Weight-loss shots tend to come with extra credit. Better blood sugar, possibly calmer inflammation, even early hints about drinking habits: the list of possible side benefits keeps growing. Now a late-stage trial of an experimental drug called retatrutide is putting real numbers to some of those perks.
The study followed 1,152 adults who had both obesity or overweight and type 2 diabetes, a group that often finds weight loss especially hard.
Over 80 weeks, people on the drug lost far more weight than those on placebo, and their blood sugar readings improved as well.
The figures come with some fine print, though. Depending on how the data is crunched, the same dose can produce different weight-loss numbers, and the dose a person was assigned isn’t always the dose they stayed on.
Then there is the phrase “benefits beyond weight loss,” which covers claims with very different levels of proof.
A Triple-Action Drug, Tested Against Placebo
Retatrutide goes after three hormone targets at once, and one of them looks like an odd choice.
Retatrutide is a weekly injection that activates receptors for three hormones: GIP, GLP-1, and glucagon. Glucagon is the odd one out, since it normally tells the liver to release sugar, yet blood sugar improved in the trial.
Researchers are pursuing the combination partly because glucagon activity may increase energy expenditure, though that remains a proposed explanation.
Results were published September 29 in The Lancet and presented at the European Association for the Study of Diabetes meeting in Milan. Adults averaging 55 years old, with an average BMI of 38.2, were randomized to 4 mg, 9 mg, or 12 mg of retatrutide or a placebo. They had lived with obesity for a median of 21 years and with diabetes for 5.6 years, and everyone also received dietary counseling and activity guidance.
The comparison was against placebo only. Ozempic, Wegovy, and other drugs were not part of the trial, so it cannot say whether retatrutide beats them.
What the Scale and the Blood Tests Showed
Weight loss climbed with each dose, but blood sugar did not follow the same pattern.
At week 80, average weight loss ranged from 11.9% on the lowest dose to 18.8% on the highest, compared with 5.1% on placebo. In the 12 mg group, 47% lost at least a fifth of their starting weight, versus 6% on placebo. Those are group averages, and the placebo group got the same lifestyle support.
Blood sugar, measured by HbA1c, started at an average of 7.71%. It fell by 1.38 to 1.50 points across the three doses, compared with 0.45 on placebo, and the 9 mg dose showed the biggest drop.
At 12 mg, 72% reached an HbA1c of 6.5% or lower, compared with 29% on placebo. The report does not call that remission, and 92% of participants were taking at least one glucose-lowering drug when they enrolled.
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The Side Effects That Came With It
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Stomach trouble led the list, and a few less familiar complaints also appeared.
Diarrhea affected 27% to 34% of participants across the retatrutide groups, compared with 13% on placebo, and nausea ranged from 14% to 28%, versus 8%.
Dysesthesia, which includes burning or discomfort, appeared in up to 7% of people at the top dose, compared with 1% on placebo. None of those cases were severe or serious, and low blood pressure events reached 6% at 12 mg, against under 1% on placebo.
Stopping treatment because of side effects or death was most common at 9 mg, at 12%, versus 5% on placebo. Seven participants died during the trial: two on 4 mg, three on 9 mg, one on 12 mg, and one on placebo.
The investigator judged the deaths unrelated to the study treatment, and causes were not listed.
Beyond the Scale, the Evidence Thins Out
The bigger claims about these drugs rest on very different levels of proof.
An editorial in the journal Obesity by Steven Heymsfield of Louisiana State University’s Pennington Biomedical Research Center and Adam Gilden of the University of Colorado describes possible additional benefits of GLP-1-based drugs.
These include less inflammation, a lower risk of some cardiovascular and musculoskeletal diseases, and reduced alcohol use. Alcohol use was not part of the retatrutide trial.
The best-developed example involves semaglutide, the ingredient in Ozempic and Wegovy. In a randomized trial of 48 adults with alcohol use disorder who were not seeking treatment, nine weeks of low-dose semaglutide cut drinks per drinking day and weekly cravings compared with placebo. Average drinks per calendar day and the number of drinking days did not change significantly.
Retatrutide itself remains investigational and cannot legally be sold or marketed. Researchers plan to submit it to the FDA in the first quarter of 2027, and researchers are also studying it for cardiovascular disease, metabolic liver disease, knee osteoarthritis, chronic low back pain, and sleep apnea.
This trial’s findings apply to adults with type 2 diabetes, not to everyone interested in losing weight.
What would you want to know about a weight-loss drug beyond the number on the scale before deciding it was worth trying?
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