Wow, my post does seem a bit negative.
I think that it all matters.
Height.
Weight.
Physical conditioning.
But, none of these things are important unless you are otherwise qualified. Lots of threads on the qualifications - and go to your intended program. Most will share the academic/experience requirements. Even above academics/experience and physical req's - attention must be given to your communication abilities.
For every physical absolute - I can find someone that is tall, heavy, etc.
Ask around - the program that you are considering will be able to give you the best answer.
Weight is less important in fixed wing operations, but even if you weigh 350-400# and cannot sit/move comfortably in a confined space - you may find the reality of the job very difficult.
Good Luck!