it is true that the more severe the degree of obesity the greater the odds of type 2 diabetes. that's because the excess body fat fuels insulin resistance in the muscles and organs. there may be adverse hormonal effects on the beta cells as well. after years of insulin resistance the beta cells wear down to the point where prediabetes or full type 2 diabetes occurs but only in a certain fraction of indiviiduals with obesity. we don't fully understand why some people with obesity are at risk for diabetes while others can be obese their whole lives without getting it. the answer is likely in the genetics but we don't know which genes confer protection or susceptibility. similarly some thin people develop type 2 diabetes despite minimal insulin resistance. again the answer is in the genes but we don't know which genes.
why is it that obesity doesn't always cause type 2 diabetes?