This study can be seen as a pilot trial. The central hypothesis of this field trial is that using the multi-source b-SLIM digital Super Coach will support and assist overweight and obese adults to change their health behavior (i.e., physical activity and nutrition) and to lose body weight by improving their self-control, self-determined motivation and attitude towards regular physical activity and healthy diet. The investigators will check if the Super Coach can be a valuable alternative for a conventional physical activity and nutrition coaching.