Nutritional and behavioral factors associated with the occurrence and duration of winter weight gain

Background Obesity is rising worldwide, including Japan. Seasonal “holiday weight gain,” well documented in Western settings, may similarly contribute to long-term body mass index increases in Japan. Aim To estimate the prevalence and magnitude of winter weight gain in Japanese university students and identify lifestyle factors associated with prolonged weight retention. Methods A cross-sectional survey was conducted among 339 students (141 men, 198 women; mean age 19.4 years). Participants self-reported winter weight change, time needed to return to their usual pre-winter weight, diet, physical activity, sedentary time, alcohol use, and sleep. Sex-stratified binary logistic regression identified predictors of winter weight gain and prolonged weight retention (≤1 month vs. >1 month). Results Winter weight gain was reported by 51.1% of men and 68.2% of women; the mean (standard deviation) increases were 2.3 ± 1.2 and 2.0 ± 1.1 kg, respectively. Among participants who reported winter weight gain, 61.8% indicated that their weight returned to normal within 1 month, whereas 38.2% required more than 1 month. In men, prolonged retention was predicted only by longer sedentary time during holidays. In women, predictors of prolonged retention included more frequent alcohol consumption and shorter sleep; winter weight gain itself was associated with lower intake of instant/retort foods, less weekday sitting, and more frequent exercise. Conclusions Winter weight gain is common among Japanese university students, particularly women, with sex-specific predictors of persistence. Reducing sedentary time in men and addressing alcohol use, taste preferences, and sleep in women may inform prevention.