A few days before Thomas Page McBee was due to step into the boxing ring at Madison Square Garden for the first big fight of his life, his trainer, Danny Mangual, was scrolling through Instagram when he was pulled short by one of McBee’s posts. “He put something up about [Caitlyn] Jenner, when she transitioned, talking about, ‘Oh this is my idol,’” Mangual recalls one recent evening in Manhattan. “I thought, ‘OK, kinda weird.’” We are sitting in an innocuous Mexican bar eating stale tortilla chips. Mangual, who is short and compact, describes his dawning awareness as he continued scrolling through McBee’s images. “Then I come to a baby picture, a #ThrowbackThursday photo of Tommy, and I just said out loud: ‘Oh shit.’ I was bugging out because the whole time I was training this guy and he didn’t tell me anything.”

McBee knew that he was not a girl before he knew almost anything else

In 2012 at the age of 31, McBee received a new birth certificate from North Carolina Vital Records, an experience he would describe as like being born again. Getting the word “female” changed to “male” was the culmination of “thousands of dollars, a major surgery, two trips to probate court, two physicals, a doctor’s letter, plus the 80 oily milligrams of testosterone self-shot into my thigh every week,” he wrote in an article for Salon. But it wasn’t the end of the story; in some ways, it was just the beginning. McBee knew he was not a girl before he knew almost anything else, but even after starting hormones at the relatively late age of 30, he was aware that science couldn’t resolve the much bigger question of what kind of man he wanted to be. It’s a question he now directs at his readers in Amateur, a follow-up to his 2014 memoir, Man Alive, in which he charts his efforts to understand what makes a man a man – and why so few of us seem interested in interrogating the question. “Fish don’t know that the water is wet,” he writes in an allusion to the way we so rarely recognise our privileges.

McBee has spent years thinking about how men can be more accountable to themselves and those around them. Amateur is an odyssey starting with a simple question: what makes a man want to punch another man? It was an existential question for him, as his body changed, about who he was, and what men were. “I felt: ‘I’m experiencing male socialisation in rapid time, and I’m an adult, so I can see what’s happening to me,’” he says. “I thought in exchange for everything I got out of having a male body, and also everything I lost, I had a responsibility to make that process not just visible, but also universal, because it was.”

Thomas Page McBee. Photograph: Michael Sharkey/The Observer

We are in a coffee shop in Manhattan, sharing chocolate eclairs. McBee has smiling eyes and a quiet, generous disposition. It’s hard to imagine him sparring in a boxing ring, but that’s exactly what he chose to do. Violence had bookended McBee’s pre-transition life, and he thought that the rich and complex culture of boxing would help answer why men so often communicate with their fists.

“It seemed like a way to ask a lot of questions about male violence, which at the time seemed like the root of toxic masculinity,” says McBee. Before his journey to Madison Square Garden was complete, he’d discover much more, about himself, but more critically about the ways in which men socialise, and the harm they do to themselves as well as to others in the absence of archetypes of the kinds of men they could be.

Toe to toe: Thomas Page McBee (left) at Madison Square Garden. Photograph: Natalie Keyssar

Back when McBee used to date high-school cheerleaders and homecoming queens, the calculus was simple. They were straight girls tired of the jocks they dated. McBee was sensitive, attentive and masculine. The fact that he was also a queer, butch person didn’t seem to faze anyone. “You’re like a guy, but better,” he recalls a girl in 10th grade telling him. It was many years later that McBee began taking testosterone, enjoying the way it reshaped his body to give him biceps and a beard. In his 20s he had surgery to reconstruct his chest, watched his shoulders square up, his thighs slim down. The metamorphosis pleased him, but he was troubled by what came with it. Other men started responding differently to him – with more respect, but also more combatively. He noticed that to women he was no longer a benign presence, but a vague threat. Jogging early one morning, he startled a woman as he ran up behind her, and thereafter resolved to announce his approach. On dates, his old swagger and confidence leached away as he second-guessed himself, confused by what was appropriate and what wasn’t. A well-meaning gay friend suggested his sensitivity was transmitting as vulnerability. It wasn’t sexy, she told him. McBee’s answer, for a while, was to stop dating altogether.

Jessica Bloom, who is now married to McBee, recalls their first meeting as an equally confusing negotiation about gender. “I thought he should be the one interested in me, that I shouldn’t try very hard, that I just wanted to be pursued, and if he wasn’t going to pursue me then I guess he’s not interested,” she recalls. “It made me feel uncomfortable because I really had to think about what my expectations were with desire and romance.”

For much of his life, transitioning had not seemed necessary to McBee, who regards the “born in the wrong body” narrative as a reductive media trope, however true it might be for some people. But then, one night in Oakland, California, 29-year-old McBee was forced to the ground by an armed mugger. His partner at the time, Parker, was with him at the time, but McBee was the one at the end of the gun. “I was very boyish and masculine, so I looked like a man,” he recalls. “I don’t think he realised I wasn’t a man until I spoke, and then he went off and shot these two other guys, killing one.” McBee believed he’d been saved because his voice betrayed him, a reprieve that represented, paradoxically, a failure. “I was liberated by this thing about me that felt false,” he says. “It saved me, but it also made me aware that it wasn’t who I was. It was really primal. That was the moment I thought: ‘I need to transition.’”

Mother’s boy: Thomas Page McBee with his mother Carol Lee McBee. Photograph: courtesy of Thomas Page McBee

Until he began taking testosterone, McBee didn’t have much empathy for men – his own stepfather had abused him from the age of four to nine, and almost all the women he knew had been sexually assaulted, coerced into sex, or raped. What were the challenges for men compared with those for women? He remembered the girl at high school who told him he was like a guy, only better. But he hadn’t realised just how much our notions of gender influence the way we move through the world, or how it alters the way the world moves through us.

“When I began my transition, I thought I could still be ‘better,’ even if I traded being ‘like a guy’ for becoming one,’ he writes in Amateur. “What I wasn’t prepared for, when I began injecting testosterone, was the way the filter of my body changed the meaning of the way I spoke, the way I dated, the way I touched and was touched.” Behaviour that had seemed forward and confident in the past now seemed predatory. Overturning female stereotypes, such as the idea that women enjoy cooking, had given the old McBee transgressive cred, but post-transition, those same things seemed like reflexive male behaviour. “It sucked,” he admits.

McBee had grown up playing with a snot green He-Man and a Masters of the Universe castle, while his half-sister had a pink She-Ra castle, but going through puberty as a 30-year old was as confounding as it was clarifying. “I felt I was in what psychologists call a ‘man box,’” he says. “I felt very restricted in my abilities to express myself, be myself, by the feedback I was getting culturally.” When his mother died of alcoholism – shortly after he’d met Bloom – it tipped him into a full-blown crisis. “What was scariest about losing my mum is that this is the person who has known me so intimately throughout my whole life, but she’s also been there as my body evolved from one recognisable thing to another,” he says. “We didn’t have a lot of time after my transition before she died, so I felt very stressed about it, that she didn’t totally know me as a man.”

A pivotal moment came when McBee was accosted in Manhattan as he stopped to take a photo of a restaurant to send to Bloom. A man approached and accused him of taking a picture of his car. Uncharacteristically, McBee stood his ground. He recalls thinking: “Men don’t run.” There was a staring match and curses were exchanged. Just as it looked like fists would fly, McBee snapped back: “I. Did. Not. Take. A. Picture. Of. Your. Fucking car.” Challenged, his antagonist backed off. But the encounter stayed with McBee. “I really believe if I kept going that way, I was going to become the kind of guy I didn’t want to become,” he says. “It felt like the natural thing to do would be to face that down.” He found the solution in a boxing gym, punching other men, being punched back, shadowboxing with the man he was afraid he was becoming. What he learned in the ring was surprising, cathartic and healing: “There was so much beauty in that experience that I wasn’t expecting. It was profound.”

Family affair: Thomas Page McBee (right) holds his baby brother Brett, while his mother Carol Lee McBee holds his sister Clare, 1985. Photograph: Courtesy of Thomas Page McBee

Church’s Boxing Gym lies three flights of metal stairs below ground, near a busy intersection in downtown Manhattan. The walls are a cacophony of prizefight posters and flags from Puerto Rico, Brazil, Mexico, the UK. On a sweltering July night, the air is sour with the scent of stale sweat, as giant floor fans work overtime to keep the room cool. In Amateur, McBee memorably sums up his months in this subterranean temple as “a messy mosaic of blurred senses, damp armpits, hot lights, tangy throat, rubber-mouth guard bite marks, squeaky pivots, spangles of stars.” Tonight, the gym is a mass of bodies in motion. His trainer, Mangual, says: “These people that come to the gym to work out, every day they look for a way to sweat. But when you’re preparing for a fight you’re not just trying to sweat – you’re trying to turn into a beast, you’re trying to rip somebody’s head off.”

When you’re preparing for a fight, you’re trying to rip somebody’s head off

Did he see that instinct in McBee? “I think Tommy was trying to find out what turns him into a beast,” he says. “He’s a naturally nice guy, and I feel like when he did this he was trying to find his inner anger.”

When he wasn’t training, McBee was exploring the ways in which class, race and national identity influence the way masculinity is constructed. He’s aware of the apparent contradiction in believing that gender is both a construction and an imperative, but he’s at peace with it. “Life is a paradox, it’s a mystery,” he says. “I don’t know why we are the way we are. I know that in my apartment, when I’m just at home by myself, I feel great in my body and always did. But every single thing that would happen to me when I left the door felt bad to me, and I needed a language and narrative to stay true to who I was before my transition, and that required asking stupid questions, but also realising that nobody asked questions about masculinity, because to question masculinity is to put your privilege at risk.”

Man alive: Thomas Page McBee. Photograph: Michael Sharkey/The Observer

It takes much of the book for McBee to comprehend the enigma of the boxing ring, where men are comfortable hugging, or swatting each other on the ass, showing affection. “With its cover of ‘realness’ and violence, it provides room for what so many men lack: tenderness and touch, and vulnerability,” McBee writes. It’s not violence that lies at the root of masculinity, he concludes – it’s shame.

When McBee started writing Amateur in 2015, Obama was still in office, and Hillary Clinton looked a safe bet to succeed him. Trump and the cascade of #MeToo revelations were yet to convulse America. McBee would tell friends he was writing a book on the masculinity crisis and would be met with polite smiles and glazed eyes. “A lot of people felt as if we had been talking about a certain kind of man for long enough,” he writes. “It was easier to believe that we lived in the age of progress, and that progress would just keep moving us all forward on its tide.” As we all now know, whatever optimism we felt then was about to be upended by Brexit and the election of Trump, both of which inspired a rise in nationalist rhetoric and an endless parade of men behaving badly. In an age when identity feels so splintered and fractional, McBee’s empathy with men feels refreshing, but it’s his determination to be accountable that is radical. He resolves his own masculinity crisis by doing the things men often think they’re doing, but so often are not: listening, asking questions, seeking help, being vulnerable.

McBee did not win his fight at Madison Square Garden, but neither did he lose. With the help of a charity, Haymaker for Hope, McBee secured his slot there as part of a reporting assignment. Although he stopped training after his fight, he says: “I’m surprised to find I’m always thinking about returning to it.” Above all, he’d found Mangual, who’d made him a better man for having met him. The feeling was mutual. “I don’t know what it is, but we developed some kind of bond,” Mangual says. “I felt sad after the fight because I knew we wouldn’t have the same reason to see each other any more, because we’d reached the goal.” Would it have changed anything for him if he’d been aware that he was training the first transgender man to fight at Madison Square Garden? Mangual considers this for a moment. “It wouldn’t have bothered me either way. Maybe he thought I’d train him differently, but I don’t know why. I would have trained him the exact same way. He’s one very cool mother.”

Amateur by Thomas Page McBee (Canongate Books, £14.99). To order a copy for £12.74, go to guardianbookshop.com