Hi, I'm 15 and am extremely active, I run every other day, have ballet, and workout on weekends. Recently, I have been diagnosed rheumatoid arthritis. What I am worried about is that I have gained 6.5 lbs in one week eating no more than 1000 calories. My great aunt has hypothyroidism and is couch bound and I am so scared that I might end up like her, why am I gaining so much weight on no meds???