Eating late at night may make it harder to maintain a healthy weight, with a growing body of scientific research suggesting that meal timing can influence how the body regulates hunger, burns calories and stores fat.
While experts stress that late-night eating alone does not cause obesity, several recent studies indicate that regularly consuming meals close to bedtime may increase the risk of weight gain.
A 2024 systematic review published in JAMA Network Open analysed 29 studies involving 2,485 participants and found that people who limited food intake during late-night hours and consumed most of their calories earlier in the day generally achieved greater weight loss than those who ate later.
The review, conducted by researchers Hiu Yee Liu, Ashley A. Eso, Nathan Cook, Hayley M. O’Neill and Loai Albarqouni, concluded that meal timing can affect the body’s digestion, fat metabolism and appetite-regulating hormones.
A separate study by researchers at Harvard University, led by Dr. Frank Scheer and Dr. Nina Vujović, compared two groups of adults with obesity who consumed identical meals but at different times.
One group ate its final meal about 6.5 hours before bedtime, while the second group ate approximately 2.5 hours before going to sleep.
Participants who ate later experienced a 16% reduction in leptin, the hormone that signals fullness, and a 34% increase in ghrelin, the hormone responsible for stimulating hunger. They also burned around 5% fewer calories than those who ate earlier.
Similar findings were reported by researchers at the Johns Hopkins University School of Medicine in a study published in the Journal of Clinical Endocrinology & Metabolism. The study compared people who ate dinner at 10:00 p.m. with those who ate at 6:00 p.m.
Late-night diners recorded blood glucose peaks nearly 18% higher than the early dinner group, while their rate of fat burning was approximately 10% lower.
Animal research has also produced comparable results. Scientists at Northwestern University found that mice fed a high-fat diet just before their inactive period gained nearly twice as much weight as mice that consumed the same number of calories during their active period.
Researchers caution that these findings should not be interpreted to mean that eating at night automatically causes obesity. Total calorie intake, diet quality, physical activity, sleep patterns, genetics and overall lifestyle remain the strongest determinants of body weight.
However, the evidence increasingly suggests that regularly consuming large, high-calorie meals close to bedtime may reduce the body’s ability to efficiently regulate appetite and burn fat, making long-term weight management more challenging.
