Effect of raised body fat on vitamin D, leptin and bone mass

To estimate leptin, vitamin D and bone mineral density levels in individuals with high fat mass, and to assess any correlation.

The cross-sectional study was conducted at the Basic Medical Sciences Institute, Jinnah Post Graduate Medical Centre, Karachi, and Aga Khan University, Karachi, from August 2012 to July 2014, and comprised healthy male volunteers between the ages of 18-60 years. Body fat percentage was determined using bioelectrical impedance analysis and the participants were classified as: Group A (15-21.9); Group B (22-27.9); and Group C (>28). Bone mineral density was calculated by ultrasound bone densitometer (T-score between +1 and ?1 considered normal). Enzyme-linked immunosorbent assay kits were used to determine the levels of vitamin D and leptin. SPSS 19 was used for statistical analysis.

A total of 132 male subjects participated in this study, with each of the 3 groups having 44(33.3%). Despite all groups having low Vitamin D, a marked decrease was observed in group C compared to groups A and B (p <0.018). Bone mineral density T-score was <-1; total calcium was within normal range in all three groups. Serum leptin was raised in Group C compared to group A and B (p=0.03). Body fat percentage was negatively associated with vitamin D (p=0.004; r = -0.351), while it was positively correlated with leptin (p =0.038; r = 0.256).

Excess of body fat percentage led to decreased vitamin D and raised leptin. However, bone mineral density and calcium levels were within normal range, suggesting that other factors might have played a role in maintaining bone mass in obese individuals, such as leptin.