Weight-loss injections such as Ozempic, Wegovy or Mounjaro have a greater effect on the body than previously thought, a study by St Vincent’s University Hospital in Dublin has found.
The drugs make people feel satiated, and therefore inclined to eat less, but they have also been found to increase metabolic activity.
A randomised controlled trial with 30 patients looked at medications based on the hormone Glucagon-like peptide-1 (GLP-1).
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The findings published on Thursday in the Journal of the Obesity Society show a strong relationship between the increase in metabolic activity from a once-daily treatment with GLP-1 and the amount of weight lost. It also found people with low metabolic activity before starting treatment gained the most from it.
“This study challenges the main narrative about these newer treatments, which is that they simply make you eat less, and that any action on energy burn is minimal," said Prof Donal O’Shea, at the hospital and the UCD School of Medicine.
"The strength of the association is surprising given the relatively small numbers studied and suggests this increase in metabolic activity is a significant contributor to how these drugs work.
“Safe medical treatment for obesity is still in its infancy and we need to understand fully how the treatment works. Understanding how these agents increase energy burn should be an important part of future research."
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The 30 patients had specialised imaging of the fat in their abdomen using a Pet-CT scanner, with scans carried out before and after six months of treatment with GLP-1.
“It always seemed over-simplistic to me that these new treatments were just making people eat less, so this study finding is an exciting step forward in our understanding of how these new medicines for obesity work," Prof O’Shea said.
"The findings also provide science to support the fact that the treatment of obesity is not simply to eat less and move more. That’s the prevention piece. Treatment is more complex than that."
The use of weight-loss drugs such as Ozempic has exploded in popularity in recent years, with Elon Musk and celebrities such as Oprah Winfrey, Whoopi Goldberg and Rebel Wilson openly discussing their use of slimming injections.
Ozempic received authorisation for its use in the US in 2017 and the EU in 2018.
Its ability to help people lose large amounts of weight effortlessly and quickly soon spread on social media.
In the US, 20 million prescriptions were made for Ozempic in 2023, an increase of 5,000 per cent since 2018. There are global shortages of the drug, leading authorities worldwide to warn users about counterfeit injection pens in circulation.
