Large review finds intermittent fasting may make little difference to weight loss
A large review of clinical trials suggests popular intermittent fasting regimens produce little to no additional weight loss or quality-of-life benefit for adults who are overweight or obese when compared with standard diet advice or no guidance. Researchers caution that the current evidence is limited and that individual responses vary, meaning clinicians should keep an open, case-by-case approach.
What the review examined
Researchers pooled results from 22 trials that enrolled nearly 2, 000 adults and evaluated short-term intermittent fasting interventions lasting up to 12 months. The trials spanned multiple continents and tested different fasting strategies, including time-restricted feeding—where eating is limited to a daily window of roughly eight hours—and intermittent calorie restriction on select days of the week.
The review compared intermittent fasting with standard dietary counseling, such as advice to reduce calories and improve diet quality, and with groups that received no immediate weight-loss guidance. Across these comparisons, the review team judged the overall effect on body weight and self-reported quality of life to be minimal.
Interpretation and practical implications
Lead review authors voiced concern about the gap between online enthusiasm for fasting and the modest benefits seen in controlled trials. One author noted that intermittent fasting "may be a reasonable option for some people, but the current evidence doesn't justify the enthusiasm we see on social media. " At the same time, senior authors emphasized that clinicians should tailor advice to the individual—some patients may find fasting easier to follow, and behavioral fit matters for long-term adherence.
The review also signalled potential non-weight outcomes where fasting might produce measurable changes in physiology, but evidence on clinical benefits remains sparse. Researchers urged that intermittent fasting not be presented as a universally superior strategy; instead, it should be offered alongside other evidence-based approaches to eating and weight management, with attention to personal preference and medical background.
Limitations and calls for better evidence
The review team rated confidence in the weight-loss and quality-of-life findings as moderate, but highlighted several limits that weaken conclusions about other health effects. Many included trials were small and used methods that the reviewers judged to be less robust, increasing the risk that true effects were missed or misestimated. Trials varied widely in fasting protocol, duration, participant characteristics, and geographic setting, making it difficult to draw firm conclusions about who may benefit most.
Researchers called for larger, higher-quality trials that directly compare different fasting patterns, explore sex-specific and BMI-specific responses, and assess impacts on cardiometabolic markers and conditions such as type 2 diabetes. They also recommended longer follow-up to see whether initial effects persist or change over time.
For now, the practical takeaway for clinicians and people trying to lose weight is straightforward: intermittent fasting can be one tool among many, but it is not a guaranteed shortcut. Behavior, sustainability, and individual medical needs remain the key determinants of whether a dietary plan will succeed.
