Semaglutide loses the weight loss crown to retatrutide

The GLP-1 drug field is moving extremely fast, with newer agents that stimulate two or three hormone receptors at once arriving behind established single-target drugs like semaglutide and liraglutide. For people with obesity or overweight, and for the clinicians treating them, the pressing question is comparative: which of these drugs produces the most weight loss, and at what cost in side effects? Direct head-to-head trials between all of them do not exist, so a network meta-analysis, which links trials through their shared comparators, is currently the best way to rank them.

The researchers searched the Cochrane Library, PubMed and Embase from inception to 30 August 2024 for randomised controlled trials of at least 16 weeks testing seven GLP-1 receptor agonists and polyagonists in people with obesity or overweight: mazdutide, retatrutide, tirzepatide, liraglutide, semaglutide, orforglipron and beinaglutide, at specified doses. Twenty-seven trials covering 15,584 patients were included. The primary outcome was percentage change in body weight from baseline; secondary outcomes included waist circumference, haemoglobin A1c, fasting glucose, adverse events, serious adverse events, withdrawals due to adverse events and hypoglycaemic events, analysed with a frequentist random-effects network model.

Retatrutide 12 mg was the most effective treatment, cutting body weight by 22.10% and waist circumference by 17.00 cm versus placebo, followed by retatrutide 8 mg at 20.70% and 15.90 cm, and tirzepatide 15 mg at 16.53% and 13.23 cm. The same drugs were less effective in patients with type 2 diabetes, while people with higher BMI or longer treatment cycles lost significantly more. On safety, no intervention increased serious adverse events or hypoglycaemic events, withdrawals due to side effects did not differ between drugs, and patients without diabetes actually reported more adverse events than those with diabetes.

This updated analysis extends the now-familiar finding that tirzepatide outperforms semaglutide by placing retatrutide, a triple agonist targeting GLP-1, GIP and glucagon receptors, above both. The authors' broader conclusion is structural: dual and triple receptor agonists are more effective for weight loss than single GLP-1 receptor agonists. The caveats are real, though. Most comparisons run through placebo rather than direct trials, the analysis pools different populations and treatment lengths, and responses split clearly by diabetes status, BMI and duration, so individual results will vary around these averages.

For anyone following the weight loss drug landscape, this is a reason to think the current headline drugs are not the ceiling: the pipeline agents targeting multiple gut hormones produced larger reductions in weight and waist size in trials. It is also a reason to read individual results carefully, because the same drug performed differently depending on whether someone had type 2 diabetes, how high their starting BMI was, and how long they stayed on treatment. The safety picture across the class was reassuring on serious events, though everyday adverse events remained common.