A French study on anorexia nervosa affirms that physical effort generates positive emotions in women who suffer from it but also in their relatives who are not ill. Physical activity would therefore be associated with a reward effect which would itself be involved in the heritability of the disease. This discovery explains the vicious circle of the disease and advances the management of patients.

Anorexia, nervosa:, "spending, more", still, more, important, than, "eating, less", to, explain, the, disease

Anorexia nervosa is an eating disorder that affects mostly young girls between 15 and 25 years old. The lifetime prevalence of anorexia is estimated to be slightly more than 1% in women, according to Inserm, whose team* has been trying for years to better understand the disease and improve its management. In their recent work published in the International Journal of Eating Disorder, they were interested in the reward effect associated with not eating and losing weight. Indeed, in patients suffering from anorexia nervosa, weight loss due to food deficiency is accompanied by fatigue and a decrease in physical capacities.

However, they often continue to practice intensely a sport activity that helps them to lose weight. "We know that anorexia nervosa is organized in a vicious circle, where what makes me lose weight is so rewarding that I can ignore the dangers that I can understand. This abnormality in the decision-making process is linked to the reward effect (the brain sends back messages valuing the maintenance of the disorder). But it is complicated to understand how a lack (deficiency) can be a 'reinforcer'. Instead, we looked at the other side of weight loss, physical activity. "Philip Gorwood of Inserm explains. 

Patients, their relatives and others

Based on these questions, the scientists had already shown in a previous study that anorexia nervosa is more associated with the pleasure of losing weight than with the fear of gaining weight, and that this aspect is genetically influenced. In their new work, they continue their reflections on the clinical criteria of the disease and on its heritability, by focusing on the notion of physical exercise. This is an atypical approach because physical effort is not considered a clinical manifestation of anorexia, even though many patients exercise a lot, especially to manage their hunger and lose calories," adds Philip Gorwood. "Philip Gorwood adds. 

Heritability refers to the contribution of genes to the differences between individuals, i.e., to the variance of a trait expressed by a sample of individuals (in this case, anorexia). The researchers felt that this was an especially interesting aspect to study because anorexic patients persist in exercising even though being underweight causes a progressive decrease in their physical capacities. "The protocol of the study is original because it allows us to look not only at the emotions and perceptions of the patients following a standardized physical exercise, but also at those of their family members. ", they indicate. 

Reconsidering sports practice in a positive way

Thus, 88 patients suffering from anorexia nervosa, 30 of their non-sick relatives (mothers and sisters in particular) and 89 healthy "control" individuals were recruited for the study. All were invited to perform a standardized physical exercise and then to answer questionnaires concerning their emotions after the effort and their perception of their body image. The results showed that for the same amount of effort, the anorexic patients reported more positive emotions than the healthy "control" individuals: the fact of doing sports sent them a positive reinforcement message which made these patients continue this activity despite their fatigue or weakness. 

In concrete terms, "the caloric expenditure associated with this physical activity is a determining factor that leads to the continuation of this effort", underlines Philip Gorwood. The results also show that while this aspect was not found in the control subjects, it was present in the patients' relatives. The study therefore suggests that this trait is shared within the family of people suffering from anorexia: the search for a reward effect through physical effort would therefore constitute an important aspect of the disease which would be genetically influenced. These results are important because they allow us to focus the management of patients suffering from anorexia nervosa. 

Faced with these conclusions, they insist on the importance of focusing part of the care on physical effort, on caloric expenditure (sport), rather than exclusively on deficiencies in intake (diet). The precise idea would be to reteach patients to discover the pleasure of physical effort (i.e. moderate) and to unlearn addictive physical effort, associated with the goal of weight loss. "This aspect of treatment was already considered important by specialized teams, but the study provides concrete scientific arguments to continue in this direction, legitimize this care practice and generalize its use. "The researchers conclude. 

 * Researchers from Inserm and the University of Paris at the Paris Institute of Psychiatry and Neurosciences and the Paris Psychiatry & Neurosciences GHU