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Weight Loss

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How does Mounjaro work for weight loss? A complete guide

Written by Dr. Kasra Tayebi

Published: Feb 14, 2024

Medically Reviewed by Goldina Erowele, PharmD, MBA

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Prescription medication is a popular option for weight loss when dieting and/or exercise fails. 2 weight loss drugs, Wegovy and Ozempic, became so popular that they’ve become hard to find. A new alternative, Zepbound hit the market in November 2023. But it was available sooner in an identical medication sold by a different name, Mounjaro. But how does Mounjaro work for weight loss?

This guide gives you a detailed look at Mounjaro’s mechanism, efficacy, potential side effects, and how it compares with other prescription weight loss medications.

Get a prescription for Zepbound or Mounjaro online in as little as 24 hours.

What is Mounjaro?

Mounjaro is a brand-name injectable medication approved by the FDA in May 2022 to treat type 2 diabetes. Its active ingredient is tirzepatide, which works by mimicking two of the body’s natural hormones: glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1). 

Other medications, like Ozempic and Wegovy, known as GLP-1 agonist receptor medications, mimic GLP-1 to work for weight loss and promoting satiety (a feeling of fullness after you eats). It also helps people with type 2 diabetes by regulating blood sugar levels.

While Ozempic and Mounjaro were both approved for type 2 diabetes treatment, it was discovered they also help people lose weight. 

By mimicking both GIP and GLP-1, Moujaro regulates blood sugar levels, promotes satiety, and impedes the brain’s hunger signals to suppress appetite. 

Weight loss on Mounjaro was so significant in patients with type 2 diabetes, that the manufacturer, Eli Lilly, received FDA approval to market it specifically for weight loss under the brand name Zepbound. Zepbound is identical to Mounjaro except for the name.

Let’s examine how tirzepatide in Mounjaro and Zepbound works for weight loss.

How does Mounjaro work for weight loss?

Tirzepatide, the active ingredient in both Zepbound and Mounjaro, mimics GLP-1 and GIP to target your metabolism, the way your body processes food. It increases feelings of fullness, so you eat less. And it slows down the rate at which food leaves your stomach (gastric emptying) to further promote how full you feel. You eat less, which helps with ongoing weight loss. 

How GIP works

GIP works by stimulating the release of insulin, particularly in response to food intake, which helps with glucose (blood sugar) control. When blood sugar is high, people feel hungrier and are prone to overeat. By controlling blood sugar and keeping it under control, GIP in tirzepatide staves off hunger.

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.

Excessive 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 individuals with type 2 diabetes.

How GLP-1 works

The GLP-1 receptor agonist in Mounjaro and other GLP-1 agonists stimulates the body’s receptor for GLP-1 to increase insulin production and satiety. This lowers appetite by telling your brain that you’re full, so you want to eat less. The combined effect is to help with weight loss because you’re satisfied eating fewer calories. 

By targeting these key aspects of metabolism, Mounjaro and other weight loss injections contribute to sustained weight reduction, offering individuals a unique, science-backed solution on their journey to achieving a healthier weight. 

What does Mounjaro do to your body?

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 gastrointestinal discomfort, such as nausea and diarrhea, which are more likely during the initial phase of treatment but often decrease or stop with time. 

In some cases, more serious side effects have occurred including: 

  • Pancreatitis
  • Severe allergic reactions, that include swelling or difficulty breathing and require immediate medical attention 
  • Infection

It’s important to monitor for signs of pancreatitis, such as persistent abdominal pain, as well as potential kidney-related issues, including changes in urine color or frequency.

There is also an FDA black box warning for an increased risk of thyroid cancer with tirzepatide. As with any prescription medication, talking to a healthcare professional before taking any new medication is important. 

While most people take Mounjaro with no or only mild side effects, understanding potential side effects can help you make an educated decision about your weight loss journey and communicate with your healthcare provider.

How much weight can you lose with Mounjaro?

Clinical trials have shown that people who are overweight or obese can lose up to 26.6% of their body weight on Mounjaro.

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. On average, study participants on the higher doses of 15 milligrams a week, lost 52 pounds. And even those on lower doses of 5 or 10 milligrams lost between 35 and 49 pounds. 

A later trial published in Nature Medicine showed participants who combined tirzepatide with intense lifestyle changes lost up to 26.6% body weight. Participants spent 12 weeks making lifestyle changes only and then followed with 72 additional weeks of lifestyle changes combined with tirzepatide. Participants who made lifestyle changes but didn’t take tirzepatide had only a 3.8% reduction in weight.

These results are significant compared to Ozempic and Wegovy, which have become so popular that the manufacturer, Novo Nordisk, is struggling 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 250-pound person, that’s the difference between a potential weight loss of 66.5 pounds on Mounjaro compared to 37.25 pounds on Wegovy.

How long does Mounjaro take to work for weight loss?

While the studies cited above span 18 months, weight loss on Mounjaro starts soon after treatment and more quickly than on Wegovy.

Randomized trials found that patients with type 2 diabetes started losing weight on Mounjaro right away. And in one month, they had lost an average of 2% of their body weight. In 2 months, they had lost 4%.

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

These studies show Mounjaro’s ability to help people lose weight and maintain significant weight loss. In these studies, participants weren’t restricted as to what diets to follow, and even though some of those who took Mounjaro may not have followed ideal weight-loss diets, they were still able to lose a significant amount of weight. 

How do you maximize weight loss on Mounjaro?

To optimize the benefits of Mounjaro, following the instructions on the prescription is critical. But eating some foods and following some practices can help you maximize weight loss while taking Mounjaro or any other weight loss medication, 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.
  • Adhering to a Mediterranean diet focusing on 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. 

What happens if you stop taking Mounjaro for weight loss?

A study in The Journal of the American Medical Association per CNN suggests a gradual return to baseline weight over several weeks after stopping Mounjaro. Patients who stayed on Zepbound continued to lose about an additional 6% of their body weight. Their loss did eventually plateau. People who stopped Zepbound maintained about 80% of their original weight loss, regaining the other 20% over a year. 

Transitioning to a healthy lifestyle during and after taking Mounjaro is crucial to maximize results and minimize the chance of regaining the weight you lose.

Is Mounjaro better than Ozempic or Wegovy?

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

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.

Other 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 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. Most medications included here result in a greater than 5% weight loss in the studies. Mounjaro is included for comparison.

MedicationIndicationsAdministrationWeight loss potential
Zepbound and Mounjaro (tirzepatide) Zepbound is FDA-approved for weight management in adults who are clinically obese or clinically overweight with weight-related health conditions and is used along with diet and exercise.

Mounjaro is approved for adults with type 2 diabetes to improve blood sugar when used with diet and exercise.
Weekly 2.5, 5, 10, or 15 mg injections. Patients start on a smaller dose and work up to a recommended maintenance dose of  5, 10, or 15 mg a week.Up to 26% of body weight over 72 weeks
Wegovy (semaglutide)Approved for weight management in adults who are clinically obese or clinically overweight with weight-related health conditions and when used along with diet and exercise.Weekly 1.7 or 2.4 mg subcutaneous injections.

Patients start at .25 mg a week and work up to a maintenance dose of  2.4 mg at 17 weeks. 
14.9% of initial body weight in 68 weeks
Ozempic (semaglutide)Approved for adults with type 2 diabetes to control blood sugar levels and used along with diet and exercise. Used off-label for weight loss. Weekly  0.5 mg, 1 mg, or 2 mg subcutaneous injections. Patients start on a .25 mg dose and work up to a .5 mg dose with optional doses of 1 or 2 mg if needed.10.9% weight loss in 6 months
Rybelsus (semaglutide)Approved to improve blood sugar in adults with type 2 diabetes when used along with diet and exercise. Used off-label for weight loss. One 7 or 14 mg tablet taken daily.15.1% body weight loss after 68 weeks
Saxenda (ligiratude)Approved for chronic weight management in adults who are clinically obese or clinically overweight with weight-related health conditions and when used along with diet and exercise.Weekly 3 mg subcutaneous injections. Patients start on a 0.6 mg dose and work up to a recommended 3 mg dose over 4 weeks. 5 to 10% body weight in 30 to 180 days
Qsymia (phentermine-topiramate)Approved for adults with obesity or who are overweight with a weight-related medical condition and when used along with diet and exercise.3.75 mg tablet daily for 14 days; then a 7.5 mg tablet daily.An average of 15 pounds in 3 months and 24 pounds in 1 year
Contrave (bupropion-naltrexone)Approved for adults with obesity or who are overweight with a weight-related medical condition and when used along with diet and exercise.1 tablet daily increased to 2 tablets daily over time. 5 to 10% of body weight in 52 to 56 weeks
Adipex-P (phentermine)Approved for short-term (a few weeks) weight loss management for adults as part of a weight loss regimen based on exercise, behavioral modification, and caloric restriction.1 15 to 37.5 mg tablet 1 to 2 hours before breakfast.11.2% weight loss in 6 months
Xenical (orlistat)Approved for adults with obesity or who are overweight with a weight-related medical condition.120 mg orally three times a day with a meal containing fat.An  average 2.4% body weight loss in 4 years.

New medications are also undergoing trials. Learn more about current and upcoming medications in the best prescription weight loss medications

What does Mounjaro cost and is it covered by insurance?

The average retail cost of Mounjaro at the time of publication is $1,135.24 for a 28-day supply regardless of dose. This is the approximate price you’ll pay out of pocket without insurance or a manufacturer’s or prescription savings plan discount. 

What you pay with insurance will depend on your plan, drug co-pay, and whether or not you’ve met your deductible (if applicable) and out-of-pocket costs (if applicable).

Other factors may affect your ability to get Mounjaro and what you pay. Some insurance companies require prior authorization for Mounjaro. That means they’ll only pay for it if your healthcare provider asks them to approve it and the request meets their criteria. If your provider prescribes Mounjaro only for weight loss and you don’t have type 2 diabetes, your insurance company may not cover the cost.

The alternative is to have your provider prescribe Zepbound. It’s approved for adults who are clinically obese or clinically overweight with weight-related health conditions. Its list price (the price Eli Lilly, the manufacturer, charges pharmacies) was $1,059.87 for a 28-day supply in November 2023. Retail cost (the price you pay) will be higher. Most insurers also require prior authorization for Zepbound. 

Eli Lilly offers a savings card for both Zepbound and Mounjaro where you might pay as little as $25 a month or every 3 months, provided you have insurance. 

If you pay out of pocket, prescription discount programs, such as GoodRx, can help you save a small amount on either medication. 

How to get Mounjaro or Zepbound for weight loss?

To determine the right weight loss program for you, which may include a prescription for Mounjaro or Zepbound, schedule an appointment with a healthcare provider. Your provider will know if your insurer requires prior authorization. If they do, your provider will handle the details for you.

Once you have your prescription and prior authorization, if needed, you’re ready to fill your prescription and start losing weight. Be aware there may be shortages of these medications due to high demand.

Find a weight loss specialist on Klarity and get help starting and maintaining your weight loss journey

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, find the right medication, and make the needed lifestyle changes to ensure you achieve and maintain a healthy weight. 

Find a provider on the Klarity platform.

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.

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