Vitamin status in morbidly obese patients: a cross-sectional study -- Aasheim et al. 87 (2): 362 -- American Journal of Clinical Nutrition:
"Background:Morbid obesity is associated with low circulating concentrations of 25-hydroxyvitamin D. Few data on the concentrations of other vitamins in morbidly obese patients are available."
It seems like low vitamin D and abundant fructose are two of the major factors involved with insulin insensitivity. I'm sure magnesium is big in there too.