But an International Obesity Task Force estimated in 2002 that 60% of diabetes cases around the world were due to weight gain, and in Western nations it was closer to 90%.
If you are obese or overweight, you are 90 times as likely to develop type 2 diabetes as someone who is not, according to a review of medical literature published in 2003 by University of Kentucky and other researchers.
Why belly fat is so bad
And while any excess fat cranks up the risk of diabetes, fat in your midsectionwhich tends to swaddle organs that play a key role in regulating blood sugaris a bigger contributor to risk.
"When those fat cells go in and around your belly, not down in your buttocks or your hips, but when it's around the belly … that fat in and of itself works to block the action of insulin, which is necessary to lower the blood sugar," says Gerald Bernstein, MD, director of the diabetes management program at the Gerald J. Friedman Diabetes Institute at Beth Israel Medical Center in New York City.
Insulin normally triggers the liver to take up extra blood glucose and store the energy for future use. But when the liver is submerged in fat tissue, insulin "can't get the liver to respond," he says.
As a result, blood sugar can accumulate in the bloodstream, where it can damage organs all over your body. But even a relatively moderate amount of weight loss and exercise can protect you from diabetes.