The actress embarked on a weight-loss journey after experiencing what she called "men tragedies" around age 53. She was often candid about her experience, empowering others on a similar journey.
During a 2013 appearance on The Wendy Williams Show, Alley said she initially lost weight on Jenny Craig, which she was on from 2004 to 2007, but eventually gained it back. "I just went south," she told host Wendy Williams at the time, adding that she was down again — this time 50 lbs.
In 2004, when she began losing weight, she said on The Oprah Winfrey Show that the decision to take the first step came after she garnered media attention for her appearance. "Honestly, I didn't know how fat I was," she said.
Set on losing the weight, she signed on as a Jenny Craig spokesperson in 2004, losing 75 lbs. on the program.
One year later, she launched the series Fat Actress. She used her weight as comedic inspiration and went into detail about it in the book How To Lose Your Ass and Regain Your Life: Reluctant Confessions of a Big-Butted Star, which she released that same year.
"You know, I don't usually say this, but [Jenny Craig] has been a godsend," she said. "I needed a game. I'm one of those people that if you give me a sport or a game or make something really fun for me, then I'm on board. And I was just tired of the whole subject — weight loss, blah blah blah. And this has been so much fun because they have 8,000 things you can order [to eat], and you get your own consultant!"
After reaching her goal, she returned to the The Oprah Winfrey Show in 2006 to model a bikini.
"I was so introverted about my body," she said. "When I looked back on my movies and things [I thought], 'Wow, you had a really nice body.' But, at the time, I was [feeling] not good enough." She added that she was trapped in a cycle of binge eating that at one point had her weighing around 220 lbs.
Although she maintained her 145-lb. figure for three years, she left the company in 2007, and found that her discipline — and waistline — fluctuated back to her starting weight.
"I was at maximum eating load," Alley recalled to PEOPLE in a 2011 interview. "I didn't like the way I looked. I might have had fun times getting there, but there was nothing positive about being fat. My body had gotten really weak. I felt like I couldn't move."
When the opportunity came to join Dancing with the Stars, "every single person including my agent, manager and friends said don't do it. They all thought that I'm a hotshot actress who should only act, but I was bored out of my mind," said Alley, who also solicited advice from DWTS alums Jennifer Grey and Marlee Matlin, who called the experience "excruciating" and "a killer." Alley's response? "Good, I need something killer."
She joined the show and eventually lost 100 lbs., going on to launch her own Organic Liaison weight-loss system.
She told PEOPLE of clearing the 100-lb. weight-loss hurdle. "When I hit that mark, I went, 'That's it,' " she said. "I have more energy than I've ever had in my whole life."
After ending her run on the show, she tweeted, "NO surgery, NO flippin lasers, NO barfing, NO starving...Jeez...my products, organic food, dance."
When she began to see her weight increase again in 2014, she made a return to Jenny Craig. "It's like being an athlete. No athlete is going to do well without having a coach. We have to equate that to life. Without a coach helping us along the way, I don't think someone can make it for the long haul," she said.
She stressed that she was focusing on both her physical and mental health, telling PEOPLE, "I need to get myself to where I feel cocky again."
She went into detail about her weight-loss journey in an April 2014 interview with Woman's Health.
"If someone's attacking me for my weight, I go flourish and prosper somewhere else in the universe. I'm the master blaster of turning lemons into lemonade," she said.
RELATED VIDEO: Kirstie Alley Says She Took Some 'Bad Habits' from the Set of 'Cheers' into Her Career
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"The time it hit me the hardest — because it was the first time I gained a lot of weight — was right before I did Jenny Craig. I was being attacked in the press for being fat — just brutal. I also remember that I owed the IRS a lot of money, and I needed to figure that out in 30 days [on top of] the press calling me fat. I had also broken up with a boyfriend, and that was gruesome and hideous. One day, I went in a room, locked the door, and went, 'What am I going to do? What are my options?' I wrote a TV series called Fat Actress and made it really funny. I sold it that week."
By 2015, she lost 50 lbs. and switched her focus to maintaining her weight, instead of losing it.
Instagram Kirstie Alley
"I'm on maintenance, so I have one Jenny Craig meal a day and then I'm on my own, but I also have my Jenny Craig consultant," she told PEOPLE in 2017. "So if I feel like I'm going awry, I just call her and she gives me some tips and a pep talk."
She added that she also stepped away from returning to bad habits by learning about her trigger foods in order to maintain discipline.
"I love sugar cookies that are frosted with Santa's faces and trees, so I didn't order any and I didn't have any. My friends were dismayed because I usually give them out as gifts," she said.