This exact info came out in a report on the news (CNN I think) last week. But there is a big distinction between anorexia and anorexia nervosa. Gina's article mentioned anorexia - which by definition is loss of appetite.
Seems with this newer research those lines are blurred. Previously, to have anorexia nervosa, one must meet four criteria:
1) Disrtorted body image
2) Underweight (disproportionate BMI)
3) Desire to be thinner
4) Loss of menses
Not sure how the article you post (thank you) takes those points under consideration. Perhaps finally those treating patients w A/N are gaining a better understanding of the disorder. But anorexia on its own is NOT a psychological OR a genetic disorder, rather a physical condition often brought about by illness, famine, etc.