Background: Obesity often coexists with poor vitamin D status. There is emerging evidence that improving vitamin D status may lower prevalence of many chronic diseases, beyond its traditional
influence on bone health. We questioned whether vitamin D influenced body fat mass.
Methods: We searched the literature from 1995 to date for randomized controlled trials (RCTs) that had increased vitamin D per se, or were designed to examine the additional influence of vitamin D on body weight or composition. Primary and secondary studies were included for this analysis.
Results: Eleven RCTs (4 primary and 7 secondary) that supplemented vitamin D met our criteria. Nine studies were of good quality, and of these three favoured vitamin D while six showed
no differences between treatments. There were some data to suggest that better vitamin status before or during an RCT could predict greater weight or fat loss.
Conclusion: Current evidence from RCTs of good quality did not unequivocally support the contention that vitamin D accelerated weight or fat loss in obesity. Direct pathways for obesity
prevention remain untested in humans, though an indirect effect through an improvement in calcium metabolism, is expected. Outcomes from trials recently completed or in progress will strength the evidence base in this important area.
Program of Nutrition, School of Public Health, Curtin Health Innovation Research Institute, Curtin University GPO Box U1987, Perth, Western Australia 6845