Scientists are starting to unravel the secrets behind Ozempic/Wegovy and similar GLP-1 drugs. In trial data published Thursday, researchers found evidence that GLP-1 therapy can noticeably boost the body’s fat-burning potential. The findings indicate that these drugs aren’t helping people lose weight just by reducing appetite, as some have suspected.
Scientists in Ireland conducted the research, published in the Journal of the Obesity Society. They were looking to help settle an open question about how GLP-1 drugs work to treat obesity. People taking these drugs often report feeling less hunger and cravings and taking in fewer calories as a result. But the researchers’ earlier work, in mice, had shown that GLP-1s also seemed to increase the mice’s ability to use up their stored visceral fat, burning off more calories as a result. Visceral fat is the fat surrounding the abdominal organs, and having too much of it is thought to be a major contributor to obesity-related health problems.
To further study this phenomenon, the team performed a small, randomized, and controlled trial with 30 patients who had obesity and obstructive sleep apnea, or OSA. OSA is often linked to obesity, and people with OSA also often have higher levels of visceral fat inflammation. So the researchers wanted to see if GLP-1 therapy could help these patients in particular.
People in the control group received continuous positive airway pressure (CPAP) machine, a gold-standard apnea treatment. Those in the second group received liraglutide, a long-used GLP-1 drug for type 2 diabetes and obesity, while the third group received both liraglutide and CPAP therapy. To measure their fat-burning ability, the volunteers were given PET-CT scans both before and six months into their treatment (PET imaging uses a radioactive tracer to measure how specific cells or tissues metabolize).
Compared to controls, the researchers found that people on liraglutide experienced a significant increase in their ability to burn off visceral fat. Those who had lower baseline visceral fat-related metabolism also tended to respond the best to GLP-1 therapy, and those who saw the biggest increases in metabolism were also more likely to lose more weight overall.
“It always seemed overly 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,” said study researcher Donal O’Shea, an endocrinologist at the University College Dublin and St Vincent’s University Hospital Dublin, in a statement.
O’Shea and his team do note that this research was a proof-of-concept study, so more work will be needed to confirm the findings here. At the same time, liraglutide is an older GLP-1 drug, and newer medications like semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound) are substantially more effective at helping people lose weight, with people losing an average 15% to 20% of their body weight in clinical trials. That could also mean that they’re even better at helping us burn off fat—a question that the researchers hope others, including the drugmakers themselves, will continue to explore.
“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,” O’Shea said.
