The Chicago Tribune reports the results of a meta analytic study of several earlier studies which turns up a counterintuitive result. Obese people who develop diabetes have a better prognosis - live longer - than slender people who develop the same disease!
The article puzzles about this outcome, I'll give you another possible reason. Suppose being obese causes otherwise healthy people to get diabetes. Because they are otherwise healthy, they live longer.
Slender people who get diabetes may have a different set of causal factors for their diabetes, factors which degrade their health and cause earlier deaths. Let's be clear, this is just me guessing.
