This meta-analysis [published by] The BMJ rigorously and comprehensively analyses the impact of different intermittent fasting strategies on body weight and cardiometabolic risk factors, comparing them with traditional calorie restriction [diets]. The authors do an excellent methodological job, combining direct and indirect data through a network of clinical trials, which allows more precise estimates to be extracted.

Particularly noteworthy is the clarity with which they state the limitations of the study (relatively short trial duration, high heterogeneity between strategies, low to moderate certainty of the evidence), which adds value and transparency to their conclusions. Although the weight loss benefits are modest, this study positions alternate-day fasting as a valid additional tool within a personalised dietary approach, without claiming to replace other strategies. In the clinic, it could be useful as long as it is tailored to the needs and characteristics of the patient.

The study is well executed, and results are presented in a balanced way reflecting the results of the analysis.  The press release is also well written and is in line with the evidence in the field, that any strategy reducing calorie intake results in a proportional weight loss, either at each meal (CER) or by skipping meals (intermittent fasting). The missing additional benefit on cardiovascular risk markers of any intermittent fasting schemes aligns with our study that indicated that much longer periods fasting would be needed to change those.  However, we’ve seen that even those reverse quickly to levels seem before the intervention. 

One point to stress might be the rather moderate level of weight loss achieved with any intervention and the missing long-term follow-up in terms of weight maintenance and reduction in the onset of major diseases. For example, all dietary regimens, including the different forms of intermittent fasting, are unlikely to be sustainable. A fact also indicated by the decline in adherence in most studies. 

In brief, eating less leads to weight loss, irrespective on how you do it. Aspects that are missed but would have been of interest, are any effects on muscle mass, which is a major concern for current pharmacological interventions on obesity.

This meta-analysis of mainly small trials helps to give a general sense of the benefits of intermittent fasting, even if some of the included trials were suboptimal.  Overall, the results do not surprise as there is nothing magical about intermittent fasting for weight loss beyond being another way for people to keep their total calorie intake lower than it would be otherwise – this helps people maintain a lower weight than they would normally.  Hence, it becomes another lifestyle option for weight management.  Whether it is sustainable over the longer term is worth to examine, whereas for those who need to lose much more weight, other options are now clearly available.