These days, you hear a lot about diabetes, particularly type 2 which some people develop as they get older and their bodies change. This topic has been at the root of tasteless jokes about people having hands and feet chopped off due to continued sugar consumption in the face of diabetic problems. The Simpsons, for instance, created a character called "Diabetty".
Because weight does affect one's chances of developing type 2 diabetes, there's an assumption that any obese or overweight person is at serious risk of developing it. While it is certainly true that being overweight increases your risks of contracting a variety of diseases, it isn't a lock that you're going to be a diabetic if you are fat.
Every time I discuss health with a doctor or a thin person, they're absolutely shocked that I don't have diabetes because they believe fat = diabetic. If I've been fat most of my life, then of course I must have developed this problem. The truth is that there are a lot of people who are thin who develop it, too. In fact, I've known more moderately overweight to thin people with diabetes than very fat people.
My entire family is overweight and not one of them has diabetes. I'm not trying to undermine the seriousness of weight and type 2 diabetes, but it's wrong to think that every fat person will ultimately suffer from it. It's a myth that is perpetuated in large part to frighten fat people into losing weight. Trust me when I say if the daily humiliation, disgust and anger you experience as a fat person can't push you to lose weight, fear of developing diabetes isn't going to do the trick.