Just reading about vitamin d and found this:
Individuals with a body mass index (BMI) ≥30 typically have a low plasma concentration of 25(OH)D [47]; this level decreases as obesity and body fat increase [48]. Obesity does not affect skin's capacity to synthesize vitamin D, but greater amounts of subcutaneous fat sequester more of the vitamin and alter its release into the circulation. Even with orally administered vitamin D, BMI is inversely correlated with peak serum concentrations, probably because some vitamin D is sequestered in the larger pools of body fat [47].
and also this:
A growing body of research suggests that vitamin D might play some role in the prevention and treatment of type 1 [65] and type 2 diabetes [66], hypertension [67], glucose intolerance [68], multiple sclerosis [69], and other medical conditions [70-71]. However, most evidence for these roles comes from in vitro, animal, and epidemiological studies, not the randomized clinical trials considered to be more definitive. Until such trials are conducted, the implications of the available evidence for public health and patient care will be debated.
So it looks good, but weight is still an issue.
The full article can be found here:
http://ods.od.nih.gov/factsheets/vitamind.asp