"Since the age of 18, I have had bulimia nervosa.
"It is a disorder of overeating followed by fasting or self-induced vomiting or purging.
"It was a secret I was still battling to control as I stepped on to the pitch to referee the Rugby World Cup in 2015," Owens says.
Owens reveals that growing up in a small Welsh town he realised he was different to his friends when he became attracted to other men.
"I had no idea what being gay was, I'd never even met a gay person before, " Owens writes.
"Desperate not to become this person, I struggled to suppress him. I felt I was lying to my parents, the people that mattered the most to me, which went against everything I'd been taught.
"I became very depressed.
"Add to the burden the fact that I was overweight, about 16.5 stone (105 kg).
"In my eyes I was obese and thought "no-one who I find attractive was ever going find me attractive while I'm fat".
"So, I started making myself sick."
Owens says he lost more than 30kg in four months.
"Before long I was bringing up every meal I ate," Owens says.
"No-one suspected a thing. I was running and training a lot and my friends and family could see me scoffing food every mealtime, so as far as they were concerned I was eating well. I was training hard so outwardly I looked fit and healthy.
"An eating disorder wouldn't have crossed anyone's mind. There wasn't much awareness back then and if there was it was associated with young girls.
"Meanwhile, I was about to get sucked even further into the vortex of self-harm and depression."
Owens reveals he used steroids for eight years because he thought he was too thin and didn't get on top of the bulimia battle until he was 36 when he mother was diagnosed with cancer.
However he says the pressure of the 2015 Rugby World Cup saw the bulimia return on the eve of the tournament.
"Fitness expectations are extremely high, particularly for somebody who was 44 years of age. Bear in mind international athletes in their prime, in their 20s, are expected to reach that level and I was expected to do the same.
"I was training hard but knew that if I could only shed four to five kilos my chances of passing the fitness test would improve - I'd be carrying less weight and my body would take longer to get tired.
"I remember looking at the mirror and thinking: "Damn. I could get rid of this quite quickly."
"And so the bulimia returned.
"Once I'd passed the test, I resumed a good routine of fitness and nutrition and went into the Rugby World Cup in peak condition."
Owens, who will take charge of the All Blacks' clash with the Springboks in September, says he's opening up about his bulimia in hope to give other people the courage to face admit if they face the same battle.
"I'm speaking openly about it because I know that men and boys can view it as a sign of weakness by admitting there's a problem that you can't sort out yourself.
"But it's not a sign of weakness; it's a sign of great strength to do that."
"One thing I absolutely do know is that the bulimia can't carry on. And I just hope that by speaking about my experience I can help many others reach the same conclusion.
"It's not always easy to get the help you need when you need it so the sooner you start talking to people the better.
"Don't be in my situation; 27 years on and still suffering from it."
