- A major phase 3 trial suggests retatrutide may outperform current blockbuster weight loss drugs, with people on the highest dose losing more than 28% of body weight over 80 weeks.
- Unlike existing GLP-1 medicines, retatrutide also acts on glucagon pathways, which may help the body burn more energy as well as eat less.
- The results are impressive, but the drug is not yet licensed in the UK and side effects still look similar to those seen with other weight loss jabs.
A new trial suggests retatrutide may become the most effective weight loss injection yet tested.
In the phase 3 TRIUMPH-1 study, adults taking the highest 12mg dose lost an average of 28.3% of their body weight over 80 weeks.
That is more than has typically been seen with currently licensed options such as Wegovy and Mounjaro.
The average waist reduction was also substantial, with participants losing around 24.1cm from their waistlines.
Nearly half of those on the highest dose achieved at least 30% weight loss, which is the sort of result more often associated with bariatric surgery than with medication.
What makes retatrutide different is that it is a triple agonist.
That means it acts on three hormone pathways rather than one or two.
Like other modern obesity drugs, it helps curb appetite and slow gastric emptying.
But it also acts on glucagon, which appears to increase energy expenditure and help the body burn more calories.
That is why some researchers have started describing it as something like exercise in a jab.
The trial included 2,339 adults with obesity or overweight plus at least one weight-related health problem, although people with diabetes were excluded.
Alongside the weight loss, researchers also reported improvements in several cardiometabolic markers, including blood fats, bad cholesterol, blood pressure and inflammation.
That is important, because obesity treatment is not just about the number on the scales.
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The health impact matters just as much.
There is still no point pretending this is a miracle cure.
The side effects were broadly similar to those seen with other GLP-1 based drugs, including nausea, diarrhoea, constipation and vomiting.
And like the rest of this drug class, it will raise the usual questions about long-term use, cost, access and what happens when treatment stops.
Still, the result is hard to ignore.
If the data hold up and regulators approve it, retatrutide could become the new benchmark for medical weight loss.
