It could be my thyroid I know most people on my dad's side of the family have a thyroid problem...a few years back my aunt was in the hospital because she passed out and it was malnutrition...she's about 5'9 and 300 pounds, but she almost never eats, she eats like a bird, she has a thyroid problem and so does my grandma. I guess our thyroids do not produce enough metabolic hormones.
PS: Also when I was prego with Hunter, I had to spend a few nights in the hospital because of malnutrition because everything I ate pretty much came back up and I wasn't really ever hungry anyways and the doctor said it was probably a thyroid problem so the likelihood of me having a thyroid problem now as I near my 30's is pretty good since a woman's body begins latent hormonal changes about this age.