In the case of anorexia there are certain tracks that can be see how to avoid meal times, avoid eating in public, they put excuses to eat and notice a significant decrease in weight and an over-concern for the body. In the case of bulimia, the tracks are more complicated to observe, have epic restriction and moments in which they eat large amounts of food in a very short time. Many after eating rise up to the bathroom to induce vomiting. But there is also the anorexia restrictive purgative. At a point both have things in common.
When you see any of these attitudes is essential to consult a physician, nutritionist, psychiatrist, and psychologist.