But after taking up exercise in exchange for a PlayStation 2, he is now the UK’s fittest man ­— crowned champion at the 2020 CrossFit Open.

The 30-year-old said he led a really unhealthy lifestyle, “practically inhaling chocolate” and ate McDonald’s and KFC — a family bucket — five times a week, The Sun reports.

“The more fast food I ate, the more I craved it. It was a vicious cycle,” Zack said.

“When mum bought sweets for me and my older sister, I’d eat all mine within two minutes — and then I’d eat hers.

“We’d have a row about it but I just couldn’t help myself.”

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CrossFit combines elements of high-intensity interval training (HIIT), powerlifting, gymnastics and other exercises for an all-round fitness programme of gruelling workouts.

And Zack won last year’s title after lifting 360lb (163kg) — equivalent to the weight of two average men — walking more than 13 metres on his hands and running a mile in just over five minutes.

The real-life Hulk has come a long way from his early years with mum Jackie, dad Dudley, 56, and sister Martine, 38, in Evington, Leics.

On visits to McDonald’s as a ten-year-old he would order a super-sized McChicken meal with a milkshake and 20 chicken nuggets. Then he would continue eating treats at home.

Zack, who now lives in Birstall, West Yorks, with girlfriend Samantha, 27, says: “Dad would always say to my mum, ‘You’ve got to stop feeding him that!’, but she would do it anyway because it made me happy.

“My dad wanted me on a healthier path. He was very straight-talking and would tell me to my face to lose weight.

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“Mum didn’t care what shape or size I was. She loved me and thought I was perfect. There was a lot of conflict.”

Zack believes his mum’s desire for more children, combined with a series of miscarriages, could be the root of his childhood weight problems.

He says: “Mum always wanted at least eight kids.

“She had my sister, but then had six or seven miscarriages — about one a year — before I finally arrived.

“She was so happy to have me, she hated saying no.

“She smothered me with love and affection. If I wanted sweets or chocolate she would give them to me.”

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Every Friday night, Zack and his mum would enjoy “snack night” — something he looked forward to all week and an event that only happened thanks to his dad’s weekly card game away from home.

He says: “With dad out of the house we’d go mad on sweets.

“We’d get a tray and load it with chocolate bars, crisps and tons of sweets, then we’d tuck in.

“It sounds awful now but I used to love Friday nights with mum — they are really happy memories.

“I definitely got my sweet tooth from her.”

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Zack, who is now releasing a book about his fitness journey, always felt confident around his family, who made light of his weight.

He says: “My sister would draw a six-pack on my big belly and I’d run around pretending I was ripped.

“I’d do a dance and wobble my stomach. The whole family would be cracking up.”

But showing off his body in front of other people was a different matter.

Zack says: “I was hugely insecure about the way I looked. Certain clothes were always too tight and I never took off my top.

“I always got out of swimming lessons at school. I didn’t want to be the fat kid wearing a T-shirt in the pool.

“I was too self-conscious to think about girls.

“When I was playing sport I’d get tired quickly and pack it in after 20 minutes. The other teams would often call me fat.

“I brushed it off, but it’s never nice to be called nasty names. But most people liked me.

“If my family tried to get me out for a walk at the weekend I kicked up a massive fuss. I was really lazy.

“Being overweight makes you feel rubbish. You can’t walk or run far so you don’t want to exercise and you often end up finding comfort in fast food.”

But after being coaxed into a game of rugby at school, something began to click.

Zack says: “I struggled with the academic side of school but I started to really enjoy rugby, I could just bulldoze over the other team!

“My nickname was ‘The Washing Machine’ because I was so solid.”

His weight was still taking a toll on his health, however.

It was a contributing factor to the asthma and severe hay fever he suffered, as well as several knee and ankle injuries.

It was a PlayStation 2 that acted as the big turning point. Zack explains: “It was a new games console and massive at the time — I was desperate for one. I knew my dad wouldn’t just buy it for me, he’d make me earn it in some way.”

Seeing his chance, Dudley struck a deal with his son.

The youngster was told if he cleaned up his diet and made an effort to be active, the PlayStation 2 would be his.

Zack says: “All I had to do was eat less junk food and go for walks with my family. They started eating more healthily as well. We did it together and that support really helped.

“After the first month I lost some weight and that was a big confidence boost.”

His dad stuck to his word and Zack got his reward. But the youngster felt so good that he decided to keep going.

And by the time Zack was 16, he had gone from being the overweight kid to the sportiest kid in school, playing squash, tennis and rugby, and going to the gym.

He says: “I cut out all the fast food, sweets and chocolate completely, not even at the weekends.

“Later on, I didn’t even go down the pub with mates. I ate healthy food and exercised.

“But I wasn’t missing out. I had a great social life and liked having such a good body.

“I was losing fat and was fitter than ever but my weight was staying the same, and that was really confusing at the time.

“But it was all because I was gaining muscle. That’s why it’s so important not to focus on what the scales say.”

It was Zack’s dad who introduced him to CrossFit when he turned 23, and the rest is history.

He says: “I was hooked just watching clips of it on YouTube. With the rugby I got too many injuries and stopped.

“CrossFit was exactly what I needed and I made a goal.”

He now does gruelling four-hour gym sessions six days a week and lives on a diet of chicken, rice and potatoes to maintain his ripped body.

Zack, who owns a CrossFit gym, says: “I never imagined I’d be the fittest man in the UK.

“But here I am. It doesn’t matter how heavy, old or unmotivated you are.

“It’s never too late to change. And if I can do it, anyone can.”

This article originally appeared on The Sun and was reproduced with permission