Interval fasting has not been shown to be highly effective
Interval fasting, which has been heavily promoted on social media in recent years as a quick way to lose weight, has no advantage over conventional diet recommendations.
This is the conclusion reached by the authors of a new review in the Cochrane Database of Systematic Reviews: in overweight and obese adults, they assessed that this approach does not lead to clinically significant weight loss compared to a standard diet - and in some comparisons the results are close to no intervention.
The research team analysed data from 22 randomised clinical trials involving 1995 participants from North America, Europe, China, Australia and South American countries. The studies examined different interval fasting regimens: fasting every other day, intermittent fasting and time-restricted eating. Most participants were followed for up to 12 months.
The main conclusion of the review is that there is no significant difference in weight loss when interval fasting is compared with traditional advice to reduce caloric intake.
The authors also note that data on side effects in the trials were recorded unevenly, so it is difficult to confidently assess risks and tolerability. In addition, the evidence base is still limited: there are few studies, many of them small and short-term.
Separately, it is emphasised that obesity is a chronic condition, and short-term observational studies do not answer what will happen years from now. Also, most of the participants in the studies were from affluent countries and predominantly white, so the results cannot be automatically transferred to all populations: the effect may vary according to age, gender, ethnicity, comorbidities and eating behaviour.