136kg man changed his lifestyle and diet after he stopped breathing during sleep

Just six years ago, Mr Hayden Sum tipped the scales at 136kg.

Two half-marathons later, he is 40kg lighter and has just two goals left: getting to a fighting-fit 75kg for his 1.79m frame and completing a full 42km marathon in December.

''I no longer feel like every day is a bad day and I can do so much more,'' said the 31-year-old, who works in a brokerage firm advising clients on their trades. ''If you had asked me to run before, it would have killed me. Now I can't wait.''

He signed up for the One Million KG Challenge last week, pledging to lose 20kg by the end of the year.

Overweight since he was a child, he had learnt to accept all the teasing and hurtful comments directed at him.

He could never buy clothes off the rack - nothing was ever quite big enough - so his wardrobe consisted of specially tailored pieces.

He still remembers how on a trip to Tokyo Disneyland seven years ago, the sight of him in an orange shirt stretched over his belly prompted a stranger to tell him:

''You look like a pumpkin.'' But it was a health scare that persuaded him to change his lifestyle.

In mid-2012, his breathing had become wheezy and tests showed he ceased to breathe altogether during short periods in his sleep.

''That really scared me,'' said Mr Sum, who has never dated and lives with his parents. ''I had high cholesterol, high blood pressure, and blood in my urine. I needed to do something or I would be dead even before I reached 40.''

Also tired of his weight being a ''turn-off'' for potential employers, and being too embarrassed to be photographed, he hired a personal trainer and started with three gym sessions a week.

He drastically changed the way he ate. ''I had one of the worst diets - high fat, high sugar. Every time I ordered food, it would be more, more, more. I loved suppers too.'' Now he begins each day with three scoops of oats washed down with milk, before heading to the gym for a 6am workout.

Then it's two protein shakes, five hard-boiled eggs and steamed fish for dinner.

''It was difficult. The food was bland, but my family has been very supportive,'' said Mr Sum, who weighs about 95kg now.

''My mum is the one who drags me out of bed every day at 5am.'' Dating will come later.

''The focus now is my personal health and to show others who struggled like me that it's possible to change your life if you want it enough.''