Why is low self-esteem a major part of eating disorders?
Your question hit the nail right on the head. Since we are all social beings, we gain our self-image from the world around us. If our self-image is healthy, they we are more apt to act in ways that are socially and physically healthy. However, if our self-image and self-esteem is warped or low, then we might do things that are destructive to ourselves and others. Each person is different in how they respond.
For example, if we feel that we are overweight (even if we are not at all), then this might lead to eating disorders. If we feel that we need to act and be a certain way to gain the approval of certain people, we might conform to an impossible ideal of physical perfection and this could lead to eating disorders. The opposite can happen as well, depression could lead to overeating. In a word, a poor view of self can lead to many disorders and one of these disorders can be eating disorders.