Anorexia is a disorder where a woman sees food as her enemy, has a body image that is quite distorted (appearing fat to her while she appears thin
to others), and where an unrealistic fear of getting fat pretty much runs her life. Anorexics often eat less and less food, starving themselves to a level that disrupts their lives and hurts their health.
In bulimia, which is more common than anorexia, a woman has just as distorted a body image and also sees food as her enemy, but she will eat it -- and then purge it from her body, either by forced vomiting or overuse of laxatives. There is an actual shame she feels from eating and almost a rush from being able to remove the food from her system without digesting it, leading to the "binge" part of the cycle. Some bulimics will binge and purge several times in a day. Their low body weight threatens their health the same way it does in anorexia, but they can also have problems from the laxatives or from stomach acid eating away the enamel on their teeth.
Here's a page on the symptoms, effects and treatment of anorexia:
http://www.womenfitness.net/anorexia.htm
and here's a page on the symptoms, effects and treatment of bulimia:
http://life.familyeducation.com/bulimia/nutrition-and-diet/48918.html
It's important to realize that eating disorders are control disorders, too. The person who is managing their weight with anorexia or bulimia feels an enormous amount of control in doing so, and the thought of losing that control is so frightening that the disorder continues.
Here are some links to Brown University studies on why eating disorders begin, why control seems so important, and links with definitions and resources for getting help:
http://www.brown.edu/Student_Services/Health_Services/Health_Education/nutrition/ec_ued.htm
Have you ever had an eating disorder, or known someone who has suffered from one? Are there experiences or insights that you can share that might help others in your shoes?