Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND: This systematic review and meta-analysis summarized the most recent evidence on the efficacy of intermittent energy restriction (IER) versus continuous energy restriction on weight-loss, body composition, blood pressure and other cardiometabolic risk factors. METHODS: Randomized controlled trials were systematically searched from MEDLINE, Cochrane Library, TRIP databases, EMBASE and CINAHL until May 2018. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). RESULTS: Eleven trials were included (duration range 8-24 weeks). All selected intermittent regimens provided ≤ 25% of daily energy needs on "fast" days but differed for type of regimen (5:2 or other regimens) and/or dietary instructions given on the "feed" days (ad libitum energy versus balanced energy consumption). The intermittent approach determined a comparable weight-loss (WMD: - 0.61 kg; 95% CI - 1.70 to 0.47; p = 0.87) or percent weight loss (WMD: - 0.38%, - 1.16 to 0.40; p = 0.34) when compared to the continuous approach. A slight reduction in fasting insulin concentrations was evident with IER regimens (WMD = - 0.89 µU/mL; - 1.56 to - 0.22; p = 0.009), but the clinical relevance of this result is uncertain. No between-arms differences in the other variables were found. CONCLUSIONS: Both intermittent and continuous energy restriction achieved a comparable effect in promoting weight-loss and metabolic improvements. Long-term trials are needed to draw definitive conclusions.