Retatrutide Produced Steep Weight Loss in Adults Without Diabetes

CATEGORY: DIET & WEIGHT

Adults on the highest dose of retatrutide, an experimental weekly injection that acts on three gut hormones at once, lost an average of 25% of their body weight over 80 weeks in the drug’s first completed phase 3 obesity trial. The placebo group lost 3.9%.¹ For a 250-pound person, a quarter of body weight is over 60 pounds. None of the 2,339 participants had diabetes, which makes this the first large test of the drug in the population most likely to use it.

Three hormones instead of two

Semaglutide mimics one gut hormone, GLP-1. Tirzepatide adds a second, GIP. Retatrutide adds a third, glucagon, which is thought to raise the body’s energy burn on top of quieting appetite. Whether stacking a third hormone pays off was the question this trial existed to answer. A computer randomly handed each participant one of three weekly doses or a placebo, and nobody involved knew who had what. Weight was tracked for 80 weeks, about a year and a half. The middle dose took off 23.7%, the lowest 17.6%.

Knees and breathing improved too

The trial built in two subgroups with weight-linked conditions. Among 574 participants with knee osteoarthritis, the wear-and-tear arthritis of the joint, pain scores fell roughly twice as much on the drug as on placebo. Among 243 with obstructive sleep apnea, where the airway repeatedly collapses during sleep, breathing interruptions dropped by about 32 per hour on the top dose against about 10 with placebo. Side effects followed the familiar pattern for this drug class: nausea, diarrhea, constipation and vomiting, mostly mild to moderate and concentrated in the dose-escalation months. An earlier, smaller phase 2 study had pointed the same way at 24 weeks.²

What it doesn’t settle

Retatrutide isn’t approved anywhere yet, and this trial measured weight and symptoms, not heart attacks or lifespan. Whether the extra weight loss over existing drugs translates into better long-term health is being tested in separate outcome trials still underway. Experience with the approved drugs in this class also says weight tends to return once injections stop, a question this 80-week result leaves open.

Key Takeaways

• Retatrutide, a triple-hormone weekly injection, cut body weight by 17.6% to 25% depending on dose over 80 weeks in adults with obesity and no diabetes, versus 3.9% with placebo.
• Knee arthritis pain and sleep apnea severity improved alongside the weight loss in built-in subgroups.
• The drug is unapproved, the trial didn’t measure long-term health outcomes, and durability after stopping remains untested.

References

1. Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a triple hormone receptor agonist, for the treatment of obesity. New England Journal of Medicine. 2026; doi 10.1056/NEJMoa2604169. link
2. Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial. New England Journal of Medicine. 2023;389(6):514–526. link