Eating Disorders & The Microbiome

In recent years there’s been increasing recognition that eating disorders are physical diseases with a biological etiology. Once deemed to be driven by a preoccupation by body image, it’s now understood that they are complex illnesses with varied causes.

There is a growing body of literature that associates gut microbiota and eating disorders. Given that food intake plays a determining role in the gut microbial profile and eating disorders are characterized by an irregular diet, this makes a lot of sense.

Anorexia is a physical and mental illness with dietary and brain components, and just like the microbiome, is linked to both the gut and the brain. Communication pathways between the gut microbiome and the brain are influenced by the diet. ‘Given the established gut–brain and gut–diet interactions, the gut microbiota may well be the critical mechanistic link between psychological and biological factors in these illnesses’ say Lam, Maguire and colleagues in a 2017 article in Nutrients Journal. The gut–brain axis is influences appetite control and brain function and so any alteration to the gut bacteria through eating patterns and psychological stress can compromise physiological, cognitive, and social functioning – all the aspects of life that an eating disorder impacts. The impact is not one way. Unhealthy and distorted gut microbes can impact brain functioning and eating patterns, and dysfunctional diet will affect the microbiome. A limited food profile, long periods of fasting, binging and purging will all impact the health of the intestine and gut microbes.

Cynthia Bulik, PhD, Distinguished Professor of Eating Disorders, and her team of researchers at the University of North Carolina at Chapel Hill have been researching the link between the microbiome and eating disorders. In the first study they identified an microbial imbalance in anorexia nervosa. Individuals with anorexia nervosa displayed lower diversity of the gut microbiota than healthy individuals. Since a healthy microbiota is a diverse microbiota, this result made sense. They also found that as they were renourished, their microbiota became partially restored, adding another reason for recovery. A nutritionally dense and diverse diet was linked to a healthy and diverse microbiome. Finally, they also found that microbial diversity was inversely correlated with depression and anxiety (higher depression, lower diversity), providing evidence for the microbe-gut- brain axis. The prevalence of comorbidities is high, and again this might be linked to the impact that the gut microbiome has on brain function.

The research could play a critical role not only in understanding the etiology of eating disorders, but their treatment. For one, the intestinal microbiota plays a critical role in metabolic function and weight regulation. It also places a challenge to the tendency to psychopathologise all patients. Many people with eating disorders do not experience hunger and satiety in the same was as a healthy individual might. Refeeding is also typically very uncomfortable for individuals with anorexia nervosa, and they experience gut pain, bloating, constipation and other gastrointestinal symptoms. UNC are looking to see whether targeted probiotics could ease the discomfort of refeeding and improve our ability to renourish individuals with anorexia nervosa.

Beate Herpertz-Dahlmann and colleagues concluded in their meta study that ‘gut–brain interactions may be important for treatment regarding the determination of target weight, rapidity of weight gain, refeeding methods and composition of the diet.’ It’s been found that a proportion of certain bacteria is significantly correlated with BMI, suggesting that a higher target weight is crucial.

The research is powerful because it offers an opportunity to understand causes and alter treatment. Less than half of people with eating disorders fully recover. This isn’t because they fail treatment, but because treatment fails them. Any opportunity to improve treatment and outcomes is an opportunity to change lives.