Diabetes affects the way the body uses food. It is caused by a lack of insulin, a hormone made in the pancreas that is essential for converting energy from food. Insulin is necessary for the body to process nutrients (carbohydrates, fats, and proteins), and its absence causes high sugar (glucose) levels in the blood. In type 1 diabetes, which usually starts in childhood, the pancreas stops making insulin altogether. In type 2 diabetes, which starts in adulthood (and in some teenagers), the body still makes some insulin, but it doesn't make enough insulin, or the body can't use it properly. Type 2 diabetes can often be controlled by weight loss, sensible eating, and pills to improve the insulin supply or help it work better. Type 1 diabetes must always be treated with insulin injections.