Methodology and implementation of the WHO European Childhood Obesity Surveillance Initiative (COSI).

Establishment of the WHO European Childhood Obesity Surveillance Initiative (COSI) has resulted in a surveillance system which provides regular, reliable, timely, and accurate data on children's weight status-through standardized measurement of bodyweight and height-in the WHO European Region. Additional data on dietary intake, physical activity, sedentary behavior, family background, and school environments are collected in several countries. In total, 45 countries in the European Region have participated in COSI. The first five data collection rounds, between 2007 and 2021, yielded measured anthropometric data on over 1.3 million children. In COSI, data are collected according to a common protocol, using standardized instruments and procedures. The systematic collection and analysis of these data enables intercountry comparisons and reveals differences in the prevalence of childhood thinness, overweight, normal weight, and obesity between and within populations. Furthermore, it facilitates investigation of the relationship between overweight, obesity, and potential risk or protective factors and improves the understanding of the development of overweight and obesity in European primary-school children in order to support appropriate and effective policy responses.

Parental Perceptions of Children's Weight Status in 22 Countries: The WHO European Childhood Obesity Surveillance Initiative: COSI 2015/2017.

INTRODUCTION: Parents can act as important agents of change and support for healthy childhood growth and development. Studies have found that parents may not be able to accurately perceive their child's weight status. The purpose of this study was to measure parental perceptions of their child's weight status and to identify predictors of potential parental misperceptions. METHODS: We used data from the World Health Organization (WHO) European Childhood Obesity Surveillance Initiative and 22 countries. Parents were asked to identify their perceptions of their children's weight status as "underweight," "normal weight," "a little overweight," or "extremely overweight." We categorized children's (6-9 years; n = 124,296) body mass index (BMI) as BMI-for-age Z-scores based on the 2007 WHO-recommended growth references. For each country included in the analysis and pooled estimates (country level), we calculated the distribution of children according to the WHO weight status classification, distribution by parental perception of child's weight status, percentages of accurate, overestimating, or underestimating perceptions, misclassification levels, and predictors of parental misperceptions using a multilevel logistic regression analysis that included only children with overweight (including obesity). Statistical analyses were performed using Stata version 15 1. RESULTS: Overall, 64.1% of parents categorized their child's weight status accurately relative to the WHO growth charts. However, parents were more likely to underestimate their child's weight if the child had overweight (82.3%) or obesity (93.8%). Parents were more likely to underestimate their child's weight if the child was male (adjusted OR [adjOR]: 1.41; 95% confidence intervals [CI]: 1.28-1.55); the parent had a lower educational level (adjOR: 1.41; 95% CI: 1.26-1.57); the father was asked rather than the mother (adjOR: 1.14; 95% CI: 0.98-1.33); and the family lived in a rural area (adjOR: 1.10; 95% CI: 0.99-1.24). Overall, parents' BMI was not strongly associated with the underestimation of children's weight status, but there was a stronger association in some countries. DISCUSSION/CONCLUSION: Our study supplements the current literature on factors that influence parental perceptions of their child's weight status. Public health interventions aimed at promoting healthy childhood growth and development should consider parents' knowledge and perceptions, as well as the sociocultural contexts in which children and families live.