WHO European Childhood Obesity Surveillance Initiative (COSI) Report on the fourth round of data collection, 2015–2017 (2021)

The WHO Regional Office for Europe established the WHO European Childhood Obesity Surveillance Initiative (COSI) in 2007 in response to the need for standardized surveillance data on the prevalence of overweight and obesity among school-aged children.

The availability of such information is essential to develop effective policies and strategies to tackle childhood obesity in the WHO European Region. Since its first round of data collection, which involved 13 countries, COSI has grown dramatically: 38 countries participated in the fourth round that took place during the 2015–2016 and 2016–2017 school years, involving more than 250 000 primary school-aged children in anthropometric measurements (36 of the 38 participating countries collected data).

In addition, 34 of the countries collected further data on the school environment, and 23 countries collected data on children’s diet and physical activity. The systematic collection and analyses of these data allow intercountry comparisons and a better understanding of the progression of childhood overweight and obesity in Europe. Together, they clearly show that childhood obesity remains a major public health problem in the WHO European Region.

_{This item was amended on 11 May 2021. An earlier version mistakenly indicated that 24 countries collected data on children’s diet and physical activity.}