Researchers found that for adults who are overweight or obese, eating on some days and fasting on others appears to make little or no difference to weight loss or overall quality of life. While the approach may still lead to positive changes in how the body functions, the team says stronger evidence is needed to confirm broader health benefits.
Intermittent fasting comes in different forms, including the 5:2 diet, limiting food intake to a short daily window (often around eight hours), fasting on specific days of the week, or alternating between normal eating days and days of very low intake.
The review analysed 22 previous studies involving nearly 2,000 adults, looking at whether short-term intermittent fasting — up to 12 months — was more effective than standard dietary advice or no guidance at all. The findings showed little to no difference when intermittent fasting was compared with traditional approaches such as reducing calories and eating a healthier diet. The results were similar when compared with people who received no advice or were waiting for weight-loss support, although the impact on quality of life was less clear.
The researchers said they were “moderately confident” in these findings but noted limitations. Many of the studies included small sample sizes and less robust research methods, making it harder to draw firm conclusions.
Luis Garegnani, the lead author from the Universidad Hospital Italiano de Buenos Aires, said the popularity of fasting online does not match the scientific evidence. He noted that while intermittent fasting may work for some individuals, the enthusiasm seen on social media is not currently supported by strong data.
Senior review author Eva Madrid added that weight-loss advice should be tailored to the individual, as responses can vary widely from person to person.
The review, published in the Cochrane Database of Systematic Reviews, also called for more research into how intermittent fasting affects conditions such as type 2 diabetes, how satisfied people feel following these diets, and whether the effects differ by sex, body mass index, or location. The studies analysed were carried out across Europe, North America, China, Australia, and South America.
Commenting on the findings, Dr Baptiste Leurent from University College London said the evidence clearly suggests intermittent fasting offers little benefit, highlighting a gap between public belief and scientific research.
Prof Keith Frayn, emeritus professor at the University of Oxford, said intermittent fasting has often been promoted as having special metabolic effects, but those claims appear to have limited relevance. He stressed that there are no shortcuts to weight loss beyond consistently reducing calorie intake.
While many people find intermittent fasting helpful for maintaining their weight, this aspect was not examined in the review. The report also comes amid growing use of weight-loss injections in the UK, with around 1.6 million adults estimated to be using drugs such as Wegovy and Mounjaro, mostly through private prescriptions. Recent research suggests people who stop using these injections may regain weight much faster than those who stop conventional dieting and exercise.
Overall, the review raises questions about the widespread perception of intermittent fasting as a powerful weight-loss tool, suggesting its benefits may be more limited than often claimed.
