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.
More about type 2 diabetes
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.
How exercise helps, even if you don't lose weight
Regular exercise makes cells more sensitive to insulin, so they absorb more blood sugar. Exercise also improves your cholesterol and lowers blood pressure.
All three factors are important. People with either prediabetes or diabetes have a much greater risk of heart attack and stroke than other people in the population and controlling all three can lower that risk.
In addition, exercise can also help prevent or delay diabetes in those with prediabetes and can help prevent or delay complications in those with diabetes.
In a 2002 study, people with prediabetes reduced their risk of diabetes by 58% after losing weight, eating better, and exercising 150 minutes weekly compared to those who did not.
It can be difficult to squeeze in 150 minutes each week, or about 30 minutes five days a week. But you don't have to run a marathon. There is a wealth of studies on the best weight-loss and exercise strategies for people who are at risk for type 2 diabetes, and they include walking with a friend, exercising in a group, and having a goal (even if you don't hit it every time).
One common goal is to use a pedometer and aim for walking at least 10,000 steps a day.
Weight loss helps too, independently of exercise
Exercise helps even if you don't lose weight. But if you do, you have added protection against the disease. You don't need to lose a ton of weight to benefit.
"Losing approximately 7% of your weight will prevent or delay diabetes," says Nadine Uplinger, RD, a certified diabetes educator and director of the Gutman Diabetes Institute at the Albert Einstein Healthcare Network in Philadelphia.
That means if you weigh 200 pounds, a loss of 14 pounds will help. If you weigh 150 pounds but are carrying too much on your frame, just shedding a little less than 11 pounds will also help.
Still, weight loss "is a struggle, and it is a struggle forever. It never goes away," notes Dr. Bernstein. "Those fat cells are waiting to fill up."
While lifestyle changes are the best way to prevent diabetes, medication can help too, he notes. In the 2002 study, patients with prediabetes who took the oral diabetes drug metformin reduced the chance of developing diabetes by 31%.
"So actually, if you did some diet and some exercise and took metformin, there's a good probability that you would slow the progression" from prediabetes to diabetes, says Dr. Bernstein.