Intermittent fasting for adults with overweight or obesity.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 41692034 · doi:10.1002/14651858.CD015610.pub2
What was done
A Cochrane systematic review and meta-analysis evaluated randomized controlled trials and cluster-RCTs comparing intermittent fasting (time-restricted feeding, periodic fasting, alternate-day fasting, and modified alternate-day fasting) with regular dietary advice, no intervention, or waiting list control in adults with overweight or obesity. Studies required a minimum intervention duration of four weeks and at least six months of follow-up. Primary outcomes included weight loss, quality of life, participant satisfaction, diabetes status, and adverse events. Risk of bias was assessed using RoB 2, and evidence certainty was graded using GRADE.
What was found
The review included 22 studies with 1,995 participants. Compared with regular dietary advice, intermittent fasting resulted in little to no difference in percentage weight loss from baseline (MD -0.33%, 95% CI -0.92 to 0.26; 21 studies, 1,430 participants; low-certainty evidence), achieving a 5% weight reduction (RR 0.98, 95% CI 0.82 to 1.18; 4 studies, 472 participants; very low-certainty evidence), quality of life (SMD 0.11, 95% CI -0.27 to 0.49; 3 studies, 106 participants; low-certainty evidence), or adverse events (RR 1.45, 95% CI 0.64 to 3.28; 7 studies, 619 participants; very low-certainty evidence). Compared with no intervention or waiting list, intermittent fasting showed a difference in percentage weight loss (MD -3.42%, 95% CI -4.95 to -1.90; 6 studies, 427 participants; moderate-certainty evidence), but effects on quality of life (MD 3.49, 95% CI -49.35 to 56.33; 1 study, 60 participants) and adverse events (RR 1.84, 95% CI 0.88 to 3.85; 2 studies, 189 participants) were very uncertain. No included studies reported participant satisfaction, diabetes status, or overall comorbidity measures.
Why it matters
Intermittent fasting offers equivalent short-term weight loss and quality of life outcomes compared to standard dietary advice, indicating that dietary choice can be tailored to individual patient preference and adherence feasibility rather than presumed superiority.
Limits
Evidence certainty was downgraded across most outcomes to low or very low due to risk of bias, inconsistency, and imprecision. All studies assessed outcomes only up to 12 months, leaving long-term efficacy and safety beyond one year unknown. Diabetes status, comorbidity measures, and participant satisfaction were not reported in any study.
Cited by
- contradicts Intermittent fasting can achieve a similar 5% to 10% body weight loss as the lowest dose of GLP-1 drugs like Ozempic.