The relationship between obesity indices and serum vitamin D levels in Chinese adults from urban settings

Background and Objectives: With an increased incidence of obesity in China, this study sought to investigate the correlation between serum 25-hydroxyvitamin D levels and adiposity phenotypes in Chinese adults from urban settings. Methods and Study Design: A total of 1277 subjects aged 20-82 years old were recruited into this cross-sectional study. Anthropometric parameters and blood biochemistry panels were measured. Statistical analysis using partial correlation, multivariable regression and covariance were performed to assess the impact of obesity parameters on serum 25-hydroxyvitamin D levels. Results: After adjustment for age and gender, serum-25-hydroxyvitamin D levels were found to be inversely related to body mass index, waist circumference, waist/hip ratio, body fat, body fat percentage and waist fat to hip fat ratio. In multivariable regression analysis, serum 25-hydroxyvitamin D levels were negatively associated with waist circumference, waist/hip ratio, body fat, body fat percentage and waist fat/hip fat ratio (p<0.05), while there was no correlation with body mass index (p>0.05). After inclusion of body fat, body fat percentage and waist fat to hip fat ratio in one model, only waist fat to hip fat ratio remained significantly associated with serum 25-hydroxyvitamin D levels (p<0.05). The covariance analysis results showed that abdominal obesity subjects had lower serum 25-hydroxyvitamin D levels compared to the counterpart group, as defined by waist circumference or waist/hip ratio (p<0.05). Conclusion: Our results affirm the relationship between serum 25-hydroxyvitamin D levels and abdominal obesity, suggesting that adiposity phenotypes were strongly linked to serum 25-hydroxyvitamin D levels.