The next weight-loss drug may beat them all: retatrutide hit 22.1%

Most of the original evidence for GLP-1 drugs came from people with type 2 diabetes, yet a large share of real-world demand now comes from people without it who want to lose weight. Whether the drugs are as effective and as safe in otherwise healthy adults is therefore a question in its own right. On top of the three commercially available agents, a pipeline of new single and combination drugs is moving through trials. This review set out to size up efficacy and safety across the whole field, in adults with overweight or obesity and no diabetes.

The researchers searched three databases from inception to 4 October 2024 for placebo-controlled randomised trials of GLP-1 receptor agonists and dual or triple co-agonists in otherwise healthy adults with overweight or obesity. Twenty-six trials qualified, covering 15,491 participants, 72% of them female, with mean ages of 34 to 57 years and mean BMI of 30 to 41. Twelve agents were assessed: liraglutide, semaglutide and tirzepatide plus nine premarket drugs. Treatment ran from 16 to 104 weeks, with a median of 43 weeks, and outcomes covered weight change, deaths, serious adverse events and gut side effects.

Tirzepatide at 15 mg weekly produced up to 17.8% weight loss versus placebo after 72 weeks, semaglutide at 2.4 mg weekly up to 13.9% after 68 weeks, and liraglutide at 3.0 mg daily up to 5.8% after 26 weeks. The premarket triple agonist retatrutide at 12 mg weekly went further, with up to 22.1% weight loss after 48 weeks. Adverse events were frequent in both drug and placebo groups, with most drug-related complaints gastrointestinal: nausea, vomiting, diarrhoea and constipation. Events forcing discontinuation and serious adverse events were rare, and the trials were too different from one another to combine into a single pooled estimate.

This confirms that the headline results from diabetes populations carry over to people without diabetes, and it puts the current drugs and the pipeline side by side for the first time in one place. The retatrutide figure suggests the ceiling on drug-induced weight loss is still rising. The major caveat is that no trial compared the drugs directly, so differences between the percentages come from separate studies in different populations over different durations. Head-to-head trials remain the missing piece.

If you have followed the weight-loss drug story, this is a snapshot of where the science stands for people without diabetes: substantial weight loss across the class, a premarket drug posting the largest figures yet, and side effects that are common but mostly confined to the gut. It is also a reminder that the numbers come from trials of different drugs in different people, not a direct contest. Whether any of these agents is appropriate for an individual is a clinical question, not a leaderboard one.