Intermittent Fasting is Popular, but New Evidence Questions its Edge for Weight Loss

Intermittent fasting has become a common approach to weight loss, promoted on social media and in popular diet books. Many people adopt it hoping it will deliver better results than traditional calorie‑cutting diets. A new international review suggests those expectations may be misplaced.

Intermittent fasting is not a single diet but a set of eating patterns that alternate periods of eating with periods of very low or no calorie intake. The most widely used approaches include alternate‑day fasting, the 5:2 diet, and time‑restricted eating, often described as the 16:8 method.

The appeal is simple. Rather than counting calories every day, people restrict when they eat or limit intake on certain days. Previous studies have suggested fasting can help people eat less overall, which may lead to weight loss.

But results have varied widely, and experts have disagreed about whether fasting offers any clear advantage over standard dietary advice.

A new review from the Cochrane Collaboration, known for its rigorous and independent assessments of medical evidence, has examined this question in detail. Researchers analysed 22 randomised controlled trials published between 2016 and 2024, involving 1,995 adults who were classified as overweight or obese.

The studies followed participants for up to 12 months and compared intermittent fasting with conventional dietary advice, such as calorie restriction or healthier food choices, as well as with no intervention at all.

The main finding was clear. On average, intermittent fasting led to similar weight loss as traditional dietary advice. Across the studies, people in both groups lost anywhere from about 10 per cent of their starting weight to a small amount of weight gain.

When fasting was compared with doing nothing, the difference was also small. People assigned to intermittent fasting lost around 5 per cent of their body weight, while those in control groups lost about 2 per cent. A difference of this size is generally not considered clinically meaningful. This finding is supported by other previous review.