LOW FAT OR A LOW CARBOHYDRATE DIETARY AND BREAST CANCER RISK

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Obesity is linked to the risk of breast and many other cancers as well as cardiovascular disease, diabetes, musculoskeletal disorders, and reduced life expectancy. Establishing effective behaviors regarding diet and exercise are the foundations of weight control. The most effective dietary pattern for cancer prevention or weight loss is a controversial topic and the subject of great debate among various facets of the scientific community. Low carbohydrate diets such as the Atkins Diet, the Scarsdale Diet and the Zone Diet advocate a diet consisting of between 10% and 30% of total calories from carbohydrates and approximately 40% of total calories from protein. This amount of protein is exceeds the National Academy of Sciences recommended range of between 10 and 35% of total calories from protein (Food and Nutrition Board, 2002). Proponents of low carbohydrate diets report that diets high in carbohydrates result in higher plasma insulin levels and promote lipogenesis. Low carbohydrate diets have been extraordinarily popular among the general public and some short-term studies report greater loss of body fat and greater maintenance of lean body mass when compared with a diet rich in carbohydrate but low in fat (Farnsworth, 2003; Foster, 2003). However, there are only a few studies of reduced carbohydrate diets that are greater than six months in duration and long-term weight maintenance and safety are unknown. Furthermore, the published studies have not utilized intense education, feedback, and monitoring which are likely to be key determinants of success. Thus, we propose an 18-month clinical trial in premenopausal women with intensive combined nutrition and physical activity counseling to examine the efficacy in inducing and maintaining weight loss. This randomized phase II pilot trial will provide intensively monitored intervention to all participants, and will compare a low-fat dietary intervention to a protein-sparing (low carbohydrate) intervention. We hypothesize that calorie-restriction/calorie expenditure is the major determinant of successful weight loss and that macronutrient distribution is less important with no significant long-term difference between diets. Adherence to each diet and physical activity recommendations are key outcomes. These data will provide essential feasibility data for a future larger, multi-institutional, randomized study of weight control, physical activity and cancer risk factors. Secondary goals of the study include a number of anthropometric and biological measures that may be related to cancer risk.