Children and adolescents with overweight and obesity are predisposed to significant health problems. It is known that childhood obesity can adversely affect almost every organ system, and if left untreated, the major impact of childhood overweight is likely to be felt in the next generation of adults.

The aim of " Kijk op overgewicht bij kinderen" is to collect and follow-up longitudinal data from a population of different degrees of children with overweight regarding etiological factors, risk factors and early stages of chronic disease in different degrees of childhood overweight.

Furthermore, from april 2020 onwards, a prospective sub study will be conducted. This sub study aims to investigate the changes in lifestyle behaviour of children with overweight or obesity and their families during the COVID-19 pandemic, including the (governmental) measures taken for this, and the effect of obesity and different weight-related risk factors on the host response of these children.

The goal of this sub study is to collect data to enable analyses for future research questions regarding the influence of the COVID-19 on the lifestyle of a child with overweight and their family. Endpoints are for example physical activity, eating behavior, BMI-z score, remote lifestyle coaching, quality of life and parental practices regarding nutrition and physical activity behavior. We will also measure symptoms associated with COVID-19 and the host response that target COVID-19.

Inclusion Criteria:

• Participation in the COACH program
• Aged till 18 years old (at time of inclusion)
• Overweight or obesity according to International Obesity Task Force (IOTF) criteria

Exclusion Criteria:

• None

overweight or obese children according to the International Obesity Task Force (IOTF) criteria < 18 years old.