On his Celebrity Fit Club: Boot Camp debut Monday, Kevin Federline grimaces after weighing in at 232 lbs.

"I look like a pregnant man right now," he tells Fit Club's Dr. Ian Smith in this exclusive clip (watch above).

With fellow contestant (and ex-wife) Shar Jackson looking on, Federline, 31, blames "a period of depression" -- including a 2006 divorce from Britney Spears -- for plumping up.

"Probably about a year ago, I started coming out of that," he tells Smith. "I picked up so many bad habits along the way that it was a balloon effect."

Watch the premiere of VH1's Celebrity Fit Club: Boot Camp Monday at 9 p.m. (ET).