Most of us sometimes try to calm our nerves by binge-eating. When it is occasional, it may lead to some extra weight or guilty feelings. When it is a regular habit, however, it is clinically considered an eating disorder. In fact, more than 8% of the population experiences some kind of eating disorder at some point in their lives (US data). And, unfortunately, around 5% of women and 2% of men are affected by serious conditions, such as anorexia, bulimia or binge eating disorder (especially teenagers and young adults).

Until now, research in this field had been focused on the brain and the cognitive causes of these disorders. Now, a French team of scientists has shed some more light on the issue: What if the intestine and, specifically, the gut microbiota could also play a role?

In a study just published in the journal Translational Psychiatry, researchers from the French National Research Institute (INSERM – Institut national de la santé et de la recherche médicale) and the University of Rouen claimed to have discovered some bacteria in the gut that may interfere with the way the body regulates effectively appetite, at least in rodents. 

It appears that some healthy and normal gut bacteria, such as Escherichia coli, produce a specific protein called CIpB. When the immune system recognises this protein, it makes antibodies to attack it. The problem is that CIpB is almost identical to the main satiety hormone, melanotropin, which works to regulate appetite. When antibodies attack the protein, they also attach onto the hormone, so the body doesn’t understand when it is satiated. In anorexics, this process makes them feel satiated too early; in the case of bulimia, people tend to overeat, since they don’t feel full until it is too late.

The French researchers used mice for this study. They had two groups of rodents: one was given strains of modified E coli not producing CIpB, and the other received common gut bacteria. They found the first group did not change their eating behaviour and levels of antibodies, whereas the second one did. They were also able to test their hypothesis on 60 test subjects, and noticed that those who had a high level of CIpB antibodies also were the ones suffering from the most severe eating disorders.

In any case, these are preliminary results. Scientists still do not fully understand how physical function interacts with the psychological disorder. In a statement given to the British newspaper The Daily Mail, Professor Serguei Fetissov, co-author of the study, said, “There does seem to be a logical connection, when you think that the main risk factor for these disorders is stress. That could be psychological stress, physical stress or intestinal stress. These antibodies are produced when the body is put under stress, in form of risk of infection from the bacteria”.

Although it is still just a hypothesis, Professor Fetissov thinks psychological factors may trigger anorexia or bulimia but the molecular condition could maintain the disease. If this hypothesis could be demonstrated in humans, specific and individualised treatments for eating disorders could be at view. The aim would be to neutralise the protein using specific antibodies, without affecting the appetite hormone. The researchers are already working to develop a blood test to detect this CIpB bacterial protein.