The prevalence of prediabetes and diabetes among US adolescents aged 12-19 years more than doubled during the first decade of this century, from 9% to 23%. This serious, progressive disease is a particular concern among Hispanic/Latino individuals and other minority groups, who have an even higher prevalence than the white population. For many people, the diagnosis of type 2 diabetes mellitus (T2DM) is delayed until symptoms and, often, irreversible complications occur. Thus, prevention—or at least delay—in the development of this disease is an urgent public health concern. Effective treatment often must address a host of clinical, cultural, and psychological issues that go beyond diet and exercise. This interactive Case Clinic illustrates how lifestyle changes centered on a low-carbohydrate weight-loss diet can prevent the progression of prediabetes to overt T2DM.