Purpose: Obesity affects both mental health and the quality of life, and it also causes diseases associated with increased mortality. The aetiology of obesity is thought to be multifactorial with biological, psychological and social elements. The psychological realm includes the capacity to be aware of one’s own and others’ mental states, that is mentalizing. We hypothesized that poor mentalizing might contribute to the development and/or persistence of obesity among adolescents. The present study aims to investigate the components of the mentalization model to better identify the psychological status of obese adolescents. Methods: This study was carried out on 100 adolescent girls aged 15 to 19 years who were either obese (N=50, Mean age=17.04, Mean BMI=30.24) or normal weight (N=50, Mean age=16.94, Mean BMI=20.95). All completed the reflective functioning questionnaire (RFQ), reading the mind in the eyes test (RMET), difficulties in emotional regulation scale (DERS), and Toronto alexithymia scale (TAS). Results: Multivariate analysis of variance, univariate analysis of variance, and independent t-test were used. Lower certainty and higher uncertainty on the RFQ were confirmed in the OB group indicating reduced mentalizing ability. Misperception and misinterpretation of emotional states conveyed in the eyes in the RMET were consistent the RFQ results. Alexithymia, including difficulty recognizing, expressing and reflecting on emotions, was also found and this also fits with poor mentalizing capacity. The OB group had difficulty in all components of DERS, apart from the “Strategies” subscale. Conclusion: Mentalization or reflective function is significantly poorer in obese, compared to normal weight adolescents. Poor mentalizing could be a cause of obesity, a factor leading to its persistence, or a consequence of obesity. Further research is required to differentiate these possibilities.Level of evidence Level III: case-control analytic study.

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