It doesn't really work.
Nothing really works properly. It has shaky graphics and appauling prensentation. You have to unlock practically every and the weight and fitness assements don't work. I played this game for about one day, until I realised it was secound hand for a reason (I bought for a discount).
If you want to get fit. Just go to ther gym or get excercise, don't pay the ridiculous £69 for it. I might pay £4 for it. Wii Fit is probably the most overrated game ever made for the Wii.