Admittedly, this isn't research. It's an observation by author and anthropologist Sharman Apt Russell in her book Hunger: An Unnatural History. Although only a chapter is spent looking at anorexia nervosa in particular, the book is haunting and well worth a read.
Russell spends much time on events that took place during World War II: the Minnesota Starvation study, the Dutch Hunger Winter, and the tragedies in the Warsaw Ghetto. This excerpt is from Russell's summaries of the refeeding portion of the Starvation Study- the most important part. After all, the purpose of the study was not just to learn what exactly happened when people starved (that was generally well known). It was also to learn how to most effectively refeed a group of starving people on the lowest amounts of calories, funded by the war effort to help keep Europe out of Communist hands after the Nazis surrendered.*
But the men were not initially allowed free access to food. Their calories were only increased slowly, much to the chagrin of the men who thought that their ordeal would finally be over. They got irritable, cranky, desperate.
By the end of the sixth week of refeeding, almost all the subjects were in active rebellion. Many "grew argumentative and negativistic." Some questioned the value of the project, as well as the motives and competence of the researchers. A few admitted that their desire to help the relief effort had completely disappeared. At the same time, unnoticed by the subjects themselves, their energy was returning. They became more responsive, albeit in a negativistic way. They were annoyed at the restrictions still imposed on them. They rejected the buddy system, which was removed "in the face of imminent wholesale violation." They resisted going back to a regular work schedule. At times, the experimenters felt they were watching "an overheated boiler, the capacity of the safety values an unknown variable."
Later, the researchers compared this with what they learned about refeeding camps after the war, where aid workers also noted a growing aggressiveness and surprising "lack of gratitude" in men and women who had previously been dull and apathetic with hunger.
So it seems from these anecdotal cases that some of the resistance seen by eating disordered children during refeeding seems almost purely organic and NOT related to the eating disorder. Perhaps the brain is reawakening and is not happy. Perhaps the person is unable to process what the hell just happened. The anxiety around food that is, of course, related to the eating disorder, seems only to make this worse.
But the negativity and hostility may also be the intrinsic response of a starving brain.
*I thought this was fascinating- obviously, because I included it.