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.

Mobilizing governments and society to combat obesity: Reflections on how data from the WHO European Childhood Obesity Surveillance Initiative are helping to drive policy progress.

To meet the need for regular and reliable data on the prevalence of overweight and obesity among children in Europe, the World Health Organization (WHO) European Childhood Obesity Surveillance Initiative (COSI) was established in 2007. The resulting robust surveillance system has improved understanding of the public health challenge of childhood overweight and obesity in the WHO European Region. For the past decade, data from COSI have helped to inform and drive policy action on nutrition and physical activity in the region. This paper describes illustrative examples of how COSI data have fed into national and international policy, but the real scope of COSI's impact is likely to be much broader. In some countries, there are signs that policy responses to COSI data have helped halt the rise in childhood obesity. As the countries of the WHO European Region commit to pursuing United Action for Better Health in Europe in WHO's new European Programme of Work, COSI provides an excellent example of such united action in practice. Further collaborative action will be key to tackling this major public health challenge which affects children throughout the region.

Waist circumference and waist-to-height ratio in 7-year-old children-WHO Childhood Obesity Surveillance Initiative.

Childhood obesity is a serious global health problem. Waist circumference (WC) and waist-to-height ratio (WHtR) reflect body fat distribution in children. The objectives of this study were to assess WC and WHtR in 7-year-old children and to determine body mass index (BMI), WC, and WHtR differences in children from 10 selected countries across Europe (Bulgaria, Czechia, Greece, Ireland, Latvia, Lithuania, North Macedonia, Norway, Spain, and Sweden) participating in the World Health Organization (WHO) Europe Childhood Obesity Surveillance Initiative (COSI). The 50th and 90th percentile of WC (according to COSI and "Identification and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS" (IDEFICS) cutoff values) and WHtR above 0.5 were used as measures of abdominal obesity in a unique sample of 38,975 children aged 7.00-7.99 years. Southern European countries, including Greece and Spain, showed significantly higher BMI, WC, and WHtRin both genders (p < 0.0001) than Eastern and Northern Europe. The highest values for WC were observed in Greece (60.8 ± 7.36 cm boys; 60.3 ± 7.48 cm girls), North Macedonia (60.4 ± 7.91 cm boys; 59.0 ± 8.01 cm girls), and Spain (59.7 ± 6.96 cm boys; 58.9 ± 6.77 cm girls). WC and WHtRin may add an information about the occurrence of central obesity in children.

New bioelectrical impedance analysis equations for children and adolescents based on the deuterium dilution technique.

BACKGROUND AND AIMS: Body composition in childhood is not only a marker of the prevalence of obesity, but it can also be used to assess associated metabolic complications. Bioelectrical impedance analysis (BIA) shows promise as an easy to use, rapid, and non-invasive tool to evaluate body composition. The objectives of this study were to: (a) develop BIA prediction equations to estimate total body water (TBW) and fat-free mass (FFM) in European children and early adolescents and to validate the analysis with the deuterium dilution as the reference technique and (b) compare our results with previously published paediatric BIA equations. METHODS: The cohort included 266 healthy children and adolescents between 7 and 14 years of age, 46% girls, in five European countries: Bosnia and Herzegovina, Latvia, Montenegro, North Macedonia, and Portugal. TBW and FFM were the target variables in the developed regression models. For model development, the dataset was randomly split into training and test sets, in 70:30 ratio, respectively. Model tuning was performed with 10-fold cross-validation that confirmed the unbiased estimate of its performance. The final regression models were retrained on the whole dataset. RESULTS: Cross-validated regression models were developed using resistance index, weight, and sex as the optimal predictors. The new prediction equations explained 87% variability in both TBW and FFM. Limits of agreement between BIA and reference values, were within ±17% of the mean, (-3.4, 3.7) and (-4.5, 4.8) kg for TBW and FFM, respectively. BIA FFM and TBW estimates were within one standard deviation for approximately 83% of the children. BIA prediction equations underestimated TBW and FFM by 0.2 kg and 0.1 kg respectively with no proportional bias and comparable accuracy among different BMI-for-age subgroups. Comparison with predictive equations from published studies revealed varying discrepancy rates with the deuterium dilution measurements, with only two being equivalent to the equations developed in this study. CONCLUSIONS: The small difference between deuterium dilution and BIA measurements validated by Bland-Altman analysis, supports the application of BIA for epidemiological studies in European children using the developed equations.

Socioeconomic differences in food habits among 6- to 9-year-old children from 23 countries-WHO European Childhood Obesity Surveillance Initiative (COSI 2015/2017).

BACKGROUND: Socioeconomic differences in children's food habits are a key public health concern. In order to inform policy makers, cross-country surveillance studies of dietary patterns across socioeconomic groups are required. The purpose of this study was to examine associations between socioeconomic status (SES) and children's food habits. METHODS: The study was based on nationally representative data from children aged 6-9 years (n = 129,164) in 23 countries in the World Health Organization (WHO) European Region. Multivariate multilevel analyses were used to explore associations between children's food habits (consumption of fruit, vegetables, and sugar-containing soft drinks) and parental education, perceived family wealth and parental employment status. RESULTS: Overall, the present study suggests that unhealthy food habits are associated with lower SES, particularly as assessed by parental education and family perceived wealth, but not parental employment status. We found cross-national and regional variation in associations between SES and food habits and differences in the extent to which the respective indicators of SES were related to children's diet. CONCLUSION: Socioeconomic differences in children's food habits exist in the majority of European and Asian countries examined in this study. The results are of relevance when addressing strategies, policy actions, and interventions targeting social inequalities in children's diets.

Urban and rural differences in frequency of fruit, vegetable, and soft drink consumption among 6-9-year-old children from 19 countries from the WHO European region.

In order to address the paucity of evidence on the association between childhood eating habits and urbanization, this cross-sectional study describes urban-rural differences in frequency of fruit, vegetable, and soft drink consumption in 123,100 children aged 6-9 years from 19 countries participating in the fourth round (2015-2017) of the WHO European Childhood Obesity Surveillance Initiative (COSI). Children's parents/caregivers completed food-frequency questionnaires. A multivariate multilevel logistic regression analysis was performed and revealed wide variability among countries and within macroregions for all indicators. The percentage of children attending rural schools ranged from 3% in Turkey to 70% in Turkmenistan. The prevalence of less healthy eating habits was high, with between 30-80% and 30-90% children not eating fruit or vegetables daily, respectively, and up to 45% consuming soft drinks on >3 days a week. For less than one third of the countries, children attending rural schools had higher odds (OR-range: 1.1-2.1) for not eating fruit or vegetables daily or consuming soft drinks >3 days a week compared to children attending urban schools. For the remainder of the countries no significant associations were observed. Both population-based interventions and policy strategies are necessary to improve access to healthy foods and increase healthy eating behaviors among children.

Socioeconomic disparities in physical activity, sedentary behavior and sleep patterns among 6- to 9-year-old children from 24 countries in the WHO European region.

Physical activity, sedentary behavior, and sleep are important predictors of children's health. This paper aimed to investigate socioeconomic disparities in physical activity, sedentary behavior, and sleep across the WHO European region. This cross-sectional study used data on 124,700 children aged 6 to 9 years from 24 countries participating in the WHO European Childhood Obesity Surveillance Initiative between 2015 and 2017. Socioeconomic status (SES) was measured through parental education, parental employment status, and family perceived wealth. Overall, results showed different patterns in socioeconomic disparities in children's movement behaviors across countries. In general, high SES children were more likely to use motorized transportation. Low SES children were less likely to participate in sports clubs and more likely to have more than 2 h/day of screen time. Children with low parental education had a 2.24 [95% CI 1.94-2.58] times higher risk of practising sports for less than 2 h/week. In the pooled analysis, SES was not significantly related to active play. The relationship between SES and sleep varied by the SES indicator used. Importantly, results showed that low SES is not always associated with a higher prevalence of "less healthy" behaviors. There is a great diversity in SES patterns across countries which supports the need for country-specific, targeted public health interventions.

Thinness, overweight, and obesity in 6- to 9-year-old children from 36 countries: The World Health Organization European Childhood Obesity Surveillance Initiative-COSI 2015-2017.

In 2015-2017, the fourth round of the World Health Organization (WHO) European Childhood Obesity Surveillance Initiative (COSI) was conducted in 36 countries. National representative samples of children aged 6-9 (203,323) were measured by trained staff, with similar equipment and using a standardized protocol. This paper assesses the children's body weight status and compares the burden of childhood overweight, obesity, and thinness in Northern, Eastern, and Southern Europe and Central Asia. The results show great geographic variability in height, weight, and body mass index. On average, the children of Northern Europe were the tallest, those of Southern Europe the heaviest, and the children living in Central Asia the lightest and the shortest. Overall, 28.7% of boys and 26.5% of girls were overweight (including obesity) and 2.5% and 1.9%, respectively, were thin according to the WHO definitions. The prevalence of obesity varied from 1.8% of boys and 1.1% of girls in Tajikistan to 21.5% and 19.2%, respectively, in Cyprus, and tended to be higher for boys than for girls. Levels of thinness, stunting, and underweight were relatively low, except in Eastern Europe (for thinness) and in Central Asia. Despite the efforts to halt it, unhealthy weight status is still an important problem in the WHO European Region.

Socioeconomic inequalities in overweight and obesity among 6- to 9-year-old children in 24 countries from the World Health Organization European region.

Childhood overweight and obesity have significant short- and long-term negative impacts on children's health and well-being. These challenges are unequally distributed according to socioeconomic status (SES); however, previous studies have often lacked standardized and objectively measured data across national contexts to assess these differences. This study provides a cross-sectional picture of the association between SES and childhood overweight and obesity, based on data from 123,487 children aged 6-9 years in 24 countries in the World Health Organization (WHO) European region. Overall, associations were found between overweight/obesity and the three SES indicators used (parental education, parental employment status, and family-perceived wealth). Our results showed an inverse relationship between the prevalence of childhood overweight/obesity and parental education in high-income countries, whereas the opposite relationship was observed in most of the middle-income countries. The same applied to family-perceived wealth, although parental employment status appeared to be less associated with overweight and obesity or not associated at all. This paper highlights the need for close attention to context when designing interventions, as the association between SES and childhood overweight and obesity varies by country economic development. Population-based interventions have an important role to play, but policies that target specific SES groups are also needed to address inequalities.

Impact of COVID-19 confinement on eating behaviours across 16 European countries: The COVIDiet cross-national study.

We aimed to evaluate the changes in eating behaviours of the adult population across 16 European countries due to the COVID-19 confinement and to evaluate whether these changes were somehow related to the severity of the containment measures applied in each country. An anonymous online self-reported questionnaire on socio-demographic characteristics, validated 14-items Mediterranean diet (MedDiet) Adherence Screener (MEDAS) as a reference of a healthy diet, eating and lifestyle behaviours prior to and during the COVID-19 confinement was used to collect data. The study included an adult population residing in 16 European countries at the time of the survey. Aggregated Stringency Index (SI) score, based on data from the Oxford COVID-19 Government Response Tracker, was calculated for each country at the time the questionnaire was distributed (range: 0-100). A total of 36,185 participants completed the questionnaire (77.6% female, 75.2% with high educational level and 42.7% aged between 21 and 35 years). In comparison to pre-confinement, a significantly higher adherence to the MedDiet during the confinement was observed across all countries (overall MEDAS score prior to- and during confinement: 5.23 ± 2.06 vs. 6.15 ± 2.06; p < 0.001), with the largest increase seen in Greece and North Macedonia. The highest adherence to MedDiet during confinement was found in Spain and Portugal (7.18 ± 1.84 and 7.34 ± 1.95, respectively). Stricter contingency restrictions seemed to lead to a significantly higher increase in the adherence to the MedDiet. The findings from this cross-sectional study could be used to inform current diet-related public health guidelines to ensure optimal nutrition is followed among the population, which in turn would help to alleviate the current public health crisis.

A Snapshot of European Children's Eating Habits: Results from the Fourth Round of the WHO European Childhood Obesity Surveillance Initiative (COSI).

Consuming a healthy diet in childhood helps to protect against malnutrition and noncommunicable diseases (NCDs). This cross-sectional study described the diets of 132,489 children aged six to nine years from 23 countries participating in round four (2015-2017) of the WHO European Childhood Obesity Surveillance Initiative (COSI). Children's parents or caregivers were asked to complete a questionnaire that contained indicators of energy-balance-related behaviors (including diet). For each country, we calculated the percentage of children who consumed breakfast, fruit, vegetables, sweet snacks or soft drinks "every day", "most days (four to six days per week)", "some days (one to three days per week)", or "never or less than once a week". We reported these results stratified by country, sex, and region. On a daily basis, most children (78.5%) consumed breakfast, fewer than half (42.5%) consumed fruit, fewer than a quarter (22.6%) consumed fresh vegetables, and around one in ten consumed sweet snacks or soft drinks (10.3% and 9.4%, respectively); however, there were large between-country differences. This paper highlights an urgent need to create healthier food and drink environments, reinforce health systems to promote healthy diets, and continue to support child nutrition and obesity surveillance.

Energy, macronutrients and dietary fibre intake among adults in North Macedonia.

OBJECTIVE: The present research aimed to estimate macronutrients intake among adults in North Macedonia and to identify their predominant food sources. METHODS: Within this cross-sectional study dietary data were collected using repeated 24h recall interviews. Nationwide, adults aged 18+ were recruited. Dietary data, anthropometric measures and socio-demographic characteristics were available for 496 participants. Nutrient intake was analyzed using the Balkan Food Composition Database and Diet Assess and Plan platform. Macedonian dietary guidelines were used for estimation of inadequacy. RESULTS: Significant differences in macronutrients intake are noticed between age groups within certain socio-demographic factors. Total sugar intake was significantly higher among young adult females comparing with those older than 25 years (p = 0.049). Young urban females have significantly higher fats intake than older participants (p = 0.038). Higher total daily energy, proteins, fats and carbohydrates intake (p = 0.033, p = 0.043, p = 0.032, p = 0.042, respectively) was noticed among young urban males when compared to older ones. Only dietary fibre intake was higher among older urban males (p = 0.030). Univariate linear regression models showed that obese participants had significantly higher relative proteins intake comparing with those having BMI within recommended range (p = 0.024, ß = 1.21). Relative carbohydrates intake was significantly lower among males (p = 0.018, ß = -2.077) and among highly educated participants (p = 0.018, ß = -4.304). Participants with tertiary education had higher relative fats intake (p = 0.012, ß = 4.213). CONCLUSION: Macronutrients intake of adults should be improved. There is higher intake of dietary fats and need for an increase of complex carbohydrates intake, particularly dietary fibre. Findings of this survey should be used in shaping, fine-tuning and implementing food and nutrition policies that will stimulate healthier diets for prevention of diet related non-communicable diseases.

Prevalence of Severe Obesity among Primary School Children in 21 European Countries.

BACKGROUND: The World Health Organization (WHO) European Childhood Obesity Surveillance Initiative (COSI) was established more than 10 years ago to estimate prevalence and monitor changes in overweight and obesity in children aged 6-9 years. Since then, there have been five rounds of data collection in more than 40 countries involving more than half a million children. To date, no comparative studies with data on severe childhood obesity from European countries have been published. OBJECTIVES: The aim of this work was to present the prevalence of severe obesity in school-aged children from 21 countries participating in COSI. METHOD: The data are from cross-sectional studies in 21 European WHO member states that took part in the first three COSI rounds of data collection (2007/2008, 2009/2010, 2012/2013). School-aged children were measured using standardized instruments and methodology. Children were classified as severely obese using the definitions provided by WHO and the International Obesity Task Force (IOTF). Analyses overtime, by child's age and mother's educational level, were performed in a select group of countries. RESULTS: A total of 636,933 children were included in the analysis (323,648 boys and 313,285 girls). The prevalence of severe obesity varied greatly among countries, with higher values in Southern Europe. According to the WHO definition, severe obesity ranged from 1.0% in Swedish and Moldovan children (95% CI 0.7-1.3 and 0.7-1.5, respectively) to 5.5% (95% CI 4.9-6.1) in Maltese children. The prevalence was generally higher among boys compared to girls. The IOTF cut-offs lead to lower estimates, but confirm the differences among countries, and were more similar for both boys and girls. In many countries 1 in 4 obese children were severely obese. Applying the estimates of prevalence based on the WHO definition to the whole population of children aged 6-9 years in each country, around 398,000 children would be expected to be severely obese in the 21 European countries. The trend between 2007 and 2013 and the analysis by child's age did not show a clear pattern. Severe obesity was more common among children whose mother's educational level was lower. CONCLUSIONS: Severe obesity is a serious public health issue which affects a large number of children in Europe. Because of the impact on educational, health, social care, and economic systems, obesity needs to be addressed via a range of approaches from early prevention of overweight and obesity to treatment of those who need it.

Benefit of routine preprocedural radial artery angiography in STEMI patients.

AIMS: To assess the benefit of routine preprocedural radial artery (RA) angiography in patients with ST segment elevation myocardial infarction (STEMI). METHODS AND RESULTS: All consecutive STEMI patients, in the period from January 2010 until December 2016 were included in the study. Preprocedural radial artery angiography was performed in all patients since March 2011. We compared clinical and procedure characteristics, access site bleeding complications and failure of primary chosen TRA between two groups of STEMI patients before and after we started performing routine RA angiography. We compared 762 STEMI patients from 2010 until March 2011 and 4306 STEMI patients after March 2011 until December 2016. Mean age of patients was 60 ± 11 years with 73% males. The latter group had more elderly and obese patients (P < .0001 both). Prior percutaneous coronary interventions was present in 7% of patients and 0, 1% had prior coronary bypass surgery. Procedure duration (38 ± 16 vs. 32 ± 20 min) was significantly longer in the first group (P value < .0001), but contrast volume (120 ± 33 vs. 110 ± 35 ml), and fluoroscopy time (8.6 ± 6 vs. 8.7 ± 8 min) were similar in both groups. Access crossover from primary TRA was 4, 6% in the first group, with a significant decrease to 3, 1% in the second (P < .0001), after introducing preprocedural RA angiography. Access site bleeding complications were significantly higher in the first group 6.8% vs. 4.3% in the second (p < .0001). CONCLUSION: Routine preprocedural radial artery angiography in STEMI patients is associated with lower rate of access site bleeding complications and reduced overall procedural time and TRA crossover rate.

Macedonia: coronary and structural heart interventions from 2010 to 2015.

The aim of this report is to describe invasive cardiology procedural practice in Macedonia during the period from 2010 to 2015. Details of all consecutive 39,899 patients who underwent cardiovascular, peripheral or structural heart procedures during the period from 2010 until 2015 were examined. Clinical and procedure characteristics, access site, procedural success and complications were analysed. The number of coronary angiographies increased from 5,540 in 2010 to 8,550 in 2015. Transfemoral access (TFA) was present in 4% of coronary angiographies in 2010 and had decreased to 1% in 2015. The number of primary percutaneous coronary interventions (PCI) for acute ST-segment elevation myocardial infarction increased from 763 to 1,175 and both chronic total occlusion and left main coronary artery interventions also increased over time. In 2015, the drug-eluting stent penetration rate was 65%. Structural heart interventions, including transcatheter aortic valve implantations (TAVI) were introduced in 2014 and 23 TAVI cases have since been performed. Transradial access was performed in 38,455 (96%) of all patients. Wrist access adoption in the majority of cardiovascular interventions is possible in all PCI centres in Europe if an appropriate national strategy is developed.

Transradial versus transfemoral access for female patients who underwent primary PCI in STEMI: Two years follow-up data from acute STEMI interventional registry.

BACKGROUND: Female patients possess a higher risk for poorer outcome in ST segment elevation myocardial infarction (STEMI). There is possibility that transradial access (TRA) for primary percutaneous coronary intervention (PPCI) could provide better outcome than transfemoral access (TFA) in female patients with STEMI. METHODS: From 2008 to 2010, 418 female patients (out of 1808 patients) underwent PPCI for acute STEMI. The registry recruited all-comers patients with acute STEMI. Cardiac mortality, major bleeding, and overall MACE rates (composite of death, stroke, re MI and target vessel revascularization-TVR) after 2years follow-up were compared between TRA and TFA. RESULTS: TRA for PPCI was performed in 261 patients and 157 underwent TFA PPCI. The 30-days, 1year mortality and 2year mortality rates were lower in TRA compared to TFA (6.9% vs.14.6%, p=0.012, 8.8% vs. 15.3%, p=0.045, and 9.2% vs. 16.6%, p=0.027respectively). After 2years follow-up, the overall MACE rates were similar (26.4% vs. 31.2%, p=0.336). The overall major bleeding and major vascular access site bleeding were more favorable for TRA than TFA (4.4 vs. 14%, p<0.001, and 2.7 vs. 10.8%, p<0.001, respectively). CONCLUSION: Transradial access for primary PCI in female patients provided better clinical outcomes with lower cardiac mortality and reduced major bleeding in comparison to TFA. There was no significant difference at 2years MACE between TRA and TFA.

Improving nutrition surveillance and public health research in Central and Eastern Europe/Balkan Countries using the Balkan Food Platform and dietary tools.

The objective of this paper is to share experience and provide updated information on Capacity Development in the Central and Eastern Europe/Balkan Countries (CEE/BC) region relevant to public health nutrition, particularly in creation of food composition databases (FCDBs), applying dietary intake assessment and monitoring tools, and harmonizing methodology for nutrition surveillance. Balkan Food Platform was established by a Memorandum of Understanding among EuroFIR AISBL, Institute for Medical Research, Belgrade, Capacity Development Network in Nutrition in CEE - CAPNUTRA and institutions from nine countries in the region. Inventory on FCDB status identified lack of harmonized and standardized research tools. To strengthen harmonization in CEE/BC in line with European research trends, the Network members collaborated in development of a Regional FCDB, using web-based food composition data base management software following EuroFIR standards. Comprehensive nutrition assessment and planning tool - DIET ASSESS & PLAN could enable synchronization of nutrition surveillance across countries.

Complete transitioning to the radial approach for primary percutaneous coronary intervention: a real-world single-center registry of 1808 consecutive patients with acute ST-elevation myocardial infarction.

OBJECTIVES: To compare the short- and long-term outcomes of transradial approach (TRA) versus transfemoral approach (TFA) for primary percutaneous coronary intervention (PPCI) during a complete institutional transition from TFA to TRA. METHODS AND RESULTS: An all-comer population of ST-elevation myocardial infarction (STEMI) patients (n=1808) who underwent PPCI using TRA (n=1162) and TFA (n=646) from October 2007 to December 2010 were enrolled. TRA was used in 25% of PPCIs by 2007 and in 96% of PPCIs in 2010. Primary endpoints were cardiovascular death and major adverse cardiac event (MACE), defined as a composite of death, stroke, reinfarction, and target vessel revascularization at 30 days and 1 year. At 30 days, TRA compared to TFA was associated with a significant reduction of cardiovascular mortality (5.2% vs 10.5%; P<.001), significant MACE reduction (7.3% vs 12.5%; P<.001), fewer access-site complications (0.9% vs 8.2%; P<.001), and lower TIMI major bleeding (1.1% vs 4.3%; P<.001). At 1 year, the cardiovascular mortality and MACE rates were also in favor of the TRA group (6.9% vs 11.5%; P<.001 and 11.6% vs 20.1%; P<.001), respectively. CONCLUSION: Complete transition from femoral access to a preferred radial access is safe and effective for STEMI patients undergoing PPCI, with a favorable effect on short- and long-term outcomes.

WHO European Childhood Obesity Surveillance Initiative: body mass index and level of overweight among 6-9-year-old children from school year 2007/2008 to school year 2009/2010.

BACKGROUND: The World Health Organization (WHO) Regional Office for Europe has established the Childhood Obesity Surveillance Initiative (COSI) to monitor changes in overweight in primary-school children. The aims of this paper are to present the anthropometric results of COSI Round 2 (2009/2010) and to explore changes in body mass index (BMI) and overweight among children within and across nine countries from school years 2007/2008 to 2009/2010. METHODS: Using cross-sectional nationally representative samples of 6-9-year-olds, BMI, anthropometric Z-scores and overweight prevalence were derived from measured weight and height. Significant changes between rounds were assessed using variance and t-tests analyses. RESULTS: At Round 2, the prevalence of overweight (including obesity; WHO definitions) ranged from 18% to 57% among boys and from 18% to 50% among girls; 6 - 31% of boys and 5 - 21% of girls were obese. Southern European countries had the highest overweight prevalence. Between rounds, the absolute change in mean BMI (range: from -0.4 to +0.3) and BMI-for-age Z-scores (range: from -0.21 to +0.14) varied statistically significantly across countries. The highest significant decrease in BMI-for-age Z-scores was found in countries with higher absolute BMI values and the highest significant increase in countries with lower BMI values. The highest significant decrease in overweight prevalence was observed in Italy, Portugal and Slovenia and the highest significant increase in Latvia and Norway. CONCLUSIONS: Changes in BMI and prevalence of overweight over a two-year period varied significantly among European countries. It may be that countries with higher prevalence of overweight in COSI Round 1 have implemented interventions to try to remedy this situation.