Intermittent Fasting No Better Than Traditional Diets for Weight Loss

Intermittent fasting does not help overweight people lose more weight than a standard daily calorie-reduced diet, a new global review has found. The study adds to growing evidence that popular “feast-and-famine” eating plans are not a miracle solution for obesity. 

The research, led by Dr Luis Garegnani from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre, looked at 22 randomised clinical trials involving 1995 overweight or obese adults. Trials were done in North America, Europe, China, Australia, and South America. He covered several fasting styles, such as fasting on certain days, alternating low-intake and normal-intake days, and eating only within a fixed window each day. 

Results showed that people on intermittent fasting lost roughly the same amount of body mass as those on traditional diets that simply cut calories every day. The difference was small: intermittent fasters lost about 3.4% more weight than control groups that did nothing, but this was not considered clinically meaningful. Experts say the main benefit of fasting is likely overall calorie reduction, not any special effect on metabolism.

Scientists also found no strong proof that intermittent fasting improves heart health, cholesterol, or blood pressure more than a standard diet. Keith Frayn, emeritus professor of human metabolism at the University of Oxford, said the data do not support claims that fasting has “special effects on metabolism beyond simple restriction of calories.” The review was published in the Cochrane Database of Systematic Reviews and has reignited debate about the best ways to manage weight.

Obesity rates have soared worldwide, with adult obesity doubling over three decades and childhood and adolescent rates rising even faster. New anti-obesity drugs can produce large weight loss, but they are costly and in short supply, and many people regain weight once treatment stops. This has pushed people toward simpler lifestyle changes, including fasting, even though evidence for long-term success remains weak. 

Researchers warn that current studies on intermittent fasting are often small, short-term, and poorly designed. Many trials enrolled mainly white participants from rich countries and did not measure satisfaction, diabetes status, or other health conditions. Some also failed to report how well people stuck to the fasting plans. The team called for larger and higher-quality trials in low- and middle-income countries. 

Some experts outside the study say intermittent fasting can still work for motivated individuals who choose it themselves. Paul Garner, a global health evidence expert at the Liverpool School of Tropical Medicine, noted that none of the trials studied people who freely decided to fast, so real-world motivation may differ. Adam Collins, a nutrition researcher at the University of Surrey, added that control groups often lose simply because they know they are being watched, a phenomenon known as the Hawthorne effect. 

Intermittent fasting may suit people who prefer structured eating windows over counting calories every day. But for most, the key to weight loss remains a sustained calorie deficit, regular physical activity, and patience to pick an eating pattern they can stick to for years, not just weeks.