Study Objectives: To investigate whether dietary patterns explain the possible association between short sleep duration and obesity.
Design: Longitudinal study.
Setting: Annual health checkup at a Japanese workplace over a 4-year period from 1994-1995 (baseline) to 1998-1999 (follow-up).
Participants: Nonobese Japanese male workers aged 40 to 59 years (n = 2632)
Measurements and Results: Trained health professionals conducted a questionnaire-based survey. Preference for fatty food, skipping breakfast, and eating out were significantly associated with short sleep duration. Snacking and preference for fatty food significantly predicted the incidence of obesity, which was defined as a body mass index of at least 25 kg/m2. Hierarchic logistic regression analyses were conducted to test the significance of the association between sleep duration and the incidence of obesity, before and after controlling for covariates, including dietary patterns (preference for fatty food, skipping breakfast, snacking, and eating out). Participants who slept less than 6 hours were compared with those who slept 7.0 to 7.9 hours. The odds ratio for the incidence of obesity was 2.55 (95% confidence interval [CI] 1.48, 4.42; trend P = 0.007) with covariate adjustment, except for dietary patterns, and 2.46 (95% CI 1.41, 4.31; trend P = 0.011) with complete adjustment, including dietary patterns.
Conclusions: Preference for fatty food, skipping breakfast, snacking, and eating out only partially explained the effects of short sleep duration on the incidence of obesity, suggesting that other factors, including physiologic mechanisms, may largely explain the sleep-obesity association.
Keywords: Diet, eating behavior, Japanese, longitudinal studies, obesity, sleep, workplace