Daily 16:8 Versus Weekly 5:2 Intermittent Fasting for Weight Loss and Metabolic Health: A Randomized Controlled Trial

Objective This study compared the effects of 16:8 and 5:2 intermittent fasting on body weight, metabolic outcomes, and temporal response patterns in adults with overweight or obesity. Methods In this open‐label randomized trial, 68 women with overweight or obesity were assigned to either a 16:8 regimen or a 5:2 regimen using a fasting‐mimicking diet on fasting days for 4 weeks. Primary outcomes were changes in body weight and body composition; secondary outcomes included waist circumference, blood pressure, dietary intake, and glycemic metrics. Results Across both groups, body weight decreased by 2.7 kg (95% CI −2.9 to −2.4), fat mass by 1.7 kg (−1.9 to −1.5), and muscle mass by 0.6 kg (−0.7 to −0.4). Weight and fat mass reductions were greater over time in the 5:2 group than in the 16:8 group, whereas muscle mass changes were similar. Waist circumference and blood pressure decreased significantly, with no between‐group differences. Both regimens reduced eating window duration, energy intake, mean and peak glucose levels, and time spent in hyperglycemia. Conclusions Both regimens improved body weight and metabolic outcomes over 4 weeks. Despite similar overall effectiveness, the regimens exhibited distinct temporal response patterns, suggesting that temporal dynamics may inform individualized intermittent fasting strategies. Trial Registration Clinical Research Information Service ( cris.nih.go.kr ) identifier: KCT0010806