Effect of intermittent versus chronic energy restriction on breast cancer risk biomarkers in premenopausal women: a randomised pilot trial

Postmenopausal breast cancer risk increases twofold in women who gain significant amounts of weight [1] and there is evidence that energy restriction may reduce risk [2]. Animal studies indicate that intermittent energy restriction (IER) reduces risk and may be superior to continuous energy restriction (CER) [3]. We have shown chronic energy restriction reduces biomarkers of breast cancer in women at risk but is hard to maintain. We hypothesise that IER may be superior to CER in reducing biomarkers of breast cancer risk and may also be more acceptable to women.

We are undertaking a 6-month randomised trial to compare the two approaches in 104 premenopausal women aged 30–45 years at high risk of breast cancer because of adult weight gain >7 kg. Women will be randomly assigned to either CER (75% estimated energy requirements: ~1,500 kcal 7 days/week) or IER (75% estimated energy requirements: 650 kcal for 2 days and ~1,800 kcal 5 days/week) over 6 months. Study end points will be measures of insulin sensitivity (HOMA, SHBG and testosterone), potential breast cancer growth factors (IGF axis, leptin and adiponectin), inflammatory markers (C-reactive protein and sialic acid), oxidative stress marker (urinary F2 isoprostane), weight and body composition (waist/hip circumference, fat free and total fat mass). The relative acceptability of IER and CER will be assessed using a quality of life questionnaire (RAND SF-36) and scales of behaviour change and adherence. The relative efficacy and acceptance of intermittent and chronic calorie restriction will inform future weight loss programmes to prevent breast cancer. Thirty-seven women have currently been recruited to the study (18 CER and 19 IER) and recruitment is planned to be completed by December 2006.