Kirstie Alley: Why I Got Fat!

(Photo: Cindy Ord/Getty Images)

Kirstie Alley has famously struggled with her weight, and now she’s opening up about how she gained so much in the first place.

“It’s not in my nature to plan,” the actress, 65, tells PEOPLE. “I’m a very spontaneous person, and that’s how I got fat.”

Her lifestyle got in the way of healthy habits, saying it’s easy to gain weight “if you travel a lot and you’re wined and dined and you love holidays.”

And while many people indulge during the holiday season, Alley let herself indulge the rest of the year too.

“I always joked that my holidays lasted from Halloween to New Year’s Eve, and maybe even into Valentines Day,” she admits. “I would think it was okay for me to eat whatever I wanted during those months.”

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Alley knew this pattern wasn’t healthy, but she felt like it was a positive thing to let herself truly enjoy the holidays.

“It was very social and joyous, like, ‘I’m going to have a big Halloween party and have caramel apples,’ but then I realized, 'Wow, that’s your real trap zone,’ ” she says. “So I still do the holiday thing, but I’ve learned something that wasn’t in my vocabulary before, and that’s a little bit of 'discipline.’ ”

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Helping her maintain that discipline is her commitment to Jenny Craig.

“I love doing Jenny Craig and being their spokesperson,” says Alley. “I’m not exaggerating when I say my consultant is my lifesaver! She has taught me how to maintain my weight fairly effortlessly.”