Underweight, overweight, and obesity in childhood and adolescence are associated with adverse health consequences throughout the life-course. Our aim was to estimate worldwide trends in mean body-mass index (BMI) and a comprehensive set of BMI categories that cover underweight to obesity in children and adolescents, and to compare trends with those of adults. We pooled 2416 population-based studies with measurements of height and weight on 128·9 million participants aged 5 years and older, including 31·5 million aged 5-19 years. We used a Bayesian hierarchical model to estimate trends from 1975 to 2016 in 200 countries for mean BMI and for prevalence of BMI in the following categories for children and adolescents aged 5-19 years: more than 2 SD below the median of the WHO growth reference for children and adolescents (referred to as moderate and severe underweight hereafter), 2 SD to more than 1 SD below the median (mild underweight), 1 SD below the median to 1 SD above the median (healthy weight), more than 1 SD to 2 SD above the median (overweight but not obese), and more than 2 SD above the median (obesity). Regional change in age-standardised mean BMI in girls from 1975 to 2016 ranged from virtually no change (-0·01 kg/m2 per decade; 95% credible interval -0·42 to 0·39, posterior probability [PP] of the observed decrease being a true decrease=0·5098) in eastern Europe to an increase of 1·00 kg/m2 per decade (0·69-1·35, PP>0·9999) in central Latin America and an increase of 0·95 kg/m2 per decade (0·64-1·25, PP>0·9999) in Polynesia and Micronesia. The range for boys was from a non-significant increase of 0·09 kg/m2 per decade (-0·33 to 0·49, PP=0·6926) in eastern Europe to an increase of 0·77 kg/m2 per decade (0·50-1·06, PP>0·9999) in Polynesia and Micronesia. Trends in mean BMI have recently flattened in northwestern Europe and the high-income English-speaking and Asia-Pacific regions for both sexes, southwestern Europe for boys, and central and Andean Latin America for girls. By contrast, the rise in BMI has accelerated in east and south Asia for both sexes, and southeast Asia for boys. Global age-standardised prevalence of obesity increased from 0·7% (0·4-1·2) in 1975 to 5·6% (4·8-6·5) in 2016 in girls, and from 0·9% (0·5-1·3) in 1975 to 7·8% (6·7-9·1) in 2016 in boys; the prevalence of moderate and severe underweight decreased from 9·2% (6·0-12·9) in 1975 to 8·4% (6·8-10·1) in 2016 in girls and from 14·8% (10·4-19·5) in 1975 to 12·4% (10·3-14·5) in 2016 in boys. Prevalence of moderate and severe underweight was highest in India, at 22·7% (16·7-29·6) among girls and 30·7% (23·5-38·0) among boys. Prevalence of obesity was more than 30% in girls in Nauru, the Cook Islands, and Palau; and boys in the Cook Islands, Nauru, Palau, Niue, and American Samoa in 2016. Prevalence of obesity was about 20% or more in several countries in Polynesia and Micronesia, the Middle East and north Africa, the Caribbean, and the USA. In 2016, 75 (44-117) million girls and 117 (70-178) million boys worldwide were moderately or severely underweight. In the same year, 50 (24-89) million girls and 74 (39-125) million boys worldwide were obese. The rising trends in children's and adolescents' BMI have plateaued in many high-income countries, albeit at high levels, but have accelerated in parts of Asia, with trends no longer correlated with those of adults. Wellcome Trust, AstraZeneca Young Health Programme.

Background: In Europe, although the prevalence of childhood obesity seems to be plateauing in some countries, progress on tackling this important public health issue remains slow and inconsistent. Breastfeeding has been described as a protective factor, and the more exclusively and the longer children are breastfed, the greater their protection from obesity. Birth weight has been shown to have a positive association with later risk for obesity. Objectives: It was the aim of this paper to investigate the association of early-life factors, namely breastfeeding, exclusive breastfeeding and birth weight, with obesity among children. Method: Data from 22 participating countries in the WHO European COSI study (round 4: 2015/2017) were collected using cross-sectional, nationally representative samples of 6- to 9-year-olds (n = 100,583). The children’s standardized weight and height measurements followed a common WHO protocol. Information on the children’s birth weight and breastfeeding practice and duration was collected through a family record form. A multivariate multilevel logistic regression analysis regarding breastfeeding practice (both general and exclusive) and characteristics at birth was performed. Results: The highest prevalence rates of obesity were observed in Spain (17.7%), Malta (17.2%) and Italy (16.8%). A wide between-country disparity in breastfeeding prevalence was found. Tajikistan had the highest percentage of children that were breastfed for ≥6 months (94.4%) and exclusively breastfed for ≥6 months (73.3%). In France, Ireland and Malta, only around 1 in 4 children was breastfed for ≥6 months. Italy and Malta showed the highest prevalence of obesity among children who have never been breastfed (21.2%), followed by Spain (21.0%). The pooled analysis showed that, compared to children who were breastfed for at least 6 months, the odds of being obese were higher among children never breastfed or breastfed for a shorter period, both in case of general (adjusted odds ratio [adjOR] [95% CI] 1.22 [1.16–1.28] and 1.12 [1.07–1.16], respectively) and exclusive breastfeeding (adjOR [95% CI] 1.25 [1.17–1.36] and 1.05 [0.99–1.12], respectively). Higher birth weight was associated with a higher risk of being overweight, which was reported in 11 out of the 22 countries. Bulgaria, Croatia, France, Italy, Poland and Romania showed that children who were preterm at birth had higher odds of being obese, compared to children who were full-term babies. Conclusion: The present work confirms the beneficial effect of breastfeeding against obesity, which was highly increased if children had never been breastfed or had been breastfed for a shorter period. Nevertheless, adoption of exclusive breastfeeding is below global recommendations and far from the target endorsed by the WHO Member States at the World Health Assembly Global Targets for Nutrition of increasing the prevalence of exclusive breastfeeding in the first 6 months up to at least 50% by 2025.

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.

Summary: The objective of this study was to synthesize available information on prevalence and time trends of overweight and obesity in pre‐school children in the European Union. Retrieval and analysis or re‐analysis of existing data were carried out. Data sources include WHO databases, Medline and Google, contact with authors of published and unpublished documents. Data were analysed using the International Obesity Task Force reference and cut‐offs, and the WHO standard. Data were available from 18/27 countries. Comparisons were problematic because of different definitions and methods of data collection and analysis. The reported prevalence of overweight plus obesity at 4 years ranges from 11.8% in Romania (2004) to 32.3% in Spain (1998–2000). Countries in the Mediterranean region and the British islands report higher rates than those in middle, northern and eastern Europe. Rates are generally higher in girls than in boys. With the possible exception of England, there was no obvious trend towards increasing prevalence in the past 20–30 years in the five countries with data. The use of the WHO standard with cut‐offs at 1, 2 and 3 standard deviations yields lower rates and removes gender differences. Data on overweight and obesity in pre‐school children are scarce; their interpretation is difficult. Standard methods of surveillance, and research and policies on prevention and treatment, are urgently needed.

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.