What is the added value of psychological treatment prior to gastric bypass surgery?

- Weight: The calibrated weighing scale of the department bariatric surgery Maasstad Ziekenhuis or Sint Franciscus Gasthuis is used. Definitions stated in the guidelines for morbid obesity are used for the operationalisation of the outcome measure weight. The ideal weight will be calculated per patient, based on length and the below calculation from the guideline. Subsequently, the excess weight can be determined by subtraction of the ideal weight from the actual weight.

Ideal weight = female:5ft=119 lb + 3 lb for every extra inch male: 5.3 ft= 135 lb + 3 lb for every extra inch.

1cm= 0.0328 ft, 1 cm= 0.394 inch, 1 kg= 2.205 lb, 1 ft= 12 inch.

The weight loss will be expressed in terms of % Excess Weight Loss: Excess Weight = actual weight -/- ideal weight % Excess weight loss = weight loss after surgery/excess weight x 100.

In the guidelines, the success of the operation is expressed conform the criteria in terms of percentage of overweight loss: : > 75% excellent 50-75% good 25-50% fair < 25% treatment failure.

- Eating behavior: DEBQ, Dutch Eating Behavior Questionnaire. This questionnaire has been developed by T. van Strien, University of Nijmegen, and assesses eating behavior. Four subscales are distinguished, including eating in response to clearly labeled emotions, eating in response to diffuse emotions, external eating, and restraint eating. Three types of eating behavior are distinguished: emotional eating (divided into clearly labeled emotions and diffuse emotions), restraint eating and external eating. The items can be answered on a 5-point scale ranging from 1 ‘never’ to 5 ‘very often.’ The scores are classified in 7 categories ranging from ‘very high’ to ‘very low’.

- Eating disorder: EDE-Q, Eating Disorder Examination Questionnaire is self report questionnaire developed by prof. C.G. Fairburn from Oxford and in is translated into Dutch by H. Nauta, university of Amsterdam. The EDE-Q has four subscales; restraint, eating concern, weight concern, and shape concern.

- Depression: QIDS-SR, , Quick inventory of depressive symptomatology-Self rating is a self report questionnaire for depression based on the DSM-IV criteria and measures the severity of depressive symptoms based on the total score. Five level of severity categories can be distinguished, ranging from ‘no depression’ to ‘very severe’.



- Quality of life: WHOQOL-bref, World Health Organisation Qualit of Life is a questionnaire developed by the WHO to assess quality of life. Four subscales are distinguished; physical health, psychological health, social relations, and environment. The total score reflects the overall level of quality of life.

- Psychological distress: BSI, Brief Symptom Inventory is the brief form of the SCL-90-R that assesses psychological symptoms. The following subscales are distinguished; somatization, obsessive-compulsive, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychoticism. The total score represents the leven of psychological distress,

- Demographic variables, weight course: At the first moment of measurement, a number of social demographic questions are asked concerning weight course, the number of diet attempts, and somatic complaints.

- Somatic comorbidity: Prior to the randomization, the somatic comorbidity is assessed by the surgeon/nurse practitioner . Subsequently the research assistant ticks the applicable boxes of the checklist containing the most frequently occurring somatic health problems, including diabetes, high blood pressure, sleep apnea, high cholesterol, heart- and cardiovascular diseases, joint diseases, and thyroid abnormalities, and gout. This is done on each of the following moments of measurement.