The actor - who played Kyle Braxton on the Channel 7 TV series - took to social media platform to share his results while promoting his online personal training program which is set to launch soon.
"A few of you have been asking what my physique looked like during my photo shoot without all the lights and the fancy camera.
"Here's a raw image from my phone. And if you swipe, you'll see where I started five months before that, around when I started training people as a PT (personal trainer)."
Fans were quick to praise him, with one writing: "Damn, what a incredible transformation!"
Another added: "Even your chin is ripped. Great work, well done."
Westaway only recently became a PT, explaining he found it rewarding to make a difference by simplifying the process.
"I find the fitness world over complicates things sometimes.. Last year I became a qualified Personal Trainer and saw simple changes make big impacts in people lives.
"Fitness should complement the other things in your life, not take over or stress you out. Training can be simple. And when I say training, I mean exercising, eating well and letting your body recover."