Credit: John M. Heller/Getty Images; Sam Sharma/ Nathanael Jones/

Goodbye, K-Fat, hello, K-Fit!

A dramatically slimmer Kevin Federline hit an L.A. golf course on Thursday. The ex-husband to Britney Spears and father to her two sons famously shocked the world in spring 2009 with a new, rotund physique. The 31 year-old ex-rapper (and fried food fan) had gained an estimated 85 pounds in the wake of his divorce from Spears.

Most of that fat is apparently in the past now: Federline has reportedly lost 50 pounds as a contestant on the next season of VH1's Celebrity Fit Club, airing in January.

Shar Jackson, Federline's ex-girlfriend and a fellow Fit Club contestant, recently told, "I think everybody will be very, very shocked to see the end results," noting that they both survived a "very painful" boot camp on the show.

Still, Federline should be careful now that Fit Club is over: a staffer at L.A. eatery Casa Vega observed the reality star scarfing down chips and salsa with girlfriend Victoria Prince Dec. 2. His appetite? "Healthy!" the employee told Us.