Intermittent fasting may offer little extra weight-loss benefit, large review finds
Intermittent fasting — which includes regimens such as the 5: 2 plan or daily time-restricted eating — may not help people who are overweight or obese lose more weight than traditional dieting advice or no intervention, a major review of existing trials concludes. The analysis, which pooled data from 22 studies and nearly 2, 000 adults, also found little clear impact on quality of life over follow-up periods up to 12 months.
What the review found
Researchers examined short-term trials that compared intermittent fasting with either standard dietary guidance (for example, calorie reduction and healthier food choices) or with no active advice. Across the studies, intermittent fasting produced little to no additional weight loss when compared with conventional dieting approaches. The same lack of clear benefit held when intermittent fasting was compared with groups receiving no immediate advice.
Different fasting methods were included in the evidence base: daily time-restricted eating — often limiting intake to about an eight-hour window — and approaches that alternate days of restricted intake with days of normal eating. Despite the popularity of these methods online, the review's lead author warned that the evidence does not support the level of enthusiasm seen on social media. At the same time, the research team acknowledged that intermittent fasting may still be a reasonable option for some individuals.
Limits, uncertainties and other health effects
Confidence in the core finding — that intermittent fasting offers little extra weight-loss benefit in the short term — was rated as moderate. The review team noted several important caveats: many individual trials were small, follow-up was generally limited to 12 months or less, and study designs varied in robustness. These limitations make it difficult to draw firm conclusions about the full effects of fasting strategies.
Beyond weight and general well-being, the reviewers suggested intermittent fasting could influence other aspects of health through favorable changes to physiological markers. However, the evidence for effects on conditions such as type 2 diabetes and other underlying illnesses remains limited and inconsistent. The review also highlighted gaps in subgroup analysis: more data are needed on how fasting affects people of different sexes, body mass index categories and cultural or regional backgrounds.
The trials included in the analysis were conducted across several regions, reflecting some geographic diversity, yet the authors stressed that differences in study methods and participant characteristics hinder direct comparisons. They called for larger, longer and more rigorous trials to clarify whether certain fasting patterns might benefit particular patient groups or lead to meaningful improvements in metabolic health.
Practical takeaways for people considering fasting
For clinicians and people thinking about intermittent fasting, the message is pragmatic: fasting can be one tool among many, but it should not be assumed to be superior to traditional calorie-reduction or healthier-eating strategies for weight loss. Health professionals are advised to take a case-by-case approach when discussing weight-management options, weighing an individual's preferences, lifestyle, medical history and potential benefits beyond weight.
Ultimately, the review tempers the strong online claims that fasting is a broadly superior shortcut to weight loss. Those interested in trying intermittent fasting may find it suits their routine or helps them reduce calories, but current evidence does not show a consistent advantage over established dietary advice. More high-quality research is required to resolve outstanding questions about long-term outcomes and effects on specific health conditions.
