Glucose is used as fuel by every cell in the body. When glucose is eaten, it is absorbed into the blood from the small intestine. Once it reaches a cell, it must cross the fine membrane that forms the cell’s outer skin. This is normally impermeable to all substances, but insulin has the ability to combine with glucose and transport it across the membrane from the blood into the interior of the cell. Insulin is made in the pancreas, which sits in the centre of the abdomen.
Nine out of ten of diabetics suffer from the maturity onset form of diabetes mellitus, which is far more common in obese patients. There is a combination of reduced insulin production and cells throughout the body fail to respond to the insulin (insulin resistance), so glucose cannot enter the cell. The liver also tends to produce increased glucose.