The relationship between body mass index and poor self-rated health in the South Korean population.

OBJECTIVE: This study aimed to examine the association between body mass index (BMI) and self-rated health (SRH) in Korean adults. METHODS: The study included 214,997 adults who participated in the 2016 Korean Community Health Survey. Participants were categorized into four groups according to WHO Asian classification based on their BMI: underweight (<18.5 kg/m2), normal-weight (18.5-22.9 kg/m2), overweight (23.0‒24.9 kg/m2), obese (25.0‒29.9 kg/m2), and severely obese (≥30.0 kg/m2). Multivariate Poisson regression analysis with sampling weights and robust variance estimators was performed to evaluate the relationship between BMI categories and poor SRH. RESULTS: A J-shaped association was observed between BMI and poor SRH in both sexes. Compared to normal-weight subjects, the age, lifestyle, and comorbidities adjusted prevalence rate ratios (PRRs) in men for poor SRH were 1.73 (95% confidence interval [CI], 1.60-1.88) for underweight, 0.87 (95% CI, 0.83-0.92) for overweight, 0.98 (95% CI, 0.93-1.03) for obese, and 1.79 (95% CI, 1.63-1.97) for severely obese. In women, compared to normal-weight subjects, the age, lifestyle, and comorbidities adjusted PRRs for poor SRH were 1.33 (95% CI, 1.26-1.41) for underweight, 1.02 (95% CI, 0.98-1.06) for overweight, 1.15 (95% CI, 1.10-1.19) for obese, and 1.42 (95% CI, 1.31-1.53) for severely obese. Associations between underweight and SRH were stronger at older ages than at younger ages, whereas those between high BMI and SRH were stronger at younger ages than at older ages. CONCLUSIONS: This cross-sectional study using a nationally representative survey observed a J-shaped relationship between BMI and poor SRH. This association differed depending on age and presence or absence of comorbidities.