SummaryBackgroundUnderweight, 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.MethodsWe 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).FindingsRegional 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 wor...

Accelerometers are a feasible and accurate instrument for use in large epidemiological studies of children's activity. Boys tend to be more active than girls, and there is a marked reduction in activity over the adolescent years. The great majority of younger children achieve current physical activity recommendations, whereas fewer older children do so-especially older girls.

OBJECTIVE -Features of the metabolic syndrome are becoming increasingly evident in children. Decreased physical activity is likely to be an important etiological factor, as shown previously for subjective measures of physical activity in selected groups. The purpose of this study was to examine the relationship between the metabolic syndrome and objectively measured physical activity and whether fitness modified this relationship. (MTI actigraph) worn at the hip for at least 3 days (Ն10 h/day) and fitness with a maximal bike test. As outcomes, we measured sitting systolic and diastolic blood pressure, degree of adiposity (sum of four skinfolds), and, finally, insulin, glucose, triglicerides, and HDL cholesterol in fasting blood samples. The outcome variables were statistically normalized and expressed as the number of SDs from the mean. (i.e., Z scores). A metabolic syndrome risk score was computed as the mean of these Z scores. Multiple linear regression was used to test the association between physical activity and metabolic risk, adjusted primarily for age, sex, sexual maturation, ethnicity, parental smoking, socioeconomic factors, and the Computer Science & Applications unit, as well as for fitness. Robust SEs were computed by clustering on school. RESEARCH DESIGN AND METHODSRESULTS -All children were in the nondiabetic range of fasting glucose. Metabolic risk was inversely related to physical activity (P ϭ 0.008). The relationship was weakened after adjustment for fitness, but there was a significantly positive interaction between physical activity and fitness.CONCLUSIONS -Physical activity is inversely associated with metabolic risk, independently of potential confounders. The interaction between physical activity and fitness suggests that the potential beneficial effect of activity may be greatest in children with lower cardiorespiratory fitness.

Activity counts from the CSA activity monitor seems to be a useful measure of the total amount of physical activity in 9-yr-old children. Activity counts contributed significantly to the explained variation in TEE and was the best predictor of AEE.