New research challenges belief that weight loss drugs only reduce appetite

A study carried out in St Vincent's University Hospital (SVUH) Dublin challenges the belief that weight loss medications such as Ozempic, Wegovy or Monjaro work just by promoting satiety and making you eat less.

The randomized controlled trial with 30 patients was led by Professor Donal O'Shea, SVUH and UCD School of Medicine, and examined the family of medications based on the hormone Glucagon-like peptide-1 (GLP-1).

The findings published today in the Journal of the Obesity Society shows that there is a strong relationship between the increase in metabolic activity caused by once daily treatment with GLP-1 and the amount of weight lost. Furthermore, people with low metabolic activity before starting treatment benefited 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. 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. I hope the companies involved in the development of these treatments will examine this area in more detail because these are very expensive studies to carry out and we are very grateful to the Health Research Board and University College Dublin for supporting it."

It always seemed oversimplistic 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. 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."

Professor Donal O'Shea 

The 30 patients had specialised imaging of the fat within their abdomen using a PET-CT scanner, with scans carried out before and after six months of treatment with GLP-1.

The study 'GLP‐1 therapy increases visceral adipose tissue metabolic activity: lessons from a randomized controlled trial in obstructive sleep apnea,' was co-authored by Professor Silke Ryan, SVUH, funded by the Health Research Board and supported by University College Dublin.