The effect of intermittent versus continuous energy restriction on biomarkers of breast cancer risk.

Abstract

Abstract Abstract #506 Excess energy, whether it is the form of high energy diets or low energy expenditure (sedentary lifestyle), is a risk factor for breast cancer. Observational studies show that continuous energy restriction (CER) and exercise reduce risk, particularly of postmenopausal breast cancer. Animal data indicate that intermittent energy restriction (IER) may be superior or at least as effective as continuous energy restriction in preventing or reducing the growth rate of mammary tumours. IER may also be more acceptable than CER which has been difficult to implement.
 We have tested the effectiveness and acceptability of IER and have performed a randomised trial of IER (n=53) versus CER (n=54) in overweight or obese premenopausal women. Energy restriction was 25% in both arms. IER subjects had approximately 550 kcal on 2 days per week and add lib food on other days; CER subjects had approximately 1500 kcal / day over 7 days. Nineteen women (18 %) withdrew from the study before 6 months (IER = 12, CER = 7, main reasons: stress = 4, pregnancy = 3, change in employment = 3, couldn't stick to diet = 3).
 Change in weight and biomarkers for last observation carried forward are reported.
 At 6 months. Both IER and CER are effective for loss of weight -7.9 vs. - 6.7% P = 0.26 and waist circumference -6.3 vs. -5% P = 0.13, and for lowering serum levels of leptin -43.3 vs. -39.8% P = 0.53; C – reactive protein -14.8 vs.-20.3% P = 0.15 and free androgen index -9.8 vs.-14.4% P = 0.90. Both IER and CER increased circulating levels of sex hormone binding globulin + 18.1 vs. 10.8% P = 0.51, and plasma adiponectin +11 vs. +1% P = 0.09. IER is better at lowering insulin resistance at 6 months than CER -29.6 vs. -15.3 % P <0.05.
 These data indicate that 2 days IER gives similar results to CER with respect to weight loss and many of the risk parameters measured and may be an alternative approach to continuous energy restriction. The superior reductions in insulin resistance with IER which may be related to periods of very low calorie intake (approximately 70% restriction). We are waiting data of the effects of IER vs. CER on the IGF-1 axis and oxidative stress. Future studies will investigate the mechanism of IER, its optimal duration and its influence on mammary cell function. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 506.