On today's segment of About Health on KPFA, Vitamin D was the topic. Vitamin D evidently plays a role in insulin sensitivity and, because it is fat-soluble, fat people may do well to have more of it than average.
http://aud1.kpfa.org/data/20100104-Mon1400.mp3
http://aud1.kpfa.org/data/20100104-Mon1400.mp3