How does Mounjaro work for weight loss? And should you try it?

Mounjaro (tirzepatide) is approved to lower blood sugar for people with type 2 diabetes. But it also helps with weight loss. So much, Eli Lily who makes it, got it approved as Zepbound just for weight loss in November 2023. If you’re thinking about using it, learn how does Mounjaro work for weight loss here.

This article covers how Mounjaro helps people lose weight, how effective it is, its potential side effects, and how it compares with other prescription weight-loss medications.

What is Mounjaro?

Mounjaro is a brand-name medication approved by the US Food and Drug Administration (FDA) in May 2022 to treat type 2 diabetes when used with a reduced calorie diet and increased exercise. Its active ingredient is tirzepatide, which is a glucose-dependent insulinotropic peptide (GIP)/glucagon-like peptide-1 (GLP-1) receptor agonist. More on that below.

Tirzepatide in Mounjaro and Zepbound is the only GIP/GLP-1 agonist there. While you can get compounded tirzepatide, you can’t get generic Mounjaro or Zepbound. You take either as a weekly injection. 

How does Mounjaro make you lose weight?

Tirzepatide, the active ingredient in Mounjaro and Zepbound, mimics natural hormones in your body called GLP-1 and GIP. By mimicking these hormones, tirzepatide gives your body has a better blood sugar balance. Your metabolism, the way your body processes food, is also affected. Food leaves your stomach more slowly (called gastric emptying) so you feel fuller longer and want to eat less. And when you eat less, you can lose weight.

How mimicking GIP helps Mounjoaro cause weight loss

GIP stimulates the release of insulin, particularly when you eat, which helps with glucose (blood sugar) control. When blood sugar is high, you can feel hungrier and might overeat. By controlling blood sugar and keeping it under control, GIP in tirzepatide reduces your desire to eat.

As an added weight loss benefit, GIP also stimulates lipolysis, which is a fancy word for burning fat. Mounjaro is particularly effective at burning visceral fat, which is fat deep in the belly and around internal organs.

Spikes in blood sugar after meals can also increase the risk of diabetes and negatively impact the control of type 2 diabetes, which is why Mounjaro benefits people with type 2 diabetes.

How Mounjoro causes weight loss by mimicking GLP-1

The GLP-1 receptor agonist in Mounjaro and other GLP-1 agonists, like Wegovy and Ozempic, stimulates your body’s receptor for GLP-1 to increase insulin production and feelings of fullness (called satiety). This lowers your appetite by telling your brain that you’re full, so you want to eat less. You lose weight because you’re satisfied eating fewer calories. 

By affecting blood sugar and metabolism, Mounjaro and other weight loss injections contribute to weight loss.

How much weight can you lose with Mounjaro?

In clinical trials that studied tirzepatide to lower blood sugar in people with type 2 diabetes, people lost up to 13.9% of their body weight in 104 weeks (2 years). That’s almost 28 pounds if your starting weight is 200 pounds. 

Other trials point to potentially higher weight loss. 

• An early clinical trial presented at the American Diabetes Association’s 2022 Symposium showed that people who were overweight or obese without type 2 diabetes lost as much as 22.5% of their body weight in 72 weeks on tirzepatide. 
• A later trial published in Nature Medicine showed participants who combined 12 weeks of intense lifestyle changes followed by 72 more weeks of lifestyle changes and tirzepatide lost up to 26.6% of their body weight. Participants who made the same lifestyle changes but didn’t take tirzepatide lost only 3.8% body weight.
• In another trial published in JAMA Network, obese people using tirzepatide lost 20.9% of their body weight in 36 weeks and 5.5% more after 52 weeks. 

Bottom line: tirzepatide in Mounjaro can help people lose between 13.9 and 26.6% of their body weight when used with diet and exercise. That’s between 28 and 53 pounds with a starting weight of 200 pounds.

Weight loss results with tirzepatide are better than with Ozempic and Wegovy too. Both are so popular that the manufacturer, Novo Nordisk, has struggled to keep them in stock. Average body weight loss on Wegovy was just 14.9% of initial body weight in one clinical trial as reported in The New England Journal of Medicine. For a 200-pound person, that’s the difference between a potential weight loss of up to 53 pounds on Mounjaro compared to 29 pounds on Wegovy.

How long does Mounjaro take to work for weight loss?

While the studies cited above span 16 months, weight loss on Mounjaro starts quickly.

Randomized trials found that patients with type 2 diabetes started losing weight on Mounjaro right away. In 1 month, they’d lost an average of 2% of their body weight. In 2 months, they had lost 4%. That means a 200-pound person could lose around 8 pounds in 2 months or a pound a week.

The previously mentioned trial published in Nature Medicine found sustained weight loss of up to 6.9% after 12 weeks on Mounjaro.

And in these studies, participants didn’t have to follow a restricted diet (but may have), but still lost weight. 

How do you maximize weight loss on Mounjaro?

To optimize the benefits of Mounjaro, you need to follow your provider’s advice and dosing schedule and eat a reduced-calorie diet while increasing your physical activity. You can also eat specific foods and follow some best practices to help maximize weight loss while taking Mounjaro, including:

• Limiting processed foods, which is any food altered when prepared, such as cake, bacon, cheese, cereal, potato chips, etc.
• Including more low-glycemic fruits and vegetables in your diet, which are foods that have a low impact on blood sugar levels, such as most fruit, raw carrots, kidney beans, and lentils. 
• Eating a Mediterranean diet that includes lean protein, seeds, and whole grains. 
• Maintaining a healthy exercise routine to increase the amount of fat you lose and the overall muscle you retain. 

How do you take Mounjaro?

Mounjaro is a once-a-week injection that you give yourself or have someone give you. 

Mounjaro comes in 6 doses — 2.5, 5, 7.5, 10, 12.5, and 15 milligrams. You’ll most likely start on the 2.5 milligram dose and then increase your dose 2.5 milligrams after a month and then again every month until you reach your maximum dose. The maximum dose can be 15 milligrams, but some people stay on a lower maximum dose of anywhere from 5 to 15 milligrams a week. 

Each dose comes in a prefilled single-dose injection pen. You inject yourself in the thigh, belly, or upper arm by placing the base of the pen flat against your skin and pushing the button on the top of the pen for 10 seconds. You’ll hear a click when the injection starts and another one when it’s done.

If you stop Mounjaro, do you stop losing weight?

Participants in the SURMOUNT-4 clinical trial published on JAMA Network did regain about 14.9% of the 20.9% body weight they lost in the 24 weeks after stopping tirzepatide, but they didn’t regain all of the weight they’d lost. 

Maintaining an active lifestyle and healthy diet during and after taking Mounjaro is crucial to maximize results and minimize the chance of regaining the weight you lose.

Does Moujaro have side effects?

While Mounjaro presents a good opportunity to control blood sugar and help with weight loss, it has potential side effects. Common side effects associated with Mounjaro include nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, and stomach (abdominal) pain. These side effects are more likely when you start taking Mounjaro and when you increase your dose. They may decrease or stop as you continue taking it. 

A small number of people have had more serious side effects when taking Mounjaro, including: 

• Pancreatitis or an inflammation of the pancreas, which can cause severe abdominal pain and possibly vomiting. 
• Low blood sugar or hypoglycemia, which can cause you to feel shaky, confused, or light-headed; sweat or feel sleepy; or have a headache, blurred vision, or slurred speak, among other things.
• Severe allergic reactions that include swelling or difficulty breathing can happen and require immediate medical attention.
• Kidney problems including kidney failure.
• Severe stomach problems.
• Changes in your vision.
• Gallbladder problems, which might include pain in your stomach, fever, yellow skin, or clay-colored stools

There’s also an FDA boxed warning for Mounjaro due to an increased risk of thyroid cancer with tirzepatide found in rats during studies. Even though it’s not known if this risk applies to people, you shouldn’t take Mounjaro if you or someone in your family has a history of medullary thyroid carcinoma (MTC) or you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

There are other considerations when using Mounjaro not included here. Before starting it, talk to your healthcare provider and tell them about your health history and any medication you take to make sure you have the best possible experience. 

Is Mounjaro better than Ozempic or Wegovy?

The comparison between Mounjaro, Ozempic and Wegovy involves individual factors, and effectiveness varies. 

• Mounjaro and Zepbound show potentially significant results — up to 26% weight loss
• Wegovy shows a potential of 14.9% weight loss
• Ozempic shows a potential 10.9% weight loss

There are also weight loss pills, including Rybelsus, an oral version of semaglutide, the active ingredient in Ozempic and Wegovy.  

Consultation with a healthcare provider about medically supervised weight loss is essential to determine the most suitable medication for weight management based on your personal health needs and goals. Get tips on how to ask your doctor for weight loss pills.

Mounjaro alternatives: a comparison

If Mounjaro isn’t right for you or your healthcare provider recommends a different option, here’s a quick comparison of alternative weight-loss medications, some intended for type-2- diabetes, but sometimes used off-label (for a condition they’re not approved to treat) for weight loss. 

The table includes drug names, administration methods, dosing information, and approval for weight loss or other benefits of weight loss as well as weight-loss potential. Mounjaro is included for comparison.

How can you get Mounjaro for weight loss?

To determine the right weight loss program and medication for you, which may include a prescription for Mounjaro, schedule an appointment with a healthcare provider. Your provider will take your health history and determine if a weight loss medication and which one is right for you. They can also help you if your insurer requires prior authorization for a medication and find a medication if it’s in short supply.

Get in to see a weight loss provider within 24 hours and see if Mounjaro is right for you

If you’re struggling to lose weight or want to start, get the help of a healthcare provider. A provider can help you create a tailored weight loss plan, prescribe the right medication, and help you make the needed lifestyle changes to ensure you achieve and maintain a healthy weight. 

Find a provider and find out if Mounjaro is right for you.

Sources

Cardiovascular Diabetology, Reduction of prevalence of patients meeting the criteria for metabolic syndrome with tirzepatide: a post hoc analysis from the SURPASS Clinical Trial Program, Stephen J. Nicholls et al., Feb. 2024, https://cardiab.biomedcentral.com/articles/10.1186/s12933-024-02147-9

Clinical Trials Arena, Contrave for the Treatment of Obesity, Oct. 2014, https://www.clinicaltrialsarena.com/projects/contraveforthetreatm/?cf-view

Diabetes, Metabolic Syndrome, and Obesity, Clinical utility of phentermine/topiramate (Qsymia) combination for the treatment of obesity, Jin Hee Shin and Kishore M. Gadde, Apr. 2013, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3626409/

FDA.gov, Zepbound Label, https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf

FDA.gov, Medication Guide Wegovy, https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/215256Orig1s006lbl.pdf

JAMA Network, Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity, The SURMOUNT-4 Randomized Clinical Trial, Lous J. Aronne, MD. et al., Dec. 2023, https://jamanetwork.com/journals/jama/article-abstract/2812936

Nature Medicine, Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity: the SURMOUNT-3 phase 3 trial, Thomas A. Wadden et al, Oct. 2023, https://www.nature.com/articles/s41591-023-02597-w

The Lancet: Diabetes & Endocrinology, Efficacy and safety of once-weekly semaglutide 2.0 mg versus 1.0 mg in patients with type 2 diabetes (SUSTAIN FORTE): a double-blind, randomised, phase 3B trial, Juan P. Frias et. al., Jul. 2021, https://pubmed.ncbi.nlm.nih.gov/34293304/

The New England Journal of Medicine, A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management, Xavier Pi-Sunyer, MD, et al., Jul. 2015, https://www.nejm.org/doi/full/10.1056/nejmoa1411892

The New England Journal of Medicine, Once-Weekly Semaglutide in Adults with Overweight or Obesity, John P.H. Wilding, D.M. et al, Feb. 2021, https://www.nejm.org/doi/full/10.1056/NEJMoa2032183

The New England Journal of Medicine, Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes, Juan P. Frias, M.D. et al., https://www.nejm.org/doi/10.1056/NEJMoa2107519

The information provided in this article is for educational purposes only and should not be construed as medical advice. Always seek the guidance of a qualified healthcare professional with any questions or concerns you have regarding your health.

How we reviewed this article: This article goes through rigorous fact-checking by a team of medical reviewers. Reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the author.