Restriction in meal timing has emerged as a promising dietary approach for the management of obesity and dysmetabolic diseases. The present systematic review and meta-analysis summarized the most recent evidence on the effect of time-restricted feeding (TRF) on weight-loss and cardiometabolic variables in comparison with unrestricted-time regimens. Studies involving TRF regimen were systematically searched up to January 2019. Effect size was expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). A total of 11 studies, 5 randomized controlled trials and 6 observational, were included. All selected studies had a control group without time restriction; hours of fasting ranged from 12-h until 20-h and study duration from 4 to 8-weeks. Most studies involved the Ramadan fasting. TRF determined a greater weight-loss than control regimens (11 studies, n = 485 subjects) (WMD: -1.07 kg, 95%CI: -1.74 to -0.40; p = 0.002; I2 = 56.2%), unrelated to study design. The subgroup analysis showed an inverse association between TRF and fat free mass in observational studies (WMD: -1.33 kg, 95%CI: -2.55 to -0.11; p = 0.03; I2 = 0%). An overall significant reduction in fasting glucose concentrations was observed with TRF regimens (7 studies, n = 363 subjects) (WMD: -1.71 mg/dL, 95%CI: -3.20 to -0.21; p = 0.03; I2 = 0%), above all in trials (WMD:-2.45 mg/dL, 95%CI: -4.72 to -0.17; p = 0.03; I2 = 0%). No between-group differences in the other variables were found. TRF regimens achieved a superior effect in promoting weight-loss and reducing fasting glucose compared to approaches with unrestricted time in meal consumption. However, long-term and well-designed trials are needed to draw definitive conclusions.
Keywords: Fasting glucose; Observational studies; Randomized controlled trials; Time restricted feeding; Weight loss.