I know that teenage girls are in danger of developing a bad self image and creating all sorts of problems, physical, psychological and emotional because they get the idea they are not acceptable - there are depressed women on this site that started that way
now is the time to AVOID developing these problems
guys get it too
I started my yoyo dieting when I was 14 - it affected my whole life
if I had NEVER dieted I would not be as huge as I am now - it messes with yr metabolism
I might observe in passing that a 14 year old is still growing and I cannot think of any scenario where it is good for one to lose 12 pounds quickly