Human beings can never be satisfied. It is our nature,we were actually designed this way.Some people think it is bad while some say it is good.My own opinion is that nothing is good and nothing is bad,only appropriateness exists.
For instance, we can take the case of an assasin who kills someone in a particular place but on trying to escape he is shot down and killed. IS KILLING GOOD OR BAD? I think you now have an idea of what i mean.
Man must advance and this can only happen when man is not satisfied with the present state of things.Imagine if man had been satisfied with nokia 3310,would you be browsing ,snapping pictures and enjoying social networks on your phone today?You are enjoying your tablets (ipad,notebooks e.t.c) because man was not satisfied with the very first analytical engine.There are so many examples to cite in various industries, and the point remains that man must advance.So if you decide to make your body better,it is the appropriate thing to do.
It is a good thing when you want to improve your body,it could be that you are skinny and you want to put on more weight or it could be that you are too fat and you want to lose some weight.
However, you must never be desperate because things might go wrong and unstable if you are desperate. For instance if you become desperate, you can start using all sorts of drugs and drinking teas without actually finding out how these things work and their side effects.
Finally, no matter the condition or state that you are,always be thankful and try to improve.
God bless you.