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 have an upper body and visceral fat storage pattern.[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 (e.g., enterovirus) 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, often after a viral infection.