There is convincing evidence that being overweight or obese increases the risk of breast cancer. Furthermore, adult weight gain has been associated with an increased risk of breast cancer in several studies. Conversely, physical activity reduces breast cancer risk. However, the link between specific dietary patterns and breast cancer risk is unclear. Additionally, the biological mechanisms linking diet, physical activity, and breast cancer are uncertain. Therefore we conducted a study to determine the impact of a low-fat versus a low-carbohydrate diet and exercise on weight loss and biomarkers of breast cancer risk. We conducted a 52 week randomized intervention trial of low-fat (20% of total calories from fat, 20% from protein, and 60% from carbohydrate) vs. low-carbohydrate (40% of total calories from carbohydrates, 30% from fat, and 30% from protein) diet along with physical activity (10,000 steps/day) among premenopausal women with a body mass index (BMI) of 25 or higher. Forty-two women were randomized to the low-fat arm and thirty-seven were randomized to the low-carbohydrate arm. Anthropometric measurements and blood draws were conducted at baseline, week 12, week 34, and week 52. Levels of insulin-like growth factor-1 (IGF-1) and IGF binding protein-3 (IGFBP-3) were measured in association with weight. Overall, there were no significant differences among the women in the two groups with respect to race, education, marital status, smoking status, insurance, work status, occupation, or income. Women in both groups lost a significant amount of weight during the study (p<0.0001) although there was no difference between the two groups in weight loss (p=0.07), or in waist-to-hip ratio either over time or between groups. Although IGFBP-3 did not change with weight, the average trend of IGF-1 across groups was associated with weight loss even though there was no difference across interventions. Adherence to the diets was low with only 29% of the women adherent to the low-carbohydrate intervention and 22% adherent to the low-fat intervention. In conclusion, both a low-fat and low-carbohydrate diet plus exercise resulted in significant weight loss although there was no difference between the two groups. Examination of biomarkers of breast cancer risk demonstrated that neither intervention was significantly better at altering levels. IGFBP-3 did not significantly change with weight loss, however, IGF-1 was significantly positively associated with weight loss. Although calorie restriction and physical activity are effective in reducing obesity, the most effective type of diet that best reduces obesity and can impact breast cancer prevention was not identified. These results suggest that a larger randomized trial is needed to examine diet, physical activity, and biomarkers of breast cancer risk.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4456. doi:1538-7445.AM2012-4456