Anorexia is an eating disorder where people obsess about their weight (not eating, throwing up, eating very little). The people who have it try to maintain a low body weight by not eating, hardly eating, or working out a lot. Not everyone who has this is bone skinny. They must just be trying to lose or maintain a weight in ways that aren't very safe. Bulimia is when someone is very skinny, abnormally. It is an eating disorder marked by binging to avoid weight gain. It is an obsessive desire to be skinny or lose weight. Both can lead to serious health risks