Bristol Palin has acknowledged she slimmed down between the time of her first Dancing with the Stars appearance and her All-Stars debut.

"I'm definitely in better shape than I was last time, definitely. I'm just more active and I cut all the crap out of my diet! It's that simple," Palin told Us Weekly backstage after Monday night's premiere of Dancing with the Stars: All-Stars.

"And my kid's a lot more rowdy, a lot more active. I'm running after him a lot! He's huge! He thinks he's a teenager already."

Palin also added that she aggressively supports her mother, controversial former Alaska governor and U.S. vice presidential candidate Sarah Palin, and her family and insisted haters just add fuel to her fire in the competition. 

"If I ever hear anything bad that's being said about me or my family, it just gives me motivation to do better, and that's what I do!" said the 21-year-old reality TV star, who starred in Lifetime's Life's a Tripp reality series earlier this year after competing on Dancing with the Stars' eleventh season in 2010.

Professional dancer Mark Ballas, whom Palin is paired up with again for Dancing with the Stars' current fifteenth season, said it was easy for him and his partner to get right back into the swing of things. 

"We picked up where we left off. We stayed in touch since last time and we just went back into it. We balance each other," Ballas told Us. "I'm loud and obnoxious and she's quiet and chill."

Added Palin, "Mark says he's like a chimpanzee and I'm like a turtle, poking out of my shell!"

Palin and Ballas received 19.5 out of 30 possible points from Dancing with the Stars judges Len Goodman, Carrie Ann Inaba and Bruno Tonioli for their cha cha performance during Monday night's Dancing with the Stars: All-Stars premiere broadcast.