How long does it take for anorexia to develop in teens?

Usally a few months: Anorexia nervosa often starts with attempts at dieting or eating in a more healthy manner. As anorexia nervosa is defined by weight below what would be considered normal, it often takes a number of months for weight to get to the point when all symptoms are present. Someone with anorexia nervosa will typically minimize the severity of symptoms and not seek treatment for months or years.

It varies: We have seen teens whose anorexia is of long standing (years) and has gone unrecognized because doctors and families tend to minimize weight loss in these days where everyone is focused on preventing obesity. We have seen other patients, especially young ones, where the onset was abrupt and the child became quite ill within months.