How Mounjaro works

Before delving deep into the science, let’s start by gaining an understanding of the medicine in question: Mounjaro.

Mounjaro is a once-weekly injection that helps support weight loss by reducing your appetite and delaying stomach emptying. Manufactured by Eli Lilly, it was approved in Europe in April 2024, and is increasingly prescribed as a treatment option for chronic weight management.

It comes in the form of a subcutaneous injection pen containing four doses, with dose strengths ranging from 2.5 mg to 15 mg.

Mounjaro works by mimicking two natural hormones in our body called GLP-1 and GIP. These hormones are released after you eat and play an important role in regulating appetite, digestion, and blood sugar levels. Below is a quick breakdown of how this process works, step by step.

The active ingredient, tirzepatide, binds to GLP-1 and GIP receptors in the body, activating them and mimicking the effects of these hormones.

This separates it from most other weight loss injections, like Wegovy, which only target GLP-1. By working on both hormones, Mounjaro helps to:

Mounjaro isn’t a magical drug that burns fat automatically; it needs to be combined with a healthy diet and regular exercise to be effective. The good news is, Mounjaro makes it far easier to maintain this.

By reducing your appetite and enhancing the feeling of fullness, Mounjaro should naturally make you eat less. And when your daily calorie intake is lower than what you burn, your body uses alternative energy sources, such as stored fat. This is known as a calorie deficit.

When you keep this up over an extended period, small losses add up and weight falls off gradually. Most of my patients say they feel a change in appetite within days, but it can take weeks or even months to notice a significant change in your weight.

Mounjaro can lead to significant weight loss when combined with a calorie-controlled diet and regular physical activity.

In one clinical study on Mounjaro, the 15 mg dose led to up to 21% weight loss after 72 weeks. Additionally, 83.5% of patients lost at least 10% of their starting weight during this same timeframe.

In my clinical experience, Mounjaro often leads to more significant weight loss when compared to other weight loss treatments. This is largely due to the dual-hormone approach I explained earlier.

Here is a table comparing the effectiveness of some of the most widely used weight loss treatments:

Comparing weight loss treatments

Keep in mind that no matter what the data says, the right treatment for you depends on your health profile and individual response to treatment. While one person may see the best results from Mounjaro, another may benefit more from Wegovy. It all comes down to personal preference.

For a more detailed comparison of these two weight loss treatments, see my article on Wegovy vs Mounjaro.

While Mounjaro mainly affects appetite and cravings, it can also affect other systems in the body:

Please note that Mounjaro is only approved for weight loss and type 2 diabetes. However, these additional benefits have been observed in some people.

Because Mounjaro works on digestion and appetite, the most common side effects are gastrointestinal. The most common side effects of Mounjaro include:

You can see a full list of potential side effects in the patient information leaflet.

Most gastrointestinal side effects like these are usually a sign that treatment is working and, in my experience, most people get over them once they get used to the medication.

If you want a more detailed explanation, including some helpful tips on how to manage side effects, see my article on Mounjaro side effects.

Using Mounjaro becomes second nature once you’ve done it a few times, but there are some things you should keep in mind to make your weight loss journey even easier, and more effective.

Managing side effects

If you’re experiencing any gastrointestinal side effects, I recommend:

If you experience side effects that are severe or persistent, contact your prescribing doctor for personalised advice. They can lower your dosage to better suit your needs.

Maximising effectiveness

Mounjaro works best when you put in the effort. That’s why I always recommend that my patients follow a healthy diet with lots of fruit, veggies, and fibre, and that they follow an exercise routine.

A lot of people think the best way to do this is to restrict yourself from the things you love, but this is the wrong way to go about it. You just have to find recipes you can enjoy that also fit within your health goals.

Building long-term habits

Mounjaro makes it easier to succeed on your weight loss journey, but that’s only half of the story. Once you stop taking it, your appetite and digestion return to normal.

That’s why it’s important to build healthy habits during treatment so you can maintain your weight going forward. Otherwise, you risk regaining all the weight you’ve lost. Things like meal prepping, exercise routines, and mindful eating can be the difference between someone who loses weight with Mounjaro and someone who keeps it off after they stop treatment.

I always remind my patients to think of Mounjaro not as a short-term solution to excess weight, but as a tool to help you transform your relationship with food and nutrition. Once you understand that, long-term success becomes more likely.

Mounjaro works on your hormones to reduce your appetite, stop cravings, delay stomach emptying, and manage blood sugar levels. When combined with a healthy diet and an active lifestyle, this can lead to significant weight loss over time.

The first step on your weight loss journey with Mounjaro is checking whether you’re eligible. In order to be prescribed treatment, you must be over 18 years old with:

If you want to get started on Mounjaro, all you need to do is complete a short online consultation with euroClinix. If approved by our EU-registered doctors, you can get your medicine delivered directly to your door in discreet packaging.

Also read: Foods to avoid during weight loss treatment: a practical guide