Fisher, who rocketed to fame with the 1977 science fiction movie "Star Wars," is attempting to lose 30 pounds.
"A day comes when you can no longer face not wanting to leave the house because you don't like the way you look," Fisher, 54, said in a statement. "A day comes when you want to stop apologizing for it. When you want to make a decision to live the rest of your life in a healthy way. I haven't been able to enjoy what otherwise is a good part of my life because so much of what's on my mind is about my weight."
Fisher will appear in Jenny Craig's new advertising campaign to begin in February.
Previous Jenny Craig spokespeople include Valerie Bertinelli, Sara Rue, Nicole Sullivan and Jason Alexander.