The risk for developing diabetes follows a continuum. The higher your blood sugar level, the greater the chance that you will subsequently develop diabetes.
If your fasting blood glucose is between 100 mg/dL and 126 mg/dL, you have what’s known as pre-diabetes. (A fasting blood sugar level of 126 mg/dL is defined as diabetes.) An estimated 57 million Americans have pre-diabetes and, therefore, are much more prone to developing diabetes. Like people with diabetes, those with pre-diabetes tend to be overweight, have high blood pressure and abnormal lipid levels, and have a higher risk for cardiovascular disease.
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 diabetes.
Fat location also matters
The risk of added pounds is especially high when the excess weight is distributed around the abdomen—often referred to as an “apple” shape—as opposed to around the hips, called the “pear” shape. Excess weight around the waist also puts you at risk for a condition known as metabolic syndrome (see “What is metabolic syndrome?”).
Fat can accumulate both under the skin (known as subcutaneous fat) and around the abdominal organs or viscera (known as visceral fat). A large belly suggests the presence of this harmful visceral fat, which produces hormones called cytokines that 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 when they are distributed in muscle, making muscle more resistant to insulin’s action. Although further research is needed, it is becoming clearer that fat—especially abdominal fat—adversely affects insulin action and contributes to the development of diabetes.
What is metabolic syndrome?
More than 50 million Americans have metabolic syndrome, a term used to describe a constellation of risk factors for heart disease and stroke. Diabetes (or pre-diabetes), high cholesterol, high blood pressure, and obesity (especially abdominal obesity) are all part of the syndrome, which is diagnosed if you have three or more of the following attributes:
- a large waist size (greater than 40 inches in men or 35 inches in women)
- blood pressure that is 130/85 millimeters of mercury (mm Hg) or higher
- HDL (good) cholesterol that is less than 40 mg/dL in men and less than 50 mg/dL in women
- triglyceride level that is 150 mg/dL or higher
- fasting blood glucose level of 110 mg/dL or higher.
Some experts believe insulin resistance could be the underlying problem in metabolic syndrome. In addition, if you have diabetes, your risk for eye, kidney, and nerve disease increases dramatically, along with your risk for vascular disease affecting your heart, brain, and extremities.