The 28-year-old Sarnelli dropped 51kilograms from his 145-kilogram frame using the show's controversial hard-core fitness regime. He still sticks to a rigid program of diet and exercise to maintain his slimmed-down figure.
Now a qualified personal trainer, he recently opened a weight loss retreat, The New Me.
He says on his website: Winning the title of The Biggest Loser was one of the proudest moments in my life. I had finally overcome my life long burden of being obese and I had seen something through to the end. What an accomplishment that was for me!
I promised Australia on that night, I was going to help as many people as I can to overcome and win their battle against excess weight and obesity.
If you are genuine about losing weight and reclaiming your life, I can provide the support you need and work with you to help "You" achieve your goals and dreams.
Losing weight is not easy. You need a plan, you need support and you need to make changes in your life style. It was hard for me and it is hard for everyone else who does it - no matter which approach you decide to take.
But even his family members prefer an easy out. His sister Stephanie, 22, is having $14,000 lap-band surgery.
Weighing 149 kilograms, Ms Sarnelli says she does not have the motivation for boot-camp-style training.
"I go to university all day and work nights, so I don't have time to exercise. I've tried [meal replacement] shakes, I've tried taking out carbs, but the weight drops off and then comes right back on again."
Sarnelli says his parents, two brothers and four sisters blame their genes for weight problems and think he just "got lucky".
"It breaks my heart to think that I can, and have, offered my whole family the program I provide here and the only response I have had is from my older brother Mac who in his first two weeks has dropped an amazing 11.4kilograms.
"My sister on the other hand just eagerly awaits her surgery."
Sarnelli moved from the Central Coast to set up the retreat outside Melbourne in March.
Morbidly obese people attend the $1500-a-week live-in diet, exercise, education and counselling program for two, four, six or 12 weeks. Since March, his clients have lost a total of 316 kilograms, averaging three kilograms each a week.
Many had tried weight-loss surgery, he said.
"Although surgery has helped many people there are numerous others it fails to help, as they just go back to making the same poor lifestyle choices," he said.
"We are focused on teaching our guests the right way to live a healthier, thinner, happier life, by being responsible for their actions."
University of Sydney Professor of Human Nutrition Ian Caterson said about 40 to 70 per cent of obesity had a genetic background.
"There is no single gene, it's a multi-gene problem," he said.
New South Wales Health Minister Reba Meagher announced a $36million obesity strategy this month including public funding of weight-loss surgery, reports Sydney Morning Herald.