There was a research study by The University of Minnesota, Dr. Sibley on vitiman D levels with greater weight loss. It was a small study but it is signifigant and worth more reasearch. It is thought that vitamin D levels help weight loss. It was discussed at an annual Endocrine Society Meeting as well.
The Annals of Epidemiology published a report on genetic mutations, University of California. Reserach has shows that inadquate vitamin D levels may result in cells loosing their stickiness or intercellular adhence. Check out the DINOMIT model for preventing and treating cancer.