She doubted she could lose a lot of weight, so Ann Anderson set her sights low.

Twenty pounds.

That was her goal when she signed up for Pete Thomas’ “Lose It Fast/Lose It Forever” program.

“I’d tried in the past,” Anderson says. “I’d lose 10 pounds and gain it – and more – back.”

But that was two years and 60 pounds ago.

Anderson lost that weight and became more active thanks to Thomas, a walking, talking testimony to the ability to lose weight, keep it off and become fitter and healthier in the process.

Thomas, 44, of Ann Arbor, Mich., once tipped the scales at 401 pounds. He began dropping weight after becoming a contestant on the hit NBC reality show, “The Biggest Loser.” Three months in, in May 2005, he was voted off the show.

But he took what he learned there, plus what he learned on his own, to become the show’s most successful at-home weight-loss contestant.

He lost 83 pounds on “The Biggest Loser” and another 102 after leaving the show.

Thomas was so excited about what he had accomplished that he started teaching others through seminars, boot camps and corporate wellness programs, coaching and coaxing numerous others to shed weight and become fitter.

Anderson, 46, of Pinckney, Mich., had tried to lose weight many ways. She knew she was in for something different the first day of Thomas’ 10-week program.

“I’ll never forget it,” she said. “He said, ‘We need to make a decision to commit now or quit.’ That really struck me because that told me this guy is not in it for money or fame. We had paid for the class and he was telling us ‘I’d rather give you your money back, because we want serious people here.’

“Then, when you see that life-size poster of him when he was that 400-pound person, and you see what he looks like now … it’s inspiring.”

Anderson ended up losing 27 pounds during the class, and eventually shed 33 more. She has kept it off for about eight months now.

What made the difference for Anderson, a hairstylist who was overweight all her adult life?

She says she learned how to eat smarter and exercise more in ways that made it stick, and it became so routine she doesn’t think about it anymore.

“Every week he focused on a specific topic and gave us homework assignments,” she recalls. “It wasn’t just coming to class and sitting and listening. He had challenges every week, and he made them fun and interesting.”

For example, one day the class went to a grocery store and participants competed to find the lowest- and highest-calorie food items. “Some of the foods I thought were low-calorie, weren’t,” Anderson says.

Getting active also made a huge difference for Anderson and others. “I remember the first time he told us to run on a treadmill for 15 minutes,” she says. “I thought, ‘Oh my God! He’s crazy.’ ”

But then he talked her through it. “He said, “Run two minutes, walk one minute.’ Well, you sort of feel like you can do anything for two minutes.”

The two minutes turned into 15, and five months later, in October 2010, she ran her first half-marathon. This October, she’ll run her fifth.

“I think about how crazy I thought he was when he told us to run 15 minutes, and now I’ve been running two hours every Monday for the past two years,” she says.

Unlike Anderson, Ann Guttman, 46, of Ann Arbor, was physically active. She biked and she played soccer and field hockey, but over time she packed 20 extra pounds onto her 4-foot- 8 frame.

She didn’t think it was possible because she was so active.

But one of the most important things Thomas told her: “You can’t outrun your mouth.”

Guttman realized she was engaging in self-defeating behavior. “I’d go on a 40-mile bike ride and eat a huge plate of food at Coney Island afterward,” she says. “I’m little, but I can pack away the groceries.”

Guttman started the program in February and dropped 20 pounds before the class ended in April. She did it by increasing the amount of exercising she does, adding strength training to her regimen and choosing lower-calorie options when she goes to restaurants.

Not only did Guttman lose weight, but painful symptoms of arthritis disappeared, she says.

She and others say team spirit built into the program – which Thomas calls the secret sauce of success – is also extremely encouraging, both in person in the seminars and boot camps and online through a private Facebook page where members post successes and challenges and connect with workout buddies.

“You can post that you’re looking for someone to walk or run at a particular park and a particular time and you’re bound to get at least two or three people responding that they’ll join you,” Guttman says.

Jessica Towers knew she needed to do something when she saw a photo of herself with husband, Matt, and their two daughters, in December 2010.

“I’m seeing that picture and thinking, ‘Am I really that big?’ ”

Towers signed up for the boot camp in January 2011. Six months later, Matt joined, too .

“I learned I needed to cut the amount of calories I was eating by almost half. At first, I thought, ‘How can I get by eating this little?’ I was cranky, irritable. But after about a week, I got used to it,” she says.

Both of them also started exercising, including running.

This month, they’ll both run a half-marathon in Detroit. It will be her second; his first.

Thomas “has given me the knowledge that I need and showed me that I can do it,” she says.

Meanwhile, Towers, who dropped from a size 18 to a size 10, says she feels better than she has ever felt. “I’m wearing sizes I don’t even remember wearing in college. It’s nice to be able to shop in regular stores. That’s probably the best part.”

Matt Towers achieved his goal of getting to 200. The 6-foot-1 software consultant went from 290 pounds in July 2011 to 200 this past April. He was so encouraged by the program that, at Thomas’ suggestion, he became a certified fitness instructor .

He also started a fitness program at his church so he and his wife can share what they’ve learned with congregants at Peace Lutheran Church in Ann Arbor.

But there’s another big bonus.

“I used to love to play basketball in high school and college. There’s a group of guys who play at lunch. I used to drive by and watch them play for years and I used to think, ‘I wish I could join them.’ But I just didn’t have the energy.”

He plays with them now.

“It’s hard to put into words how fulfilling that is,” says Matt.

Thomas’ plan

Pete Thomas ( mixes his weight loss story, and those of people he helped, in a new how-to book that he hopes will help others do what the title suggests – “Lose It Fast, Lose It Forever” (Avery, $26).

The book maps out the key components of his approach, such as engaging your mind in the battle, developing an individualized plan that involves reducing calories and increasing exercise, using a support team, journaling and viewing weight loss not as a goal itself, but as a means to a healthier, more purpose-driven life.

Thomas’ philosophy is: “Master your mind, manage your mouth and multiply your muscles.”

“My goal is to help people develop a plan that works for them,” he says.

Thomas quit his job as a real estate investor to devote all his time to helping others succeed in living healthier lives. “My misery has become my ministry,” he says.

He believes the mind is one of the most important tools for healthier living.

“The reason we fail is because of broken focus,” he says. “Your most powerful weight loss weapon is your mind.”