Alternate Day Fasting Versus Calorie Restriction for Weight Loss and Cardio-Protection

Background: Alternate-day modified fasting (ADF) has been shown to be effective for reducing body weight when tested for a short duration (8-12 weeks). However, no trial to date has examined adherence to ADF for longer periods, or compared ADF to daily calorie restriction (CR) for weight loss and improvement in cardiometabolic parameters. Objective: Accordingly, this study compared the effects of ADF versus CR on dietary adherence, weight loss, and cardiometabolic disease risk factors. Design: In a controlled feeding trial, overweight and obese participants (n = 102) were randomized to 1 of 3 groups: 1) ADF (24-h feast day = 125% of needs, alternated with 24-h fast day = 25% of needs); 2) CR (75% of needs every day); or 3) control (100% of needs every day). In this way, the prescribed average daily energy restriction (25%) was the same for both intervention groups. The intervention period was 6 months, and consisted of a 3-month controlled feeding period followed by a 3-month self-selected feeding period. Dietary adherence, body weight, body composition, and cardiometabolic parameters were measured at month 0, 3, and 6. Results: Actual energy restriction (ADF: 21 ± 4%; CR: 24 ± 4%, P = 0.89) was similar between the intervention groups and greater when compared to the control group (8 ± 5%, P = 0.03). Weight loss (ADF: -6.9 ± 0.8 kg; CR: -7.6 ± 1.0 kg, P = 0.79) and total fat mass reduction (ADF: -4.5 ± 0.6 kg; CR: -5.6 ± 0.7 kg, P = 0.33) were also similar between groups and greater than the respective reductions in the control group (-0.7 ± 0.5 kg, P < 0.001; -0.6 ± 0.3 kg, P < 0.001). ADF demonstrated within-group reductions in total cholesterol, systolic blood pressure, heart rate, fasting insulin, and insulin resistance by month 6. CR experienced decreases in total cholesterol, LDL cholesterol, systolic blood pressure, and fasting insulin, post-treatment. No differences were noted between intervention groups or versus control for any of these vascular endpoints (P > 0.05 for all comparisons). Conclusion: Dietary adherence and weight loss are similar between ADF and CR; however neither intervention alters other measured cardiometabolic parameters versus controls.