, Paim S. (2019). Eating Late Negatively Affects Sleep Pattern and Apnea Severity in Individuals With Sleep Apnea. Available at: https://jcsm.aasm.org/doi/10.5664/jcsm.7658. Accessed: 04.02.2025.
10. Hogan CL, Mata J, Carstensen LL. (2013). Exercise holds immediate benefits for affect and cognition in younger and older adults. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC3768113/. Accessed: 04.02.2025.
11. Johns Hopkins Medicine. Exercising for Better Sleep. Available at: https://www.hopkinsmedicine.org/health/wellness-and-prevention/exercising-for-better-sleep. Accessed: 05.02.2025.