Causes of Type 2 Diabetes

Age, Obesity, and Lifestyle
The most important environmental trigger of type 2 diabetes appears to be obesity. Obesity is defined as having a body mass index of 30 or greater (see p. 5). Genetics may play a role in obesity and, thus, in triggering type 2 diabetes.

In some way, having too much body fat promotes resistance to insulin. This is why, for so many years, type 2 diabetes has been treated with diet and exercise. Losing weight and increasing the amount of muscle while decreasing the amount of fat helps the body use insulin better. There is also a link between type 2 diabetes and where fat is stored. People with central body obesity, which means carrying excess fat above the hips, have a higher risk of developing type 2 diabetes than those with excess fat on the hips and thighs.

Central body obesity, as well as overall obesity, is more common in African Americans than in Caucasians. This may be one reason why type 2 diabetes is also more common in African Americans than in Caucasians.

Age also appears to play a role. Half of all new cases of type 2 diabetes occur in people over age 55. Because people tend to gain weight as they age, many researchers think that the reason more older people develop diabetes is because more older people are overweight.

Leading an inactive, sedentary lifestyle and consuming a high-calorie diet can also lead to type 2 diabetes in susceptible people, presumably by contributing to obesity.

Prevention of Type 2 Diabetes
The best way to prevent type 2 diabetes is to maintain an active lifestyle and to keep your weight at a healthy level. In the Diabetes Prevention Program (DPP)  study,  researchers tested whether changing lifestyle habits or taking the oral diabetes medication metformin (Glucophage) could delay or prevent the onset of diabetes in people at high risk for developing type 2 diabetes.

The study evaluated 3,234 volunteers who were overweight and had impaired glucose tolerance (IGT). IGT or pre-diabetes is a condition in which blood glucose levels are higher than normal but not as high as levels in a person with diabetes. The subjects were placed in one of three groups. People in the first group, the lifestyle intervention group, used a low-fat diet and exercised for 30 minutes a day five times a week. People in the second group were treated with 850 mg metformin twice a day, and the people in the third group took placebo pills instead ofmetformin. The last two groups also received information on diet and exercise.  The study ended a year early when researchers found that people in the lifestyle group who lost 5 to 7 percent of their body weight (10–20 lbs) and exercised 30 minutes a day, 5 days a week (usually by walking), had a 58 percent lower incidence of diabetes. Metformin also lowered the incidence of diabetes by 31 percent.

The results clearly indicate that moderate exercise and modest weight loss can go a long way in preventing type 2 diabetes.

Martha M. Funnell, MS, RN, CDE
Michigan Diabetes Research and Training Center
University of Michigan Medical School
Ann Arbor, Michigan

Robert M. Anderson, EdD
Michigan Diabetes Research and Training Center
University of Michigan Medical School
Ann Arbor, Michigan

Shereen Arent, JD
National Director of Legal Advocacy
American Diabetes Association

American Diabetes Association Complete Guide to Diabetes

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