Definatley not, join a gym or just excercise on your own. The Wii is extremely sensitive and even the slightest flick or touch can get the desired response. The adverts with people waving their hands about wildly? Doesn't happen. Unless you like doing that.
Have you noticed the fact that running on the Wii Fit constitutes as twirling the remote horizontally between the thumb and index finger... I'd be less surprised if you got an STD from it...
You know what's sad?? I went to my little cousin's b'day a couple of months ago at some sporting arena and all the kids that were there had rich-ass parents who got them whatever they wanted. Thats not the sad part, its the fact that they rather play sports on a Wii/PS2/PS3/PSP than actually play the sport. It depressing because their parents fall for the trick. How many times do people with logic have to say it?? You lose weight & stay healthy by excersising with sit-ups/ push-ups/ walks/ runs/ jogging/ weights/ swimming or team sport AND don't forget to eat healthy, this means eat three main meals a day and if you can't eat big meals then try FIVE smaller meals each day. If you don't get any of this jamm'd in your brain NOW, you will probably end up like teh people in WALL-E.