A new review of studies suggests that intermittent fasting offers no significant advantage over traditional dieting or no intervention for weight loss among overweight or obese adults. Researchers analyzed data from 22 trials involving nearly 2,000 participants. While the approach remains popular, experts highlight limitations in the evidence.
Intermittent fasting, a dieting method that alternates between eating and fasting periods, has gained popularity as a strategy for shedding excess weight. Common forms include the 16:8 approach, where individuals fast for 16 hours and eat within an eight-hour window, and the 5:2 method, which involves normal eating five days a week and severe calorie restriction on the other two. The core premise is that time-restricted eating naturally lowers overall calorie consumption.
However, a systematic review published in the Cochrane Database of Systematic Reviews challenges its effectiveness. Led by Luis Garegnani at the Italian Hospital of Buenos Aires in Argentina, the analysis examined 22 randomized controlled trials with almost 2,000 adults aged 18 to 80 from regions including North America, Europe, China, Australia, and South America. All participants were overweight or had obesity.
The findings indicate no meaningful difference in weight loss when comparing intermittent fasting to standard dietary guidance. Against a control group making no changes, the diet also showed no superior results. "Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight," Garegnani stated in a press release.
Challenges in the data include inconsistencies across studies, complicating definitive conclusions. Even when results were stratified by gender or fasting type, benefits remained elusive. Satchidananda Panda at the Salk Institute for Biological Studies in California critiqued the review, pointing out that most trials failed to verify participant adherence. "If we don’t know whether participants actually followed the intervention, what, exactly, are we systematically reviewing?" he remarked. "It’s a bit like building a cathedral on quicksand and then performing a meta-analysis of the architecture."
The review concentrated solely on weight loss outcomes, leaving other potential health impacts—such as effects on heart disease risk, immunity, gut function, or liver health—unaddressed, as prior research offers mixed signals. Garegnani emphasized that while intermittent fasting might suit some people, it is no panacea. "Intermittent fasting is not a miracle solution," he said. "[It] may be a useful option for some individuals, but it shouldn’t distract from broader, population-level strategies to prevent and manage obesity."
