Zumba Fitness

I have found that the 20 min Intermediate class 2 is actually 18 minutes long, the shortest I've found. The rest are at least 20 min, and most are a little more. So subtract out the 19 classes plus the 3 difficulties for the zumbathon and you have 78 classes of a little more than 18 minutes each (to account for the 6 second water break between songs).
That's 1404 minutes or almost 24 hours.

You'll get a lot of these while going for the other achievements in the game like the online stuff and zumbathon. Keep in mind though that if you don't wanna dance, you don't have to. You can just stand in front of the kinect or sit in front of it if it will pick you up. Do 20 minute workout sessions this way on your down time and you'll get it eventually.