why do they lose weight? i see them in the future being like michael jackon

First of all, where did you read that?
I have never read or seen that the boys were forced to lose weight and if they do that, i suppose its their management who is more concerned about their image than their music.

Secondly, they will NEVER end up like Michael Jackson because they arent (no offence to the fans of the king of pop) crazy dark skin people who think being white is going to stop criticism and racism. Sorry again to the fans but thats my opinion :(

Again, the boys are healthy and im quite sure if they exercise is for their own good