Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.
Level 1 - systematic review of randomized trials
Systematic review and network meta-analysis of randomized clinical trials
PubMed 40533200 · doi:10.1136/bmj-2024-082007
What was done
Systematic review and frequentist network meta-analysis of randomized clinical trials searching Medline, Embase, and CENTRAL up to November 14, 2024. The review evaluated intermittent fasting protocols (alternate day fasting, time-restricted eating, and whole day fasting) compared with continuous energy restriction and ad-libitum diets in adults. The primary outcome was body weight, with secondary outcomes including anthropometry, glucose metabolism, lipid profiles, blood pressure, C-reactive protein, and liver disease markers. Evidence certainty was assessed using GRADE.
What was found
Across 99 RCTs (6,582 adults; 720 healthy, 5,862 with existing health conditions), all intermittent fasting and continuous energy restriction regimens reduced body weight compared with ad-libitum diets. Alternate day fasting was the only fasting strategy to produce greater weight reduction than continuous energy restriction (mean difference -1.29 kg, 95% CI -1.99 to -0.59; moderate certainty). Alternate day fasting also showed modest weight reductions compared with time-restricted eating (-1.69 kg, 95% CI -2.49 to -0.88) and whole day fasting (-1.05 kg, 95% CI -1.90 to -0.19). In trials with follow-up >= 24 weeks (n=17), active diet strategies only outperformed ad-libitum diets, with no significant differences between active diets. No differences were observed across diets for HbA1c and HDL.
Why it matters
This large synthesis confirms that intermittent fasting regimens provide comparable weight loss and cardiometabolic benefits to continuous calorie restriction, indicating that dietary adherence and preference can guide strategy selection rather than presumed metabolic superiority.
Limits
Most included trials were short-term (<24 weeks, n=76), and advantages of specific fasting types over continuous restriction were not sustained in longer-term trials. The abstract omits numerical estimates for several secondary outcomes including blood pressure, C-reactive protein, and liver markers.
Cited by
- contradicts There are no clinical trials in humans showing a clear lifespan or health benefit from fasting.