The objective as stated in the actual game, is to better your balance by toning key muscle groups. Most people have poor posture and balance caused by modern lifestyles.
Getting fit, or improving fitness, is a side-effect of improving your balance.
Chet's lost 2lbs this week, it's not the game that makes you fit, it's the effort you put in. The game is just an aid to spot you and keep you motivated.