PMID: Abstract Obesity is associated with lower serum 25 OH D level via several mechanisms including sequestration of fat soluble vitamin D in increased fat mass.
Since obesity is the major cause of insulin resistance and type 2 diabetes, lower serum 25 OH D level is also associated diabetes causes these conditions.
Non-surgical weight reduction, especially that results in decreased visceral fat mass, is associated with an improvement in insulin resistance and a small but significant increase in serum 25 OH D level.
Whether the latter is independently associated with the former is not known. Plural meta-analyses reported that vitamin D supplementation per se without life-style intervention is not associated with a significant weight reduction. The beneficial effects of vitamin D supplementation on glucose metabolism appeared to be more prominent in non-obese subjects in whom higher serum 25 OH D level were attained, suggesting potential benefits of vitamin D on glucose metabolism is not mediated by weight or fat mass control.