There may not be enough receptors for insulin to bind to, or a defect in the receptors may prevent insulin from binding. A second possible cause involves the process that occurs after insulin plugs into the receptor. Insulin may bind to the receptor, but the cells don't read the signal to metabolize the glucose. Scientists are studying cells to see why this might happen. In people with noninsulin-dependent diabetes, insulin doesn't lower blood sugar, a condition called insulin resistance.
Obesity is a risk factor for diabetes.