While vitamin D is known mostly for its ability to metabolize calcium for strong bones and teeth, it plays a crucial role in many other critical aspects of biology, one of which is associated with regulating the amount of fat that is stored on the body. In a DNA microarray study examining which genes are triggered in fat cells by the presence of vitamin D, a total of 93 genes were identified to respond, many of which were associated with the generation and destruction of fat cells.
The vitamin D in fat cells influences the efficiency of the fat cells' ability to store and release calcium. And calcium plays a critical role in the storing and releasing of fats. Thus a vitamin D deficient person needs more calcium to get the same level of efficiency from the fat cells as a person who has adequate vitamin D. It stands to reason, then, that increasing the amount of vitamin D available to the fat cell is in some sense equivalent to increasing the amount of calcium, because it improves the ability of the fat cell to use the calcium that it has available.
There is plenty of evidence that vitamin D deficiency is associated with obesity, but this does not necessarily mean that vitamin D deficiency causes obesity. However, a recent study assessing the direct relationship between serum vitamin D levels and weight loss while dieting (Vitamin D Promotes Weight Loss) , found a consistent linear relationship between the amount of vitamin D in the blood and the amount of weight lost -- subjects who had more vitamin D at the start of the study lost more weight. Each 1 ng/mL increase in the vitamin D measure was associated with an additional half pound of weight loss during the diet.
