(Image Credit: ABC News)

By Robert Zepeda and Erica Butler

Starving herself then bingeing on Cool Whip and Graham crackers; shifting her weight to trick the scale; even disguising herself and going through McDonald's Drive-Thru - these are the kinds of self-sabotage behaviors "Ruby," the hit weight-loss reality show that ran from 2008 to 2011, was supposed to be an antidote to.

But that's what Ruby Gettinger, the show's star, did, she said in an interview with "20/20."

Watch the full story on "20/20? TONIGHT at 10 ET

For four seasons, "Ruby," which aired on the Style Network, followed Gettinger's every move as she struggled to go from more than 700 pounds to 250. Her bubbly personality won hundreds of thousands of fans, who cheered her on through achievements like driving, riding a bike and swimming.

Dr. Oz, Regis and Kelly and even Oprah came calling, making Ruby the face of obesity.

With the show came counselors, a nutrition plan, trainers - all working toward the goal: 250 pounds.

But secretly, Gettinger now says, off camera her goal was dramatically different.

"I never, ever say this, but in my head, my goal was 128," Gettinger told ABC News' Amy Robach. "I wanted to be so thin that someone would look at me and say, 'Are you anorexic?'"

She didn't quite get to 128, but after season one, she was at 373, almost 130 pounds less than where she began. In the second season, while having some personal setbacks, she still managed to pull out a new low, 357. At the start of season three, Ruby was arguably one of the most documented stories of obesity and weight loss in America.

While the show brought on a celebrity high, the pressure to keep losing was bringing her down, causing stress and meltdowns.

"I didn't realize this is such an addiction," Gettinger said. "Like alcoholism, drugs, you know?"

Tennie McCarty, who was a counselor on "Ruby," runs Shades of Hope, a treatment center for those with eating disorders. She said food addiction is not only real - it can be even worse than alcohol and drugs.

"[With] alcoholism, drug addiction, nicotine addiction … [y]ou could live the rest of your life and not drink alcohol, take drugs or smoke nicotine," she said, whereas food is everywhere, and you have to eat.

Ruby was spiraling out of control - and going off her program for healthy weight loss.

"There was a lot of pressure," she said. "It made me start starving myself to death. I literally did not eat for four days because I knew I had to weigh. … And then after I weighed, I would binge eat."

One day, Gettinger's niece came over, and she had some Chicken McNuggets.

"For a week after that," Gettinger said, "I would go through the Drive-Thru - and I'm not kidding you - put a hat on, glasses, so no one would recognize me. … But just in case they'd recognize me, I would have the phone like this and go, Okay, now, what is it that you wanted? … It was two McNuggets? Okay. … That's just horrible to admit. But it was almost like just that one bit triggers something in me."

Gettinger stopped using her exercise equipment, and covered up her secret.

"When I was in a bad place I didn't use them at all. I'd get a washcloth and dust them off. I didn't want people to think, 'She's not using her equipment.'"

But the numbers on the scale couldn't lie, so Gettinger devised a way to deceive the scale, the show and the fans rooting for her.

"I could figure out a way to lean to this way or that way," Gettinger said. "I could make a 28-to-30-pound difference."

She even believed her own lie, Gettinger said.

"[I was] almost getting excited later on in the day, because people are bragging about the number that I have convinced myself that is the number, too," she said.

The show's producers weren't fooled and sent Gettinger to a weight-loss camp to restore her motivation. Nothing worked, and "Ruby" was cancelled, leaving fans wondering what happened.

"[The producers] said, 'We love you … we're just not going to continue the show," Gettinger said. "No one said this, but my personal belief is [they cancelled it] because I gained weight," she added. She said she blamed herself for the show's end and for "letting so many people down."

Soon after the show ended, Gettinger's brother died. She lay in bed, depressed and eating, she said. She gained 50 pounds, taking her back almost to 400.

"I woke up with, like, This is it, I'm doing this. It's not about the show; it's not about anything else. I got to finish this for me."

Desperate and with no money, Gettinger turned to her former trainers from the TV show.

"I said, Of course, I'm here for you no matter what," said Shazia Edmonds. "That phone call to me was so refreshing. It felt like she gets it, she wants to do it on her own."

Gettinger has named her new campaign Ruby's Challenge, and has a website to encourage fans to watch her progress and join themselves. She is back in the gym regularly and eating right, and has worked her weight down to 360.

Gettinger said she had learned some hard yet valuable lessons.

"The hard road is the best road, and just in the past two months I have never worked out [so] hard, been so strict, been so consistent."

Watch the full story on "20/20? TONIGHT at 10 p.m. ET