Intermittent energy restriction may result in greater improvements in insulin sensitivity and weight control than daily energy restriction (DER). We tested two intermittent energy and carbohydrate restriction (IECR) regimens, including one which allowed ad libitum protein and fat (IECR þ PF). Overweight women (n 115) aged 20 and 69 years with a family history of breast cancer were randomised to an overall 25 % energy restriction, either as an IECR (2500 -2717 kJ/d, , 40 g carbohydrate/d for 2 d/week) or a 25 % DER (approximately 6000 kJ/d for 7 d/week) or an IECR þ PF for a 3-month weight-loss period and 1 month of weight maintenance (IECR or IECR þ PF for 1 d/week). Insulin resistance reduced with the IECR diets (mean 20·34 (95 % CI 2 0·66, 2 0·02) units) and the IECR þ PF diet (mean 2 0·38 (95 % CI 20·75, 2 0·01) units). Reductions with the IECR diets were significantly greater compared with the DER diet (mean 0·2 (95 % CI 2 0·19, 0·66) mU/unit, P¼0·02). Both IECR groups had greater reductions in body fat compared with the DER group (IECR: mean 2 3·7 (95 % CI 22·5, 24·9) kg, P¼0·007; IECR þ PF: mean 23·7 (95 % CI 2 2·8, 24·7) kg, P¼0·019; DER: mean 22·0 (95 % CI 21·0, 3·0) kg). During the weight maintenance phase, 1 d of IECR or IECR þ PF per week maintained the reductions in insulin resistance and weight. In the short term, IECR is superior to DER with respect to improved insulin sensitivity and body fat reduction. Longer-term studies into the safety and effectiveness of IECR diets are warranted.Key words: Intermittent energy restriction: Low-carbohydrate diets: Weight loss: Daily energy restriction: Insulin resistanceThe global health burden of obesity-related conditions such as diabetes, CVD, dementia and certain cancers, including breast cancer, may be reduced by weight loss and the associated improvements in insulin sensitivity. The difficulties of achieving and sustaining weight loss by energy restriction are well known (1) . Even when reduced weights are maintained, metabolic benefits achieved with weight loss are often attenuated because of non-compliance or adaptation (2 -4) . Effective dietary interventions are needed that promote long-term adherence and sustained beneficial effects on metabolic and disease markers. Such interventions need to be palatable and satiating, meet minimal nutritional requirements, promote loss of fat and preserve lean body mass, ensure long-term safety, be simple to administer and monitor and have widespread public health utility. Multiple dietary approaches have been studied that vary in macronutrient composition (5) and the degree of energy restriction (6) . These typically achieve long-term 5 % weight loss in

BACKGROUND: Breast cancer diagnosis may be a teachable moment for lifestyle behaviour change and to prevent adjuvant therapy associated weight gain. We assessed the acceptability and effectiveness of two weight control programmes initiated soon after breast cancer diagnosis to reduce weight amongst overweight or obese women and prevent gains in normal-weight women. METHODS: Overweight or obese (n = 243) and normal weight (n = 166) women were randomised to a three-month unsupervised home (home), a supervised community weight control programme (community) or to standard written advice (control). Primary end points were change in weight and body fat at 12 months. Secondary end points included change in insulin, cardiovascular risk markers, quality of life and cost-effectiveness of the programmes. RESULTS: Forty-three percent of eligible women were recruited. Both programmes reduced weight and body fat: home vs. control mean (95% CI); weight −2.3 (−3.5, −1.0) kg, body fat −1.6 (−2.6, −0.7) kg, community vs. control; weight −2.4 (−3.6, −1.1) kg, body fat −1.4 (−2.4, −0.5) kg (all p < 0.001). The community group increased physical activity, reduced insulin, cardiovascular disease risk markers, increased QOL and was cost-effective. CONCLUSIONS: The programmes were equally effective for weight control, but the community programme had additional benefits. CLINICAL TRIAL REGISTRATION: ISRCTN68576140