Comparison of Different Intermittent Fasting Patterns or Different Extents of Calorie Restriction for Weight Loss and Metabolic Improvement in Adults: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials.

Context: Continuous energy restriction (CER) and intermittent fasting (IF) are both prevalent diet regimens recommended for weight loss and metabolic improvement.

Objective: The objective of this study was to evaluate the efficacy of CER and IF on weight loss and metabolic improvement in adults with overweight, obesity, or metabolic abnormalities.

Data sources: PubMed, Embase, and the Cochrane Library (CENTRAL) were searched for randomized controlled trials of 3 degrees of CER diet regimens and 4 categories of IF diet regimens, from inception of the databases to December 2022.

Data extraction: Two reviewers independently extracted demographic information, the intervention duration, details of the dietary interventions, and data on the outcomes of interest.

Data analysis: Bayesian random-effect network meta-analyses were used to pool the results and the Grading of Recommendations, Assessment, Development, and Evaluation framework was used to assess the certainty of the evidence and to present the findings.

Results: The study included 167 eligible trials with a total enrollment of 11 998 participants. Most IF diet regimens induced significant weight loss that was comparable with that induced by CER diet regimens with a similar absolute energy restriction, based on low- to high-certainty evidence. Severe CER proved to be the most effective regimen for obtaining weight loss, based on moderate-certainty evidence (mean difference of weight change 11.50 kg [95% CI 10.07 to 12.93]), followed by alternate-day fasting, based on high-certainty evidence (mean difference of weight change (5.07 kg [95% CI 3.44 to 6.72]) and moderate CER, based on moderate-certainty evidence (6.09 kg [95% CI 5.26 to 6.93]), when the regimens being compared were consistent in their absolute energy restriction extent. Similar results were noticed for body measurements, blood pressure, blood lipids, and glycemic profiles. In the subgroup analysis, the weight-loss effects of the IF but not the CER diet regimens experienced rebound after 12 weeks.

Conclusion: In adults with overweight, obesity, or metabolic abnormalities, effectiveness in weight loss mainly depends on the extent of the energy restriction, regardless of the mealtime patterns.

Systematic review registration: PROSPERO registration no. CRD42022379621.