'Extra' Lean Challenge: Jimmy Pena Explains the Progress

"Extra Lean" participant Tammi Fuller asks fitness expert Jimmy Pena, co-author of Mario Lopez's "Extra Lean" book, why it all seems to be working -- and so fast!

"When you eat well and do little bursts of energy each day, the body will respond!," Pena says. Watch what else he says about the Extra Lean-ers progress!