Late mealtime and short sleep are known to be associated with obesity risk due to a misaligned circadian rhythm. This study aimed to investigate the relationship between obesity and mealtime and sleep duration using the Korean Genome and Epidemiology Study (KoGES) data.

Longitudinally prospective cohort study.

Population-based.

KoGES analysed data from 9,474 Korean adults with an average age of 54- years old at baseline.

Meal timing was defined as the eating occasions of the day reported by the participant eating a 24-h dietary recall method. Sleep duration was categorized as <6, 6–7, 7–8, and ≥8 h. The Cox proportional hazard model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident obesity according to meal timing, sleep duration, and nightly fasting duration.

During a mean follow-up of 3.5 years, 826 participants developed obesity. In the multivariable-adjusted analysis, midnight snack eating (HR, 1.20; 95% CI, 1.02–1.41) and higher energy intake from midnight snacks (HR, 1.26; 95% CI, 1.06–1.49) were associated with a higher risk of obesity. Sleeping 8 h or more (HR, 0.67; 95% CI, 0.53–0.85) was associated with a lower risk of obesity.

Our findings highlight the importance of meal and sleep times and suggest that healthy eating habits related to the time of day.