Illusionist Penn Jillette on Shedding 100 Pounds: 'It's Night and Day'

— -- Penn Jillette is crediting his dramatic weight loss to winning the brave battle to save his life.

The world-famous illusionist captured his journey in his new book "Presto: How I Made Over 100 Pounds Disappear and Other Magical Tales."

Jillette, a 6-foot, 7-inch father of two, tipped the scales at 322 pounds when his doctors discovered a 90 percent blockage in his heart.

Jillette attempted the "potato diet" under a doctor's supervision, eating only plain potatoes for two weeks straight, then phasing in vegetable stews.

The 61-year-old dropped 75 pounds in just 83 days following this strict, no-exercise approach that experts don't necessarily agree with.

"For the body to function optimally, it really needs a wide variety of foods that provide vitamins and minerals," said registered dietitian Maya Feller. "You need to have fiber, protein, fiber, fats and carbs. Eating one food alone can be really detrimental."

Jillette said on "GMA" today: "The potatoes, first of all , they weren't raw and that's an arbitrary thing. I'm not good at moderation. I wanted to do hardcore stuff. I wanted to lose the sense of eating socially ... it was just a way to lose all the habits I had gotten into. So, it didn't have to be potatoes. They aren't magic. I picked potatoes because it's the funniest word."

During that time, Jillette said he didn't exercise. Now, he eats very differently.

"The thing is, I don't respect moderation so I had to do stuff really intense," he said. "What I was most surprised about was I used to consider myself a happy guy. I look back on it now and I kind of, sort of wasn't. I feel so great now. It's night and day."

"Presto" hits bookstores this morning.