4:3 Intermittent Fasting Outperforms Daily Caloric Restriction for Weight Loss

A U.S. randomized clinical trial found that 4:3 intermittent fasting (IMF) led to slightly greater weight loss than daily caloric restriction (DCR) in adults with overweight or obesity. The study included 165 participants (mean age: 42; mean BMI: 34.1 kg/m²; 73.9% female), randomly assigned to either 4:3 IMF (n=84) or DCR (n=81) between January 2018 and April 2021, 125 completed the trial. All participants received a high-intensity behavioral weight loss program, including group support and a recommendation to engage in 300 minutes of moderate-intensity physical activity per week. The 4:3 IMF group fasted 3 nonconsecutive days per week, consuming only 20% of their energy needs (~400-600 kcal/day for women, 500-700 kcal/day for men) and ate freely on the other 4 days. The DCR group reduced daily intake by 34% to match the weekly energy deficit of the IMF group. At 12 months, the 4:3 IMF group lost 2.89 kg more on average than the DCR group in an intention-to-treat analysis. The 4:3 IMF might be an optimal fasting approach, with better adherence potentially driving the greater weight loss. https://www.acpjournals.org/