This study aims to evaluate the effectiveness of Family-based behavioral social facilitation therapy (FBSFT) in the treatment of severe obesity in children and adolescents compared to treatment as usual (TAU). The FBSFT condition includes 17 weekly family-based treatment sessions at the hospital obesity clinic followed by monthly follow-up sessions with their local nurse and follow-up sessions at the hospital every third month for 2 years. The treatment targets both child and parent life-style; eating habits, physical activity, sedentary activity and sleep habits. Behavior modification techniques are employed; such as self-monitoring, goal setting, reward systems, problem solving and stimulus control. In addition, FBSFT focuses on facilitating lifestyle change across different settings (family, friends, school and community) and harnessing social support for healthy habits, which is considered important for long-term weight control. The TAU condition involves an assessment day with the multidisciplinary team (pediatrician, dietician, physical therapist and psychologist) at the hospital obesity clinic. Further a session with the nurse at the hospital clinic making a plan for behavioral lifestyle changes followed by monthly follow-up sessions with their local nurse and follow-up sessions at the hospital clinic every third month for one year.

SAMPLE AND STUDY DESIGN. The sample will consist of children and adolescents (aged 6-18) referred to the Obesity Outpatient Clinic at Haukeland University Hospital. Criteria for admission to the clinic is an (IOTF) isoBMI of > 35, or a isoBMI > 30 with obesity related co-morbidity. Based on current clinic data, estimations suggest that about 60 families of children with severe obesity will be referred to the Obesity Outpatient Clinic every year and be offered treatment. Recruitment will start in February 2014 and will continue in 2015 and 2016. After consenting to participation and completion of the initial assessments the families will be randomized to either FBSFT or treatment as usual (TAU). After one year the families randomized to TAU will be offered the FBSFT treatment. Measurement points for the most important outcome measures will be pre-treatment, post-treatment (at approximately 6 months), at 12 months, 18 months and 24 months.

OUTCOME VARIABLES. Anthropometrical measures: Height, weight and waist-circumference, DXA-scans and bio-impedance measurements for determining the distribution of fat and muscle tissue. Physiological measures: Blood samples will be drawn in the morning after an overnight fast. Including measurements of total-cholesterol, HDL, LDL, TG, ASAT, ALAT, gamma-GT, bilirubin, creatinin, HbA1c and fasting insulin, c-peptide and glucose, TSH, fT4, CRP. Cortisol measurements from saliva and urine. Measurement of bloodpressure. Food records: The parents will be instructed to help their children to keep a diary of food and beverage intake for five days. They will use an electronic kitchen scale to weigh the food. Physical activity: Physical activity and sleep will be measured by using accelerometers. Psychological measures: The Child Behavior Checklist (CBCL) is a 138-item rating scale assessing behavioral and emotional symptoms in children/youth. Children's Depression Inventory (CDI). CDI is a 27-item self-report test assessing symptoms of depression in children (7-17 years). Self-Perception Profile for Children (SPPC). SPPC is a self-report measure of self-perception in children aged 8 to 14 years. The Dutch Eating Behavior Questionnaire Child version (DEBQ) is a measure of disturbed eating patterns in children and youth. The Youth Eating Disorder Examination-Questionnaire (YEDE-Q) is a self-reported measure of eating patterns and eating disorder psychopathology. OTHER MEASUREMENTS INCLUDED. The Parenting Scale (PS) is a 30-item questionnaire designed to measure different parental disciplines with children/youth. The scores on three sub-scales are calculated - Laxness, Overreactivity and Verbosity. The Barriers to Treatment Participation Scale (BTPS). The 44-item scale is developed and validated to address drop-out from treatment with out-patient psychological treatment of children and adolescents. Child and parent acceptability of the treatment will be measured by the FBSFT Acceptability Questionnaire.

STUDY AIMS:

1. To evaluate the effect of FBSFT compared to TAU for treatment of severe childhood and adolescent obesity in an ordinary health care setting on BMI, BMI SDS, body composition, cardio-metabolic health, eating habits, physical activity as well as psychological well-being.
2. To identify predictors of treatment success and treatment drop-out with a focus on family variables and mental health.
3. To evaluate treatment (FBSFT) implementation and treatment acceptability for children, parents and health care workers and experienced barriers to treatment, and how these factors influence children's and parents' treatment response.

Inclusion Criteria:

• The sample will consist of children and adolescents (aged 6-18) referred to the Obesity Outpatient Clinic at Haukeland University Hospital by their general practitioner.
• Criteria for admission to the clinic is an (IOTF) isoBMI of > 35, or a isoBMI > 30 with obesity related co-morbidity.
• Both the child and at least one of the parents agrees to actively participate in the treatment.

Exclusion Criteria:

• Severe somatic or psychiatric illness that makes adherence to the treatment program impossible.
• Somatic conditions, syndromes or medications that lead to pathological weight gain.
• Participation in other obesity treatment programs.