Trends in the distribution of body mass index and waist circumference among South Korean adults, 1998-2014.

BACKGROUND/OBJECTIVES: An increase in mean body mass index (BMI) or prevalence of obesity may be accompanied by changes in the population BMI distribution. This study aimed to examine how the distributions of BMI and waist circumference (WC) have changed in South Korea over a 16-year interval (1998-2014).

SUBJECTS/METHODS: Using the Korea National Health and Nutrition Examination Survey, we analyzed changes in mean, standard deviation (SD), 5th, and 95th percentile values of BMI and WC distributions for 46,343 (BMI) and 46,327 (WC) adults aged 25-64 years.

RESULTS

For men, mean BMI increased at an annual rate of 0.060 units (95% CI: 0.047-0.073) with annual increases of 0.029 units in SD (95% CI: 0.019-0.039), 0.121 units in the 95th percentile (95% CI: 0.097-0.145) and 0.042 units in the 5th percentile (95% CI: 0.021-0.062). The 95th percentile and SD of the WC distribution increased, but not mean WC and the 5th percentile. For women, mean BMI decreased at an annual rate of 0.030 units (95% CI: 0.010-0.049) with a 0.030-unit increase in SD (95% CI: 0.012-0.048) and a 0.049-unit decrease in the 5th percentile (95% CI: 0.029-0.070). Mean WC also decreased with an increase in SD and a decrease in the 5th percentile.

CONCLUSIONS

These findings suggest increasing dispersion in the distribution of BMI and WC derived from significant shifts in the upper tails for Korean men, but not women. Future research needs to identify the factors that underlie the increasing dispersion of obesity measures.