Age Associated Changes in Body Mass Index and Body Fat Distribution

ABSTRACT

BACKGROUND: Body mass index is currently applied as the diagnostic standard of overweight and obesity, regardless of age. Percentage body fat ratio applies separate standards among different sex, but does not have separate standards for different age groups. Since body mass index and percentage body fat may differ according to age, we conducted this study to see if a separate standard for overweight and obesity is indeed necessary for different age groups. METHODS: We selected 2,190 subjects, who were the 10 percent picked randomly by computer, among 21,921 clients who had visited the St. Mary's Hospital's health promotion center in Seoul. Those diagnosed with diabetes, thyroid disease, renal failure, and tuberculosis were excluded, leaving 1,939 over the age of 20, as final subjects. Anthropometric measurements were done using electronic scales and height meters, while body composition was measured with a multi-frequency bioelectric impedance analysis (Inbody 3.0 Biospace, Seoul). The results of this study were shown in mean and standard deviation, and mean values according to ages were compared by Ancova test. RESULTS: In the case of adult men, percentage body fat increased with age. This was observed especially with subjects over 30 compared to subjects in their 20s, although not proven to be statistically significant. A decrease in fat free mass rather than increase in body fat mass was noted with aging. With adult women, percentage body fat increased markedly with subjects over 50, mainly due to increased body fat mass rather than decreased fat free mass. Subjects exceeding a body mass index of 25, which is the standard limit of body mass index for obesity, was 60th percentile for adult men, and 70~80th percentile for adult women. Percentage body fat in this case was 22.54% for men and 31.99~33.46% for women. CONCLUSION: Our study indicates that both men and women show changes in body mass index and fat free mass with aging. Hence, there are limitations to applying a universal standard for body mass index, regardless of age. We suggest that further studies on standards for adult obesity should be conducted based on specific Korean epidemiologic data.