A network meta-analysis compares treatments that were never tested against each other, by chaining them through the comparisons that were actually run. If A beat B in some trials and B beat C in others, the network estimates A against C. The strength is that it uses all the evidence at once. The weakness is that the answer depends on whether the trials being chained together are similar enough to chain.
Drawn from standard methodology, not from this paper.
Continuous energy restriction and intermittent fasting are both recommended for weight loss, and the authors set out to evaluate them against each other rather than each against a control. The design choice that matters is that they held the absolute size of the energy restriction constant, which turns the question from whether fasting works into whether the eating pattern adds anything on top of the deficit.
Drawn from the paper's stated objective.
One hundred and sixty seven eligible randomised trials, 11,998 participants, searched from database inception to December 2022. Bayesian random effects network meta-analysis, GRADE applied throughout, registered on PROSPERO.
Most fasting regimens induced significant weight loss that was comparable with the weight loss from ordinary calorie restriction at a similar absolute energy restriction. Certainty across those comparisons ran from low to high.
Severe continuous energy restriction was the most effective single regimen, at 11.50 kilograms, interval 10.07 to 12.93, on moderate certainty evidence.
Alternate day fasting came next at 5.07 kilograms, interval 3.44 to 6.72, and this one carries high certainty evidence. Moderate continuous energy restriction was 6.09 kilograms, interval 5.26 to 6.93, moderate certainty.
The same pattern held for body measurements, blood pressure, blood lipids and glycemic profiles.
In subgroup analysis the weight loss effects of the fasting regimens rebounded after twelve weeks. The continuous restriction regimens did not.
| Trials and participants | 167 trials, 11,998 participants |
| Severe continuous energy restriction, weight change | 11.50 kg, 95 percent credible interval 10.07 to 12.93, moderate certainty |
| Alternate day fasting, weight change | 5.07 kg, 95 percent credible interval 3.44 to 6.72, high certainty |
| Moderate continuous energy restriction, weight change | 6.09 kg, 95 percent credible interval 5.26 to 6.93, moderate certainty |
| Subgroup analysis after twelve weeks | fasting regimens rebounded, continuous restriction regimens did not |
| Search cutoff | database inception to December 2022 |
Proposed by the authors This is the explanation the authors offer in their discussion. This study did not test it.
The authors offer no physiological mechanism for fasting, because their result is that there is nothing left to explain. They rank the regimens by how much energy each removes, find that the ranking reproduces the weight loss ordering, and write the conclusion as a negative: effectiveness in weight loss mainly depends on the extent of the energy restriction, regardless of the mealtime patterns.
Drawn from the paper's stated conclusion.
The largest analysis in this field says the eating window is not the active ingredient. The size of the deficit is.
Adults with overweight, obesity or metabolic abnormalities, in randomised trials indexed up to December 2022.
A trial that holds the deficit constant and varies only the window, with food supplied, which is the next study in this issue.
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