What is anorexia and bulimia besides the symptoms of starvation?

The Minnesota starvation study showed that the men became nervous, anxious, apathetic, withdrawn, impatient, self-critical with distorted body images and even feeling overweight, moody, emotional and depressed. A few even mutilated themselves, one chopping off three fingers in stress. They lost their ambition and feelings of adequacy, and their cultural and academic interests narrowed. They neglected their appearance, became loners and their social and family relationships suffered. They lost their senses of humor, love and compassion. Instead, they became obsessed with food, thinking, talking and reading about it constantly; developed weird eating rituals; began hoarding things; consumed vast amounts of coffee and tea; and chewed gum incessantly (as many as 40 packages a day). Binge eating episodes also became a problem as some of the men were unable to continue to restrict their eating in their hunger.
The act of restricting food and the constant hunger “made food the most important thing in one’s life,” said one of the participants. “Food became the one central and only thing really in one’s life.

So what is restricting eating disorders then, besides the symptoms of starvation like the healthy men showed? Fear of gaining?