Nighttime eating: commonly observed and related to weight gain in an inpatient food intake study

Background: Nighttime food intake has rarely been studied in inpatient settings and only one study observed a relation between self-reported nighttime eating and weight gain. Objective: We investigated the prevalence of nighttime eating and its effect on weight change. Design: Healthy nondiabetic Pima Indians (n = 117; 67M, 50 F) and whites (n = 43; 29 M, 13 F) were admitted to a clinical research unit. After consuming a standardized diet for 3 d, participants ate ad libitum from a computer-operated vending machine that recorded the time of food selection. Energy intake was calculated as mean kcal/d. Follow-up weight was available for 94 volunteers. Results: Fifty-five subjects (36%) were nighttime eaters (NEs; persons who ate between 2300 and 0500 on >= 1 of the 3 d). Prevalence was similar among whites and Pima Indians (37% and 35%, respectively). There were no significant differences in body mass index or percentage body fat between NEs and non-NEs. NEs consumed more calories per day (4758) than did non-NEs (4244; P = 0.02), but the percentage of calories from macronutrients did not differ. NEs consumed approximate to 15% (690 kcal) of their daily energy during nighttime episodes. After control for baseline weight and follow-up time ((x) over bar +/- SD: 3.4 +/- 1.8 y), NEs (n = 29) gained more weight (6.2 kg) than did non-NEs (n = 65; 1.7 kg; P = 0.03). Conclusions: Nighttime eating was common, and it predicted weight gain. It remains to be determined whether this behavior indicates abnormal sleep patterns leading to nighttime wakefulness and food intake in those prone to weight gain.