Want a little celeb thin-spiration for the new year?

Just check out Jennifer Aniston's derriere!

"She's always wearing those little short dresses and that butt just goes boom," trainer Jackie Warner, creator of the new Crunch-Free Xtreme Abs dvd, tells UsMagazine.com of her pick for best celeb behind.

"I guarantee she's in the gym and she's doing a lot more than Pilates." Other star's making the pro's list of 2010's hottest bodies: Kelly Ripa for her "Madonna arms", Gisele Bundchen for her "mind-blowingly good" legs and Gwen Stefani and newly-single Ryan Reynolds for their amazing abs.

To check out Warner's tips for scoring your own hot six-pack, and to find out her pick for most improved celeb bod, check out her Us video above!