Seven years after parting ways with the weight-loss company, the actress, 63, returns to Jenny Craig commercials after putting on 30 lbs. in the last six months.
"I was good for a while and then I wasn’t good, and the weight crept up," Alley tells PEOPLE. "Like I say in the ad, I'm not circus fat. I didn’t hugely screw up. I didn’t gain 75. I gained 30."
Alley initially found success with Jenny Craig in 2004, when she lost an astounding 75 lbs. on the program. She maintained her 145-lb. figure for three years, but once she left the company in 2007, her discipline – and waistline – fluctuated.
Despite losing 100 lbs. in 2011 after launching her own Organic Liaison weight-loss system and competing on Dancing with the Stars, Alley recently found the number on the scale going up.
She returned to Jenny Craig because "I love that you have a consultant," Alley says. "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."
Now Alley is ditching her beloved sugar cookies and sticking to Jenny Craig meals along with supplements from her Organic Liaison line, which will also be sold at Jenny Craig centers.
Besides looking good, Alley has her heart set on feeling good, too.
"I need to get myself to where I feel cocky again," says Alley.
For more about Kirstie Alley's weight-loss struggles, pick up this week's issue of PEOPLE, on newsstands Friday.