In the three decades since he was named Australian of the Year for his achievements in marathon running, ''Deek'' has used his fame as an

opportunity to promote positive change in health.

He speaks with pride of the projects that led to his appointment this year as an officer of the Order of Australia, but none more so than the Indigenous Marathon Project he has been overseeing for the last four years.

''The marathon project is much more important to Australia than what I did as an athlete,'' he said. ''It's a real blight on Australia, the statistics on indigenous health and incarceration and suicide and in opportunity, and if I can make a contribution to [improve] that, that's far more important than what I did as an athlete.''

In addition to running projects aimed at improving the health and wellbeing of schoolchildren, running a health bakery and practising traditional karate - he's a third-dan black belt - his team selects 12 indigenous runners each year to train for and run the New York City Marathon.

De Castella singled out Charmaine Patrick, a mother of two from Hermannsburg in the Northern Territory.

''We've taken this single mother of two who's smoked all her life and didn't really believe she could do a great deal, she's run the New York marathon and she's just become a hero,'' he said.

''If you've got someone in the family who has really changed their life, then you really stop and listen and take note and believe you can maybe do something as well.''

Although De Castella has met challenges in promoting measures to beat childhood obesity - his program lost ACT government funding last year - he has refused to give up. ''I feel privileged as an athlete, after having done what I did, to represent Australia and have a great career and great life chasing and achieving my dreams. I feel a bit of an obligation to give back.''