My daughter - 12.5 has never had weight issues.  She swcah.   She is now 12.5 yrs old, 5’5" and 100lbs.  She had a few more lb’s on her before 7th grade started, but school athletics keep her very very active plus the fact that she went through puberty, started her period, and is now quite thin.  She is very very strong.  She is tall for her age, but she comes from a family of "giants", her endo has said she will probably reach between 5’6" - 5’8" tall. 
She has never had the weight issues I hear so much about on these boards.  She does have them most severe form of cah.  She has always been very healthy.  I keep tight control of her meds.  She takes 10mg cortef 3/day.  .1mg Florinef 1/day.  We had a problem with controlling hormones for 1 year - due to puberty, but otherwise her cah has been quite controlled.