Since Ali Vincent became the first woman to win “The Biggest Loser,” she has battled ups and downs — and struggled on the scale.

After shedding 112 pounds to win the show in 2008, Vincent says she has gained back most of the weight she fought so hard to lose, nearly returning to her pre-“Biggest Loser” weight of 234 pounds. Her struggles, she revealed, have made her ashamed.

“I have had successes and I have had major losses,” she wrote on Facebook last week. “I have gone from feeling alone to having thousands of people reach out with support. I have experienced ultimate highs that I could have never dreamed of as well as nightmares I wouldn’t wish on an enemy. Quite frankly some of them have gotten the better of me and I have struggled.

“When I struggle I shut down, I feel alone, I push people away, I hide, I sleep all day, I eat, I try to feel satisfied and comforted but do nothing to allow true satisfaction or comfort.”

Vincent became a celebrity during “The Biggest Loser’s” fifth season, when the 5-foot-5 champion walked away from the competition 112 pounds thinner.

But the next year, she told NBC’s “Today” that she already was apprehensive about regaining the weight, explaining that she was worried that she would put the pounds back on unless she spent every spare minute at the gym.

She said she continued to use her BodyBugg, a calorie-management system that the contestants wore on their arms, and threw away all of the junk food in her home.

“I childproofed my life,” she told “Today” in 2009. “I don’t want to leave anything to guesswork when I have the tools not to.”

But the weight started to creep back on anyway.

Vincent recently appeared on Oprah Winfrey’s OWN series “Where Are They Now?” and talked about a low point several months ago, when she was slammed with comments about her weight during a Facebook Live chat.

“I really started hiding after that,” she said.

On April 15, the eighth anniversary of her victory, she didn’t get out of bed, Vincent said.

“I was ashamed,” she said. “I was just ashamed. I was embarrassed. It was a low point. It was probably my lowest point. I won ‘The Biggest Loser.’ I was the first female to win ‘The Biggest Loser.’ Like, I’m Ali Vincent. I’m supposed to be strong. I’m supposed to know how to do this – I do know how to do it.”

Vincent said she realized that she was headed in a dangerous direction.

“If I keep going in the direction I’m going,” she said, “I don’t know if I’ll ever come back. I don’t know if I’ll ever be able to have the strength to do something different.”

Then, Vincent said, on April 16, she did “one of the hardest things in my life.”

She decided to lose the weight — again — and announced publicly that she has joined Weight Watchers.

“I swore I would never be there again, be here again,” she wrote on Facebook. “I couldn’t imagine a day again that I would weigh over 200 pounds. I feel ashamed. I feel embarrassed. I feel overwhelmed. I feel like failure.”

Vincent is chronicling her latest weight-loss efforts online. Weight Watchers, which is partially owned by Winfrey, said Vincent is a not a paid spokesperson.

“I’ve decided to feel proud of myself again,” she wrote. “To hell with shame. I’ve been so afraid and worried of public shame and ridicule that I’ve created more pain for myself than anyone else can but not anymore.

“I know there is going to be a lot of faking it until I make it on the proud front but I’m starting with taking action.”