To carry out this study, 120 patients (age ≥6 and <18 years at the screening visit) will be enrolled in this observational study. After obtaining the informed consent from the parents and the patient, the followings will be performed: clinical examination by a physician, dual-energy X-ray absorptiometry to assess bone density mineral and body composition, collection of a blood sample to assess the inflammatory status of the IBD patient. The patient will be asked also to fill in a questionnaire in order to assess quality of life. He will wear an accelerometer during 7 consecutive days for assessing daily physical activity in free living conditions. The main objective is to assess the relationship between daily physical activity and bone health in children and adolescents with IBD. The secondary objectives are to assess the relationship between daily physical activity and: 1) body composition and 2): quality of life in IBD children and adolescents. To our knowledge, this study is the first to assess the relationship between bone health and daily physical activity in IBD children and adolescents.