Richard Parks A new study shows that Mounjaro, a popular weight-loss drug, helps people lose and keep off a large amount of weight for up to three years. Also known by its scientific name tirzepatide, the drug is given as a weekly shot. It works by copying the action of two gut hormones—GLP-1 and GIP—that reduce hunger, slow digestion, and boost insulin.
The study tracked 700 adults who were overweight or had obesity and also had prediabetes. It followed them for 176 weeks as part of a major trial known as Surmount-1.
How the Mounjaro Study Was Conducted
The long-term trial was led by drugmaker Eli Lilly in partnership with academic researchers. The goal was to see how much weight people could lose and keep off with continued use of Mounjaro.
Researchers divided participants into three groups based on how quickly they lost weight at the beginning:
- Slow starters
- Moderate responders
- Fast responders
Everyone in the study eventually hit a plateau. That means their weight loss slowed or stopped, even though they continued the treatment.
Here’s how the average total weight loss broke down by group:
- Slow group: 9.2% body weight loss
- Moderate group: 20.2% body weight loss
- Fast group: 30.8% body weight loss
Each group made up roughly one-third of the 700 participants.
According to Prof. Luca Busetto of the University of Padova, how quickly someone loses weight early on can help doctors predict long-term results. “This could help tailor treatment to individual patients,” he said.
Weight Loss Maintained for Most Users
A second part of the study looked at how much weight people were able to keep off after reaching their lowest point.
On average, participants hit their lowest weight after about 22 months. At that point, they had lost about 23.1% of their starting weight.
By the end of the three-year study, they had maintained an average weight loss of 19.4%—even with some minor weight regain.
Interestingly, 70% of those who lost weight had gained back less than 5% of their starting body weight. This suggests that Mounjaro could help people maintain their results over the long term.
Dr. Simon Cork of Anglia Ruskin University said these results show that tirzepatide is effective over time. “This is very promising for how we treat obesity in the future,” he noted.
Health Experts Urge Long-Term Access
Despite the positive results, many countries still limit the use of such weight-loss drugs to just two years. That’s much shorter than the three years studied in Surmount-1.
Prof. Naveed Sattar from the University of Glasgow, who was not part of the trial, believes the results may help doctors decide when to give patients stronger or added treatments.
With obesity rates rising worldwide, experts say drugs like Mounjaro could reduce the burden on healthcare systems. But they also stress the need for long-term safety studies and fair access for all who may benefit.
UK Regulators Warn Against Ads for Weight-Loss Drugs
At the same time, UK regulators are cracking down on ads for prescription-only weight-loss drugs like Mounjaro, Wegovy, and Saxenda.
The Advertising Standards Authority (ASA) warned that promoting these medications directly to the public is illegal. This includes ads on websites, Google, and social media—especially those involving influencers.
The Medicines and Healthcare products Regulatory Agency (MHRA) and General Pharmaceutical Council joined the ASA in the warning. They said promoting these drugs without proper medical advice puts people at risk.
This follows earlier reports showing illegal marketing of weight-loss injections in the UK, often through paid social media promotions.
A Big Step in the Fight Against Obesity
The full results of the study will be presented at the European Congress on Obesity in Málaga. Experts hope the findings will lead to longer access, safer use, and better support for patients.
For now, the evidence is clear: Mounjaro helps many people lose weight and keep it off for years, making it a key tool in treating obesity.