Mounjaro: The new weight loss drug set to rival Ozempic and Wegovy

Ozempic, Wegogy, now Mounjaro: Here's what to know about the latest weight loss "wonder" drugs.
Ozempic, Wegogy, now Mounjaro: Here's what to know about the latest weight loss "wonder" drugs. Copyright Canva
Copyright Canva
By Euronews with AP
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Ozempic has a new rival: Mounjaro, also a diabetes drug, has led to average weight losses of 15 to 24 kg.


A powerful new diabetes drug is poised to become a hit on the global weight loss market.

Tirzepatide, which is sold under the brand name Mounjaro, has helped diabetes patients who were overweight or had obesity lose on average more than 15 kg over the course of 17 months, according to drugmaker Eli Lilly.

Previous research found that similar participants without diabetes who took the highest dose of the drug lost up to 24 kg over that period with weekly injections.

If approved for weight loss, tirzepatide could become the most effective drug to date to tackle obesity, which affects more than one in eight adults worldwide and is linked to scores of health problems that can lead to disability or even death - including high blood pressure, diabetes, heart disease, stroke, cancer, and joint problems.

Researchers have long looked for medications that can help people lose weight, mostly with disappointing and, in some cases, dangerous results.

In recent years, however, drugs designed to help people with type 2 diabetes control their blood sugar levels have had the added effect of paring pounds.

If everybody who had obesity in this country lost 20 per cent of their body weight, we would be taking patients off all of these medications for reflux, for diabetes, for hypertension
Dr Caroline Apovian
Center for Weight Management and Wellness, Brigham and Women's Hospital

Ozempic, a diabetes drug sold by Novo Nordisk, skyrocketed in use after celebrities and ordinary people on TikTok reported that their doctors prescribed it "off-label" for weight loss.

Wegovy, a higher dose version of the same medication, called semaglutide, was approved for weight loss for adults in the US in 2021 and for children aged 12 and older the following year.

Now, Lilly’s tirzepatide - already approved for type 2 diabetes under the brand name Mounjaro - is poised to become the most potent obesity drug on the market, promising users losses of more than 15 to 24 kg over time.

Having diabetes makes it notoriously difficult to lose weight, said Dr Nadia Ahmad, Lilly’s medical director of obesity clinical development, which means the recent results are especially significant. 

“We have not seen this degree of weight reduction,” she said.

Based on the new results, which have not yet been published in full, company officials said they will finalize an application to the US Food and Drug Administration (FDA) for fast-track approval to sell tirzepatide for chronic weight management. A decision could come later this year.

Game-changer in the fight against obesity

“If everybody who had obesity in this country lost 20 per cent of their body weight, we would be taking patients off all of these medications for reflux, for diabetes, for hypertension,” said Dr Caroline Apovian, a director of the Center for Weight Management and Wellness at Brigham and Women's Hospital. “We would not be sending patients for stent replacement”.

Industry analysts predict that tirzepatide could become one of the top-selling drugs ever, with annual sales topping $50 billion (€45.5 billion). It is expected to outpace Novo Nordisk’s Ozempic - a diabetes drug used so commonly to shed pounds that comedian Jimmy Kimmel joked about it at the Oscars - and Wegovy, a version of the drug also known as semaglutide approved for weight loss in 2021.

Together, those drugs made nearly $10 billion (€9.1 billion) in 2022, with prescriptions continuing to soar, company reports show. Their success as a weight-loss treatment has also led to shortages for the diabetes patients they were originally meant to serve.

How do Ozempic, Wegovy, and Mounjaro work?

The medications work by mimicking the actions of gut hormones that kick in after people eat. They lower blood sugar and slow down digestion, so people feel full longer.

Doing so, the medications help overcome a biological mechanism that kicks in when people diet and triggers a coordinated effort by the body to prevent weight loss.

Ozempic and Wegovy are two versions of semaglutide. That drug mimics a key gut hormone, known as GLP-1, that is activated after people eat, boosting the release of insulin and slowing the release of sugar from the liver. It delays digestion and reduces appetite.


Tirzepatide is the first drug that uses the action of two hormones, GLP-1 and GIP, which Lilly says contributes to its increased effectiveness. It also targets the chemical signals sent from the gut to the brain, blunting cravings for food.

Mounjaro was first approved to treat diabetes in May 2022. Since then, thousands of patients have obtained the drug from doctors and telehealth providers who prescribed it “off-label" to help them slim down.

The drugs are delivered through once-weekly injections. Users are advised to follow a healthful, reduced-calorie diet and to exercise regularly while using them.

How effective is Wegovy, and how does Mounjaro compare?

In a trial, adults who took Wegovy saw a weight loss of nearly 16 kg, or about 15 per cent of their body weight. Adolescents lost about 16 per cent of their body weight.

The latest study of tirzepatide studied the drug in more than 900 patients with diabetes who were overweight or had obesity over nearly 17 months. It showed weight loss of up to 16 per cent of body weight - more than 15 kg - when using the highest dose of the drug. Patients who received placebo, or dummy injections, only lost about 3 per cent of their weight, or 3 kg.


An earlier trial of tirzepatide on patients without diabetes showed weight loss of about 15 to 22 per cent of body weight, or about 16 to 24 kg, depending on the dose.

A head-to-head trial comparing tirzepatide and semaglutide is planned.

The drugs appear effective for chronic weight management over many months. In addition to weight loss, they also reduce health problems associated with obesity, such as high blood sugar and markers of heart and metabolic disease.

However, it appears that if people taking the drugs stop, they regain the weight they lost - and the health problems that came with it.

What are the side effects of Mounjaro, Ozempic, and Wegovy?

The most common side effects are short-lived gastrointestinal issues such as nausea, vomiting, constipation, diarrhoea, and stomach pain.


Other possible effects include serious issues such as inflammation of the pancreas, kidney, gallbladder, and eye problems.

People with a history of certain thyroid cancers or a rare, genetic endocrine disorder should avoid the drugs, because it is not clear if tirzepatide causes thyroid problems, including cancer.

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