The reasons for the epidemics of diabetes and prediabetes, and why individuals from certain populations suffer at higher rates are not well known. In the Pathobiology and Reversibility of Prediabetes in a Biracial Cohort (PROP-ABC) study, nearly 400 African Americans and Caucasians whose parents have type 2 diabetes will undergo repeated testing to determine what factors lead to the occurrence of prediabetes, and whether race still plays a major role in a setting where everyone being studied has one or both parents with diabetes. The PROP-ABC Study also will test the hypothesis that the ability of intensive lifestyle intervention to reverse prediabetes and return people's metabolism back to normal is dependent on how long people have had prediabetes.