Medical costs attributable to overweight and obesity in Japanese individuals.

Objective: We aimed to reveal the association between body mass index (BMI) and medical costs in the current Japanese population, and to estimate the population attributable fraction (PAF) of medical costs due to overweight and obesity.

Methods: A generalized linear mixed model with log link function and gamma distribution was used to evaluate the association between BMI and medical costs in 34,537 beneficiaries of the National Health Insurance aged 40-69 years in Chiba City. Medical cost data were obtained from insurance claims submitted between April 2012 and March 2016. PAFs due to overweight (BMI ≥25.0 and <30.0kg/m) and obesity (BMI ≥30.0kg/m) were calculated.

Results: Overweight and obesity were significant predictors of excessive medical costs in all age and sex groups. PAF due to overweight and obesity was estimated to be 9.62% (95% confidence interval, 8.52-10.73%). Additionally, PAFs in 40-59-year-old individuals (12.76% in men and 11.63% in women) were greater than those in 60-69-year-old subjects (6.55% in men and 7.80% in women) for both sexes.

Conclusions: In the Japanese population, overweight and obesity are an excessive financial burden with an estimated PAF of 9.62% of total medical costs.