People with BMI \>30 kg/m2 will be included in at population-based cohort. Additionally, one control group with BMI 18.5-25 kg/m2 and one control group with BMI 25-30 kg/m2 will be included. All participants with age 18 and 60 years. To evaluate health status participants will be screened by for undetected obesity-related diseases (hypertension, diabetes, dyslipidemia, sleep apnea, non-alcoholic fatty liver disease, chronic obstructive pulmonary disease, EKG-abnormalities, polycystic ovary syndrome (PCOS), and joint pain and for quality of life at baseline, 1 year, and 5 years. Additionally, anthropometric measurements are collected and a biobank is established for future research studies. People with obesity related disease will be offered participation in a 12 month personalized lifestyle intervention program aimed at improvement of health and self-perception. The collected data will be used to detect the prevalence for obesity-related disease to identify predictors for future obesity related disease and to evaluate the effect of a lifestyle intervention on health and quality of life.