Low blood concentrations of vitamin D are associated with obesity. Low vitamin D levels have been correlated with increased weight, body mass index (BMI), waist to hip ratio (WHR), body fat percentage, fat mass and fat-free mass.
The mechanism is not fully understood, but Vitamin D improves insulin and leptin signaling. The benefits appear to work in conjunction with calcium levels.
I’ve blogged about this before, but optimal Vitamin D levels can probably only be achieved through supplementation. Sun exposure can effectively raise Vitamin D levels at southern latitudes. If you live above the midline latitude of the United States, you must supplement to achieve optimal levels. Many authorities believe it takes at least 1000 IU of supplemental Vitamin D per day to effectively raise blood levels to the optimal range.