1. objectives: 1. to compare the effectiveness and cost-effectiveness of two inpatient interventions to each other and to usual care for severely obese children and adolescents; 2. to study psychosocial determinants of the outcome of the interventions after one year treatment and one year of follow-up; 3. to integrate intensive lifestyle treatment in a national standard for chronic disease management for overweight and obesity.
2. study design: randomized clinical trial (objective 1); prospective analyses of psychological characteristics to the outcome of the interventions (objective 2); process-evaluation of integration of interventions for severely obese children in a standard for chronic disease management (objective 3).
3. study population(s) / datasets: patients (8-19 yrs of age) admitted to a specialized obesity center for their morbid obesity with an SDS-BMI > 2.3 and obesity associated morbidity or an SDS-BMI > 3.0. Before admission, these children have, unsuccessfully, received usual obesity care elsewhere.
4. intervention: patients will be randomized into three groups. Group A will be hospitalized for six months during weekdays. Group B will be hospitalized during weekdays for 2 months, followed by biweekly hospital admission for 2 days during 4 months. Both inpatient interventions are intensive lifestyle intervention programs with emphasis on nutrition, exercise, behavior (especially self-regulation). Both inpatient interventions last one year. During the second six months groups A and B will receive six 'clinical booster sessions' each of 2 days duration aimed at reinforcement of the interventions. In both inpatient interventions there is intensive participation of the parents. Group C, the waiting list control, will receive usual care for a year after which they will be randomized into one of the two inpatient intervention groups.
5. outcome measures: primary endpoint: SDS-BMI; secondary endpoints: quality of life, obesity related morbidity (blood pressure, triglycerides, total cholesterol, HDL and LDL cholesterol, glucose and insulin concentrations in plasma; liver function tests and liver-echoscopy), physical fitness (modified shuttle walk test), psychological characteristics.
6. sample size calculation: 40 patients in groups A and B and C are needed to detect a significant difference between the groups of 0.5 SDS-BMI score after one year treatment. There are three null hypotheses, one for each of the three comparisons: A=B, A=C and B=C with respect to the change in BMI. If at least one of the last two comparisons is rejected then patients in groups A and B are also compared after two years. Analyses will be done on an intention-to-treat basis.
For objective 1 the costs of the interventions will be evaluated in relation to the change in SDS-BMI. In addition, cost-effectiveness will be estimated as incremental costs per QALY and uncertainty of this estimate expressed on a cost-effectiveness plane; an acceptability curve will be presented as well.
For objective 2 there will be a comprehensive psychological evaluation of the children before, during and after the interventions; these results will be related to the outcome of the interventions.
For objective 3 there will be yearly meetings with representatives of organizations of health professionals, health insurance companies and patient organizations (organized in the 'Partnership Overweight Netherlands') to integrate intensive lifestyle treatment for severe obesity in children and adolescents into a national standard of chronic disease management for overweight and obesity.
8. time schedule (see appendix 1 for a detailed schedule): measurements will be done at baseline, and after 6, 12 and 24 months. There will be two main comparisons. After one year the treatments A, B and C will be compared in terms of effectiveness and cost-effectiveness. If group A and/or B are significantly different from group C (in terms of change in SDS-BMI) then patients in groups A and B will also be compared after two years.