The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women.
Level 2 - randomized trial
Individual randomized controlled trial in humans
PubMed 20921964 · doi:10.1038/ijo.2010.171
What was done
Researchers randomized 107 overweight or obese premenopausal women (mean BMI 30.6 kg/m2) to either intermittent energy restriction (IER: approximately 2710 kJ/day for 2 days per week) or continuous energy restriction (CER: approximately 6276 kJ/day for 7 days per week), both aiming for an overall 25% energy restriction. Participants were followed for 6 months. Outcomes included body weight, anthropometry, insulin resistance (HOMA-IR), lipid profiles, inflammatory markers, and other disease-related biomarkers assessed at baseline, 1, 3, and 6 months.
What was found
Using last observation carried forward analysis, weight loss was not significantly different between groups: mean weight change was -6.4 kg (95% CI: -7.9 to -4.8) for IER versus -5.6 kg (95% CI: -6.9 to -4.4) for CER (P = 0.4). Reductions in leptin, free androgen index, high-sensitivity C-reactive protein, total cholesterol, LDL cholesterol, triglycerides, and blood pressure were comparable between groups. Reductions in fasting insulin and insulin resistance were modest in both groups but greater with IER than CER: difference between groups was -1.2 uU/ml (95% CI: -1.4 to -1.0; P = 0.04) for fasting insulin and -1.2 uU*mmol/l (95% CI: -1.5 to -1.0; P = 0.04) for insulin resistance.
Why it matters
This study provides randomized trial evidence that intermittent energy restriction (the 5:2 diet pattern) is a viable alternative to continuous daily calorie restriction for weight reduction and metabolic risk factor improvement.
Limits
The study was restricted to premenopausal overweight and obese women, limiting generalizability to men, postmenopausal women, or normal-weight individuals. The primary analysis relied on last observation carried forward, which can bias effect estimates. Follow-up was limited to 6 months, leaving long-term adherence, weight maintenance, and clinical cardiovascular or metabolic endpoints unmeasured.
Cited by
- supports In a study of 100 overweight women at risk for breast cancer by Michelle Harvie and Dr. Mattson, both 5:2 fasting and daily 25% caloric restriction led to ~8% weight loss over 6 months, but 5:2 fasting caused greater improvements in insulin sensitivity and greater loss of belly fat.
- supports In a clinical trial by Michelle Harvie, women on a 5:2 intermittent fasting diet lost more abdominal fat and had significantly greater improvements in insulin sensitivity than women on daily calorie restriction with identical total weight loss and calorie intake over 6 months.