"You know what, I lose weight, not gain it, during the holidays," she told PEOPLE recently at the Bloomingdale's Coat Kick-Off Drive with Sundance Channel's All on the Line with Joe Zee. "You have more days off, so you have more time to go to the gym and be active. I have so much more time to work out this time of year."
Bertinelli, 51, says preparing holiday food also sometimes leaves her cold.
"I'm spending hours running around cooking in the kitchen, and by the time it comes around to getting to eat, I don't even want to eat that turkey anymore, I'm sick of it," she says. "So keeping fit for me is easy this time of year."
That said, when the Hot in Cleveland star, who is also a spokesperson for Jenny (formerly Jenny Craig), does find herself faced with a tempting treat, she'll occasionally indulge.
"My dieting philosophy is, you never have to give up anything completely," she tells the January, 2012 issue of Woman's Day, on newsstands Dec. 20. "If there's something you really like, you'll always be pining for it. Then, if it's put in front of you, you'll go crazy for it."
One of her favorite snacks? "I love movie popcorn, but I don't have it very often because I know there's a healthier alternative in unbuttered popcorn and it's still satisfying," she tells the magazine, whose cover she graces – the first celebrity in 20 years to have that honor. "But occasionally I'll indulge when [husband Tom Vitale] and I go to the movies, and I'm not going to feel guilty about it."
Reporting by KIM PEIFFER