Author: Kristina Palmer, MD | Reviewer: Alyssa Billingsley, PharmD
Key Takeaways:
- Tirzepatide (Mounjaro) is FDA-approved for the treatment of type 2 diabetes. People using it usually lose weight. In November 2023, the FDA approved tirzepatide for weight management in people with or without diabetes under the brand name Zepbound.
- Tirzepatide is currently the only medication in its class and is administered as a once-weekly injection. It works by affecting insulin levels, blood glucose production, and hunger hormones.
- In clinical trials, people without diabetes lost an average of 34 to 48 pounds (approximately 15.5–21.8 kg) on the highest dose of Zepbound over 72 weeks (about 16.5 months).
Tirzepatide is rapidly gaining popularity — and for good reason. Originally approved under the name Mounjaro for type 2 diabetes, this injectable medication is now also available as Zepbound for weight loss. But how exactly does tirzepatide promote weight reduction, and who can benefit from it?
What Is Tirzepatide (Mounjaro, Zepbound)?
Tirzepatide is a newer medication that was first approved by the FDA in May 2022 for the treatment of type 2 diabetes in adults. It is a once-weekly injection. When used together with a suitable diet and regular physical activity, it helps lower blood glucose (sugar) levels. In addition to treating type 2 diabetes, tirzepatide is also approved for chronic weight management and for treating obstructive sleep apnea (OSA) in certain adults under the brand name Zepbound.
Can Tirzepatide Be Used for Weight Loss?
Yes, tirzepatide is FDA-approved for long-term weight management in adults. You may qualify for tirzepatide for weight loss if:
- You have been diagnosed with obesity.
- You have overweight along with at least one weight-related condition, such as type 2 diabetes or high cholesterol.
Even if you don’t meet these criteria, a healthcare provider may still prescribe tirzepatide off-label for weight loss. Your medical team may also prescribe it if you have type 2 diabetes and weight reduction is one of your treatment goals. In that case, they may prescribe Mounjaro instead of Zepbound, since Mounjaro is specifically FDA-approved for diabetes.
How Does Tirzepatide Promote Weight Loss?
Tirzepatide helps with weight loss mainly by reducing appetite and prolonging the feeling of fullness, which leads to lower calorie consumption.
It is currently the only approved medication that acts similarly to two natural gut hormones:
- Glucose-dependent insulinotropic polypeptide (GIP)
- Glucagon-like peptide-1 (GLP-1)
Because of this dual mechanism, tirzepatide is known as a dual GIP/GLP-1 receptor agonist.
GIP and GLP-1 are incretin hormones released after eating. Tirzepatide mimics their effects: it signals the pancreas to release insulin after meals and tells the liver to produce less glucose. These actions help control blood sugar levels.
In addition to lowering blood sugar, tirzepatide promotes weight loss in several ways:
- It signals the brain that you are full — so you eat less.
- It slows the passage of food through the stomach — helping you stay full longer.
Other similar injectable weight-loss medications mimic only one incretin (GLP-1). Thanks to its dual action, tirzepatide can deliver greater weight loss compared to single-agonist alternatives.
How Much Weight Do People Typically Lose on Tirzepatide?
While results vary by individual, many people lose 15% or more of their starting body weight with tirzepatide.
In a major clinical trial involving over 2,500 people without diabetes who had obesity or overweight, participants on tirzepatide lost an average of 15% to 21% of their initial body weight over 72 weeks (about 16.5 months). This corresponded to an average loss of 34 to 48 pounds (15.5–21.8 kg). The placebo group lost only about 3% (roughly 7 pounds / 3.2 kg).
Moreover, more than one-third of people taking the highest dose of tirzepatide 15 mg weekly lost at least 25% of their starting body weight (over 58 pounds / 26.3 kg).
What Are the Side Effects of Tirzepatide?
Tirzepatide can cause side effects, which are usually most noticeable when starting treatment or after increasing the dose. Most are mild and improve with time.
Common side effects include:
- Nausea
- Vomiting
- Diarrhea
- Loss of appetite
- Stomach pain
- Constipation
- Indigestion
If these side effects are severe or persistent, consult your doctor.
What Are the Risks of Using Tirzepatide for Weight Loss?
Some potentially serious side effects have been reported, including:
- Severe allergic reaction: May cause rash, difficulty breathing, and requires immediate medical attention.
- Pancreatitis: Can cause severe stomach or back pain, vomiting, and fever — requires urgent medical care.
- Thyroid cancer: Your doctor may recommend avoiding tirzepatide if you or your family have a history of certain thyroid cancers. This is based on increased risk of thyroid C-cell tumors observed in animal studies (risk in humans not confirmed).
- Gallbladder problems: Including gallstones.
- Hypoglycemia (low blood sugar): Risk is higher if you also take insulin or certain diabetes medications.
Tirzepatide may also interact with other medications. Always discuss your full medication list with your doctor and pharmacist.
Frequently Asked Questions
Is Ozempic Better Than Tirzepatide for Weight Loss?
Studies show that tirzepatide can provide greater weight loss than Ozempic (semaglutide). In a head-to-head trial, people using Mounjaro lost an average of 16 to 25 pounds (7.3–11.3 kg) depending on the dose, while those on Ozempic lost about 12 pounds (5.4 kg).
Is Tirzepatide Available as a Pill?
Will Weight Return After Stopping Tirzepatide?
Summary
Tirzepatide is a once-weekly injection that helps control blood sugar in people with type 2 diabetes (as Mounjaro) and is FDA-approved for long-term weight management in adults with or without diabetes (as Zepbound). Combined with diet and exercise, it can lead to significant weight loss — averaging 15% to 21% (34 to 48 pounds) in people without diabetes.
Tirzepatide signals fullness to the brain, slows digestion, and improves blood sugar control. It can be an effective option, but it is not suitable for everyone. Always consult your healthcare team to determine if it is the right choice for you.
Sources / References
- Aronne, L. J., et al. (2023). Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity. JAMA.
- Chavda, V. P., et al. (2022). Tirzepatide, a new era of dual-targeted treatment for diabetes and obesity: A mini-review. Molecules.
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- Jastreboff, A. M., et al. (2022). Tirzepatide once weekly for the treatment of obesity. The New England Journal of Medicine.
- Nauck, M. A., et al. (2018). Incretin hormones: Their role in health and disease. Diabetes, Obesity and Metabolism.