The hypotheses are: Both the IG and the ACG are expected to have a higher motivation, to adopt a healthy lifestyle, to perform more health behavior and to be less likely to relapse into previous unhealthy routines at T2 and T3 than at T1. Also, IG and ACG will be healthier as well as they will report more quality of life and rehabilitation satisfaction at T2 and T3 than at T1. In comparison to ACG, the IG is hypothesized to be more effective than the ACG regarding motivation, behavior and social-cognitive predictors of behavior. Moreover, the interventions (ACG and IG) are supposed to be equally effective for different age and sex groups, obese and non-obese individuals. In the nutrition study, the IG2 will report higher on all outcome measures than IG1.