A comprehensive new systematic review suggests that intermittent fasting may not offer meaningful advantages over standard dietary advice for weight loss in adults with overweight or obesity.
The updated review analysed data from 22 randomised controlled trials involving nearly 2,000 participants across multiple countries. Intermittent fasting approaches included time-restricted feeding, alternate-day fasting, periodic fasting, and modified alternate-day fasting, with interventions lasting at least four weeks and follow-up extending to six months or more.
Little Difference Compared With Standard Advice
When compared with regular dietary advice, intermittent fasting resulted in little to no difference in percentage weight loss from baseline. The pooled data showed only a minimal mean difference, and the certainty of evidence was rated as low due to risk of bias and methodological limitations across studies.
Similarly, intermittent fasting appeared to make little difference in achieving a clinically significant 5% reduction in body weight. Effects on quality of life were also negligible, and evidence regarding adverse events was uncertain.
Compared With No Intervention
When compared with no intervention or a waiting list, intermittent fasting likely produced only small reductions in weight. However, the review concluded that these differences were not clinically meaningful. Evidence on quality of life and adverse events in this comparison was highly uncertain.
Notably, none of the included trials reported outcomes such as participant satisfaction, diabetes status, or broader comorbidity measures, leaving important clinical questions unanswered.
Short-Term Evidence Only
Most of the included studies assessed outcomes within 12 months of randomisation, limiting conclusions about long-term sustainability. Given that maintaining weight loss over time remains a central challenge in obesity management, the lack of extended follow-up represents a key evidence gap.
The review authors emphasise that intermittent fasting and conventional calorie-restricted approaches appear to yield similar short-term results. As such, decisions about adopting intermittent fasting may depend more on individual preference, practicality, and long-term adherence than on clear superiority in outcomes.
Implications for Practice
Intermittent fasting has gained widespread popularity through media coverage and online platforms, often promoted as a metabolically distinct strategy for weight loss. However, this synthesis of trial data suggests that its effects are broadly comparable to other structured dietary approaches.
Clinicians and patients are encouraged to consider personal readiness, lifestyle compatibility, and sustainability when selecting a dietary strategy. Future research will need to explore longer-term outcomes, effects in diverse populations, and impacts on comorbid conditions such as diabetes.
For now, the evidence indicates that intermittent fasting is neither clearly superior nor markedly harmful compared with other established dietary approaches for weight management.
