Who is Kate Tolo, Bryan Johnson’s girlfriend and fellow biohacker?

Bryan Johnson, the American biohacker who went viral in the wake of the Netflix documentary Don’t Die: The Man Who Wants to Live Forever (2025), seems to overshare a lot. In a recent X post shared with his 1.5 million followers about his girlfriend, Kate Tolo, Johnson wrote, “Just gave Kate oral sex. Goodnight, everyone.” He followed this up with another TMI post, reading, “100/100 score. Top 1 per cent of all vaginas,” accompanied by a graph of Tolo’s vaginal health test results courtesy of at-home microbiome testing platform Tiny Health.

After the post caught a wave of hate from Johnson’s followers, who called him an “incel” and his behaviour “psychopathic”, Tolo decided to weigh in herself. Alongside screenshots of Johnson’s post, Tolo wrote that she “could not be more proud” of her boyfriend for shining a spotlight on the typically taboo topic of vaginal health.

But who is Tolo – beyond her vaginal test results, that is – and how did she become linked to the world’s most famous (or infamous) biohacker? Here’s everything to know about the Australian-Bosnian woman who proclaims to be a biohacker herself, aiming to become “the female Bryan Johnson”.

She’s Bryan Johnson’s missing “puzzle piece”

The pair first met in 2021 at Kernel, Johnson’s brain-computer interface company, where Tolo worked before joining him in his broader mission to re‑engineer human biology. The two have been dating for three and a half years.

In a Facebook post from December 2025, Johnson recalled his first impression of Tolo as “luminescent” and shared how their “puzzle piece fit was immediate”. Later that month, he shared with his X followers how his biology was negatively impacted by his sweetheart’s absence. “Without her touch, my vagus nerve’s 100,000 myelinated fibres have dropped their high-frequency spectral power, squawking distress,” Johnson wrote.

She traded fashion for longevity