A major review of scientific evidence has found that intermittent fasting is no more effective for weight loss than traditional diets. Researchers analysed data from 22 global studies involving nearly 2,000 adults and concluded that fasting regimes such as the 5:2 diet produce results similar to conventional dietary approaches.
The review, published by Cochrane, found that people who are overweight or living with obesity lost only about 3% of their body weight through intermittent fasting, below the 5% threshold that doctors consider clinically meaningful. This was barely better than not dieting at all. The studies were all short-term, lasting up to 12 months.
Lead author Dr Luis Garegnani said: 'Intermittent fasting is not a miracle solution, but it can be one option among several for weight management. It doesn’t appear clearly better, but it’s not worse either.' The researchers found no strong evidence that fasting improved quality of life more than other diets.
The findings challenge the surge in popularity of intermittent fasting, which has been promoted for weight loss and other health benefits. However, experts noted that many studies are short-term and of poor quality, making it difficult to draw firm conclusions. None of the 22 studies asked participants how satisfied they were with the fasting regimen.
Dr Zhila Semnani-Azad from the National University of Singapore said the benefits may be affected by timing due to circadian rhythms, and that animal studies suggest fasting could improve insulin sensitivity and reduce inflammation. However, she noted the lack of a universal definition of intermittent fasting complicates research.
Professor Maik Pietzner from the Berlin Institute of Health said the small weight loss was surprising but consistent with evidence that people are less active when fasting. He added that his own work shows short fasts have little effect, and that significant changes only occur after three days without food.
