Before the surgery, you will be instructed about everything that awaits you during and after the surgery. This information will be provided by the employees of the lifestyle management program that you will follow after the surgery. After you (and your parents) have given permission to participate in this study, you will be placed on the waiting list for the weight loss surgery. In addition, several data will be collected and several test will be performed (see execution).

On the day of the surgery, a computer program will randomly select which of the two types of weight loss surgery you will receive. The doctors and researchers don’t have any influence on this selection.

Only the surgeon knows which type of weight loss surgery you will receive. You and your parents will not know which surgery you will receive. This is necessary to obtain objective data regarding the complications (unexpected and undesired consequences of the operation and admission) in the first 30 days after the surgery. If it is important for your health to know which surgery was performed in the first two months after the surgery, this will of course be communicated.