Scientists now suspect that anorexia nervosa, irritable bowel syndrome and chronic fatigue syndrome may all be connected with an imbalance in the bacteria in the gut. They speculate that the activities of certain bacteria may confuse the immune system and lead it to produce antibodies to the body’s nerve cells which can attack the brain, including the limbic system, which controls our emotional responses. This can affect our moods and, in the case of anorexia, perhaps lead to inappropriate feelings of fear and disgust associated with food and body image.

http://www.lancaster.ac.uk/news/articles/2016/do-anorexia-ibs-and-chronic-fatigues-share-a-common-cause