Now he's walking marathons and is training to run the 2010 Moro Dunedin Marathon.
And his dad, Tony Mamea, (51) won't be far away.
Tavita's diet and exercise regime used to consist of sitting in front of the television with about 10,000 kilojoules of chips, takeaways, lollies - and even more chips to top it all off.
He weighed 106kg, his body was 48% fat, and alarm bells rang when he felt so bad he thought he was going to die doing even mild exercise.
Given Tavita's mother died of a heart attack five years ago, his father enrolled him in a new youth fitness programme for 10- to 13-year-olds at Creative Conditioning, in Dunedin.
Mr Mamea accompanied Tavita to the gym to do a few rounds with the boxing bag for fun and to support his son.
Soon after, Mr Mamea was diagnosed with type 2 diabetes, for which excess weight is a contributing factor, and he joined a fitness programme at the gym too.
Since then, Tavita has lost 22cm from his waistline and his body fat has fallen to 29%.
A healthy male body contains 15%-20% fat and a female body contains 18%-24%.
Meanwhile, Mr Mamea has shed 18kg and has been able to stop taking diabetes medication.
"I was amazed at how much the exercise made a difference to my health.
"You don't realise what the excess weight is doing to your body until it is too late.
"I had no idea I would get diabetes from my lifestyle."
Tavita said his life had changed too.
"My self-confidence has gone way up.
"I feel a lot slimmer and healthier."
The pair continue to chip away at their body-fat percentages by going to the gym several times a week, and they hope to run together in the Dunedin Moro Marathon in September next year.
