In a double blind, placebo-controlled study of overweight and obese people, participants received either 4,000 IU daily of vitamin D or a placebo for 13 weeks, in combination with resistance training. Researchers observed a significant decrease in the waist-to-hip ratio for the supplemented group, and stated that the “study demonstrated that vitamin D supplementation improved muscular power in healthy overweight and obese individuals within four weeks, and that elevated vitamin D status was associated with greater losses in waist circumference.” According to Purdue University researchers, “the greater decrease in waist circumference associated with higher vitamin D intake represents a potential reduction in risk for metabolic disease and cardiovascular risk.”
Carrillo A, Flynn M, Pinkston C, Markofski M, Jiang Y, Donkin S, Teegarden D. Impact of vitamin D supplementation during a resistance training interven¬tion on body composition, muscle function and glucose tolerance in overweight and obese adults. Clinical Nutition. Published online ahead of print, doi: 10.1016/j.clnu.2013.08.014