Principalement abordés sous l’angle médical et physiologique, les traitements de l’obésité et l’embonpoint ne permettent pas de faire état de toute la complexité de ces problématiques. Les recherches dans le domaine de la perte de poids ont montré une relation significative entre l’obésité et certaines variables psychologiques. Ces facteurs psychologiques, dont le lien avec l’obésité et l’influence sur la perte de poids ont été démontrés, semblent être liés à l’alliance thérapeutique, une variable très étudiée dans les recherches portant sur le processus et les résultats thérapeutiques. Dans le domaine des traitements pour la perte de poids, peu d’études ont porté sur cette question. Au moyen de modélisation par équations structurelles multiniveau (MESM), la présente étude a examiné les changements dans l’interaction entre l’alliance thérapeutique, l’état de préparation psychologique et le poids. L’étude a été conduite auprès de 105 sujets âgés de 20 à 65 ans avec un indice de masse corporelle (IMC) d’au moins 25 kg/m². Les résultats indiquent que l’alliance thérapeutique agit sur la perte de poids à travers des effets interactifs, alors que le changement de l’état de préparation psychologique prédit la perte de poids. Les limites et les contributions de cette recherche sont discutées.

The study of factors involved in the process of weight loss is of great interest to researchers. Specialists in the domain of weight management encourage the reduction of calorie intake by the change of eating habits, physical exercise and in certain cases of morbid obesity, by bariatric surgery. Most often the treatment of weight loss is perceived and addressed mainly from the medical and physiological perspective; obesity and overweight are considered in terms of surplus fat that may increase the risk of harmful health consequences. However, considering the problem of excessive weight and its treatment as only a biological issue fails to grasp the complexity of the issues. Research in the field of obesity has shown a significant relationship between obesity and psychological difficulties. These psychological factors appear to be related to a variable that has been extensively studied in research on psychotherapy process and outcome, namely the therapeutic alliance. However, in the field of weight management, few studies have addressed this issue. Thus, the present study aimed to investigate the interaction between development of the therapeutic alliance over the course of weight loss treatment, along with changes in psychological variables and weight loss.

The study was conducted among 105 subjects aged between 20 and 65 years (42.94±12.17 years) with a Body Mass Index (BMI) of at least 25kg/m² (31.83±5.44kg/m²). The French version of the shortened Working Alliance Inventory (WAI) and the Larocque Obesity Questionnaire (LOQ) are the main measuring instruments. Their administration was carried out online after each consultation for the WAI and just before the meeting with the doctor for the LOQ.

Multilevel structural equation modeling indicated the importance of studying the complex interaction between the therapeutic alliance and psychological variables in the treatment of overweight. Specifically, the results showed that changes in psychological readiness predicted weight loss. However, contrary to predictions the therapeutic alliance did not directly predict improvement in psychological readiness, or weight loss. Therapeutic alliance seemed to act more on weight loss in interaction with psychological readiness.

These results shed new light on the treatment of obesity and overweight. They pave the way for treatments directed more towards the process of treatment for obesity rather than the simple result of losing the excessive weight through biological means (i.e. diet and exercise prescriptions). They suggest the importance of developing interventions aimed at improving the psychological readiness of patients since lack of readiness could jeopardize the patient's achievement of their objectives. Finally, the results of this study support the need to deepen our understanding of the role of the therapeutic alliance in the treatment of obesity and overweight, since it is strongly and significantly related to psychological variables predicting weight loss.