A method for determining an optimum control parameter of a distension system for causing distension in a stomach. The method includes the step of providing an implantable distension system for causing distension in a stomach, the system including an adjustable distension device configured to form a distension in a stomach. The method also involves adjusting the distension device, and determining the value of a control parameter of the distension system. The method also involves repeating the steps of adjusting the distension device and determining the value of the control parameter until the control parameter is substantially convergent as a function of time.