When most people think of eating disorders, unhealthy patterns of eating alongside negative body image comes to mind. Whether it is depression or anxiety, those with eating disorders are often much more likely to suffer from other conditions.
Eating disorders are proving to be more biologically complicated than we realized. These diseases have a serious impact on the physiological, cognitive, and social functions of those affected. Specifically, anorexia nervosa, which is characterized by weight loss due to extreme restriction of caloric intake, has the highest mortality risk of all psychiatric disorders, at about 10%. 1
Because eating disorders have long been recognized as mental illness, most therapeutic interventions have looked to solve issues of the mind. Traditional treatments typically include cognitive interventions involving medications or psychotherapy. However, these traditional treatments don’t have a high success rate. Only about half of those affected fully recover when they have access to a full spectrum of care.
With an estimated 13% of all American women affected by the time they are 20 years old, treatment options and recovery rates need to be addressed. 2
We Can Do Better – Using the Gut-Brain Axis
To develop new treatment options for mental illness, it’s important to understand the influence the gut microbiome has on the brain because up until now, the brain has gotten most of the blame. The gut-brain axis is a bidirectional interaction between the two areas. The trillions of microbes that make up your gut microbiome interact with your central nervous system through numerous pathways, including: 1
Neurotransmitter signaling
Neuroendocrine
Neurotrophic factors
Neuroinflammatory afferent
Neuroinflammatory efferent
The unraveling of the gut-brain axis gives new possibilities for the treatment of eating disorders. More research is proving the gut microbiome is closely linked to the pathogenesis of these disorders, which isn’t very surprising. Extreme eating patterns, psychological stress, and changes in metabolism are all characteristics of eating disorders that are known to impact the gut microbiome, and vice versa.
The gut-brain axis gives us an opportunity to develop novel approaches to eating disorder treatment using the gut microbiome – an ‘organ’ that was once wildly underestimated.
A Vicious Cycle: The Gut Microbiome and Eating Disorders
Those with eating disorders have been observed to have altered gut microbiota, which has the potential to alter gut-brain communication – what happens next is a vicious cycle that looks like this:
The gut microbiome changes, which causes dysbiosis and decreased microbial diversity.
The changing gut microbiome affects metabolism, hunger, and satiety.
The metabolic changes contribute to further dysbiosis, depression, and other psychological issues.
The altered psychology adds to poor eating habits, which reinforces everything on this list.
When this cycle continues uninterrupted it can cause altered immune system function, poor short chain fatty acid and butyrate production, and increased intestinal permeability. 3 These dysfunctions all perpetuate the problem, further contributing to the vicious cycle.
An altered microbiome is also believed to amplify the difficulties people with eating disorders face when trying to recover. Recovery from an eating disorder is often difficult because reintroduction to foods (especially high caloric foods) can cause painful gas, abdominal discomfort, and vomiting. Could it be that these strong physical responses to reintroduced foods are caused by the lack of microbiota needed for their proper digestion? Considering how we need our microbiome to digest food, and the decreased diversity in those with eating disorders, it’s highly probable. 4
Researchers at UNC-Chapel Hill School of Medicine are examining the link between the gut microbiome and anorexia and believe, “ the severe limitation of nutritional intake at the center 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. ” 5
More and more evidence is emerging to suggest that eating disorders are biologically-driven, and the ‘organ’ of most interest is the gut microbiota.
When you consider the implications of the gut microbiome and its potential power over metabolism and psychological well-being, you can imagine how the cycle between altered eating and changes in microbiota composition can create an unintentional self-fulfilling situation.
This isn’t to say that some cases of eating disorders don’t originate in the gut, that is certainly a possibility – but those who alter their eating habits unknowingly alter their gut microbiome.
The Gut Microbiome and Anorexia Nervosa: Microbes Of Interest
The link between the gut microbiome and anorexia nervosa is profound. A 2017 study examined the gut microbiomes of 15 women with anorexia nervosa and found their microbes were significantly impacted on every taxonomic level. 6
A few trends found in gut microbiomes of women with anorexia include:
An overall increase in Enterobacteriaceae – Enterobacteriaceae is associated with gut inflammation and bacterial translocation, which can contribute to systemic inflammation. Meaning, these bacteria have the potential to increase inflammation throughout the body.
Increase in the archeon Methanobrevibacter smithii – While some of us have M. smithii in our guts, they can become problematic when they aren’t in balance with other microbes. M. smithii utilizes hydrogen and carbon dioxide and produces methane gas. This is beneficial for extracting extra energy from nutrients, but in high levels, it’s associated with obesity, non-alcoholic fatty liver disease, and cirrhosis.
Depleted levels of genera Roseburia – In particular, Roseburia inulinivorans and Roseburia intestinalis. R. intestinalis is a species associated with maintaining healthy gastrointestinal lining and increasing bioavailability of beneficial butyrate. Low levels of Roseburia spp. have also been found in people with inflammatory bowel disease.
Low levels of genera Ruminococcus – Ruminococcus helps ferment carbohydrates and is necessary for healthy digestion.
Reduced Clostridium levels – Levels of Clostridium spp. were correlated with increased anxiety and depression scores in the 15 women.
There was a negative correlation between Bacteroides uniformis and BMI.
As you can see, the alterations in the gut microbiome of those with anorexia are associated with all sorts of metabolic and psychological dysfunctions – chronic eating disorders and an imbalanced gut microbiome are truly part of the same vicious cycle.
We Need a New Approach to Eating Disorder Treatment
The low rates of recovery for those with eating disorders are unacceptable. It appears eating disorder treatments have been looking in the wrong place, it’s time we look for novel ideas – and the gut microbiome is a great place to start.
Resources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5490581/#B3-nutrients-09-00602
https://www.med.unc.edu/im/gi/news/gut-bacteria-population-diversity-linked-to-anorexia-nervosa
