Changes in Body Composition According to Age and Sex among Young Non-Diabetic Korean Adults: The Kangbuk Samsung Health Study

BACKGROUND Age-related decreases in lean mass represent a serious health problem. We aimed to analyze the risks of rapid decreases in lean mass by age and sex in relatively young Korean adults during a 4-year follow-up study. METHODS A total of 65,856 non-diabetic participants (59.5% men, mean age 39.1 years) in a health screening program were subjected to bioimpedance body composition analyses and metabolic parameter analyses at baseline and after 4 years. The participants were sub-divided according to age, and additionally to six groups by age and the degree of body weight change over the 4-year period. The actual changes in body weight, lean mass, and fat mass and the percent changes over the 4-year period were assessed. RESULTS The percent change in lean mass decreased and the percent change of fat mass increased with increasing age in every age and sex group. However, the annual percent decrease in lean mass and percent increase in fat mass were significantly higher among women than among men (-0.26% vs. -0.15% and 0.34% vs. 0.42%, respectively; P<0.01). Participants who were older than 50 years and had a weight loss <-5% during the 4 years had significantly greater decreases in lean mass and smaller decreases in fat mass, compared to those who were younger than 50 years. An odds ratio analysis to determine the lowest quartile of the percent change in lean mass according to age group revealed that participants older than 60 years had a significantly increased risk of a rapid decrease in the lean mass percentage (2.081; 95% confidence interval, 1.678 to 2.581). CONCLUSION Even in this relatively young study population, the lean mass decreased significantly with age, and the risk of a rapid decrease in lean mass was higher among women than among men. Furthermore, the elderly exhibited a significantly more rapid decrease in lean mass, compared with younger participants.