What is Mounjaro™? Weight Loss with Eli Lilly’s Tirzepatide

Tirzepatide isn't currently classified as a weight loss drug with the FDA, though with the promising results it's showing, it soon might be. Learn more here.
Medical Reviewer: Florencia Halperin, MD
Published on: September 15, 2022
Updated on: April 5, 2024

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Disclaimer: The content made available on The FORM Medical Weight Loss Blog represents the views and opinions of the authors and not those of other entities, such as the manufacturers of products mentioned therein. 

The last year has been an exciting time in the medical weight loss world given the approval of two new promising medications. Prior to this, the last FDA approval for a medication to treat obesity was in 2014 and weight loss benefit topped out below 10%. In June of 2021, the FDA approved semaglutide (Wegovy), which gave patients the most weight loss we have seen to date – an average of 15%. Then in July of 2022, Lilly published a study that looked at their new diabetes medication tirzepatide, the generic name for Mounjaro™, for the treatment of obesity. Patients in the clinical trial lost around 21% of their body weight at the highest dose of tirzepatide when combined with lifestyle intervention; the highest average weight loss seen with a medication to date. While the Mounjaro drug (tirzepatide) is not yet approved for the treatment of obesity, it’s likely that it will be soon and could be a game-changer for patients struggling with their weight. Here’s what you need to know about this promising new weight loss medication. 

What is Mounjaro™ (Tirzepatide)?

Mounjaro, which contains the active ingredient tirzepatide, is a once-weekly injectable medication that is used along with diet and exercise to improve blood sugar in adults with type 2 diabetes. 

How does Mounjaro Work?

The Mounjaro medication (tirzepatide) is in a class of its own when it comes to type 2 diabetes medications. It is the first single molecule that has the ability to mimic two naturally occurring hormones in the body that help to lower blood sugar: Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). The effects of these two hormones are diminished in persons with type 2 diabetes, which leads to elevated blood sugars, so it’s not a new concept to target these receptors when designing a medication to treat diabetes. In fact, a class of medications known as GLP-1 receptor agonists (drugs that mimic naturally occurring GLP-1 hormone in the body) have been used for years to treat type 2 diabetes and more recently, obesity. But the combination of a GLP-1 and a GIP is new and has shown even more benefit compared to administering each hormone separately. Tirzepatide acts on GLP-1 and GIP receptors throughout the body, which improves insulin sensitivity, increases insulin secretion, slows down stomach emptying, and reduces food intake, all of which are favorable for reducing blood sugar and losing weight.

What is Mounjaro Used For?

The Mounjaro medication (tirzepatide) is used with diet and exercise to improve blood sugars in adults with type 2 diabetes. In clinical trials, the improvement in hemoglobin A1c levels in persons with type 2 diabetes was very impressive – a 2.3% reduction when taking the highest dose of the drug. This is compared to a 1.9% reduction seen with Ozempic 1 mg (a common GLP-1 receptor agonist used for type 2 diabetes) and a 1.4% reduction seen with long-acting insulin. Additionally, an average of 90% of patients taking tirzepatide achieved an A1c of less than 7.0%; an indicator of appropriately treated diabetes. 

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Is Lilly’s Tirzepatide (Mounjaro) an Obesity Drug?

The FDA has not yet approved the Mounjaro drug (tirzepatide) for obesity, but that is likely to change in the near future based on how effective this drug has been for weight loss in clinical trials. In a study published in July of 2022, when using tirzepatide specifically for weight reduction in people with overweight and obesity, researchers found this diabetes medication produced an average of 21% weight loss at the highest dose of the drug. To put this into perspective, Wegovy​​, currently the most effective FDA-approved medication for obesity, produced an average weight loss of 15% in clinical trials. And older medications used for chronic weight management such as Saxenda, Qsymia, and Contrave, typically help patients lose an average of 5-10% of their body weight. 

How Does Mounjaro Work for Weight Loss?

The unprecedented weight loss effect of Mounjaro likely has to do with the dual action of the drug on the GIP and GLP-1 receptors. Acting on both the GIP and GLP-1 found in the appetite center of the brain helps to reduce food intake. GLP-1 also slows down stomach emptying, so you feel fuller sooner and longer, while GIP acts on our fat stores in a variety of ways to improve function and insulin sensitivity; all of which promote weight loss.

What Are the Side Effects of Tirzepatide (Mounjaro)?

While there are many beneficial effects of Mounjaro, like with any medication, there are some  potential side effects that need to be taken into consideration. Similar to GLP-1 receptor agonists like Wegovy, the most common side effects of tirzepatide are gastrointestinal symptoms such as nausea, vomiting, diarrhea, constipation, heartburn, and abdominal pain. Headaches, dizziness, and an increase in heart rate can occur as well, though less commonly. Gallbladder disease is another potential side effect, and other rare side effects have also been described. In clinical trials, only 6.2% of patients treated with the highest dose of tirzepatide versus 2.6% of patients treated with placebo discontinued the medication due to adverse effects. 

Tolerability of tirzepatide can be improved by starting the medication at a low dose and increasing it slowly. When used for diabetes, it is recommended to increase the dose on a monthly basis. The clinical trial looking at using tirzepatide for obesity also used a monthly dose escalation approach, so it is very likely this will be recommended if the medication is approved for the treatment of obesity and should help to reduce the potential for intolerable side effects. 

What are Alternatives to Mounjaro (Tirzepatide)?

While we eagerly await the approval of tirzepatide for obesity, there are other FDA-approved medications that are available now to help you with weight loss. Saxenda and Wegovy are GLP-1 receptor agonists that also have benefits for both weight loss and improving blood sugar. Contrave can also be an effective option, especially for patients struggling with cravings. Check out FORM’s Medication Resource for more information on these options. 

How Can FORM Help?

While medications work differently for each individual, studies show that patients experience 2x more weight loss with medication and lifestyle changes, rather than medication alone. FORM™ Board Certified Doctors and Registered Dietitians use physical activity, mindset shifts, nutrition and medication, if appropriate, to help you reach your health goals. If you are looking for a program that is both personalized and sustainable, FORM may be for you. Find out if you are eligible by taking our quiz now.
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Mounjaro™is a trademark of Eli Lilly and Company

Wegovy, Saxenda, and Ozempicare  registered trademarks of Novo Nordisk A/S

Qsymia® is a registered trademark of Vivus LLC

Contrave® is a registered trademark of Currax Pharmaceutical LLC

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