'Godzilla' fat jab retatrutide sheds more fat than Mounjaro, new study finds - here's when you can get it in Britain

The 'Godzilla' fat jab could rival Mounjaro by helping users shed up to a quarter of their body weight while improving blood pressure and cholesterol, research has found. 

According to US researchers, Retatrutide is the best drug yet for obese or overweight patients with type 2 diabetes, who typically lose less weight on the blockbuster jabs than people without the condition. 

The drug, commonly known as 'Reta', is still undergoing clinical trials but has been hailed as a potential 'game changer' for weight-loss, heart disease and osteoarthritis. 

Now experts at Los Angeles Institute for Metabolic Research have found that nearly a third of users taking the highest dose can shed at least a quarter of their body weight over a period of 18 months. 

The most powerful licensed weight loss drug currently available, Mounjaro, helps users lose around 20.9 per cent of their body weight when taken for 16-and-a-half months. 

Retatrutide – also known as 'triple G' – is a triple agonist, meaning it targets three hormone pathways involved in appetite control to help the body burn fat, including GLP-1.

This is two more than Wegovy and one more than Mounjaro, which is already available on the NHS to those with the greatest need. 

The latest findings come from TRIUMPH-2, a phase 3 clinical trial evaluating the effectiveness and safety of retatrutide in 1,152 overweight and obese adults with type 2 diabetes. 

 The triple whammy drug could be available on the NHS in three years 

Participants from eight countries were randomly assigned to receive weekly injections of retatrutide at doses of 4mg, 9mg or 12mg – or a placebo, alongside diet and exercise advice. 

On average, participants had been obese for more than two decades and were diagnosed with type 2 diabetes at least five years before the study started. 

After 80 weeks, participants taking the strongest 12mg dose lost nearly a fifth of their body weight compared with 17 per cent on the 9mg dose and 12 per cent on the 4mg dose. 

Almost half of those on the highest dose lost at least a fifth of their body weight, while nearly one in three shed at least a quarter. 

Those given a placebo lost just five per cent of their weight through diet and exercise alone. 

For a typical 5ft 10in obese man, the average weight loss seen on the highest dose would equate to roughly 23kg, or more than three-and-a-half stone, over 18 months.  

Retatrutide was also found to dramatically improve blood sugar levels, helping patients control diabetes and, in some cases, put the condition into remission.

Nearly three quarters of patients on the highest dose achieved blood sugar levels at or below the target used to diagnose diabetes, compared with just 29 per cent of those given a placebo. 

Participants also showed significant improvements across other cardiovascular risk factors, including bad cholesterol and inflammation. 

However, like all other GLP-1 jabs, retatrutide was found to cause a number of side-effects, including nausea and diarrhoea. 

Abnormal skin sensations including burning and discomfort also occurred in seven per cent of participants on the highest dose. 

Seven deaths also occurred over the course of the study, which were deemed unrelated to the treatment by investigators. 

Presenting their findings at the Annual Meeting of The European Association for the Study of Diabetes (EASD) in Milan, the authors concluded: 'Retatrutide may advance the treatment of obesity and type 2 diabetes, a population where weight reduction has been challenging to achieve.'

They added that the safety profile of the drug is generally similar to the other weight loss jabs.

Further research is expected to determine whether these benefits translate to improvements in other obesity-related complications such as sleep apnoea, strokes, heart disease and cancer. 

The latest findings follow a surge in interest in the drug after early-stage trials suggested it may result in more significant weight loss than Ozempic and Mounjaro.

Eli Lilly, the pharmaceutical firm behind retatrutide, was forced to issue warnings against trying to obtain the drug via social media.

Eli Lilly were forced to issue warnings when promising results from early stage trials led to a surge in people trying to obtain the drug through social media

The company said those using fake drugs from unauthorised sources are putting their health at 'serious risk' and threatened to take action against the sellers.

Earlier this year the Daily Mail revealed a man in his thirties died after taking an unapproved version of the drug – with dozens more having suffered serious side effects. 

Since 2025, the Medicines and Healthcare products Regulatory Agency (MHRA), has recorded 77 reports of suspected retatrutide side effects – but added that reports alone do not prove that a medicine caused the suspected adverse reaction. 

Retatrutide is not currently approved or available on the NHS, but could be available to buy and even be prescribed on the NHS within three years if approved by regulators, experts say.

Separate research presented at EASD found an experimental drug called petrelintide could offer similar weight-loss to Mounjaro, but with fewer side effects than existing blockbuster jabs. 

Rather than targeting GLP-1 hormones that regulate appetite and slow digestion, petrelintide mimics the hormone amyline, helping people feel fuller for longer. 

Participants lost around 10 per cent of their body weight in under 10 months, while also seeing improvements in blood pressure and cholesterol levels. 

Experts say its main attraction is its tolerability – with users suffering far less unpleasant digestive side effects than typically seen with GLP-1s.

Scientists not involved in the study said further research is needed, including a direct head-to-head comparison with Mounjaro and Wegovy, to support these claims.