Meet the men calling out 'masculinity' trends

While the search term "bone smashing" is banned on TikTok, 18-24-year-old men are the most common demographic searching variant phrases. TikTok insight data shows they are also the most popular group searching looksmaxxing hacks on the platform, with more than 300,000 searches per day in February and rising to a peak of 1.9 million in late March.

The content that masculinity influencers share can target boys as young as 13, he says, some of whom may not yet have gone through puberty,when their faces and bodies would naturally tend to become more like those of grown men.

James Brash, a registered nutritionist and content creator, tells the BBC that fitness and diet advice are not innately bad – and he isn't discouraging people from trying to be healthier.

"Physical activity is one of the best things that people can do to improve their health, if they are able to," he says.

What he objects to is what he terms "influencer overreach", where those with mass followings share advice backed up by dodgy evidence - or no evidence at all.

Brash does not consider himself an influencer, because he is guided by professional medical standards, rather than clicks, to call out "misinformation".

"It's not sexy because it does not rely on fear or urgency," he says.

Brash has spent the past year posting videos calling out nutrition misinformation largely promoted by wellness influencers.

One influencer he calls out is a man who says "our grandads would be turning in their graves if they had seen what men were like today". He also claims that in the past, men had higher levels of testosterone and were more fertile.

Brash says the video promotes "sexism and homophobia", pushing a very narrow version of "acceptable" masculinity.

In response to the BBC's questions, the influencer says his "comments were not intended to be homophobic".

"They were focused on male endocrine health, not sexuality or identity."

Some masculinity influencers see themselves as helping young men who feel lost and are looking for practical guidance on how to feel better about themselves.

Self-proclaimed "healthmaxxer" influencer Steven Abelman says masculinity, rather than looks alone, is the focus of his content, which promotes strict diet, sleep schedules and exercise regimes.

Overstimulation from fast-paced technologies and online gaming is contributing to poor mental and physical health, Abelman believes.

His content largely centres on reaction reels responding to other people's actions and diets – casting judgement over whether they are "optimal" or not.

"Society is turning men weaker and weaker, but what I'm promoting can really strengthen men," the influencer says. "I want to promote more of the primal lifestyles."

Ben Hurst from Beyond Equality, a UK-based organisation focused on "rethinking masculinities", speaks to young men in schools. He knows they live online, and says it is important he uses his platform to "flood" those spaces with content that could shake up perceptions of mainstream masculinity.

"The beautiful thing about the internet is that there is actually space for everything, right?" Hurst says. "I'd love to see versions of masculinity that are caring, and kind and confident and gentle and loving, and passionate and powerful and strong and dynamic."

He points to personalities such as Rory Bradshaw, who shares videos about teaching yoga in men's prisons as part of his broader mission to combat violence against women and girls.

"These men are pushing the idea of community in health and fitness," says Hurst, "rather than just an individual pursuit of perfection."

Information and support is available from these organisations for eating disorders and mental health issues.