Eugene Teo, 34, began lifting weights at the age of 13, looking for validation. “I was short, skinny and I thought it would give me confidence,” he says. “Bodybuilding for me was the ultimate expression of that.”

Now living on the Gold Coast in Australia, with his partner and daughter, the fitness coach spent from age 16 to 24 training and competing. At times, he lifted weights for up to four hours a day, aiming to get as muscular and lean as possible. The ideal he was chasing? “If you grab your eyelid and feel that skin,” he says, “that’s the skin thinness you want on your bum and abs.”

That quest became an obsession: “How can I push myself to these extreme points, and then do it again and again and become better than last time?” He followed unsafe protocols shared by bodybuilding gurus to make his muscles pop, dangerously dehydrating his body ahead of competitions. He ate six to 10 times a day, restricting his diet to foods considered “clean” by the community at the time: sweet potato, brown rice, broccoli and boiled chicken breast. He skipped his own birthday for years to avoid eating off-plan and took scales to Christmas dinner to weigh out his turkey. “There were a lot of dysmorphic associations around food,” he says.

His body became a project – one he focused his entire life around, with little room for flexibility, let alone fun. “The driving force behind my bodybuilding was negative body image and confidence issues,” he says. “I alienated myself. I lost friendships. I lost partners.”

His mum often asked him, “Why can’t you eat what I eat? Why are you not having my cooking?” Alone at home, he viewed his body like a critical enemy. Even at his most muscular, he saw only flaws. “I couldn’t even wear clothes without thinking, ‘How do my shoulders feel in this? How do my arms feel?’”

The realisation came slowly to Teo, but his body was screaming for a life overhaul. “I could lift a lot of weight. I looked exceptional,” he says. “But I was out of breath from simple tasks.” Walking across the gym with clients gave him lower back pain. Even tying his shoes required him to brace himself. “The sheer size of my body wasn’t supporting all the systems appropriately,” he says.

Teo changed his training, shifting the focus from muscle size alone to mobility, power and cardiovascular endurance – adding running, stretching, jumping and cycling to his routine. He began to ask himself whether his extreme mindset was making him happy, accepting that “this is now an obsessive trait in my personality, and it’s not bringing me joy”.

A decade later, his focus is on his relationships and work as a YouTube fitness coach and app developer, rather than his body. He no longer works out every day and, while he still eats well, he’s more relaxed about it. “If I’m out with my daughter and she wants an ice‑cream, I’ll have one with her.”

His body has changed. “It’s definitely smaller,” he says. He has lost around 15kg of muscle. “But performance-wise, feeling-wise – it’s night and day better. I can move better. I’m more athletic around my daughter.” He can jump twice as high as before and can run 5km in 22 minutes. (He couldn’t even complete a 5km run when he was competing. His first took 40 minutes.)

“Ten years ago, my body was capable of turning heads on the street,” he says. “That was fun – but it was the only thing it was capable of.” Now, he says, it’s built for function.

• Eugene Teo is @coacheugeneteo on YouTube and founder of the fitness app Ganbaru Method.