Why weight matters in diabetes

Many people know that being overweight puts people at risk for getting diabetes. But most of my patients—and I assume people in general—don't know why this is the case. The below article, published originally in Harvard Medical School's special health report, Healthy Eating for Type 2 Diabetes, explains the connection between weight and diabetes.

Excess weight is the single most important risk factor for this form of diabetes, and scientists are beginning to understand why. A leading theory, bolstered by research, is that fat is more than just a storage site for extra nutrients. Fat, or adipose, tissue also functions as an endocrine organ, producing hormones that affect appetite and insulin action.

So far, scientists have found that fat cells produce the hormones leptin, resistin, and adiponectin. Leptin is normally released after a meal and dampens appetite. Resistin and adiponectin both affect cells' response to insulin. (Too much resistin may cause insulin resistance; too little adiponectin may do the same.) Although the appetite regulation system is complex and scientists are still deciphering the roles of individual hormones, it's becoming clear that excess body fat disrupts the normal balance and functioning of these hormones — thereby contributing to insulin resistance and setting the stage for type 2 diabetes.

Scientists are also learning why abdominal fat may be so risky. The visceral fat that accumulates around abdominal organs produces hormones called cytokines that normally regulate the body's immune system response, but which may also contribute to insulin resistance. For instance, animals that are obese and insulin resistant have high levels of a cytokine known as TNF-alpha. Some research suggests that this hormone may also play a role in people with insulin resistance. Other research suggests that visceral fat may affect levels of glucocorticoids, steroid hormones that also contribute to obesity and insulin resistance. Furthermore, fatty acids (the breakdown products of fat) may play a direct role in insulin resistance. Although further research is needed, it is becoming clearer that fat — and especially abdominal fat — adversely affects insulin action and contributes to the development of pre-diabetes and type 2 diabetes.

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Diabetes & Diet
One of the biggest concerns for people with diabetes is their diet. Healthy Eating for Type 2 Diabetes takes the guesswork out of meal time, providing healthy eating strategies to prevent and treat the most common form of diabetes—Type 2 diabetes. The special report from Harvard Medical School includes meal plans, physical activity ideas, and 40 original recipes to get you on the path to healthy eating and living.

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