The main cause of type 2 diabetes is excess fat accumulation in the liver and pancreas, which leads to insulin resistance and inadequate insulin production.[1] Consequently, people with overweight or obesity are at an increased risk of type 2 diabetes, especially if they store fat in the upper body and around the organs.[2]
Type 1 diabetes, formerly called juvenile diabetes, is ultimately an autoimmune disease, though it is often heritable and influenced by multiple genes,[3] with the highest incidences reported in Finland and other Northern European nations.[4] Environmental triggers (such as exposure to certain viruses) and nutritional factors may also increase the risk of type 1 diabetes.[5] The reason why some people develop type 1 diabetes is not fully known, but the evidence is at least clear that it is caused by autoimmune destruction of the beta cells in the pancreas, which secrete insulin, often after a viral infection.