How does Mounjaro work for weight loss?
In recent months, Mounjaro has become one of the most searched-for and talked-about medications in the field of diabetes and weight management. Its active substance, tirzepatide, has generated considerable interest among both patients and healthcare professionals owing to the results observed in clinical trials. However, alongside the media attention, numerous questions and myths have also arisen about its use, its actual indications and its risks. In this article we explain, from a rigorous medical perspective, what Mounjaro is, how it works and who can benefit from it.
What Mounjaro is and what its active substance is
Mounjaro is the brand name for tirzepatide, a molecule initially developed for the treatment of type 2 diabetes mellitus that has since also shown a significant effect on body weight. Unlike other medications in its class, tirzepatide acts on two distinct receptors in the body: the glucagon-like peptide-1 (GLP-1) receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor. It is this dual action that sets it apart from other treatments that act on the GLP-1 receptor alone.
According to the information published by the European Medicines Agency (EMA), Mounjaro is authorised in the European Union both for the treatment of type 2 diabetes and, in certain presentations, for the management of body weight in people with obesity or overweight.
How tirzepatide works in the body
The mechanism of action of tirzepatide is based on mimicking the effect of two intestinal hormones that are released naturally after eating. This combined action produces several notable effects:
- It stimulates the release of insulin in a glucose-dependent manner — that is, only when blood sugar levels are elevated.
- It reduces the secretion of glucagon, a hormone that raises blood glucose.
- It slows gastric emptying, which promotes a more prolonged feeling of fullness.
- It acts on brain centres related to appetite, contributing to a reduction in calorie intake.
This combination of effects explains why, in addition to improving glycaemic control, many patients experience significant weight loss during treatment.
Who Mounjaro is indicated for
It is essential to understand that Mounjaro is not a medication for unrestricted use, nor is it intended for anyone who simply wishes to lose a few kilos. It is a prescription-only medicine, whose use must be assessed on an individual basis. In general terms, its use may be considered in adults with type 2 diabetes who have not achieved adequate control with other treatments, or in people with obesity (a high body mass index) or overweight with at least one associated comorbidity, such as high blood pressure, dyslipidaemia or sleep apnoea.
Before starting treatment, the specialist must carry out a thorough assessment that includes the medical history, family history, renal and pancreatic function, and the presence of other conditions that may contraindicate its use. At the Obesity and Cardiovascular Risk Unit of Dr Christian Leyva, this assessment process is always individualised, since not all patients respond in the same way and not everyone is a suitable candidate.
Side effects and precautions
Like any medication, tirzepatide can be associated with adverse effects. The most common, according to the information compiled by the United States Food and Drug Administration (FDA), are digestive in nature: nausea, diarrhoea, constipation or abdominal discomfort, particularly at the start of treatment or following dose increases. In most cases these effects are transient and improve as the body adapts.
There are also contraindications that must be assessed strictly, such as a personal or family history of certain thyroid tumours, previous pancreatitis or certain digestive conditions. For this reason, medical monitoring during treatment is not optional but an essential part of the therapeutic process.
Mounjaro does not replace a comprehensive approach
One of the most common misconceptions is to think that a medication like Mounjaro can completely replace lifestyle changes. The available scientific evidence, including that reviewed by the World Health Organization (WHO), agrees that the best results are achieved when pharmacological treatment is combined with a suitable diet, regular physical activity and ongoing medical follow-up. Obesity and type 2 diabetes are chronic, complex diseases that require a comprehensive approach, not a single solution.
For this reason, any decision to begin treatment with tirzepatide should always be taken together with a specialist who can assess the case as a whole, set realistic goals and properly monitor the patient’s progress and any possible side effects.
Frequently asked questions from our patients
Is Mounjaro the same as Ozempic?
No. Although both belong to similar families of medications, Mounjaro (tirzepatide) acts on two distinct hormone receptors, whereas Ozempic (semaglutide) acts on the GLP-1 receptor alone. Their indications, doses and profiles may differ.
Can Mounjaro be bought without a prescription?
No. It should not be acquired or used without a prescription and medical supervision, as it requires a prior assessment of the patient’s state of health, contraindications and individualised dose adjustment.
How long is the treatment continued?
The duration of treatment is established individually according to the clinical response, the therapeutic goals and each patient’s tolerance, and it should be reviewed periodically with the specialist.
Book an appointment with Dr Christian Leyva
If you would like an individualised assessment of your case, Dr Christian Leyva offers specialist care in internal medicine, diabetes and obesity in Huelva, with an approach grounded in the most current scientific evidence. You can view all the services available or book an appointment in person or online.