Eli Lilly said its experimental weekly injection, retatrutida, caused an average weight loss of 28% during a phase 3 clinical trial [1].
These results suggest a potential pharmaceutical alternative to bariatric surgery for treating obesity. If approved, the drug could significantly change the standard of care for patients who cannot undergo invasive procedures.
The findings come from the international TRIUMPH-1 trial, which monitored participants over an 80-week treatment period [2, 3]. Data disclosed on May 21, 2026, indicated that the drug's efficacy varies among participants, with some reports showing weight loss reaching 30% [3, 4].
According to data from O Globo, 45.3% of the patients in the study lost 30% or more of their total body weight [5]. Other reports from Terra said some participants experienced an absolute weight loss of up to 32 kg [6].
Retatrutida is designed as a weekly injectable treatment. The company developed the substance to combat obesity by targeting multiple hormone receptors to reduce appetite, and improve metabolic function [1, 5].
The TRIUMPH-1 study was conducted at multiple sites worldwide to ensure a diverse patient demographic [3]. While the average loss was 28% [1], the range of results highlights the drug's potential to achieve high-magnitude weight reduction in nearly half of the trial population [5].
“average weight loss of 28% over 80 weeks”
The emergence of retatrutida represents a shift toward 'medical bariatrics,' where drug therapy achieves outcomes previously only possible through surgery. By reaching a 30% weight loss threshold for nearly half of its participants, Eli Lilly is positioning this drug to compete not just with existing GLP-1 agonists, but with surgical interventions, potentially expanding the accessible treatment pool for severe obesity.
