Diabetes is a number of diseases that involve problems with the hormone insulin. Normally, the pancreas (an organ behind the stomach) releases insulin to help your body store and use the sugar and fat from the food you eat. Diabetes occurs when one of the following occurs: 1  When the pancreas does not produce any insulin. 2  When the pancreas produces very little insulin. 3  When the body does not respond appropriately to insulin, a condition called  insulin resistance .