Intermittent Fasting Shows No Greater Weight Loss Than Standard Advice

A recent review compared intermittent fasting with regular dietary advice or no intervention or waiting list among adults with overweight or obesity and reported that pooled results suggest intermittent fasting may make little to no difference in clinically meaningful weight loss.

The report situates the findings amid intermittent fasting’s recent popularity and online claims of rapid results, while emphasizing what the randomized trial record did and did not show. In plain terms, the overall comparison was intermittent fasting regimens versus regular dietary advice or no intervention or waiting list, and the reported conclusion was that fasting may make little to no difference in weight loss beyond those comparators, with certainty varying by comparison.

As described in the report, the evidence base included 22 randomized clinical trials enrolling about 1,995 adults across North America, Australia, China, Denmark, Germany, Norway, and Brazil. The trials evaluated several intermittent fasting regimens, including alternate-day fasting, periodic fasting, and time-restricted feeding. The review required a minimum follow-up of six months, and most of the included evidence focused on outcomes measured up to 12 months. Together, these trials formed the dataset pooled to compare fasting approaches with regular dietary advice and with no intervention or waiting list.

Across the included comparisons, the review reported that intermittent fasting may make little to no difference in weight loss compared with regular dietary advice and likely makes little to no difference compared with no intervention or waiting list. Multiple intermittent fasting patterns were represented (e.g., alternate-day fasting, periodic fasting, and time-restricted feeding), and in the summary results presented, effects were reported pooled across these approaches rather than broken out by specific regimen type. This framing aligns with the review’s overall conclusion of little to no difference in most outcomes assessed, with low to moderate certainty depending on the comparison.

The report also described constraints in the underlying trial literature, including small sample sizes, risk of bias, imprecision, and limited longer-term data beyond 12 months. It noted that further research is needed across different populations, including those in low- and middle-income countries and high-income countries, men and women separately, and different body mass index categories, and that additional outcomes such as participant satisfaction, diabetes status, and overall comorbidity measures were not reported in the included trials.

Given the current evidence, physicians and patients may need to evaluate willingness and readiness to implement intermittent fasting as a treatment strategy, based on individual practicality and sustainability. Overall, the limitations highlighted in the report were presented as reasons to be cautious about extrapolating the pooled findings beyond the populations and timeframes studied.

Key Takeaways:

• Pooled randomized-trial evidence did not show clinically meaningful additional weight loss with intermittent fasting compared with standard dietary advice or no intervention.
• Trials in the review covered multiple fasting patterns (alternate-day, periodic, and time-restricted), forming the basis for the review’s overall comparisons rather than identifying a single clearly superior regimen.
• The report highlighted inconsistent side-effect reporting, generally limited longer-term follow-up and small samples, and restricted demographic/geographic diversity as factors that constrain generalizability.