Best fat jab revealed after first head-to-head trial shows patients see 20% weight loss

The Sun

12-05-2025

TWO blockbuster weight loss just have been tested against each other for the first time in a head-to-head trial.
There was a clear winner, which saw slimmers shed 20 per cent of their body weight.
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Mounjaro - dubbed the "King Kong" of weight loss jabs - helped people shed significantly more weight than it's rival Wegovy, theresearch suggested.
Though both drugs were effective for weight loss, Mounjaro helped people shed more pounds and trim extra inches off their middle.
Experts presented their findings at the European Congress on Obesity in Malaga and published them in the New England Journal of Medicine.
Previous research showed that dieters could lose up to 30 per cent of their body weight with the help of weekly Mounjaro injections.
It comes after scientists lined up weight loss jabs as a cancer-beating super weapon - as research shows they halve the risk of developing the disease.
Mounjaro's active ingredient is tirzepatide, while Wegovy's is semaglutide - the same one used for diabetes jab Ozempic.
Both are weight-loss medicines that work by mimicking hormones released by the body when you're full, making people feel fuller for longer and therefore less hungry.
They are available on the NHS under specialist weight management services, or via private providers such as online pharmacies.
Typically a patient will have to have a body mass index (BMI) of 30 or higher - classifying them as medically obese - and also have a weight-related health condition such as high blood pressure, to be prescribed them.
The new trial followed 751 adults who were obese, but didn't have type 2 diabetes.
I've lost 3 stone in 8 months on fat jabs - there's a common error new starters are making & it means nasty side effects
Most were aged around 45 and had a BMI of 39 - 65 per cent of them were women.
All had at least one known obesity-related complication, such as high blood pressure, sleep apnoea or heart disease.
They received once weekly jabs of either Mounjaro or Wegovy for 72 weeks, at the maximum tolerated dose.
Patients taking Mounjaro typically shed around 20.2 per cent of their body weight, while Wegovy users lost 13.7 per cent.
Slimmers also trimmed an average of 18.4cm off their waists with Mounjaro and 13cm with Wegovy.
People on Mounjaro were more likely to reach their weight loss goals, researchers said.
One limitation to the study was that people knew which drug they were taking, though the researchers said the findings were in line with previous studies.
Dr Louis Aronne, from Weill Cornell Medicine in New York, who led the research, said the dual action of Mounjaro may explain the findings.
Both Mounjaro and Wegovy mimic a hormone produced in the body called GLP-1 - a substance that is released in the gut when people consume food.
This hormone slows the rate at which food is emptied from the stomach, reduces appetite via the brain and regulates insulin levels.
What are the side effects of weight loss jabs?
Like any medication, weight loss jabs can have side effects.
Common side effects of injections such as Ozempic include:
Nausea: This is the most commonly reported side effect, especially when first starting the medication. It often decreases over time as your body adjusts.
Vomiting: Can occur, often in conjunction with nausea.
Diarrhea: Some people experience gastrointestinal upset.
Constipation: Some individuals may also experience constipation.
Stomach pain or discomfort: Some people may experience abdominal pain or discomfort.
Reduced appetite: This is often a desired effect for people using Ozempic for weight loss.
Indigestion: Can cause a feeling of bloating or discomfort after eating.
Serious side effects can also include:
Pancreatitis: In rare cases, Ozempic may increase the risk of inflammation of the pancreas, known as pancreatitis, which can cause severe stomach pain, nausea, and vomiting.
Kidney problems: There have been reports of kidney issues, including kidney failure, though this is uncommon.
Thyroid tumors: There's a potential increased risk of thyroid cancer, although this risk is based on animal studies. It is not confirmed in humans, but people with a history of thyroid cancer should avoid Ozempic.
Vision problems: Rapid changes in blood sugar levels may affect vision, and some people have reported blurry vision when taking Ozempic.
Hypoglycemia (low blood sugar): Especially if used with other medications like sulfonylureas or insulin.
But Mounjaro also mimics another hormone known as GIP (glucose-dependent insulinotropic polypeptide), which a hormone produced in the gut - especially after consuming carbohydrates and fats - that helps regulate blood sugar levels.
Dr Aronne said: "Our study shows that treatment with tirzepatide was superior to semaglutide with respect to reduction in body weight and waist circumference.
"Tirzepatide, while a single molecule, pharmacologically activates two metabolic receptors, GIP and GLP-1, which have both overlapping and non-overlapping expression and function.
"This dual agonism of tirzepatide may contribute to the higher weight reduction observed in the current study compared to semaglutide, a mono-agonist."
As people lost weight in the study, health factors such as blood pressure and unhealthy blood fats all improved.
Dr Aronne said semaglutide still remained an "extremely effective" weight loss medication and that the trial did not intended to minimise its effects.
He added: "For example, if you have a patient with a BMI of 32, which is class one obesity, they could get to a BMI in the mid 20s, right around 25 [with semaglutide], which is normal.
"So the majority of people with obesity will do just fine on semaglutide.
"People at the higher end - class two, class three obesity - may ultimately do better with tirzepatide."
Speaking at the European Congress on Obesity in Malaga, Spain on Sunday, Dr Aronne said: "This is actually the first head-to-head trial of two obesity medications, so I think we're going to start seeing more of these as new medications become available.
"I saw a list the other day of 150 medications that are now in development, so many people now realise how important it is to manage body weight in addition to other metabolic factors.
The research was sponsored by Eli Lilly and Company, the manufacturer of Mounjaro.