Association between body fat percentage and vitamin D deficiency among Korean adults: A cross-sectional study.

Vitamin D deficiency is associated with obesity, as vitamin D may be sequestered or diluted in adipose tissue. This cross-sectional study investigated the association between serum 25-hydroxyvitamin D [25(OH)D] levels and body fat percentage in Korean adults from the KNHANES IX. A total of 4176 participants were analyzed and stratified by sex and age. Total, appendicular, and trunk fat mass were assessed using bioelectrical impedance analysis and serum 25(OH)D3 concentrations were measured using LC-MS. Multivariable linear and logistic regression models were employed to investigate the relationship between vitamin D deficiency (< 20 ng/mL) and body fat percentage. After adjusting for age, lifestyle factors, dietary factors, and medical condition, younger adults (19-64y) in the highest quartile of body fat percentage (Q4) had significantly higher odds of vitamin D deficiency (men: OR 1.71; 95 % CI, 1.16-2.52, women: OR 1.71; 95 % CI: 1.26-2.31) compared to those in the lowest quartile (Q1). Similarly, older men (≥65y) in the second and third highest quartiles and older women in the highest quartile showed significantly higher odds. In both age and sex groups, total and appendicular body fat percentages were inversely associated with serum 25(OH)D3 levels (all p < 0.05). Trunk fat percentage was inversely associated with serum 25(OH)D3 levels in younger men and women and in older women (all p < 0.05), but not in older men (p = 0.061). These results indicate that higher body fat percentage partially contributes to vitamin D deficiency across all age and sex groups, with appendicular fat exhibiting a consistent association.