Since the last meeting of the American Heart Association, a great deal of media attention has been focused on low-carbohydrate-high-protein diets (LC-HP) and their potential impact on the practice of cardiology. It has been suggested that these diets, which were introduced originally as weight-loss regimens, also have a significantly beneficial effect on a variety of cardiovascular risk factors. It is clear that people who consume such diets have a reduced intake of calories, resulting in a predictable degree of weight loss. These diets induce a moderate level of ketosis and, in some studies, have been shown to improve the lipid profile overall. There is also a reduction in the number of low-density lipoprotein particles. However, these trends also have been observed over periods of 24 weeks or less with low-calorie diets that already have an established record of safety and efficacy. Although there is a public perception that LC-HP diets have a near-perfect "success rate," the attrition rate on these diets varies from 20% to 43%, which is similar to other conventional weight-loss regimens. Additionally, from a nutritional standpoint, these diets are seriously deficient in several micronutrients and dietary fiber, thus creating a need for nutritional supplements. In contrast, the conventional weight-loss regimens have a favorable impact on serum lipids without the accompanying ketosis and have the potential to provide a nutritionally balanced diet without the need for supplements. Because of the nutritional deficiencies inherent in LC-HP diets and the absence of long-term data on their efficacy and safety, they cannot be recommended in place of currently advocated low-fat, low-calorie diets that have an established record of safety and efficacy.