Retatrutide, a new experimental weight-loss medication, helped study participants lose an average of 70 pounds, or about 30% of their body weight, over 80 weeks. This represents a significant leap forward compared to currently available weight-loss drugs, and the results match or exceed the weight loss people typically achieve through bariatric surgery.

The drug works differently from medications already on the market. While popular weight-loss drugs like Ozempic and Wegovy target one hormone pathway, and newer medications like Zepbound and Mounjaro target two, retatrutide is designed as a "triple-agonist," meaning it activates three different hormone receptors in the brain and body. These receptors help control blood sugar levels and reduce appetite, triggering weight loss.

How Does Retatrutide Compare to Current Weight-Loss Medications?

The weight-loss results from retatrutide trials significantly outpace what people achieve with existing medications. People taking Zepbound or Mounjaro, which are dual-agonist drugs, lose an average of about 20% of their body weight. Those using Ozempic or Wegovy, single-agonist medications, lose an average of about 14% of their body weight. Retatrutide's 30% average weight loss represents a meaningful improvement.

The results are particularly striking for people with higher body mass indexes (BMI). Those with a BMI greater than 35, roughly 245 pounds for someone 5'10", lost even more weight on retatrutide, shedding about 85 pounds or 30.3% of their body weight after about two years. More than 45% of all study participants lost more than 30% of their body weight.

"We've never had a triple-agonist medication. So, this is completely new, and retatrutide seems to be more potent," said Dr. Cecilia Low Wang.

Dr. Cecilia Low Wang, Endocrinology, Diabetes and Metabolism Expert at UCHealth

What Additional Health Benefits Did Researchers Observe?

Beyond weight loss, the clinical trial data revealed surprising benefits for other health conditions. Researchers found that retatrutide reduced pain for people with knee arthritis by up to 73%. Additionally, people who had moderate to severe sleep apnea, a condition where breathing repeatedly stops during sleep, experienced about 60% fewer breathing events.

These secondary benefits suggest that the weight loss itself may be improving these conditions, or that the drug's mechanism of action provides direct benefits beyond appetite suppression. However, researchers and doctors still do not fully understand exactly why activating these three receptors is so effective in causing weight loss.

What Side Effects Did Study Participants Experience?

Gastrointestinal side effects are common with all newer weight-loss medications, and retatrutide is no exception. Some study volunteers reported nausea, diarrhea, constipation, or vomiting. About 11% of participants who received the highest dose of the drug stopped taking it and dropped out of the study due to unpleasant side effects.

However, experts note that how people take these medications matters significantly. Patients experience fewer side effects when they gradually increase their doses over time, rather than jumping to higher doses immediately.

How to Manage Expectations About Retatrutide Availability

• Timeline for Approval: Retatrutide has not yet been approved by the U.S. Food and Drug Administration (FDA), and it is unlikely to become available to patients until 2027 at the soonest. The study findings presented at the American Diabetes Association's annual meeting have not yet undergone peer review.
• Ongoing Comparisons: While retatrutide has not been compared head-to-head with earlier weight-loss medications in clinical trials, there is an ongoing trial called TRIUMPH-5 that is comparing it directly with tirzepatide, the active ingredient in Zepbound and Mounjaro.
• Administration Method: Like current weight-loss medications, retatrutide is administered as a weekly injection using an injector pen, similar to Ozempic, Wegovy, Zepbound, and Mounjaro. Oral pill forms of weight-loss drugs do exist, but injectable versions remain more established.

Eli Lilly, the pharmaceutical company that manufactures retatrutide, also makes Zepbound and Mounjaro, the current bestselling weight-loss medications. The company presented the retatrutide study data this month at the American Diabetes Association's annual meeting in New Orleans.

For people currently struggling with weight management, the emergence of retatrutide represents a promising development on the horizon. However, those interested in weight-loss medications should discuss current options with their healthcare provider, as approved drugs like Zepbound, Mounjaro, Wegovy, and Ozempic are available now and have established safety profiles.