For Jennifer, obesity was the obvious culprit for most of her problems.The litigation attorney told herself it was the reason why she wasn’t being invited to parties, and why she and her husband struggled with physical intimacy in their otherwise “solid” marriage.“If people excluded me, or if things weren’t going as I wanted them to, I often defaulted to, ‘Well, they don’t like fat people, they don’t want fat people at their event … they don’t want a fat person representing their brand,’” she says.Jennifer, who is 57 and asked to keep her surname private, had struggled with obesity since she was eight, when her parents divorced. In her 30s she underwent gastric sleeve surgery, only to put the weight and more back on. But that all changed in 2023 when she started using Mounjaro, a drug in the new class of GLP-1 (glucagon-like peptide-1) weight-loss medications.Designed to manage type 2 diabetes by regulating blood sugar, slowing digestion and reducing appetite, GLP-1s are now taken by millions of people across the world for weight loss, with Australian prescriptions increasing almost 10-fold since 2020 and use in the US more than quadruping.Jennifer’s husband had concerns about well-known potential side-effects, including abdominal pain, but ultimately agreed with her that it was a risk worth taking.Three years on – and with Jennifer 40kg lighter – the drugs seem to have resolved her lifelong struggle to manage her weight. But while she had hoped weight loss might help with the niggling issues in her relationship, she’s now contending with its fallout on her 30-year marriage, something neither she nor her husband expected.“I’m glad I had five years of therapy before I started it,” she says. “I am not sure I would have been equipped for the psychological changes otherwise.”Prescribing doctors often advise patients they might experience well-known potential physical side-effects of GLP-1s, including nausea, vomiting, diarrhoea and constipation. What is not as well researched, or understood, are their effects on romantic relationships. Some patients in forums like Reddit and Facebook support groups have shared that they have experienced changes in desire, sexual function and emotional connection.Early research suggests the GLP-1s could suppress more than just hunger through their impact on brain pathways and hormones.“A potential unique mechanism with GLP-1s is their impact on the brain in regards to dopamine reward pathways,” says Dr Terri-Lynne South, a general practitioner specialising in obesity medicine. “We see this in regards to reducing the pleasure-seeking around alcohol, nicotine, and potentially sex drives.”