What is Retatrutide? The new ‘Godzilla’ weight-loss injection

According to initial research, a new weight-loss drug has been developed that is reportedly more powerful than Ozempic. Named ‘retatrutide’, the drug works by suppressing appetites and speeding up metabolism so that the body burns more fat. In a trial, participants lost up to one-quarter of their body weight on average after nearly a year, which has led people to dub retatrutide the ‘Godzilla’ of weight-loss injections.

HOW DOES RETATRUTIDE WORK?

The reason retatrutide seems to be outperforming other similar drugs is that it targets three different receptors in the brain, as opposed to just one or two. Semaglutide – known more commonly by brand names Ozempic or Wegovy – mimics a hormone called GLP-1 which regulates hunger, making people feel full. A similar injection called tirzepatide – also known by its brand name Mounjaro – mimics GLP-1 as well as a second appetite-controlling hormone called GIP.

Retatrutide mimics both of these and also targets a third hormone, glucagon, which increases the rate of calorie burning by triggering the body to burn more fat.

“Retatrutide is basically Mounjaro but turbocharged. What glucagon does is it increases energy expenditure – the amount of energy that you burn,” Professor Alexander Miras, an obesity expert at Ulster University explained to The Times. “There are two mechanisms; decreasing food intake and increasing energy expenditure. Up until now all of the medications have just focused on reducing food intake.”

The trial was presented at the European Congress on Obesity in Venice this week, and involved 338 obese adults, half of whom were given a weekly injection of retatrutide and the other half a placebo. After 48 weeks, participants on retatrutide had lost on average 24 per cent of their body weight, compared to the 2 per cent of the placebo group. By contrast, in similar trials, users of Ozempic and Wegovy lost 15 per cent of their body weight over 68 weeks, and users of Mounjaro lost 22.5 per cent in 72 weeks.

It was Professor Julio Rosenstock who gave retatrutide its catchy, media-friendly nickname. The University of Texas professor, who conducted a separate trial looking at retatrutide in people with Type 2 diabetes, said: “We know that tirzepatide (Mounjaro) is the King Kong of the GLP-1s. And when I look at retatrutide, I think that there is no question that Godzilla is smiling.”

WHAT ARE THE SIDE EFFECTS OF RETATRUTIDE?

Alongside the weight loss, the study showed retatrutide also helped improve blood pressure and blood sugar levels. Four in ten participants were able to come off medication for high blood pressure. When it came to side effects, like all previous GLP-1 drugs, it included nausea, diarrhoea and constipation.

It isn’t yet clear whether retatrutide will also cause other side effects seen with drugs like Ozempic. In rare cases, these injections can cause renal failure, pancreatitis and intestinal obstruction. Last summer, it was reported that Europe’s drugs regulator was reviewing weight-loss drugs including Wegovy and Saxenda over a possible connection to thoughts of suicide and self-harm among users. While, this year a number of cases have emerged of women on the medication finding themselves pregnant, despite being on birth control or previously having fertility issues. 

On an emotional level, a scientist who helped pioneer GLP-1 research has warned that it numbs people’s ability to feel pleasure and makes life “so miserably boring”. It is also worth noting that, because of the way that GLP-1 drugs produce weight-loss – by suppressing appetite – when you stop taking it, the effects are often reversed.

On a more positive note, recent research on semaglutide found that it could help reduce risk of heart attacks. In a new study, also presented at the ECO this week, researchers at University College London discovered that participants taking semaglutide had a 20 per cent lower risk of heart attack, stroke, or death due to cardiovascular disease, regardless of their starting weight or the amount of weight that they had lost.

Some people also believe the drug has a future as anti-addiction medication thanks to reports that semaglutide suppresses the desire to do activities like drink alcohol and go shopping.

WHAT HAPPENS NEXT?

Eli Lilly, the American pharmaceutical firm that is developing retatrutide, is now conducting phase three trials to find out how much more weight users can lose, as well as assess side effects and any more serious problems. These results will be published in 2026 and then, if approved by regulators, the drug could be available to buy or be prescribed on the NHS within three years.

In the meantime, Eli Lilly, as well as pharmaceutical companies Novo Nordisk and Pfizer, are racing to be the first to market with the oral version of these weight-loss drugs as doctors believe it will be more palatable to people than injections. Unsurprisingly, this is because there is big money to be made. Last year, obesity and diabetes drug sales totalled nearly £25 billion and has led Ozempic manufacturer Novo Nordisk to become Europe’s most valuable company with a market value of over $500 billion. This exceeds the entire GDP of Denmark, where the company is based. Novo Nordisk has made so much profit that it’s pushed up the value of the Danish krone and driven down mortgage rates in the country.

While these pills and the upcoming retatrutide injections are still in development, some experts are already worried about the impact the drugs will have on people who take it for cosmetic weight loss – rather than the original use for GLP-1 drugs of treating diabetes. “I am concerned about these medications being broadly used just to promote weight loss and how it contributes to our general diet culture, our cultural obsession with thinness,” Dr Scott Hagan, an assistant professor of medicine at the University of Washington who has studied obesity, told the New York Times.

THE CULTURAL IMPACT OF RETATRUTIDE AND OZEMPIC

Since the weight-loss effects of semaglutide and similar GLP-1 drugs have become known to the public, they have come to dominate the cultural conversation and become so popular there is currently a national shortage; even people with diabetes are struggling to get their hands on it. It is reportedly being widely used in Hollywood, New York City and Westminster, as well as in the fashion industry, and a dangerous black market has sprung up to feed demand. Medspas and telemedicine start-ups are also offering off-brand versions of the drugs, causing concern over the blurring of the lines between a still-emerging field of medicine and cosmetic treatments. 

The medication’s soaring popularity has exposed how, despite the body-positive movement and the “slim-thick” hourglass figure that celebrities like the Kardashians championed last decade, our culture is as diet-entrenched and skinny-obsessed as it always has been. As a society, we are still trapped in the clutches of the fatphobia that is and has always been so pervasive. As a result, despite the potential danger to health and wellbeing of the drugs, many people believe the risk is worth the social benefit. 

“If being beautiful is the status marker for a woman’s worth, losing weight can feel like a matter of social life and death,” psychotherapist Charlotte Fox Weber told Dazed last year. “It can feel like the most important thing in the world and can decrease an ordinary sense of risk in the willingness to try anything. Agony and misery over body shame leads to desperation and impulsiveness.”

It is too soon to know whether retatrutide will be as successful as its makers are predicting: Dr Ania Jastreboff, the study author and director of the Yale Obesity Research Center, called the results ”striking”, ”not seen before” and said a gathering of scientists ”spontaneously clapped” when shown early results of the trial. In the meantime, however, it will pay to be cautious of any drug that is hailed as a miracle – particularly when it comes to the weight-loss industry which has a long history of medication which turns out to be too good to be true.