"A protein that's overproduced by fat cells in obese individuals appears to promote insulin resistance -- elevating the risk for diabetes, heart disease and early death, according to researchers. Until now the particular protein -- known as retinol binding protein 4, or RBP4 -- had been known solely for its innocuous role as a "transport vehicle," involved in the delivering of vitamin A to healthy tissue. Identifying RBP4's less benign function as an instigator of insulin resistance may lead doctors towards new drug interventions that focus on limiting secretion of the protein among obese patients at risk for type 2 diabetes." (reference)

Of course, it's much easier to simply avoid obesity in the first place. See VitaminDepotOnline's post about losing weight.