A new obesity drug pushed average weight loss past 24% in a year-long trial, a number that puts it in the same range as weight-loss surgery.
Quick Take
- Retatrutide, a triple-hormone drug from Eli Lilly, drove weight losses of 22.8% to 24.2% in a 48-week phase 2 study.
- The same trial found the drug slashed liver fat by more than 80%, reversing fatty liver disease in most patients tested.
- Retatrutide targets three hormone pathways at once, unlike current drugs such as Ozempic and Zepbound that target fewer.
- The drug has moved into larger phase 3 trials, but the Food and Drug Administration (FDA) has not approved it yet.
A Triple-Target Drug Outpaces Earlier Weight-Loss Shots
Retatrutide works by activating three separate hormone receptors in one weekly injection: GLP-1, GIP, and glucagon. Current blockbuster drugs like Ozempic and Wegovy only target GLP-1. Tirzepatide, sold as Zepbound, hits two of the three. Adding the third receptor, glucagon, appears to boost fat burning and calorie use beyond what the earlier drugs achieve, according to the Yale Medicine researchers tracking the obesity drug pipeline.
The numbers behind that claim come from a randomized, placebo-controlled phase 2a trial published in Nature Medicine in June 2024. Patients taking the 12-milligram dose of retatrutide lost an average of 24.2% of their body weight over 48 weeks. Those on the 8-milligram dose lost 22.8%. Both groups were compared against a placebo group that lost far less, confirming the drug, not chance, drove the results.
Fatty Liver Disease Saw Dramatic Reversal
The same 98-person study also tracked liver fat using detailed imaging scans. Patients on the 8-milligram dose saw liver fat drop by an average of 81.4%. Those on the 12-milligram dose saw an 82.4% drop. Researchers called the results the most potent liver-fat reduction ever recorded in a drug trial, a claim grounded directly in the published data.
Liver fat didn’t just shrink, it often disappeared completely. Among patients who started the trial with fatty liver disease, 79% of those on the 8-milligram dose and 86% of those on the 12-milligram dose no longer met the clinical definition of the disease by the end of the study. That matters because fatty liver disease affects roughly a third of American adults and often goes undiagnosed until it causes serious damage.
Independent Reviews Back Up the Early Numbers
Outside researchers have since run their own analyses pooling data across multiple retatrutide trials. One systematic review and meta-analysis found the drug cut body weight by an average of over 14 percentage points more than placebo, while also lowering blood pressure, blood sugar, and waist size. Another independent review of obesity trials found retatrutide produced weight loss “approaching what’s typically seen with bariatric surgery,” a comparison rarely made for a drug given by injection rather than a scalpel.
A separate network meta-analysis comparing six weight-loss drugs, covering nearly 30,000 adults, placed retatrutide among the top performers for weight reduction, alongside other dual-hormone agents. That kind of head-to-head comparison carries weight because it strips out the hype that often surrounds a single company’s trial results and checks the claims against the broader published record.
Where the Drug Stands Now
Eli Lilly has pushed retatrutide into phase 3 trials, the last major testing stage before a company can ask the FDA for approval. The company announced in recent press releases that the drug succeeded in additional late-stage obesity trials, delivering what it described as substantial improvements in weight and blood sugar control. The drug is not approved for sale anywhere yet, and patients cannot get a prescription for it outside of clinical trials.
Other companies are chasing similar ground, testing amylin-based drugs and combination therapies that could someday stack alongside GLP-1 treatments already on pharmacy shelves. None of those rivals have matched retatrutide’s published numbers yet, but the race shows how fast this corner of medicine is moving. For the millions of Americans already managing obesity with Ozempic or Zepbound, that competition likely means more options, and possibly better results, within the next few years.
Sources:
time.com, lolahealth.com, marketchameleon.com, pubmed.ncbi.nlm.nih.gov, academic.oup.com
