In fact, he'd initially put it down to indigestion after a late meal following a big night out. His love of drinking, and lack of exercise continued.
But in 2011 when he again felt something like "an elephant sitting on his chest" he knew it was another heart attack. Watching a stent being inserted into his heart arteries was "interesting" but also was the wake-up call he needed.
"The first one I thought, 'Whoopsie'. The second one gave me a fright."
Following that heart attack he was also diagnosed with diabetes. "That was a bit of a wake-up call. By that time my knee was becoming a real issue and I needed to lose weight for surgery."
It all led to a decision to get healthy - modifying his lifestyle, joining GO360 Gym and cutting his alcohol intake by more than half with the help of his personal trainer.
"It really stemmed around that second heart attack. It made me wake up and realise what I was doing to myself."
Mr Nathan said these days he made it a priority to exercise Monday to Friday - cycling the 14km round trip to the gym to do weights.
His weight dropped from 112kg to 94kg, and he said he was determined to reach his goal of being under 90kg - "even if that's 89.9kg".
Mr Nathan said his diabetes was virtually gone, and his blood pressure and cholesterol levels were also good.
"I feel the best I have in 15 or 16 years.
"I look at what I've achieved in the past 18 months and I'm pretty proud of myself. Just because you have a heart attack it doesn't mean it's the end of your life, it can be the beginning of a new chapter."