Use of Tirzepatide (Mounjaro) as an Injectable Therapy for Weight Loss: Efficacy, Mechanisms, and Clinical Challenges

Currently, obesity and overweight represent major public health concerns, as they significantly increase the risk of cardiovascular diseases, type 2 diabetes, and other metabolic disorders. Consequently, new pharmacological strategies have been developed to support weight reduction in individuals with excess body weight. Among these therapies, tirzepatide, marketed as Mounjaro® for the treatment of type 2 diabetes, has demonstrated considerable potential for weight loss, including its use as an injectable therapy for obesity, either off-label or under expanded clinical indications (BEZERRA, 2025, p. 1).

Tirzepatide acts as a dual agonist of the glucagon-like peptide-1 (GLP-1) receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor. This dual mechanism promotes glucose-dependent insulin secretion, suppresses glucagon release, and reduces appetite through central and peripheral pathways. Evidence from clinical studies indicates that this combined action improves glycemic control in patients with type 2 diabetes and promotes significant weight loss (MDPI REVIEW, 2025, p. 8).

Clinical trials and meta-analyses have consistently demonstrated the effectiveness of tirzepatide in reducing body weight. Large-scale studies report average weight loss ranging from 15% to 20% of baseline body weight, depending on dosage and treatment duration, surpassing outcomes observed with other incretin-based therapies such as semaglutide (SAFETY & EFFICACY REVIEW, 2025, p. 2). Additional studies confirm that a substantial proportion of participants achieved weight reductions of 10% to 15%, reinforcing the role of tirzepatide as a promising therapeutic option for obesity management (JODR REVIEW, 2025, p. 1).

The weight-loss effects of tirzepatide are attributed not only to appetite suppression and increased satiety but also to metabolic modulation, including enhanced insulin sensitivity and increased energy expenditure. This multifaceted mechanism may explain its superior efficacy compared to therapies that target only GLP-1 receptors, such as semaglutide, highlighting its relevance in obesity treatment (ACGNG, 2025, p. 1).

Despite these benefits, the use of injectable agents such as Mounjaro for weight loss requires caution. Initially approved for type 2 diabetes, tirzepatide has only recently been evaluated for obesity management. In Brazil, the National Health Surveillance Agency (ANVISA) has expanded its indication to include weight control in adults with elevated body mass index (BMI), in combination with dietary and lifestyle interventions (ANVISA, 2025).

Another major clinical challenge is long-term weight maintenance following treatment discontinuation. Evidence suggests that many patients experience partial or complete weight regain after stopping tirzepatide, emphasizing the importance of sustained lifestyle modifications alongside pharmacotherapy (THE GUARDIAN, 2025).

Furthermore, treatment with tirzepatide may be associated with adverse effects such as nausea, diarrhea, and constipation, in addition to its relatively high cost. Therefore, healthcare professionals and patients must carefully evaluate the balance between benefits, risks, and financial considerations before initiating injectable therapies for weight loss (PUBMED REVIEW, 2025).

In conclusion, injectable therapies containing tirzepatide, such as Mounjaro, represent a significant advancement in obesity treatment due to their innovative mechanism and substantial efficacy in weight reduction. Nevertheless, cautious use under medical supervision and long-term lifestyle changes are essential to ensure treatment safety and sustained outcomes.

🇺🇸 References

ACGNG. Tirzepatide (Zepbound, Mounjaro) – Dual GLP-1 and GIP receptor agonist profile. ACGNG – The American Center for GLP-1 Nutritional Guidance. Available at: https://acgng.org/glp-1-basics/medication-profiles/tirzepatide-zepbound-mounjaro/. Accessed on: Jan. 15, 2026.

ANVISA. Mounjaro® (tirzepatide): new therapeutic indication for weight management. National Health Surveillance Agency. Available at: https://www.gov.br/anvisa/pt-br/assuntos/medicamentos/novos-medicamentos-e-indicacoes/mounjaro-r-tirzepatida-nova-indicacao. Accessed on: Jan. 15, 2026.

BEZERRA, T. A. R. Use of Tirzepatide (Mounjaro) as a Therapeutic Agent in Obesity and Type 2 Diabetes: A Systematic Review on Metabolic Control with GLP-1 Agonists. Journal of Diabetology Research, 2025. Available at: https://directivepublications.org/journal-of-diabetology-research/use-of-tirzepatida-mounjaro-as-a-therapeutic-agent-in-obesity-and-type-2-diabetes-a-systematic-review-on-metabolic-control-with-glp-1-agonists. Accessed on: Jan. 15, 2026.

MDPI REVIEW. Emerging role of GLP-1 agonists in obesity: a comprehensive review of randomized controlled trials. International Journal of Molecular Sciences. MDPI, 2025. Available at: https://www.mdpi.com/1422-0067/24/13/10449. Accessed on: Jan. 15, 2026.

PUBMED REVIEW. Efficacy and safety of tirzepatide for the treatment of overweight or obesity: systematic review and meta-analysis. PubMed, 2023. Available at: https://pubmed.ncbi.nlm.nih.gov/37253796/. Accessed on: Jan. 15, 2026.

THE GUARDIAN. People who stop using Mounjaro experience reversal of health benefits, study finds. The Guardian, 2025. Available at: https://www.theguardian.com/society/2025/nov/24/mounjaro-health-benefits-reversed-regain-weight-after-stop-using. Accessed on: Jan. 15, 2026.