Causes

The exact cause of type 2 diabetes is unknown. But family history and genetics appear to play an important role. Inactivity and excess fat — especially fat around the belly — also seem to be important factors.

What is clear is that people with type 2 diabetes can't process glucose properly. As a result, sugar builds up in the bloodstream instead of doing its normal job of fueling the cells that make up muscles and other tissues.

Most of the sugar in people's bodies comes from the food they eat. When food is digested, sugar enters the bloodstream. Moving sugar from the bloodstream to the body's cells requires the hormone insulin.

Insulin comes from a gland located behind the stomach called the pancreas. The pancreas releases insulin into the blood after a person eats.

As insulin circulates, it allows sugar to enter the cells — lowering the amount of sugar in the bloodstream. As the blood sugar level drops, so does the secretion of insulin from the pancreas.

Type 2 diabetes develops when the body becomes resistant to insulin or when the pancreas stops making enough insulin. The resulting buildup of sugar in the bloodstream can cause symptoms of high blood sugar.