Purpose The aim of this study is to show that the differences among eating behaviours are related to the emotional dysregulation connected to the mental dimensions being part of the obese psychopathology. Eating behaviours can be considered a diagnostic feature at the initial screening for determining the obesity treatment: nutritional or bariatric surgery. Methods 1828 Obese subjects underwent psychiatric assessment before entering obesity nutritional treatment or bariatric surgery following the multidisciplinary programme. 1121 subjects were selected and enrolled in this study: 850 were inpatients visited or hospitalised at the Obesity Centre or at the Bariatric Surgery Units, 271 were outpatients visited at the Eating Disorder and Obesity Unit. Psychiatric examination was used to exclude psychiatric disorders and investigate eating behaviours distinguished on the basis of food intake rhythm in: gorging, snacking, grazing and binge. They are related to the mental dimensions: impulsiveness, body image, mood and anxiety, taking part in the emotional regulation system. Specific psychometric tools were used to investigate the different mental dimensions of the single eating behaviours and their differences. Statistical analysis of the psychopathological features was performed using ANOVA, ANCOVA, Levene test, Bonferroni’s and Tamhane post hoc test. Significance was set at p < 0.05. Results Data analysis shows significant differences of psychopathology among all the eating behaviours and an increase in the emotional dysregulation determining maladaptive behaviours. Discussion Eating behaviours are connected to the balance of the different features of mental dimensions implicated in the emotional regulation system. They could provide significant clinical information and therefore be part of the obesity diagnostic criteria and therapeutic programme.