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The problems of adherence to energy restriction in humans are well known. Animal data suggest intermittent energy restriction (IER) is comparable with or better for preventing breast cancer than continuous restriction (CER).
To compare the feasibility and effectiveness of IER with CER for weight loss and improving insulin sensitivity and other markers of breast cancer risk.
Randomised comparison of a 25% energy restriction as IER (~2,266 kJ/day for 2 days/week) and CER (~6,276 kJ/day for 7 days/week) in 107 overweight or obese (mean ± SD body mass index = 30.6 ± 5.1 kg/m2) premenopausal women over 6 months. Weight, anthropometrics, blood markers for risk of breast cancer and other metabolic diseases, insulin resistance, oxidative stress markers, leptin, adiponectin, lipids, inflammatory markers (high-sensitivity C-reactive protein and sialic acid), insulin-like growth factor-I and insulin-like growth factor binding proteins, androgens, prolactin and menstrual cycle length were assessed at baseline, 1, 3 and 6 months.
Eighteen subjects withdrew before 6 months (11 IER, seven CER). Last observation carried forward analysis showed IER and CER are equally effective for weight loss: mean (95% CI) weight change for IER was -6.4 (-7.9 to -4.8) kg vs. -5.6 (-6.9 to -4.4) kg for CER (P for difference between groups = 0.4). Both groups had significant and comparable improvements in disease risk markers; however, IER was significantly better than CER in reducing insulin resistance: mean (95% CI) change for IER was -28 (-37 to -17)% vs. -15 (-24 to -4)% for CER.
IER is as effective as CER for weight loss and biomarker change. Its additional beneficial effect on insulin sensitivity indicates that it may be an alternative approach for weight loss.