Is a new weight-loss drug making people fall out of love?

A recent TikTok video shows a man in a black baseball cap, with text over the video stating: “strange effects of Reta” and “ruining relationships”.

He is referring to retatrutide, an experimental weight-loss drug that targets three appetite-related hormones. It is still in clinical trials but has generated such interest that some users are already sourcing it illegally online before approval. The “weird theory going around”, the TikTok poster says, is that the drug can “make you fall out of love”.

Below the video, the comments fill with accounts of what users describe as emotional flattening. One person says the drug “stopped food craving and lusting as well”, another says they have “severe anhedonia [the inability to experience joy or pleasure]”, and a third says retatrutide made them feel “unbothered by 99% of everything”.

It is among several viral videos asking whether peptides stop you falling in love. While it sounds outlandish, medical researchers are beginning to investigate whether these drugs act as a “general reward dampener”. Because they target the brain’s reward centre, the mesolimbic system, they apparently do not just stop “food noise” but inadvertently the quiet joy found elsewhere.

While retatrutide is the newest and most potent, reports of “emotional flatness” have also surfaced among users of approved GLP-1 drugs, such as Mounjaro. A recent case report suggests that such medications can influence brain regions involved in emotional regulation and potentially trigger or worsen severe depressive symptoms.

The academic neuroscientist Paul Kenny, from the Icahn School of Medicine at Mount Sinai, in New York, said the world was in the midst of a “huge experiment” as millions of people started using GLP-1 drugs, with researchers only now starting to collect data on how they affect behaviour as well as physiology.

He said some of the links already emerging were surprising, suggesting the medications may influence far more than appetite and weight. “We still know very little about what GLP-1 does in the brain,” he said, though an emerging body of research suggests the drugs may help protect against neurodegenerative disorders. Recent clinical trials in people in the early stages of dementia have raised the possibility that drugs that enhance GLP-1 signalling could have neuroprotective effects.

On whether such drugs could alter love, emotion or social bonds, Kenny was more cautious, saying he could not comment directly from a neurobiological perspective. But he added that it would not surprise him if medications so closely tied to the body’s energy systems also shaped human emotions and social interactions.

“A lot of animal behaviour is influenced by energetics and energy availability, all the things tied to survival,” he said. Because GLP-1 is intimately linked to energy status, he said, it was plausible that shifting those signals could also modify behaviour.

In animals, for example, Kenny said territoriality often increased when food was scarce, suggesting energy balance can shape the nature of social interactions. “GLP-1 is also linked to how the brain processes reward and pleasurable stimuli,” he said.

These drugs have been affecting libido, as Dr Naveed Asif, a GP from London General Practice, explained: “From a physical perspective, GLP-1 medications affect smooth muscle activity, which can influence arousability and orgasm due to changes in blood flow to the genital area.

“Chemically, the effects may vary among different patient groups, but there’s also a dopaminergic component: dopamine, a hormone released in the brain in response to stimuli, may decrease when using these peptides. This creates challenges related to desire and sexual attraction, potentially impacting overall sexual function.”

He adds: “Oestrogen is a key sex hormone, so taking GLP-1s might disrupt its balance, which can lead to emotional disturbances. This issue appears to be more pronounced in women using these peptides.

“I have observed that many women experience significant side-effects that lead them to discontinue the medication. Some patients reported worsening mental health, including increased depression and anxiety, which likely affects sexual function as a secondary consequence.”

Dr Sophie Dix, from the online pharmacy MedExpress, said the “leap from ‘reduced food cravings’ to ‘unable to fall in love’ is where the science currently doesn’t follow. Romantic attachment is a much more complex neurobiological process than a single reward pathway.”

She added: “We are seeing a range of experiences in clinical practice; some users report reduced libido, others report improvement, and many of those changes are better explained by a range of other factors. Research shows that weight loss and improved metabolic health can boost confidence, self-image and sexual self-esteem, which for many patients enhances rather than diminishes desire.”

Dix noted that because GLPs affect the reward areas of the brain, they are believed to reduce compulsive behaviours. “This could indeed imply risk of anhedonia – loss of enjoyment in things. However, this isn’t generally seen … It is likely that GLPs normalise or stabilise the system rather than simply blunt it.”

She said: “The research is still early, and this is an area that genuinely warrants more clinical investigation. Patients should feel comfortable raising any concerns about emotional or sexual changes with their prescribing clinician.”