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.”

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The evidence surrounding changed sexual function is limited, and mixed. Some studies suggest GLP-1 medications may improve testosterone levels, potentially benefiting sexual health, while a 2025 analysis of US Food and Drug Administration data identified 185 reports of sexual dysfunction, particularly among men taking GLP-1 receptor agonists.

A 2025 Kinsey study showed that 18% of respondents said their sexual desire had increased on GLP-1s while 16% said it had decreased.

“Some of this we do need to tease out,” South says. “Is it weight loss? Is it GLP-1? Or is it some coexisting things that are happening at the same time? For example, a middle-aged perimenopausal female with reduced sexual function.”

What is known is that experiencing major and rapid weight loss alone can significantly affect relationships – a 2018 Swedish study that analysed 1,958 patients who had bariatric surgery found there was an increased incidence of divorce or separation for those in couples, while there was a higher likelihood of a new relationship for those who were single.

‘Maybe I hold him to a higher standard’

Jennifer isn’t sure if the intimacy problems in her marriage are related to her age, or the weight-loss medication she’s on or the new identity she’s now embracing as a result of her changed body.

While she was on a shopping trip, a man offered to take her grocery cart back to the bay for her. Before she lost weight, she says, that never happened. Meanwhile, in professional settings, people who don’t know she used to be heavier make comments about overweight colleagues that leave her stunned.

Her husband is the one who suggested couples therapy after 34 years together once Jennifer did not “magically become more physically demonstrative in the bedroom” after her weight loss. He also commented that she’ had become “meaner”.

“I’m less afraid of our relationship failing, so maybe I hold him to a higher standard than I used to,” she acknowledges.

Without her obesity to blame, Jennifer now realises that her marital problems were “always a two-person problem but my weight was easy to point to because I felt so bad about it”.

Relationship breakdown is complicated and rarely attributable to any single factor.

“Human libido and relationships are complex at their core, so it would be very difficult to extrapolate what it is about these medicines specifically that would have an impact there,” says Dr Mark Mellor, a bariatric doctor and specialist GP who regularly prescribes GLP-1s and says research would be challenging.

As people’s self-confidence soars, Mellor says, that could also play a role in “people perhaps thinking, ‘What am I doing here in this relationship?’”

A grieving process

Glenn Mackintosh, a psychologist and clinical director of Brisbane’s Weight Management Psychology Clinic, says couples who visit the clinic often mention disruption to their old lives before GLP-1s.

“Say a couple who have a shared routine of finishing the day with Netflix and a pack of chips they share – if that eating is part of a shared routine, it will impact the relationship and so there’s a grieving process,” he says.

Joanna Wood: ‘I used to be a much bigger person and the story around that feels like a character defect rather than science.’ Photograph: Christopher Hopkins/The Guardian

Renewed self-confidence and attention from others can also stir fear in partners.

“It’s like, ‘OK, now my partner is getting more attention, are they going to leave me?’”

These are issues that Mackintosh says he has seen resolved in secure, functioning relationships through communication and acceptance.

“It can really cause friction. What we often say is that weight loss doesn’t cause relationship problems but it can reveal them.”

Finding love

The social penalties paid by people living with obesity in the dating world are well known. For some on GLP-1s, changes to their bodies can improve their self-confidence in approaching dating – but not without navigating psychological challenges.

After 14 years of singledom, Joanna Wood started dating again last year after losing 25kg taking a GLP-1.

The former Australian diplomat, who is 59, remembers feeling nervous before her date with Bruce Hart, a 63-year-old social worker. She felt all the natural vulnerability that comes with a first date but she also felt shame that she used a GLP-1.

“I used to be a much bigger person and the story around that feels like a character defect rather than science,” she says.

After that initial date – which lasted eight hours – the relationship blossomed, as the couple started hiking together. When Wood finally revealed she’d been on a GLP-1, it didn’t faze him.

“To me, it was such a background issue,” Hart says. “I was more focused on what she was doing and her values and who she was as a person.”

Dr Rebecca Puhl, a psychologist who studies weight stigma at the University of Connecticut and has previously consulted for Eli Lilly, the manufacturer of Mounjaro, says people sometimes hide their GLP-1 use.

“They’re worried that they’ll be viewed as cheating or lacking willpower by a potential partner,” Puhl says. “Even though obesity is recognised as a complex chronic disease ... for some people, internalization of weight stigma can persist even after losing significant amounts of weight.”

Wood, who has heart disease, found the shame hard to shake even though her health has improved drastically.

When she briefly stopped taking the medication, “food noise” returned. She regained 10kg and found herself hiding confectionery from Hart.

She has since restarted the medication, accepting they are likely to be a lifelong treatment.

Having retrained as a counsellor, Wood has developed a program for women over 50 on GLP-1s to navigate the psychological journey of using the drugs.

Jennifer is also sure she’ll be on a GLP-1 for life.

Her marriage is another commitment she expected to last a lifetime.

“Things are stable for now,” she says. “We aren’t fighting and we continue to talk but we aren’t solving anything, either.”

She isn’t sure whether the medication changed her marriage or simply stripped away the explanation she’d relied on for decades. The weight is gone but the questions it once answered are not.

“We will adapt in some way – I am just not sure how yet.”