262 trials, 19 drugs, one ranking: the BMJ compares the whole obesity-drug field

Obesity pharmacotherapy has expanded so quickly that no single trial has directly compared most of the drugs now available or in late-stage development against each other. A network meta-analysis published this month in The BMJ pools 262 randomized trials to construct the most comprehensive comparative picture of the field to date [s1].

The design

Researchers systematically searched Medline, Embase, and the Cochrane Library through 12 November 2025, for randomized controlled trials of at least 12 weeks' duration comparing weight-loss drugs against lifestyle modification, placebo, or each other [s1]. The analysis used frequentist random-effects models and Bayesian dose-response models, graded evidence certainty using the GRADE framework, and assessed trial quality with the Cochrane Risk of Bias 2 tool [s1]. In total, 262 trials covering 99,791 participants and 19 drugs were included, with follow-up ranging from 12 to 172 weeks, across 24 different outcomes [s1].

What it found on weight loss

Compared with lifestyle modification alone, at one year, moderate-to-high certainty evidence showed substantial weight loss with tirzepatide (mean difference −14.9%, 95% CI −16.0% to −13.9%), cagrilintide-semaglutide, branded CagriSema (−14.8%, −16.9% to −12.7%), oral semaglutide (−10.9%, −12.7% to −9.1%), orforglipron (−9.9%, −12.4% to −7.5%), subcutaneous semaglutide (−9.8%, −10.6% to −9.1%), and phentermine-topiramate (−8.1%, −9.7% to −6.5%) [s1]. Emerging agents still in earlier-stage evidence — ecnoglutide, mazdutide, and retatrutide — may produce similar or even greater reductions (13.1–14.6%), though this evidence carries only very low to low certainty given the smaller and fewer trials behind it [s1].

What it found on discontinuation and side effects

Moderate-to-high certainty evidence found discontinuation due to adverse events was highest with orforglipron, naltrexone-bupropion, liraglutide, phentermine-topiramate, CagriSema, and oral semaglutide, with risk ratios ranging from 1.9 to 4.2 relative to comparators [s1]. Gastrointestinal adverse events were most increased with naltrexone-bupropion, oral semaglutide, orforglipron, and tirzepatide, with risk ratios from 3.1 to 4.2 [s1]. Fatigue risk rose notably too, particularly with naltrexone-bupropion (risk ratio 8.9, an absolute increase of 331 more cases per 1,000 people over a year), orforglipron (risk ratio 3.4, 100 more per 1,000), and CagriSema (risk ratio 3.2, 92 more per 1,000) [s1].

What it found on body composition, mortality, and organ-specific outcomes

Tirzepatide reduced fat mass the most among drugs studied — by 25.7% — but also reduced lean mass the most, by 8.3% [s1], a finding consistent with other recent research on GLP-1-class drugs and body composition trade-offs. On harder clinical endpoints, subcutaneous semaglutide stood alone: it was the only drug in the analysis associated with reduced all-cause mortality (risk ratio 0.81, 95% CI 0.72–0.93) and reduced myocardial infarction risk (0.72, 0.61–0.85) — though the study notes these estimates are "largely informed by cardiovascular outcome trials in high-risk populations," meaning they draw heavily on trials specifically designed and populated to detect cardiovascular benefit, which may not generalize evenly to lower-risk obesity populations [s1]. Both subcutaneous semaglutide (risk ratio 0.43, 95% CI 0.21–0.84) and tirzepatide (0.49, 0.27–0.88) reduced heart failure risk [s1]. No drug in the analysis convincingly reduced kidney failure risk, and none improved quality of life beyond established minimally important clinical difference thresholds, based on 43 trials covering 45,663 participants [s1].

Why the mortality finding matters more than the weight-loss rankings

The weight-loss percentages are the numbers most likely to make headlines, but the mortality and cardiovascular findings are arguably the more clinically consequential result buried in this analysis: despite tirzepatide and CagriSema producing larger weight-loss numbers than subcutaneous semaglutide, only subcutaneous semaglutide showed a reduction in all-cause mortality across the pooled evidence [s1]. That's a reminder that weight loss magnitude and hard clinical outcome benefit aren't the same thing, and that the drugs with the biggest numbers on the scale aren't automatically the ones with the strongest evidence for extending life or preventing heart attacks — at least based on the trials run and pooled so far.

What this doesn't establish

This network meta-analysis pools trials across many different populations, durations, and specific outcome definitions — indirect comparisons of this kind, even when methodologically rigorous, remain a step removed from head-to-head trials directly randomizing the same population to competing drugs. The certainty grading itself varies substantially across outcomes and drugs — the strongest weight-loss findings carry moderate-to-high certainty, while the promising numbers for emerging agents like retatrutide carry only low to very low certainty, a distinction that matters for how confidently each finding should be treated. The mortality and cardiovascular benefit findings specifically draw on trials in high-risk cardiovascular populations, which the paper itself flags as a source of potential generalizability limits to the broader population using these drugs primarily for weight management.

What to watch

Whether ongoing and future trials of the newer agents (CagriSema, orforglipron, retatrutide) eventually generate the same tier of evidence certainty currently reserved for tirzepatide and semaglutide, and whether hard outcome trials — mortality, cardiovascular events, kidney failure — are conducted for drugs where that evidence remains thin. This article is not medical advice.

Sources

1. Comparative effects of drugs for adults with overweight or obesity: systematic review and network meta-analysis — The BMJ, 8 July 2026