Hi Presynaras,
As Gina says, a healthy body weight is what is right for you as an individual, and where you feel healthy and active and full of energy. If you eat well i.e. healthily, and keep up a sensible exercise regimen - dance or sport or whatever physical activity you enjoy - you will not 'fatten up'. I recommend Daniel Nagrin's book "How to Dance Forever: Surviving against the odds" for some great advice on dancing into later life and on taking care of yourself as a dancer; it is very inspirational. Pilates is another fantastic way of keeping the body fine tuned and lithe throughout life, for dancers and in fact everyone
