What is Mounjaro? And does it work better for weight loss than Ozempic and Wegovy?

A new type of diabetes drugs is spurring a revolution in weight loss drugs as well. The newest potential medication for weight loss is called Mounjaro. But as with all drugs, there are pros and cons. What you need to know.
May 15, 2023
Women walking. A new type of diabetes drugs is spurring a revolution in weight loss drugs as well. What is Mounjaro? And does Mounjaro work for weight loss as well as diabetes? Photo: Getty Images.
Does a new diabetes drug called Mounjaro work even better for weight loss than the other popular new drugs, Ozempic and Wegovy? An expert sorts out the pros and cons. Photo: Getty Images.

Could the newest diabetes drug, Mounjaro, work even better for weight loss than the popular new medications, Ozempic and Wegovy?

The short answer is “yes,” but federal health officials have not approved Mounjaro for weight loss yet. And like Ozempic and Wegovy, the devil is in the details. (Read more about the pros and cons of Ozempic and Wegovy.) So, anyone considering using the newest diabetes drugs for weight loss will want to think carefully before racing to the doctor and asking for a prescription.

To get answers to your questions, we consulted with Dr. Cecilia Low Wang, a UCHealth expert on endocrinology, diabetes and metabolism.

Low Wang is also a professor at the University of Colorado School of Medicine on the Anschutz Medical Campus. She chairs the committee that advises the U.S. Food and Drug Administration (FDA) on drugs related to endocrinology and metabolism. (Low Wang’s views do not represent those of the FDA or the FDA Endocrinologic and Metabolic Drugs Advisory Committee.)

What is Mounjaro?

Dr. Cecilia Low Wang is an expert on diabetes and weight loss drugs. Photo: UCHealth.
Dr. Cecilia Low Wang is an expert on diabetes and weight loss drugs. Photo: UCHealth.

Mounjaro is the newest diabetes drug that also triggers dramatic weight loss in people who inject it. The U.S. Food and Drug Administration (FDA) approved Mounjaro a year ago for patients with diabetes.

FDA officials have not approved Mounjaro for weight loss yet, but Low Wang said they are fast-tracking consideration of the drug. That’s because clinical trials have shown that people who do not have diabetes but do have elevated body mass indexes (BMI) used lost considerable weight when they used Mounjaro.

An FDA recommendation regarding Mounjaro for weight loss could come by the end of this year.

In the approval for Mounjaro for people with diabetes, federal health officials said it works well for people with Type 2 diabetes. That’s the most common form of diabetes, and more than 30 million Americans suffer from it.

Like Ozempic and Wegovy, it’s an injectable medication, but Mounjaro differs in some key ways from the other new, popular diabetes medications.

How does Mounjaro work? Why does it cause weight loss for people with diabetes?

“It suppresses appetite and makes you feel more full. It changes the rate at which your stomach empties,” Low Wang said.

Are Mounjaro, Ozempic and Wegovy the same drugs?

No. Ozempic and Wegovy are brand names for a drug called semaglutide. Mounjaro is the brand name for a different drug called tirzepatide. The drugs work in similar ways to reduce appetite, but there are some differences.

The drugs also are made by different companies. Eli Lilly makes Mounjaro, while Novo Nordisk makes Wegovy and Ozempic.

How does Mounjaro work?

“It’s a completely new drug class,” Low Wang said. “Instead of being a single-receptor agonist, which semaglutide (the drug in Ozempic and Wegovy) is, Mounjaro activates two receptors at the same time. That’s why it’s called a ‘dual-agonist.’”

This double agonist approach seems to cause people who use Mounjaro injections to lose even more weight than those who use a single-agonist medication.

These receptors stimulate hormones that control blood sugar levels and reduce appetite, triggering weight loss.

The receptors are known as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

Wegovy and Ozempic activate the GLP-1 receptor, while Mounjaro activates two receptors: both GLP-1 and GIP.

How much weight do people lose with Mounjaro?

Low Wang said the weight loss data from the Mounjaro clinical trials have been stunning.

People who used the largest dose of Mounjaro, 15 milligrams, lost as much as 21% of their body weight.

“They were able to achieve unprecedented amounts of weight loss. It was dramatic and exciting,” said Low Wang, who receives no funding from pharmaceutical companies.

While losing significant weight, study participants also were able to keep their diabetes symptoms in check.

“We’ve never had a medication that is so effective for improving diabetes control and weight loss without putting patients at high risk of hypoglycemia,” Low Wang said.

Even so, time will tell how the drugs perform over time.

“The impacts on appetite and weight regulation are startling,” Low Wang said.

But people should not jump to conclusions and assume that Mounjaro will be a miracle drug.

“We still don’t know what the effects would be of taking Mounjaro for a short time, then going off of it. Does it change anything about your biology? Does it make it harder to lose weight in the future without a medication? We really don’t know yet,” Low Wang said.

Why are weight loss drugs a big deal?

In the U.S, about 70% of adults are obese or overweight, and many of these people have serious health problems that put them at greater risk for heart disease, stroke, diabetes and some types of cancer.

Did study participants lose more weight with Mounjaro than with Ozempic or Wegovy?

Yes. According to FDA regulators, the average weight loss with the maximum recommended dose of Mounjaro resulted in patients losing 12 pounds more on average than those who used semaglutide.

How do patients take Mounjaro?

Like Ozempic and Wegovy, Mounjaro is an injectable medication that patients need to use once a week.

Are there reasons to be cautious about Mounjaro?

Yes. As with Ozempic and Wegovy, there are reasons to be cautious. (Read more about eight reasons to be cautious about Ozempic and Wegovy.)

Here are some reasons to be cautious about Mounjaro:

  1. Mounjaro is not approved for everyone. So far, it’s approved only for people with diabetes, not for people who are overweight or obese and do not have diabetes.
  2. Just like Ozempic and Wegovy, if you lose weight with Mounjaro, you likely will need to keep taking the medication forever to keep the weight off.
  3. Mounjaro is expensive, and it may be hard to get.
  4. Like Wegovy and Ozempic, Mounjaro can cause unpleasant gastrointestinal side effects.
  5. Mounjaro is new. There are not long-term studies yet. So doctors don’t know if there will be potentially concerning long-term side effects.

Tell me more about long-term weight loss. If I lose weight with Mounjaro, will I have to keep taking it just like people must keep taking Ozempic and Wegovy to keep the weight off?

Yes. People who are able to control their diabetes or lose a great deal of weight with Mounjaro, Wegovy and Ozempic will need to keep taking the drugs for the rest of their lives if they want to keep their diabetes symptoms in check and want to keep weight off.

People who have stopped taking Ozempic and Wegovy typically have gained back the weight they have lost. Since Mounjaro is so new, there is little information about long-term use.

“If you stop taking these medications, and don’t change your behaviors, then the weight can pile back on,” Low Wang said.

What are the pros and cons of using Mounjaro?

The biggest benefit of Mounjaro is that it seems to work well for patients with diabetes, and it triggers major weight loss for patients.

The cons are similar to those of Ozempic and Wegovy.

They include high drug costs, unpleasant gastrointestinal side effects, poor insurance coverage and drug shortages.

Like Ozempic and Wegovy, the most common side effects of Mounjaro include nausea, vomiting, diarrhea, decreased appetite, constipation, upper abdominal discomfort and abdominal pain.

In addition, FDA officials have warned that Mounjaro causes thyroid C-cell tumors in rats. Federal health experts don’t know yet whether Mounjaro causes similar tumors — including medullary thyroid cancer — in humans.

Are stomach problems, nausea and vomiting common for everyone who uses Mounjaro, Ozempic and Wegovy?

Some patients report gastrointestinal problems with Mounjaro, Ozempic and Wegovy, but many do not have any problems, Low Wang said.

“It’s just a percentage of people who have side effects. The majority of people tolerate these medications well,” Low Wang said.

Her patients have had the best luck when they start with the lowest dose and let their bodies get used to it.

“We start patients on a low dose for four weeks, then step up on the dose,” Low Wang said.

How can people reduce gastrointestinal symptoms with Mounjaro, Ozempic and Wegovy?

Low Wang has found that patients do well if they pay close attention to when they start feeling full and stop eating at that point. People will end up dramatically reducing how much they eat. For those who love to eat and cook, taking the drugs can be a challenge.

In addition, foods that are rich in fat tend to increase negative gastrointestinal side effects.

I hear that these medications can be very expensive and hard to get. Is that true?

Yes. Insurance plans will not cover Mounjaro or Ozempic for patients who want to lose weight and don’t have diabetes because the FDA has not approved the medications for this purpose. Many insurance companies do not cover Wegovy, which is indicated for increased body weight without diabetes.

“A major problem we’re faced with is that many insurance plans are not covering medications or other therapies for increased body weight at all, or if they are, it is not to a degree that puts effective therapies within reach of most people,” Low Wang said.

Access can be a big problem for lower-income people, and due to the popularity of the drugs, there have been shortages and restrictions.

“Some patients who have started taking Mounjaro have had difficulty with insurance coverage,” Low Wang said. “Does your insurance cover it? If they do, is it within your budget, and does your pharmacy have the medication?”

If a patient asked you for a Mounjaro prescription for weight loss now, what would you tell them?

For now, Low Wang is not recommending Mounjaro for patients who want to lose weight but don’t have diabetes.

That’s because Mounjaro is not yet approved for weight loss.

“We have other good options that are FDA-approved for weight loss,” Low Wang said. “We need to wait to see the published data regarding Mounjaro for weight loss.”

What about in the future? Do you expect the FDA to approve Mounjaro for weight loss?

It’s unclear exactly what federal health regulators will decide. But the early evidence points to dramatic weight loss with Mounjaro. So Low Wang will not be surprised if FDA officials approve Mounjaro for weight loss.

“A significant percentage of people who take this drug at higher doses lose more than 20% of their body weight,” Low Wang said.

That degree of weight loss can lead to dramatic health benefits.

“We’ve never seen this degree of weight loss with other medications. It’s on the order of what you might see with bariatric/metabolic surgeries,” she said.

If Mounjaro causes greater weight loss than people can achieve with Ozempic and Wegovy, do you expect Mounjaro to replace the other drugs?

No. Low Wang does not expect Mounjaro to replace Ozempic and Wegovy.

“We always need more choices,” she said. “We need more than one drug in each class because there are differences in the medications. Sometimes people can tolerate one medication better than another.”

Along with the newest diabetes medications, there are other older drugs that also work well for some patients.

Are drugs like Mounjaro, Ozempic and Wegovy a better choice than surgery?

Not necessarily. Low Wang said that individuals who are overweight or obese need to speak with their doctors and evaluate the best option for them.

“Individuals need to weigh risks and benefits. You can’t really say that one option is better than another across the board,” she said.

Taking a medication is certainly less invasive than going through surgery. But people who take drugs like Mounjaro, Ozempic and Wegovy need to keep taking them.

If patients opt for surgery, Low Wang said they need to be sure to find a Bariatric Surgery Center of Excellence. In order to earn the designation, centers have to prove that they have low rates of complications, an extensive support team and produce excellent, documented patient outcomes.

Low Wang said that long-term studies show that some people who have bariatric surgery gain the weight back just as people who stop taking these powerful diabetes drugs are likely also to gain the weight back if nothing else has changed.

What about cardiovascular and kidney benefits? Researchers found that people who used Ozempic and Wegovy lost weight, controlled their diabetes symptoms and also improved their cardiovascular and kidney health. Is that true for Mounjaro as well?

It’s too early to know, Low Wang said. Researchers are studying the potential cardiovascular benefits of Mounjaro now but haven’t yet released the results of these studies.

Low Wang and other experts anticipate that weight loss associated with Mounjaro should lead to many health benefits. The potency of Mounjaro also has led to a significant percentage of people achieving A1c levels in the “non-diabetes” range.

What about children and teens? Are these drugs approved for young patients? Do you recommend them for kids?

Mounjaro is not approved for children or teens. It’s currently approved for adults ages 18 and older. Wegovy and Ozempic are approved for some patients who are 12 and older.

Low Wang said researchers have learned a great deal in recent years about how dangerous diabetes is in children.

“Diabetes is really different in kids as compared with adults. When kids develop Type 2 diabetes, it’s a sign that something is really, really wrong with their metabolism and/or physiology, and how their body is functioning. So it’s actually a much more severe condition than in most adults,” Low Wang said.

That’s why treating diabetes in children and teens is vital.

“They are far sicker than an adult at the same level. So I think medications for young people can be really appropriate,” Low Wang said.

Of course, children and teens also need behavior change. Everyone needs to move more and many people — young and old alike — can benefit from eating healthier diets.

Low Wang does not care for pediatric patients. Parents of children and teens who are dealing with diabetes and obesity should seek guidance from pediatric diabetes experts.

Do you think people who are overweight or obese have been unfairly blamed for their challenges, and thus, fewer have been encouraged to use medications to lose weight?

Yes. Low Wang said doctors have learned a great deal in recent years about genetic causes of obesity.

“As with many medical conditions, especially chronic conditions, there’s a genetic component and an environmental component. In the past, many people mistakenly thought that weight gain was all environmental, and it’s not,” Low Wang said.

“What we’re trying to do now is to address the end goal: decreased weight leading to better health,” she said. “This is why ‘ABCD,’ or ‘adiposity-based chronic disease,’ is a term being popularized to focus more attention on the complications that can and often do result from excess weight.”

The American Association of Clinical Endocrinology recently released updated algorithms for comprehensive management of Type 2 diabetes. Low Wang played a pivotal role in shaping these new recommendations for people with Type 2 diabetes and increased body weight.

“We’re acknowledging the physiology that is dysregulated and causes excessive weight for some. And we’re trying to address that with weight loss medications, among other effective treatments,” Low Wang said.

What do researchers know about the genetic causes of weight gain?

Finding the exact genetic causes for weight gain has proven to be challenging, Low Wang said.

“For most people, it’s not a single-gene disorder. There are numerous genes that affect appetite and how people sense hunger,” Low Wang said.

In addition, individuals have different microbiomes and different metabolic set points, all of which affect weight and weight gain. Furthermore, researchers are still working to understand the connection between the brain and the gut.

“It’s extremely complex. We’re learning a lot, but there is more to learn, and the causes for obesity are definitely multifactorial,” Low Wang said.

Are more drugs like Mounjaro, Ozempic and Wegovy in development? Do you anticipate that we will keep seeing new drugs for diabetes and weight loss?

Yes. Low Wang said there are more than a dozen drugs in development.

“We’re going to see a lot of different combinations,” she said. “There are many drugs in development right now.”

That’s because obesity rates are very high in the U.S. and worldwide.

What’s the overall message about Mounjaro and other diabetes medications for weight loss?

For people with Type 2 diabetes and those with elevated body mass indexes or BMI, Low Wang thinks the new drugs will be “game changers.”

For people who are overweight or obese but are otherwise healthy, drugs like Mounjaro, Ozempic and Wegovy may not be necessary or wise choices.

About the author

Katie Kerwin McCrimmon is a proud Coloradan. She attended Colorado College thanks to a merit scholarship from the Boettcher Foundation and worked as a park ranger in Rocky Mountain National Park during summers in college.

Katie is a dedicated storyteller who loves getting to know UCHealth patients and providers and sharing their inspiring stories.

Katie spent years working as an award-winning journalist at the Rocky Mountain News and at an online health policy news site before joining UCHealth in 2017.

Katie and her husband, Cyrus — a Pulitzer Prize-winning photographer — have three adult children and love spending time in the Colorado mountains and traveling around the world.