If most personal trainers spend hours in the gym to achieve a tone-perfect body that their clients will idolize, then Paul "PJ" James is not your typical personal trainer.

Instead, the Australian-born, former swimsuit model went the complete opposite direction, spending hours outside the gym and inside the kitchen to pack on 90 pounds in six months.

James had not fallen off the bandwagon, however, but gained the weight with a very clear purpose.

"The reason for doing it was to better understand and empathize with my personal training clients," said James, of Melbourne, Australia. "There's a lot of people who can't come into the gym for the first time because they feel embarrassed and they really appreciate someone …  to walk a mile in their shoes."

The 6 foot 2 inch  James spent two months at his max weight of 264 pounds, and then spent six months whittling his waistline back down to a more swimsuit-model-friendly weight of 176 pounds.

"I think what I totally underestimated was the actual emotional side of things," James said.  "Initially, it was fun to break from the routine, but then when you start to get a look at the way you feel and the way your body looks, things turned south very quickly."

James reclaimed his chiseled abs by following an eating and fitness plan explained in his new book, " Take it Off, Keep it Off."

James appeared on " Good Morning America" today to share the book's "KO-90? plan and his three key tips for losing weight and keeping  it off.

1) Cardio Before Breakfast, Every Day - "It's called fasting cardio because your 15 minutes of cardio is actually burning stored fat," James explained on "GMA."  "It's tapping into your stored fats and starting your day off positive."

2) Three Meals, Two Snacks, Lots of Water - "It [water] obviously hydrates you but works for skin elasticity too and your overall look," James said.  "And, fueling your body, there's no shortcuts … protein, carbohydrates are important as well and minimizing your fats. That's the secret."

3) Lift Weights Four Days Per Week - "It's really important for skin tone and also for muscle tone," James said of his recommendation to lift weights for 50 minutes four times per week.  "Women tend to shy away from weights but it really does work.  You're targeting things with a three-pronged approach of cardio, weights and healthy eating.  They all work together as a matrix to help you get in shape quickly."