Drew Manning made himself obese to prove a point, and teach himself a lesson.

The personal trainer gained 75 pounds in six months as an experiment, to see what it takes to lose that sort of weight, while also putting himself in his clients' shoes.

The 31-year-old quit exercising and completely let himself go starting May 7, 2011. At the time, he was a svelte 6-foot-2, 193-pound Adonis with a 34-inch waist.

For 26 weeks, Manning lived on a diet of starchy pastas and wheat, as well as donuts, cakes and nothing but soda. Or as some Americans call it, a balanced diet.

Manning chronicled his journey from hunky to hefty and back on his Web site, fit2fat2fit.com.

The effect bordered on the absurd. Manning put on 23 pounds in his first month. By the time he reached Week 26, he added 72.2 pounds and 13 inches to his waist.

Along the way, he learned that the effects of being fat go way beyond just looking like the Michelin Man.

Manning's internal organs began turning against him, with his liver and kidneys resembling those of a full-blown alcoholic's (which his doctor attributed to all the soda he was pounding).

Worst of all, his wife Lynn complained to ABC that he lost his mojo in the bedroom, going so far as to turn off the lights.

His self-confidence, that completely went away and depleted, she said, adding he was becoming lethargic, lazy, not helping around the house.

By Week 27, Manning was ready to get back in shape. But then he learned the troubles many face dropping their high-sugar, high-carb diets. Headaches, dizziness and a rotten disposition ensued.

And the pullups and pushups that used to come easily now required assistance.

It was hard to get back into the exercise routine, Manning told ABC. This is the first time going to the gym that I was nervous. Before I loved going to the gym, but for the first time in my life, I was humbled.

Manning recounts the whole ordeal (or transformation, if you're a glass half-full type) in his new book, Fit2Fat2Fit.

Check out the segment that aired on ABC below: