Inclusion Criteria:  Age >4.0 and <17.0 years of age at inclusion Obesity defined based on the International Obesity Task Force criteria Willingness to participate in an obesity treatment clinical trial Family ability to communicate in the language of the country of residence e.g. write and read messages in the mobile application Parents having a smart phone and an email address  Exclusion Criteria:  Morbid obesity defined as BMI>35kg/m2 independently of age Weight loss more than 0,1 BMI SDS during the last three months Endocrine disorders other than well controlled hypothyroidism Metabolic disorders of importance for weight control - to be discussed Treatment for depression and other psychiatric disorders during the last 6 months before inclusion Pharmacological treatment of importance for weight control Hypothalamic or monogenic obesity, e.g. syndromes and Mb Down Severe neuropsychiatric disorders that could affect study compliance Eating disorders requiring therapy during the last six months before inclusion or observed at the inclusion screening.