Postprandial somnolence, or the "post-lunch dip," is the feeling of sleepiness or fatigue many experience after a meal. This is caused by several factors.

Circadian rhythms play a significant role; in the early afternoon, our body’s natural wakefulness signals decrease, leading to drowsiness. Additionally, the sleep drive increases the longer we stay awake, making us more prone to feeling tired after meals, especially in the afternoon.

After eating, hormonal changes occur that promote sleepiness, with melatonin and serotonin levels rising. Cytokines, proteins linked to immune responses, also increase after eating, particularly after high-calorie meals, contributing to fatigue.

Certain foods, especially high-fat and high-carb meals, worsen this effect by causing blood sugar fluctuations. To avoid post-meal sleepiness, maintain good sleep hygiene, stay hydrated, eat smaller meals, and avoid heavy, fatty, or sugary foods.