If you're a tae-kwon-do guy looking to get into better shape, I suggest taking up a karate style or wushu. The katas and sparring is much more fast paced and much more applicable in combat. In order to burn fat you need to do alot of cardio work, and that's really hard to get from TKD.
Best of luck.
Sig by Toxic
Barnett - Toquinho -Werdum - "Nurmie"
Z. Gurgel - Morango - Rocha - Tiequan