A probiotic for binge eating?

Whole packs of cakes, chocolate bars...during an episode of binge eating, everything within reach, especially fatty and sugary foods, is swallowed in a hurry, often on the sly, to the point of stomachache. This uncontrollable overeating ends in shame and guilt, and contributes to an excessive caloric intake that induces overweight or even obesity in patients with this disorder, known as binge eating disorder (sidenote: Binge eating disorder Binge eating disorder is an eating disorder whose diagnosis is based on:

• clinical criteria : binge eating, on average at least once a week for three months; feeling of lack of control over eating.
 
• and on the presence of three or more of the following five criteria: eating much more quickly than normal; eating to the point of feeling uncomfortable; eating large quantities of food without physically feeling hungry; eating alone because of shame; feeling disgusted, depressed or guilty about having eaten too much.
 
  Binge eating behavior is a source of marked suffering. 

  Source: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition Text Revision, DSM-5-TRTM, Feeding and eating disorders. ) . Stress and repeated dieting are thought to contribute to this disorder. In fact, mice subjected to such conditions end up gorging themselves on Oreo® cookies. The study ¹ of such animals has nevertheless enabled us to decipher the underlying mechanisms, and to envisage possible solutions.

Mechanisms deciphered

A long series of experiments carried out on these rodents, as well as an analysis of the flora of patients with binge eating disorder, revealed that the combination of stress and dieting altered the gut microbiota, causing in particular the loss, in rodents as in humans, of a bacterium called Faecalibacterium prausnitzii. The consequence of the low presence of this bacterium is a low production of a small molecule called KYNA (short for kynurenic acid). Small but mighty: when production is down, nothing goes right! 

Too little KYNA sounds the alarm in the vagus nerve, which sends warning signals to two brain areas involved in eating behavior...and our mouse pounces on the Oreos®! Thus, the loss of F. prausnitzii and variations in the concentration of KYNA in their guts are enough to trigger binge eating in rodents by stimulating the gut-brain axis.

New treatment options?

However, there is some good news. Supplementing hyperphagic mice with F. prausnitzii bacteria is enough to reduce their binge eating. The same goes for taking KYNA: in fact, the more KYNA they are given, the more their binge eating episodes disappear. Another option, a little less appealing at first sight: fecal microbiota transplantation (FMT) (sidenote: Fecal transplantation This therapeutic procedure consists in placing stool from a healthy donor in a patient’s digestive tract in order to restore the balance of their intestinal flora. For the time being, it is only approved for the treatment of recurrent Clostridioides difficile infections. Quigley EMM, Gajula P. Recent advances in modulating the microbiome. F1000Res. 2020;9:F1000 Faculty Rev-46. ) from healthy mice is enough to stop the mice from binge eating.

As such, probiotics, KYNA and/or FMT could perhaps one day play a part in the treatment of patients with binge eating disorder, which affects 3.5% of women and 2% of men. But before this can be achieved, more studies are still needed, in particular to confirm that these results in mice can be reproduced in humans.