Intermittent fasting diets are ‘nothing magical’, research shows

Researchers from the University of Chicago said the paper, published in Annals of Internal Medicine, had “important clinical implications”. They said that time-restricted eating “is no more effective than other diet interventions for weight reduction” but that it can offer an easy way to help people eat less.

Prof Keith Frayn, the emeritus professor of human metabolism at the University of Oxford, said: “The finding that time-restricted eating results in no more weight loss than expected for the reduction in calories taken in should surprise nobody. If time-restricted eating were to have an effect on body weight beyond calorie restriction, that would imply that it ‘ramps up metabolism’, for which there is not a shred of evidence in humans.”

“That is not to say that time-restricted eating is not a good way to lose weight: it clearly helps some people to reduce their calorie intake. But this study shows that there is no ‘magic’ effect beyond that,” he said.

He said the size of the study meant it would need to be repeated in larger numbers of people to establish its findings for certain.

Prof Naveed Sattar, the professor of cardiometabolic medicine at the University of Glasgow, said: “This relatively small trial seems well done and tells us what we expected. In the end, we cannot reinvent physics. Lesser calories in mean lower weight over time. If time-restricted eating helps some people eat less calories than they would otherwise, great.”

Prof Nita Forouhi, a professor from the University of Cambridge’s MRC epidemiology unit said the study had some weaknesses, including that the group who ate at normal times started at a substantially higher weight and were more active than those doing intermittent fasting.

However, she said: “As the authors and the editorial state, time-restricted eating can be a useful strategy because it can help to lose weight without the need for counting calories which is not an easy exercise.”