Published: 22:00 BST, 31 August 2026 | Updated: 22:05 BST, 31 August 2026
Mounjaro is the most powerful weight-loss jab currently available – but it may soon be toppled by 'Godzilla' drug retatrutide and other emerging injections, a study suggests.
Researchers found tirzepatide – the active ingredient in the blockbuster drug dubbed the 'King Kong' of weight-loss jabs – can see patients shed more than a fifth of their body weight after around 17 months.
But retatrutide, nicknamed 'Godzilla' because it is hoped to be even more powerful, can see patients lose almost a quarter of their weight after just 48 weeks.
Known as 'Reta', the experimental jab has yet to be approved for widespread use, although it was given the green light in the US last month for select patients with an urgent need.
Another experimental jab, amycretin, produced almost the exact same level of weight loss as retatrutide after just 36 weeks.
This suggests the drugs could become the most potent weight-loss jabs ever developed if they get the green light from health officials.
By comparison, semaglutide injections such as Wegovy and Ozempic can trigger weight loss of up to 18.7 per cent over a similar period.
Mounjaro also appears to produce greater weight loss than the new once-daily tablet treatments recently approved in the UK – the Wegovy pill and Foundayo.
Mounjaro is the most powerful fat jab currently available – but it may soon be toppled by other emerging treatments, a study suggests
The Wegovy pill can see patients lose as much as 15.5 per cent of their body weight after 68 weeks, the study showed.
Meanwhile Foundayo, also known as orforglipron, can see patients lose up to 14.7 per cent – though this is after just 36 weeks.
Researchers launched a new so-called systematic review of the drugs, known as GLP-1s, after carrying out a similar analysis last year.
They analysed 38 trials with more than 25,000 participants to study the safety and efficacy of the treatments compared with placebo medicines.
This included looking at new, experimental drugs which are yet to be approved, including retatrutide and amycretin.
