Wegovy vs. Mounjaro: A Comprehensive Comparison for Weight Loss

Two of the most effective medications for weight loss are Wegovy (semaglutide) and Mounjaro (tirzepatide), both of which have been studied extensively in clinical trials [1]. Whilst similar in many ways, they also have key differences in how they work, effectiveness, side effects, and administration.

How Do Wegovy and Mounjaro Work?

Both Wegovy and Mounjaro belong to a class of drugs that influence hormonal pathways involved in appetite regulation and metabolism. However, they work in slightly different ways.

• Wegovy contains semaglutide, which is a GLP-1 receptor agonist [2]. GLP-1 (glucagon-like peptide-1) is a naturally occurring hormone that helps regulate blood sugar levels, slow gastric emptying, and reduce hunger. By mimicking GLP-1, semaglutide increases satiety (fullness), helping people eat less and lose weight.

• Mounjaro, on the other hand, contains tirzepatide, which is unique because it acts on two receptors: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) [3]. By targeting both GLP-1 and GIP, tirzepatide enhances weight loss and metabolic benefits more than GLP-1 alone [4].

What is the Effect of These Medications on Weight Loss?

Clinical trials comparing the two medications have shown Mounjaro to be more effective for weight loss in people with obesity who do not have Type 2 diabetes [5].

• The STEP trials (for semaglutide) found that Wegovy (2.4 mg weekly) led to an average weight loss of approximately 14.9% of total body weight over 68 weeks (STEP 1 Trial) [6].

• The SURMOUNT-1 trial (for tirzepatide) found that at its highest dose (15 mg weekly), Mounjaro resulted in an average weight loss of approximately 20.9% of body weight over 72 weeks [7].

• A head-to-head trial confirmed that Mounjaro users lost an average of 20.2% of their body weight, compared to 13.7% for Wegovy users, over 72 weeks [8].

This difference suggests that the dual agonist mechanism of Mounjaro may provide enhanced weight loss and metabolic benefits compared to the GLP-1 agonist, Wegovy.

Side Effects

Both medications are associated with gastrointestinal side effects, which are common among drugs that target GLP-1 receptors [9]. These side effects are typically mild to moderate and improve over time.

• The most common side effects for both drugs include nausea, vomiting, diarrhoea, constipation, and abdominal pain [9].

• A similar percentage of people reported side effects on both drugs (around 77%–79%), with around 6% of Mounjaro users and 8% of Wegovy users stopping the drug due to side effects in one study [8].

Both drugs also carry a small risk of rare but serious side effects, including pancreatitis and gallbladder disease [10].

Dosage and Administration

Both Wegovy and Mounjaro are injectable medications taken once weekly, but their dosage schedules differ. For a step-by-step guide on how to administer your treatment, please see our guide, How to Inject Wegovy and Mounjaro.

Final Thoughts

Wegovy and Mounjaro represent major advancements in medical weight loss treatments, offering effective, non-surgical options for people struggling with obesity. While both medications significantly reduce body weight, Mounjaro has demonstrated superior results in clinical trials due to its dual GLP-1/GIP receptor action. However, Wegovy remains a widely used and effective option for those seeking a proven, well-tolerated treatment.

References

1. Jastreboff, A. M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387, 205-216.

2. US Food and Drug Administration (FDA). (2021). Wegovy (semaglutide) injection prescribing information.

3. US Food and Drug Administration (FDA). (2022). Mounjaro (tirzepatide) injection prescribing information.

4. Nauck, M. A., et al. (2021). Tapping into the potential of two incretin hormones, GIP and GLP-1, for the treatment of type 2 diabetes. Diabetes Care, 44(4), 856-865.

5. Jastreboff, A. M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387, 205-216.

6. Wilding, J. P. H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384, 989-1002.

7. Jastreboff, A. M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387, 205-216.

8. Comparative Efficacy of Tirzepatide vs. Semaglutide in Reducing Body Weight in Humans: A Systematic Review and Meta-Analysis of Clinical Trials and Real-World Data

9. Nadeem, D., et al. (2022). The Effect of Glucagon-Like Peptide-1 Receptor Agonists on the Gastrointestinal System. Clinical Gastroenterology and Hepatology, 20(3), 572-585.