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Mounjaro®: What it is, how it works, and how its different from Ozempic

Mounjaro®, a new competitor to GLP-1a medications like Wegovy and Ozempic, shows promising results as a more effective medication for weight loss than what's currently available on the market. But how exactly does it work? And what makes it different?

Azeem Yussouf
Azeem Yussouf
Medical doctor
Mounjaro®: What it is, how it works, and how its different from Ozempic

You have probably heard of Wegovy and Ozempic, the appetite-reducing medications revolutionising how we treat obesity.

Well, Mounjaro® is the new kid on the block and scientific studies show that it’s more effective than the GLP-1a medications we’ve seen so far. In this article, we’ll uncover everything you need to know about Mounjaro, so you can make an educated decision whether it’s the right treatment for you.

Let’s dive into it.

What is Mounjaro®?

Mounjaro® is a novel medication approved in the UK and made available in February 2024 for both weight management and the treatment of type II diabetes.

Mounjaro® is produced by Eli Lilly, an American pharmaceutical company, and has been approved in the US since 2022. Mounjaro® is available as pre-filled injection pens that you use once per week. Unlike Wegovy and Ozempic that contain semaglutide, Mounjaro® contains the active ingredient tirzepatide that you inject under the skin and it comes in six different doses 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg. For weight management, Mounjaro is only approved for people with a BMI over 30kg/m2 or over 27kg/m2 if you also have weight-related health problems such as high blood pressure, high cholesterol or prediabetes.

How Mounjaro® works

In short, Mounjaro® makes you feel full faster and helps regulate your blood sugar levels. But how does it do that?

Tirzepatide: Mimicking more than just GLP 1 hormones

The active ingredient tirzepatide mimics the effect of two gut hormones called GLP-1 and GIP. The two hormones are released from the gut when we eat food to increase the release of insulin, a hormone regulating the blood sugar, and to slow down the stomach in releasing its content into the intestine.

When you inject tirzepatide, it’s like injecting more than a thousand times the normal concentration GLP-1 and GIP into the blood. At this high concentration, GLP-1 and GIP still slows down the emptying of the stomach and increases insulin secretion, but they also have a significant impact on your brain, causing you to feel full faster.

In other words, Mounjaro® causes you to change your behaviour because you stop craving the same amount of food. Studies have also shown that it seems in particular to be foods high in sugar and fat that you crave less (the typical comfort foods). Walmart, the biggest supermarket chain in the US, has even reported that its data show a decline in the amount of food bought by people on medications like Mounjaro.

An alternative path to satiety

What’s interesting about Mounjaro and similar drugs is that they seem to bypass the body's natural hormonal response to weight gain.

A hormone called leptin should in theory prevent excessive weight gain as it works to decrease appetite and increases in concentration as you gain body fat. However, leptin's effect on the brain seems to dysfunction as you put on weight, leading to your appetite not being suppressed to the extent that would prevent you further weight gain.

Mounjaro bypasses this leptin mechanism and makes us feel full by using a different pathway to influence our satiety signals.

What is the difference between Ozempic and Mounjaro®?

While Ozempic and Mounjaro® are similar, they’re also significantly different.

Ozempic is a drug approved for the treatment of type-2 diabetes and contains the active ingredient semaglutide whereas Mounjaro® is also approved for diabetes but contains tirzepatide.

Semaglutide and tirzepatide both work by mimicking the effect of the gut hormone GLP-1 but tirzepatide also mimics the effect of the gut hormone GIP. Both GLP-1 and GIP independently stimulate the release of insulin. Hence, tirzepatide is a potent drug for lowering the blood sugar levels with its dual effect.

The difference between GLP-1 and GIP for weight loss

Is there any difference between GLP-1 and GIP when it comes to weight management? This question is currently puzzling scientists.

First of all, We know there is a difference; GLP-1 clearly reduces appetite and causes weight loss. But when it comes to GIP the story is more complex.

Here's why.

Puzzling research results

Studying GIP, researchers first found that GIP might cause weight gain.

However, later research puzzled everyone because they found that both more or less of GIP could cause weight loss, yet larger clinical trials with humans failed to confirm that GIP treatment on its own could cause weight loss.

The mystery of Eli Lilly's marvel drug

This confusion in the research community all changed when Eli Lilly started researching tirzepatide and managed to prove that a drug mimicking the effect of both GLP-1 and GIP caused a greater weight loss than semaglutide, the GLP-1 only based drug.

It’s likely that despite their findings, not even Eli Lilly understands why this is so.

You can call it a lucky punch or an accidental pharmacological marvel. Future research will shed light on the matter but for now it remains a mystery.

Does Mounjaro® work for weight loss?

There is no doubt about it. Mounjaro® is a potent weight loss drug.

Of the two main research studies that were undertaken to demonstrate the effectiveness of Mounjaro®, the larger of the two trials enrolled adults without diabetes, specifically looking at weight loss. At the start of the trial, the average body weight was 231 pounds (105 kg) and average body mass index was 38 kg/m2.

In this trial, those randomised to receive the highest approved dosage (15 mg once weekly) lost on average 18% of their body weight compared to those randomised to placebo. 

However, as with GLP-1 medications like Wegovy, medications like Mounjaro® are not the whole solution for people living with obesity.

The downside of weight loss medications

All the research shows that once you stop taking this form of medication and lose the appetite-suppressing effect, the weight creeps back on.

The issue with this weight gain is that when you lose weight on weight loss medications you lose both muscle and fat. However, if you regain weight you will regain predominantly fat only, in some cases leading to a possibly worse body composition than when you started.

How to use medications like Mounjaro® for lasting weight loss

Because of the potential to end up worse than you started, and the fact that you’re likely to regain weight post-medication if you haven’t made any changes to your lifestyle, it’s crucial that we view this medication as a supportive aid. A tool that is best combined with lasting lifestyle changes for sustainable results and to prepare you for a life after medication.

What’s more, there’s no one-size-fit-all approach to nutrition. What works for one person depends on what they struggle with, what has worked for them leading up to tapering off the medication and – this is important – what they can sustain in the long-term.

We know that obesity is a complex condition with various root causes. Because of this, it’s so important to address the individual behavioural and psychological reasons behind the weight gain. And this is why a personal, holistic approach is crucial for overcoming obesity. It’s how you can address the likely multiple root causes of living with obesity. Your ability to identify and address those root causes will make such a profound difference in how well you can maintain your weight loss after tapering off the medication.

Our approach to lasting weight loss here at Embla goes beyond surface-level problems and recognises the deeply complex nature of obesity. Whether it's lifestyle habits, emotional eating, food guilt, lack of nutrition or physical activity, a comprehensive approach ensures that your journey is not just about taking medication but about gaining control and achieving long-term success.

The side effects of Mounjaro®

When patients undergo treatment with Mounjaro®, their individual experiences with the medication varies, but there are several common side effects that tend to emerge.

The most frequently reported side effects are:

- Nausea
- Diarrhoea
- Decreased appetite
- Vomiting
- Constipation
- Indigestion
- Stomach pain

Notably, research indicates that instances of nausea, vomiting, and diarrhoea are most prevalent during the initial phase when the dosage of Mounjaro is being escalated. However, over time, these occurrences tend to diminish as the body adjusts to the medication.

Studies have also shown that gastrointestinal side effects are more prevalent among individuals taking Mounjaro compared to those on a placebo. Consequently, patients on Mounjaro are more likely to discontinue treatment due to these adverse effects. This underscores the importance of monitoring and managing side effects to ensure patients can continue their treatment regimen effectively.

Most side effects are easy to treat

In the majority of cases, the side effects are effectively managed with over the counter medication or nutritional advice and support. For example, nausea can be prevented by eating smaller amounts, avoiding fatty foods and stopping eating when feeling full.

The side effects experienced when taking the medication highlight the importance of taking the medication with the guidance of a healthcare professional. As a member of Embla, you have access to your own healthcare team, including a nurse and a doctor. If you experience any side effects you can book a consultation directly with your health team to discuss these effects and get the adequate advice and if necessary any required alternative prescriptions.

Is Mounjaro® available online?

Mounjaro® will launch in the UK on the week beginning 12th February, however this is currently only at the lower doses of the medication, with higher doses expected to be released in due course. The market price of the medication ranges from £190 to £240 for the starter doses.

However, note that this cost is for the medication alone, and does not include the extensive weight loss support necessary for sustained weight loss results like that offered by Embla.

How we use weight loss medication at Embla

At Embla, we don’t sell weight loss medication on its own. Instead, we use it as a supportive element in our holistic and personalised weight loss approach.

This means that Mounjaro® will likely be offered depending on the needs of each individual and this will be discussed on an individual basis as part of the screening process and then ongoing consultations whilst enrolled in the program. To get more information on the service that we offer, or to speak to a healthcare professional about your weight loss goals, simply book a free consultation with one of our registered nurses today

In this article
Azeem Yussouf
Azeem Yussouf
Medical doctor

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