Why do some people experience faster Mounjaro weight loss? Here, we’ll explore why this is and which medication could be right for you.
For people trying to lose weight, GLP-1 medications such as Mounjaro and Wegovy are increasingly being considered.
But while these names are sometimes both used interchangeably, there are differences between them. One notable difference is that some people appear to experience faster Mounjaro weight loss in clinical trials.
Here, we’ll examine why this might be, as well as some other factors that may affect weight loss results.
How Mounjaro and Wegovy work
Mounjaro, which contains the active ingredient tirzepatide, and Wegovy, which contains semaglutide, are both used to help people with obesity and related chronic health conditions lose weight. They belong to a class of medications known as GLP-1 receptor agonists, meaning that they mimic the hormone GLP-1.
GLP-1 is produced by the gut after we eat, and it helps control appetite, promote appetite suppression, slow digestion, and reduce food noise, sending signals to the brain that the body feels full. As a result, people on these medications tend to eat less, and this helps them lose weight. They’re both self-administered weekly as injections.
The main difference that sets these medications apart, however, is that Mounjaro is a dual agonist. It activates receptors for the hormone GIP, or glucose-dependent insulinotropic polypeptide, too.
Why some people lose weight faster on Mounjaro
GIP works alongside GLP-1 by changing how some of the fat in the body is stored and possibly helping boost metabolism, too – meaning that the body burns more calories at rest. As a result, research has shown that Mounjaro may be more effective than Wegovy at higher doses.
In a head-to-head trial between Mounjaro and Wegovy, with the results published in 2025, 751 people with obesity – but without type 2 diabetes – took part. They had an average weight of 113 kilograms (nearly 18 stone), while some had related health conditions, including high blood pressure and high cholesterol. Patients took the maximum amount of either tirzepatide or semaglutide that they could tolerate for around a year and a half.
It was found that those on tirzepatide lost 20.2% of their body weight, while those on semaglutide lost 13.7%. Meanwhile, those on tirzepatide saw their waist sizes shrink by over 5cm (about 2 inches) more on average.
What other factors affect weight loss?
While some people do lose weight faster on Mounjaro, everybody is different, and your GLP-1 medication is just one piece of the weight-loss puzzle. There are lifestyle factors to consider, including your diet, exercise levels, sleep patterns, and even stress levels, as these can influence calorie intake, expenditure, metabolism, and appetite.
Everyone has a different metabolism and hormone profile, so we can all respond to medications differently. Some people might notice more sudden changes, while for others, they could be more gradual.
So, it’s important to keep the bigger picture in mind. Whether someone uses Mounjaro or Wegovy, the medication is still just one aspect of a wider approach to weight-loss that also involves personalised support, guidance and sensible, healthy lifestyle habits.
Is Mounjaro or Wegovy right for me?
If you’re considering using a GLP-1, it’s only natural to be weighing up the two options. Both medications are approved for weight loss in the UK, and both are shown to be effective in clinical trials, but as they aren’t identical, the right option for you will depend on your own circumstances.
While Mounjaro may be more effective than Wegovy at higher doses, this doesn’t mean that Mounjaro will be the right choice for everyone by default. Mounjaro can sometimes be more expensive depending on the provider. Meanwhile, Mounjaro is also approved for use to treat type 2 diabetes, while Wegovy is approved to help reduce cardiovascular risk in some patients.
If you’re concerned about side effects, the study from 2025 found that there wasn’t much difference in rates. Between 77% and 79% of people reported at least one side effect, and around 6% of people taking tirzepatide and 8% of those taking semaglutide stopped before the end of the study due to side effects.
If you’re not sure which could be the right medication for you, speaking with experts, like those at The Virtual Slimming Clinic, could help you come to a decision you’re comfortable with.
Frequently asked questions
Why do some people experience faster Mounjaro weight loss?
Mounjaro activates both GLP-1 and GIP receptors, whereas Wegovy only activates the former. GIP helps change how some of the fat in the body is stored, and may help boost metabolism too, meaning that Mounjaro can be more effective at higher doses than Wegovy.
Do Mounjaro and Wegovy work in the same way?
Both Mounjaro and Wegovy target GLP-1 receptors, helping promote appetite suppression and slow digestion, but Mounjaro is slightly different in that it also activates GIP receptors. This dual mechanism means that some people experience greater, or faster, weight loss on Mounjaro.
How long does it take to see weight loss results on Mounjaro?
Everybody is different, but often people notice changes in appetite in the first couple of months. Generally, weight loss will occur gradually over several months, but some people will notice faster weight loss than others.
