"My family know how hard it got for me. I was a very depressed man. It was a tough time.
"I decided that I needed to turn my life around and this is where I found happiness - in triathlon. It feels awesome. I am truly happy now."
Mr Sobanja will compete in the 40-44 age-group sprint race, which includes a 750m swim, a 20km cycle and 5km run.
He has been training since October last year and has lost 20kg in the process.
One of the incentives to train hard and go on to do well in this weekend's race is the chance to compete in another top international triathlon event, the World Series Final.
That will take place in Auckland next year.
"[Triathlon] is one of only a few sports in which you can represent your country in any age group," Mr Sobanja said. "I really want to do that - to put on a black singlet."
He hopes to set up a programme to inspire youngsters and help them to achieve at a high level.
NEED TO KNOW
* What: Barfoot &Thompson International Triathlon Union World Cup.
* When: Sunday. First race starts 7am. Last race ends 4.30pm.
* Where: Central Auckland.
* Who: About 1100 triathletes and tens of thousands of spectators are expected
* Watch out for: Dozens of full- and half-road closures and parking restrictions throughout the Auckland CBD, particularly downtown.
* Advice: Travel early or avoid the inner-city.
* Find out more at: aucklandtransport.govt.nz and triauckland.co.nz