PHOTO: Kevin Federline Loses Weight

11/09/2009 at 04:00 PM EST

He's not exactly in back-up dancer shape again, but Kevin Federline definitely appears to have a shed a few pounds thanks to his work with Celebrity Fit Club.

Britney Spears's ex-husband, who joined girlfriend Victoria Prince and his four children for a movie outing Sunday near Los Angeles, is toiling in celebrity boot camp along with Bobbi Brown, Kaycee Stroh and Federline's other ex, Shar Jackson, for the show's seventh season, which premieres Feb. 14 on VH1.

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