The International Diabetes Federation estimates that there are currently 336 million people worldwide who have type 2 diabetes (T2DM), and the global prevalence of diabetes has more than doubled since 1980. The rapid rise in rates of T2DM echoes a similar rise in rates of obesity, which causes insulin resistance and places an increased insulin secretory demand on pancreatic β cells. While diabetes is diagnosed clinically by elevated plasma glucose levels, loss of β-cell function is progressive over time and β-cell dysfunction is far advanced by the time diabetes is diagnosed. Methods for preserving or restoring β-cell function are important for the prevention and treatment of T2DM. Interventions that reduce body fat or that change fat biology provide the best evidence for slowing or arresting the deterioration of β-cell function that causes T2DM. These interventions should form the basis of interventions to prevent and treat T2DM, particularly early in its course.