Grabbing a late-night snack may feel like a small reward at the end of a long day, but growing scientific evidence suggests eating at night can interfere with digestion, disrupt hormones, impair sleep and raise the risk of weight gain and metabolic problems.
Researchers say the digestive system is designed to work in sync with the body’s biological clock, which slows at night. During late hours, stomach acid production drops, intestinal movement slows, pancreatic enzyme secretion decreases and the gallbladder releases less bile. Eating when the system is meant to rest can cause food to linger in the stomach and intestines, leading to bloating and discomfort.
People with sensitive digestive systems — including those with irritable bowel syndrome, inflammatory bowel disease, gastritis or reflux — may experience stronger effects. Doctors say the body can interpret nighttime eating as stress, often worsening symptoms the following morning.
Late eating also disrupts hormones that regulate hunger and fullness. At night, leptin levels normally rise to signal satiety, while eating late can increase the influence of ghrelin, the hormone that stimulates appetite. This imbalance may lead to increased hunger and cravings the next day.
Blood sugar control also suffers at night, when insulin sensitivity is lower. Late meals are more likely to cause sharper glucose spikes, raising the long-term risk of insulin resistance.
Sleep quality is also affected. Late meals — particularly those high in fat, sugar or caffeine — activate the nervous system and interfere with deep sleep. Studies link late-night eating to shorter sleep duration, more awakenings and next-day fatigue and irritability.
A controlled study published in 2022 in the journal Cell Metabolism found that participants who ate identical meals later in the day reported more hunger, burned fewer calories and showed metabolic changes that promoted fat storage, compared with those who ate earlier.
Researchers are also studying effects on the gut microbiome. Animal studies suggest gut bacteria follow circadian rhythms, and nighttime eating may increase fermentation, gas and inflammation. Some evidence indicates intestinal permeability may rise at night, potentially worsening inflammatory responses.
Health experts say those at higher risk include people with digestive disorders, insulin resistance, excess weight, shift workers, adolescents and individuals under chronic stress who may turn to food for emotional relief.
Nutrition specialists recommend finishing meals at least 2½ to three hours before bedtime, maintaining regular daytime meals and choosing lighter options if eating late is unavoidable.
The author is a senior nutritionist and the founder and director of “Derech HaBeten” (Belly Way), a center for holistic digestive health.