Standing next to his grandfather's grave was a life-changing moment for Mark Sosene.

The self-confessed lover of all takeaways weighed 154kg in 2010 when grandfather Daniel Akanoa died from a diabetes-related heart attack.

"I was brought up by my grandparents and when my grandad passed away he was my trigger," he said.

"It just opened my eyes to what I was doing.

"From that moment, I promised him that I would look after myself, and here I am."

By March last year, Sosene had shed 62kg - and now he is trying to help others do the same.

He arranges open walking groups twice a week and works personally with a couple of others, including 220kg Luke Pourau, who praised Sosene's efforts.

"No disrespect to the [other] people who have helped me, but they've probably never been a big person," Pourau said.

"[With Sosene] I thought, 'This guy has been there to a serious level. He's done. it. He knows what I'm going through."

Sosene recalled going to a doctor around the time of his grandfather's death, and being told he had hypertension. It was the first sign that a diabetes diagnosis was just around the corner unless something changed.

He was also an insomniac, had sore joints and was short of breath. "I was eating the wrong foods and drinking and partying," he said.

He moved to Melbourne in March 2011 to get away from his bad choices. "The first thing I did when I got there was buy a treadmill for the lounge.

"I ran on that every day and cut down my eating. I was too scared to go to the gym, because I didn't have very good self-esteem."

About 30kg dropped off in the first six months and by March 2014 he weighed 92kg. The hardest part wasn't losing the weight, but trying to gain muscle because he now weighed 100kg, he said.

"Some of it's mental, but I've been told by friends and family who are personal trainers, that putting a bit of weight on at this stage is normal and not to fret if I gain a couple of kilos in the process."

He goes to the gym every night and also plays indoor netball.

But one consequence of his previous 6XL size is loose skin around his middle. He is on the waiting list for surgery in Australia to fix it. If he does not have it, it could take him 10 years to get the skin elasticity back to where it was.

His advice for those who want to start losing weight is just that - start. "Anything you can do to improve your general health is important."