Gut bacteria has been linked with anorexia, with people suffering the eating disorder having very different microbial communities than healthy individuals, scientists have discovered. A team of researchers from the University of North Carolina at Chapel Hill found this bacterial imbalance is associated with a number of psychological symptoms of anorexia.

The team say the findings, published in the journal Psychosomatic Medicine, suggest gut bacteria plays a prominent role in the symptoms of the disorder, from which three million people in the US suffer. Ian Carroll, senior author on the paper, said because previous studies have linked gut bacteria to weight regulation and behaviour, they wanted to study the relationship between anorexia and gut bacteria further.

They collected faecal samples from 16 women with anorexia after first being admitted to the university's eating disorder centre, and tested them again after they were discharged. Researchers looked at the composition and diversity of the gut microbiota, also known as gut flora, in each sample.

Findings showed significant changes in the populations between the two samples, with those taken on admission having fewer different types of bacteria – meaning the diversity being far less diverse. After being discharged, the diversity (an indicator of overall health) had increased but was still far less varied than samples from 12 healthy individuals.

Researchers also said that as microbial communities improved, so too did the moods of patients. Carroll said: "We're not able to say a gut bacterial imbalance causes the symptoms of anorexia nervosa, including associated symptoms, such as anxiety and depression. But the severe limitation of nutritional intake at the centre of anorexia nervosa could change the composition of the gut microbial community.

"These changes could contribute to the anxiety, depression, and further weight loss of people with the disorder. It's a vicious cycle, and we want to see if we can help patients avoid or reverse that phenomenon. We want to know if altering their gut microbiota could help them with weight maintenance and mood stabilisation over time."

Carroll and colleagues then are now investigating whether improving microbial abundance would help to relieve symptoms of anorexia in mice studies. They plan to characterise the gut bacteria of anorexic people when they arrive and are discharged, then put these into germ-free mice to see if it alters their biology and behaviour.

Should the bacteria have a detrimental effect, it could mean cultivating healthy microbiota for sufferers would provide a new therapy for the disorder. "We're not saying that altering gut bacteria will be the magic bullet for people with anorexia nervosa," Carroll said. "Other important factors are at play, obviously. But the gut microbiota is clearly important for a variety of health and brain-related issues in humans. And it could be important for people with anorexia nervosa.

Cynthia Bulik, one of the researchers, added: "Currently available treatments for anorexia nervosa are suboptimal. In addition, the process of weight gain and re-nourishment can be extremely uncomfortable for patients. Often, patients are discharged from the hospital, and within months and sometimes weeks they find themselves losing weight again and facing readmission. If specific alterations in their microbiota could make renourishment less uncomfortable, help patients regulate their weight, and positively affect behaviour, then we might see fewer readmissions and more cures."