Weight reduction for breast cancer prevention by restriction of dietary fat and calories: rationale, mechanisms and interventions.

A large body of epidemiologic evidence and data drawn from animal feeding studies have led to the feasibility testing of clinical breast cancer prevention trials based on the restriction of dietary fat intake. The animal data strongly suggest that restricting calories as well as fat inhibits breast cancer promotion. Body fat correlates with dietary fat intake in human populations. Obese postmenopausal women have increased levels of circulating bioavailable estrogen capable of promoting breast cancer growth. We propose that restriction of dietary fat intake will decrease total calorie intake and result in a loss of body fat in postmenopausal women. This loss of fat will decrease estrogen production from adrenal androgens and increase bioavailable estrogen, leading to decreased promotion of estrogen-dependent breast tumors. Intervention programs targeted at weight reduction via restriction of calories, reduction of dietary fat and increased physical activity are logical, practical and measurable strategies for reducing the risk of breast cancer in women at moderate to increased risk. Failure to account for variations in adherence to a restricted-fat diet in past feasibility studies has cast doubt on the hypothesis that restricting dietary fat intake can be utilized to reduce the risk of breast cancer. Current studies examining nutritional, hormonal and physiologic data in conjunction with evidence of adherence to dietary and lifestyle change will likely clarify the hormonal and physiologic effects of this potential nutritional strategy for breast cancer prevention.