BMJ Review of 99,791 Patients Finds Weight-Loss Drugs Trade Greater Efficacy for More Harms

A systematic review and network meta-analysis published 8 July 2026 in The BMJ examined 262 randomized controlled trials involving 99,791 adults with overweight or obesity, comparing 19 available and emerging medications against lifestyle changes, placebo, or other drugs. The analysis found that treatments producing the largest weight reductions also carried the highest rates of gastrointestinal side effects, fatigue, lean-mass loss, and treatment discontinuation. After one year, tirzepatide (Mounjaro) and CagriSema led with average weight reductions of 14.9% and 14.8% versus lifestyle intervention alone, followed by oral semaglutide (10.9%), orforglipron (9.9%), subcutaneous semaglutide (Wegovy, 9.8%), and phentermine-topiramate (8.1%). Evidence for retatrutide, ecnoglutide, and mazdutide was rated low or very low certainty. Subcutaneous semaglutide was the only drug associated with lower all-cause mortality (19% reduction), heart attack (28% reduction), and heart failure (57% reduction). Tirzepatide showed a 51% reduction in heart-failure risk. No medication convincingly reduced kidney-failure risk, and none produced clinically important improvements in quality-of-life scores. Benefits were not maintained after treatment stopped. The researchers, using the GRADE framework to assess certainty, concluded that treatment decisions should be individualized by weighing expected benefits against potential harms, treatment burden, cost, availability, and patient preferences.