A collaborative study conducted by CIESAL and the Hospital Italiano de Buenos Aires has attracted worldwide attention.
7/03/2026This week, a new report from the Cochrane Library — regarded as one of the world’s leading authorities on medicine — has shaken up the debate on intermittent fasting. The systematic review, published in February 2026, concludes that intermittent fasting does not result in greater weight loss or an improved quality of life for overweight or obese adults compared to traditional low-calorie diets, at least during the first year.
This study has attracted significant attention in the international media. Dr Eva Madrid Aris, the director of the Interdisciplinary Health Centre at the Universidad de Valparaíso and an academic researcher, was involved as a senior researcher, alongside Dr Luis Garegnani from the University Institute of the Hospital Italiano de Buenos Aires. Dr Garegnani led the research as part of his doctoral thesis, which is being supervised by Dr Madrid.
Among its main conclusions, the article suggests that intermittent fasting – abstaining from food for a set period – can help with temporary weight loss but is no more effective than lifestyle changes associated with a traditional calorie-restricted diet. Furthermore, in the medium term, it can lead to significant weight regain, with people not only putting back on the weight they lost but in fact gaining more.
The article helps to debunk the current trend in alternative media, particularly on social media, of presenting planned suspension of food intake as a miracle weight-loss cure. It also warns against adopting diets that appear innovative but fail to address the core challenge. Without a radical lifestyle change involving increased physical activity, a less sedentary lifestyle, consuming nutritious foods, balancing the proportions of proteins, fats and carbohydrates, and not exceeding the daily calorie intake, it is almost impossible to maintain weight loss. The person will almost inevitably regain the lost weight, which can lead to frustration and have an impact on physical and mental health.
The article has been cited and highlighted for its impact on the debate regarding weight-loss strategies that has long dominated social media by Spanish media outlets such as El País and La Vanguardia, English-language publications such as The New York Times and The Guardian, French newspapers such as Le Figaro and Le Monde, the Italian Corriere della Sera, the Australian Broadcasting Corporation, major news agencies such as EFE, TV and radio stations from all over the world, and a variety of specialist media outlets. In a field where self-proclaimed experts with dubious academic credentials often emerge to promote fasting as a magic cure, articles such as Madrid and Garegnani’s help to clarify the picture somewhat.
A preliminary tally suggests that the article, published in the Cochrane Library (UK) and already translated into several languages, and its conclusions regarding the supposed effectiveness of intermittent fasting, have been reported on by more than 80 media outlets worldwide. Given this level of interest, the authors are pleased to contribute hard evidence — based on an extensive systematic review of the specialist literature on the subject — towards a more objective and realistic view of the most reliable methods and strategies for achieving a stable reduction in excess weight and morbidity over time without endangering health.
The researchers aim to provide users, specialists, and public policymakers with robust decision-making tools in this area, helping to improve people’s quality of life at a time when a sedentary lifestyle and being overweight have become one of the most obvious threats to public health.
However, the vast majority of studies reviewed for this research were conducted in high-income countries with predominantly white populations. Meanwhile, the global prevalence of excess weight and obesity has tripled since 1975, now affecting middle- and low-income countries to the same extent. ‘Future research will need to take this into account to determine whether the effect of a treatment such as intermittent fasting varies according to socioeconomic context,’ the authors note.
More specifically, Chile features in a recent WHO ranking as one of the countries with the highest obesity rates in the world. This poses a serious challenge to the public health system, given the serious health complications that can be associated with being overweight. Decision-makers in this field must therefore be able to distinguish between strategies that have been reasonably validated by scientific evidence and specialist research, and those proposed by ‘influencers’ who offer solutions to the problem of excess weight that lack an empirical basis.
Details of the study: from partial fasting to warrior fasting
The study analyses 22 clinical trials involving 1,995 patients, comparing different forms of intermittent fasting. The most popular involves time-restricted eating, which entails, for example, eating for 8 hours a day and fasting for 16; this is the 16-8 method. There is also the 12-12 method (which is the most common among beginners), and what social media refers to as ‘the warrior’ method: fasting for 20 hours and eating only during a 4-hour window. The authors also analysed alternate-day fasting, the so-called 5-2 method, i.e. eating for five days and fasting for two. The authors compared the results of these diets with those of traditional calorie-restricted diets, i.e. reducing daily calorie intake, in overweight or obese adults. The main finding was that there were no clinically significant differences in weight loss between the two approaches.
“The main message is that intermittent fasting should not be promoted as a superior or ‘magic’ dietary solution. The evidence suggests that it works in much the same way as other calorie-restriction strategies,” the authors note. They emphasise that weight loss is influenced by many factors, such as behaviour, environment, and long-term adherence to the diet, rather than by a specific eating pattern alone.
Garegnani and Madrid acknowledge that dietary studies are particularly challenging to design, because they depend on people’s behaviour and daily routines, which are very difficult to standardise. They note that “researchers tend to simplify their approach by focusing on laboratory findings rather than on outcomes critical to clinical decision-making, such as clinically relevant weight loss, quality of life or adverse events associated with each intervention.”
The Cochrane review is timely, as intermittent fasting has become a cultural phenomenon, with thousands of books sold, mobile apps, and a constant presence on social media. Given that two-thirds of the WHO’s health recommendations are based on at least one Cochrane review, the future impact of these findings is significant (link).
In short, while the new study does not rule out intermittent fasting, it downgrades its status from a dietary revolution to a reasonable alternative for those who can tolerate and maintain it, placing it on a par with other, more traditional dietary approaches. For the time being, the weight of the evidence points to an unspectacular yet compelling conclusion: it is not the clock, but rather a combination of habits, that tips the scales.