Background: Based on in vitro studies, it has been hypothesized that 1,25-dihydroxy vitamin D (1,25-vit D) may promote weight gain in humans, but previous studies have demonstrated conflicting results regarding the association between serum 1,25-vit D and body mass index (BMI).
Aim of the study: To evaluate the relation between serum 1,25-vit D and BMI.
Methods: Two thousand one hundred and eighty-seven subjects, recruited from a metabolic and medical lifestyle management clinic, were included in a cross-sectional study. BMI, 25-hydroxy vitamin D (25-OH-vit D) and 1,25-vit D were measured. The cohort was divided according to BMI in five groups (<25, 25-29.9, 30-34.9, 35-39.9 and >39.9 kg/m(2)). Statistical analyses were performed with multiple linear regression models. Age and gender were used as explanatory covariates.
Results: With increasing BMI group, there was a significant decrease in both serum 25-OH-vit D and 1,25-vit D (P<0.001). Those with BMI >39.9 kg/m(2) had 24% lower serum 25-OH-vit D levels and 18% lower 1,25-vit D levels than those with BMI <25 kg/m(2).
Conclusions: There is an inverse association between BMI and the serum levels of 25-OH-vit D and 1,25-vit D. This makes it highly unlikely that high levels of circulating 1,25-vit D contribute to the development of obesity.