When ABC news icon Diane Sawyer wanted to lose weight, she turned to one man: weight loss expert Jim Karas. And through hard work and exercise, Karas helped Sawyer lose 20 pounds and get in tip-top shape.

"What worked for me was getting real, not kidding yourself anymore," Sawyer told us.

But Sawyer isn’t the only famous face that Karas helped slim down. He also helped newswoman Cynthia McFadden get lean and mean -- and now he can get you on track too. But Karas warned us… before you lose the weight, you’ve got to lose the excuses.

"I don't have time, I don't have the energy, I don't have the right genes," Karas reminded us. "I always say we suffer terribly from what we call portion distortion, we just eat too much."

If this seems like too much to remember, don’t worry, all the information is in Karas’ new paperback, "Flip the Switch," an action plan for success that also puts the kibosh on the low-carb craze.

Karas insisted: "It doesn’t matter if it’s high fat, high protein, high carbohydrate, high whatever, if you reduce the amount of calories you consume and you effectively exercise, you'll lose weight."

Diane welcomed Jim to the set of "Good Morning America," where the pair dished about food and Sawyer revealed, "The emotional commitment that I have in an ongoing way to chips and hot dogs, nuts and peanut butter."

With Jim's help, Sawyer lost 20 pounds back in 2001. So how is she doing now? "See, he's the truth squad," Sawyer said of Karas. "If it were just us, I would tell you anything, but he's not going to let me. No, I don’t always stick with it, is the answer."

So, like most of us, Diane is facing her weight loss challenge again. But she claims, "One of the things I’m doing right now is figuring out a way to get it back."

You can get it back too, just "Flip the Switch," and learn all you need know.