Obesity Pharmacotherapy: Comparative Efficacy and Safety in Adults

A Nature Medicine network meta-analysis evaluated six obesity management medications across 56 randomized trials involving 60,307 adults. The primary outcome was percentage of total body weight loss at the study endpoint. Each agent was associated with greater total body weight loss than placebo at study end. Semaglutide and tirzepatide were the only medications surpassing 10% total body weight loss in the pooled endpoint analysis. Overall, the results reflected medication-level effects rather than a uniform pattern across the treatment group.

Timepoint analyses showed the same general ordering, with semaglutide and tirzepatide producing the largest body-weight reductions among the included medications. At 52 weeks, orlistat was the only agent without a significant advantage over placebo. When later follow-up data were available, estimated effects were broadly similar to the endpoint pattern. Direct drug-to-drug comparisons were limited, so most relative estimates came from indirect network comparisons. The comparative pattern remained medication-specific, with performance varying across individual agents over follow-up.

Investigators found no significant overall between-group difference in treatment discontinuation across the reviewed trials. Serious adverse events were generally not increased, although naltrexone plus bupropion was an exception. For cardiometabolic outcomes, tirzepatide showed the largest HbA1c reduction, while liraglutide and semaglutide had larger fasting plasma glucose declines. Naltrexone plus bupropion increased systolic blood pressure, whereas several other medications improved blood pressure and lipid measures. In aggregate, these non-weight findings differentiated agents by safety and metabolic profile.

Pooled cardiovascular results also varied by medication. These analyses drew on externally adjudicated endpoints for major adverse cardiovascular events (MACE), cardiovascular mortality, and hospitalization for heart failure (HHF) as reported across the included trials. Semaglutide was the only agent associated with a significantly lower rate of major adverse cardiovascular events overall. Tirzepatide was linked to fewer heart-failure hospitalizations, while semaglutide and naltrexone plus bupropion were associated with lower cardiovascular mortality. These associations suggested cardiovascular signals were not shared evenly across the medication group.

Post-discontinuation analyses showed weight regain of 47% after liraglutide discontinuation, 43% after 26 weeks off semaglutide, 67% after 52 weeks off semaglutide, and 53% after 52 weeks off tirzepatide. Researchers also reported that semaglutide and tirzepatide improved several obesity-related complications in selected subgroup analyses. Those signals included normoglycemia restoration or diabetes remission in glycemic subgroups, fewer heart-failure hospitalizations, and benefits in selected MASLD, obstructive sleep apnea, and knee osteoarthritis outcomes. The primary body-weight outcome was rated high certainty by GRADE, although the authors noted limited long-term follow-up, inconsistency in some outcomes, and sparse head-to-head data. Overall, the review described a broad but uneven evidence base.

Key Takeaways

• All included medications were associated with greater weight loss than placebo, with semaglutide and tirzepatide showing the largest reductions.
• Discontinuation rates were similar to placebo overall, while serious adverse events were generally not increased except with naltrexone plus bupropion.
• Cardiovascular, metabolic, durability, and subgroup findings varied by medication, and the primary weight-loss evidence was rated high certainty despite limited long-term and comparative data.