A new weight loss jab nicknamed ‘Godzilla’ could be the best so far, research has suggested. 

Exciting trials of the drug, retatrutide, revealed it helped people shed a quarter of their body weight in under a year. 

Unlike other slimming injections, retatrutide not only suppresses the appetite but also speeds up the metabolism.

Yet is it the most effective? A fascinating MailOnline graphic demonstrates exactly how it stacks up against its rivals. 

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Semaglutide 

Semaglutide, sold under the brand names Ozempic and Wegovy, mimics a hormone called GLP-1 that makes people feel full.

Ozempic is currently only available on the NHS for managing blood glucose levels in type 2 diabetes patients.

Its dramatic slimming effects, shown in trials and real-life scenarios, saw doctors and pharmacists dish it out ‘off-label’ for people wanting to lose weight. 

Health chiefs, however, have repeatedly urged against doing so due to supply issues, warning it put diabetics’ lives at risk. 

Wegovy, packed with the same active ingredient, was approved last year specifically for weight loss. Although it is also being hit by global shortages. 

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Trials pivotal to getting Novo Nordisk’s semaglutide approved show it can help users shed up to 15 per cent of their body weight over 68 weeks.

A month’s supply is available privately in the likes of Boots and Superdrug for around £200. 

Eligibility criteria for people wanting the get the drug on the NHS — for the standard prescription rate of £9.90 in England — is strict. 

And the drugs are not without side effects.  

Users commonly complain of nausea, constipation and diarrhoea after taking the medication. 

Tirzepatide 

Mounjaro, as it is branded, also mimics GLP-1, as well a second appetite-controlling hormone called GIP. 

Studies have found the drug, made by US pharmaceutical giant Eli Lilly, could help obese people lose up to 22.5 per cent of their body weight in 72 weeks.

It is self-injected once a week, just like semaglutide. 

The stark difference in results led US diabetes expert Dr Julio Rosenstock to declare Mounjaro ‘King Kong’ compared to ‘the gorilla’ of its rival Wegovy. 

Some patients already taking the drug have shared their results on social media, with one overweight man claiming it helped him shed 100lb (45.4kg).

Similar to semaglutide, side effects of tirzepatide (Mounjaro’s generic name) include nausea, diarrhoea, vomiting — which usually goes away over time — and constipation.

It was given the green light by the National Institute for Health and Care Excellence (Nice) for NHS use in September for patients with type 2 diabetes who do not have the condition under control.

It is not yet used by the health service for obesity. 

But in February was made available privately in Britain, with clinics charging around £40 for a week’s supply. 

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Retatrutide 

Retatrutide, meanwhile, adds a third hormone called glucagon, which triggers the body to burn more fat, increasing the rate of calorie burning.

Trial results, presented yesterday at the European Obesity Congress in Venice, showed it achieved even greater average weight loss — 24 per cent of body weight — over a shorter period of 48 weeks.

Its phase two study of 338 obese people also found results were even more stark in women, helping them lose 28.5 per cent of their body weight.

By comparison, men lost an average of 21.2 per cent.

And more obese participants lost an even greater percentage of their body weight at 26.5 per cent in 48 weeks. 

Unusually, 100 per cent of trial participants lost at least 5 per cent.

Like all previous GLP-1 drugs, retatrutide — taken once a week — has led to side effects including nausea, diarrhoea and constipation. 

But the study, published in the New England Journal of Medicine, shows that the drug also had other health benefits. 

Participants saw significant improvements in blood pressure and blood sugar levels. Four in ten participants were able to come off medication for high blood pressure.

Manufactured by American pharmaceutical firm Eli Lilly, larger trials are now underway with results expected in 2026. 

It means the treatment could be available on the NHS within around three years, pending final regulatory hurdles.

Orlistat   

Orlistat is a pill already available on the NHS for weight loss. 

Taken up to three times a day with a meal, it prevents fat being absorbed by the digestive system.

The undigested fat is instead passed out of the body as faeces.

While this stops people gaining more weight, it doesn’t help them lose it by itself.

Side effects include fatty or oily poo, oily discharge from the rectum, and high levels of flatulence.

Manufactured by pharmaceutical giant Roche, early studies suggest patients taking 120mg could lose up to (22.7lbs) 10.3kg over 52 weeks. 

Its prescription on the NHS is limited to those who are obese or overweight and have another health problem such as high blood pressure. 

Liraglutide 

Sold under the brand name Saxenda, the daily self-administered jab is another weight loss treatment already available on the health service.

It works in a similar way to semaglutide by altering the body’s metabolism, making people feel fuller and less hungry.

This leads them to eat less and, in theory, lose weight.

Saxenda, however, is one of a number of similar drugs that are experiencing a global supply shortage.

Liraglutide is generally only prescribed on the NHS after a GP refers you to a specialist weight loss management service and when orlistat hasn’t worked.

Side effects include aches and pains, diarrhoea, fever, frequent urination, and trouble sleeping.

Manufactured by Novo Nordisk, trials have found users lose an average of 6.4 per cent of their body weight over 68 weeks.