Background: Type 1 diabetes is characterized by complete or near-complete absence of insulin secretion, generally due to autoimmune disease. Cardiovascular disease (CVD) risk in type 1 diabetes is just as great as in type 2 diabetic individuals of the same age, even though type 1 diabetic individuals usually have fewer additional CVD risk factors. This is likely due to earlier age of onset of diabetes and therefore much longer exposure to hyperglycemia. The incidence of type 1 diabetes is increasing throughout the world. The reasons for this are thought to be environmental although the exact nature of the environmental precipitants is not well understood. In contrast to type 2 diabetes, in which it is clear that aerobic exercise improves glycemic control, studies in type 1 diabetes have generally not found a significant beneficial effect for aerobic exercise on glycemic control, even though there is often reduction in insulin requirements and improved insulin sensitivity. This paradoxical finding may be because individuals with type 1 diabetes are at much higher risk of hypoglycaemia than type 2 and tend to increase their carbohydrate intake in an effort to avoid exercise-induced drops in glucose.