In addition to primary (waist loss) and secondary outcome measures as given below, a health questionnaire will be performed at baseline and after 12 and 24 months with questions about general health, self-reported quality of life, medication use, living habits, physical activity, nutrition, tobacco, alcohol, personal motivation and perceived ability to change lifestyle. Furthermore, serum creatinine will be measured at baseline, and after 3, 6, 12 and 24 months.