Does Intermittent Fasting Work? Cochrane Finally Has Answers | 2026

Intermittent fasting has been one of the most hyped dietary interventions of the past decade — promoted on podcasts, social media, and wellness blogs as a metabolic cure-all. But what does the highest-quality evidence actually say? In this episode, Gregory Castelli, PharmD, FCCP, BCPS, BC-ADM, CDCES, breaks down a 2026 Cochrane systematic review and meta-analysis that analyzed 22 randomized controlled trials and 1,995 participants to answer that question once and for all.Against regular dietary advice, intermittent fasting produced a mean weight loss difference of just −0.33% (95% CI −0.92 to +0.26) — a result that earned low-certainty evidence from Cochrane. Against no intervention, IF did produce more weight loss (MD −3.42%), but fell short of the 5% threshold considered clinically meaningful. No study in the review reported diabetes outcomes, patient satisfaction, or mortality. The Castelli Coefficient for this review: 6 out of 10. The methodology was rigorous — the evidence base wasn't.• 22 RCTs, 1,995 participants — outpatient settings across North America, Australia, Asia, and Europe (2016–2024)• vs. Regular Dietary Advice: MD −0.33% weight loss (95% CI −0.92 to +0.26); RR 0.98 for ≥5% reduction — LOW certainty• vs. No Intervention: MD −3.42% weight loss (95% CI −4.95 to −1.90) — MODERATE certainty, but below 5% MCID threshold• Quality of life: SMD +0.11 vs. dietary advice (95% CI −0.27 to +0.49) — LOW certainty; no meaningful difference• Adverse events: RR 1.45 vs. dietary advice (I² = 78%) — VERY LOW certainty• Zero studies reported participant satisfaction, diabetes status, or overall comorbidity outcomesGaregnani LI, Oltra G, Ivaldi D, Burgos MA, Andrenacci PJ, Rico S, Boyd M, Radler D, Escobar Liquitay CM, Madrid E. Intermittent fasting for adults with overweight or obesity. Cochrane Database of Systematic Reviews 2026, Issue 2. Art. No.: CD015610. DOI: 10.1002/14651858.CD015610.pub2Read the full review:https://doi.org/10.1002/14651858.CD015610.pub2Gregory Castelli, PharmD, FCCP, BCPS, BC-ADM, CDCES is a clinical pharmacist and Associate Professor with an extensive background in evidence-based medicine teaching at the residency and graduate level.Dispense As Written (DAW) — "Evidence-Based Medicine Without the Fluff." Every episode breaks down clinical trials, teaches EBM methodology, and gives you a defensible, patient-oriented bottom line. No pharmaceutical sponsorships. No substitutions for profit.Produced by Dispense As Written, LLCYouTube: @dispenseaswrittenInstagram / TikTok: @gregcastellipharmdX / Twitter: @gregcastellirxEmail: [email protected] content in this video is produced by Dispense As Written, LLC and is intended for educational purposes only. It does not constitute medical advice and should not be used as a substitute for the advice of a qualified healthcare professional. The views expressed are those of the host and do not represent those of any institution or employer.#DispenseAsWritten#EvidenceBasedMedicine #MedEd #primarycare #familymedicine #internalmedicine