What causes you to feel tired after eating a meal?

After eating, your body diverts blood flow to the digestive system to help process food, which can reduce circulation elsewhere and contribute to a sluggish feeling. Your body also releases hormones like cholecystokinin and insulin in response to food, particularly carbohydrates and fats. Insulin helps move glucose into cells, and this process can influence the brain's production of serotonin and melatonin, both of which promote relaxation and sleepiness. Large meals make this effect more pronounced because more energy and blood flow are required for digestion. Foods high in tryptophan, like turkey, also contribute since tryptophan is a precursor to serotonin. This post-meal fatigue is sometimes called postprandial somnolence, and it's a normal physiological response.