Just looking at this specific paper, it suggests that eating disorders are part of a general emotional dysfunction spectrum. In practice, we're probably not talking about confident people.

From my anecdotal experience with people I've known, it makes sense that the other symptoms in that spectrum, like bloating and anxiety, could make someone more receptive to unrealistic body standards and "solutions" to achieve those standards and regain control. That's what it's really about: not feeling in control.