Vitamin D insufficiency prior to bariatric surgery: risk factors and a pilot treatment study
In a population where severe obesity is becoming increasingly prevalent, bariatric surgery is being employed more often. This study assessed the vitamin D status of such patients and looked at other influential factors as well as evaluating the efficacy of 2 preoperative vitamin D repletion regimens.
Endodiabesity 
Vitamin D status is increasingly being implicated in the pathogenesis of simple obesity. A recent article in Medical Hypotheses suggests that vitamin D deficiency can account for the secular trends in the prevalence of obesity and for individual differences in its onset and severity [1].
Reference
[1] Vitamin D deficiency is the cause of common obesity. Foss YJ. Med Hypotheses 2009;72:314-21