Inequality in physical activity, sedentary behaviour, sleep duration and risk of obesity in children: a 12-country study.

OBJECTIVE: Studies examining associations between movement behaviours (i.e. physical activity, sedentary behaviour and sleep duration) and obesity focus on average values of these movement behaviours, despite important within-country and between-country variability. A better understanding of movement behaviour inequalities is important for developing public health policies and behaviour-change interventions. The objective of this ecologic analysis at the country level was to determine if inequality in movement behaviours is a better correlate of obesity than average movement behaviour volume in children from all inhabited continents of the world. METHODS: This multinational, cross-sectional study included 6,128 children 9-11 years of age. Moderate-to-vigorous physical activity (MVPA), total sedentary time (SED) and sleep period time were monitored over 7 consecutive days using waist-worn accelerometry. Screen time was self-reported. Inequality in movement behaviours was determined using Gini coefficients (ranging from 0 [complete equality] to 1 [complete inequality]). RESULTS: The largest inequality in movement behaviours was observed for screen time (Gini of 0.32; medium inequality), followed by MVPA (Gini of 0.21; low inequality), SED (Gini of 0.07; low inequality) and sleep period time (Gini of 0.05; low inequality). Average MVPA (h d-1) was a better correlate of obesity than MVPA inequality (r = -0.77 vs. r = 0.00, p = 0.03). Average SED (h d-1) was also a better correlate of obesity than SED inequality (r = 0.52 vs. r = -0.32, p = 0.05). Differences in associations for screen time and sleep period time were not statistically significant. MVPA in girls was found to be disproportionally lower in countries with more MVPA inequality. CONCLUSIONS: Findings from this study show that average MVPA and SED should continue to be used in population health studies of children as they are better correlates of obesity than inequality in these behaviours. Moreover, the findings suggest that MVPA inequality could be greatly reduced through increases in girls' MVPA alone.

Thresholds of physical activity associated with obesity by level of sedentary behaviour in children.

BACKGROUND: It is unknown whether moderate-to-vigorous physical activity (MVPA) thresholds for obesity should be adapted depending on level of sedentary behaviour in children. OBJECTIVE: The objective of the study is to determine the MVPA thresholds that best discriminate between obese and non-obese children, by level of screen time and total sedentary time in 12 countries. METHODS: This multinational, cross-sectional study included 6522 children 9-11 years of age. MVPA and sedentary time were assessed using waist-worn accelerometry, while screen time was self-reported. Obesity was defined according to the World Health Organization reference data. RESULTS: Receiver operating characteristic curve analyses showed that the best thresholds of MVPA to predict obesity ranged from 53.8 to 73.9 min d-1 in boys and from 41.7 to 58.7 min d-1 in girls, depending on the level of screen time. The MVPA cut-offs to predict obesity ranged from 37.9 to 75.9 min d-1 in boys and from 32.5 to 62.7 min d-1 in girls, depending on the level of sedentary behaviour. The areas under the curve ranged from 0.57 to 0.73 ('fail' to 'fair' accuracy), and most sensitivity and specificity values were below 85%, similar to MVPA alone. Country-specific analyses provided similar findings. CONCLUSIONS: The addition of sedentary behaviour levels to MVPA did not result in a better predictive ability to classify children as obese/non-obese compared with MVPA alone.

Resemblance in physical activity levels: The Portuguese sibling study on growth, fitness, lifestyle, and health.

OBJECTIVES: To investigate the relationships of biological, behavioral, familial, and environmental characteristics with siblings´ physical activity (PA) levels as well as the intrapair resemblance in PA. METHODS: The sample comprises 834 (390 females) biological siblings [brother-brother (BB), sister-sister (SS), brother-sister (BS)] aged 9 to 20 years. Total PA index (TPAI) was estimated by questionnaire. Information on potential behavioral, familial, and environmental correlates was obtained by self-report; body mass index (BMI), biological maturation, and physical fitness were measured. Multilevel models were used to analyze siblings´ clustered data, and sibling resemblance was estimated with the intraclass correlation (ρ). RESULTS: On average, younger sibs, those more physically fit, and those with more parental support had greater TPAI. Further, BB pairs had higher TPAI levels than SS or BS pairs, but also had greater within-pair variance. When adjusted for all covariates, SS pairs demonstrated greater resemblance in TPAI (ρ = 0.53, 95%CI = 0.38-0.68) than BS (ρ = 0.26, 95%CI = 0.14-0.43) or BB pairs (ρ = 0.18, 95%CI = 0.06-0.44). CONCLUSIONS: Age, physical fitness, and parental support were the best predictors of TPAI levels. A moderate level of resemblance in TPAI was observed in SS pairs, while lower resemblance was found for BS and BB pairs. These findings may be due to differences in the roles of shared genetic factors, familial, and environmental characteristics across different sibling types.

Sources of variability in childhood obesity indicators and related behaviors.

The purpose of this study was to describe sources of variability in obesity-related variables in 6022 children aged 9-11 years from 12 countries. The study design involved recruitment of students, nested within schools, which were nested within study sites. Height, weight and waist circumference (WC) were measured and body mass index (BMI) was calculated; sleep duration and total and in-school moderate-to-vigorous physical activity (MVPA) and sedentary time were measured by accelerometry; and diet scores were obtained by questionnaire. Variance in most variables was largely explained at the student level: BMI (91.9%), WC (93.5%), sleep (75.3%), MVPA (72.5%), sedentary time (76.9%), healthy diet score (88.3%), unhealthy diet score (66.2%), with the exception of in-school MVPA (53.8%) and in-school sedentary time (25.1%). Variance explained at the school level ranged from 3.3% for BMI to 29.8% for in-school MVPA, and variance explained at the site level ranged from 3.2% for WC to 54.2% for in-school sedentary time. In general, more variance was explained at the school and site levels for behaviors than for anthropometric traits. Given the variance in obesity-related behaviors in primary school children explained at school and site levels, interventions that target policy and environmental changes may enhance obesity intervention efforts.

Associations between meeting combinations of 24-h movement guidelines and health-related quality of life in children from 12 countries.

OBJECTIVES: To examine whether meeting vs not meeting movement/non-movement guidelines (moderate-to-vigorous physical activity [MVPA], screen time, sleep duration), and combinations of these recommendations, are associated with health-related quality of life (HRQoL) in children from 12 countries in five major geographic regions of the world and explore whether the associations vary by study site. STUDY DESIGN: Observational, multinational cross-sectional study. METHODS: This study included 6106 children aged 9-11 years from sites in Australia, Brazil, Canada, China, Colombia, Finland, India, Kenya, Portugal, South Africa, the United Kingdom, and the United States. Participants completed the KIDSCREEN-10 to provide a global measure of their HRQoL. Sleep duration and MVPA were assessed using 24-h accelerometry. Screen time was assessed through self-report. Meeting the recommendations was defined as ≥60 min/day for MVPA, ≤2 h/day for screen time, and between 9 and 11 h/night for sleep duration. Age, sex, highest parental education, unhealthy diet pattern score, and body mass index z-score were included as covariates in statistical models. RESULTS: In the full sample, children meeting the screen time recommendation, the screen time + sleep recommendation, and all three recommendations had significantly better HRQoL than children not meeting any of these guidelines. Differences in HRQoL scores between sites were also found within combinations of movement/non-movement behaviors. For example, while children in Australia, Canada, and USA self-reported better HRQoL when meeting all three recommendations, children in Kenya and Portugal reported significantly lower HRQoL when meeting all three recommendations (relative to not meeting any). CONCLUSIONS: Self-reported HRQoL is generally higher when children meet established movement/non-movement recommendations. However, differences between study sites also suggest that interventions aimed at improving lifestyle behaviors and HRQoL should be locally and culturally adapted.

A randomized controlled trial of dance exergaming for exercise training in overweight and obese adolescent girls.

BACKGROUND: Structured exergaming with prescribed moderate intensity physical activity has reduced adiposity among adolescents. The extent to which adolescents reduce adiposity when allowed to self-select intensity level is not known. OBJECTIVE: The objective of the study was to examine the influence of exergaming on adolescent girls' body composition and cardiovascular risk factors. METHODS: This randomized controlled trial assigned 41 overweight and obese girls aged 14 to 18 years to group-based dance exergaming (36 h over 3 months) or to a self-directed care control condition. Body size and composition were measured by anthropometry, dual-energy X-ray absorptiometry [%fat and bone mineral density {BMD}] and magnetic resonance imaging. Cardiovascular risk factors included blood pressure, cholesterol, triglycerides, glucose and insulin. RESULTS: Attrition was 5%. Using analysis of covariance controlling for baseline value, age and race, there were no significant condition differences. Per protocol (attended >75%), the intervention group significantly decreased abdominal subcutaneous adiposity and increased trunk and spine BMD (ps < 0.05). Per protocol (>2600 steps/session), the intervention group significantly decreased leg %fat and decreased abdominal subcutaneous and total adiposity (ps < 0.05). CONCLUSION: Exergaming reduced body fat and increased BMD among those adolescent girls who adhered. Further research is required before exergaming is recommended in clinical settings.

Correlates of children's compliance with moderate-to-vigorous physical activity recommendations: a multilevel analysis.

This study aimed to investigate the association between individual and school characteristics associated with the number of school days children comply with moderate-to-vigorous physical activity (MVPA) recommendations. Sample comprises 612 Portuguese children, aged 9-11 years, from 23 schools. Time spent in MVPA was measured by accelerometry, while individual-level correlates were obtained by anthropometry and questionnaires. School-level variables were collected by questionnaire, and accelerometer wear time and season were also considered. Maximum likelihood estimates of model parameters were obtained via a multilevel analysis with children as level-1, and school as level-2. Children who spent more time in sedentary activities and girls were less likely to comply with MVPA/daily. More mature children and those who use active transportation to school were more likely to attain the PA recommendation. Furthermore, greater accelerometer wear time and spring season increased the chance to achieve the recommended MVPA. In terms of school-level correlates, a greater number of available facilities was negatively associated with children MVPA compliance. Given the set of variables, our results showed that individual characteristics seem to be more relevant for children's compliance rates with PA/day than school context variables, which should be taken into account in the implementation of school policies and practices.

Mid-upper arm circumference as a screening tool for identifying children with obesity: a 12-country study.

BACKGROUND: No studies have examined if mid-upper arm circumference (MUAC) can be an alternative screening tool for obesity in an international sample of children differing widely in levels of human development. OBJECTIVE: Our aim is to determine whether MUAC could be used to identify obesity in children from 12 countries in five major geographic regions of the world. METHODS: This observational, multinational cross-sectional study included 7337 children aged 9-11 years. Anthropometric measurements were objectively assessed, and obesity was defined according to the World Health Organization reference data. RESULTS: In the total sample, MUAC was strongly correlated with adiposity indicators in both boys and girls (r > 0.86, p < 0.001). The accuracy level of MUAC for identifying obesity was high in both sexes and across study sites (overall area under the curve of 0.97, sensitivity of 95% and specificity of 90%). The MUAC cut-off value to identify obesity was ~25 cm for both boys and girls. In country-specific analyses, the cut-off value to identify obesity ranged from 23.2 cm (boys in South Africa) to 26.2 cm (girls in the UK). CONCLUSIONS: Results from this 12-country study suggest that MUAC is a simple and accurate measurement that may be used to identify obesity in children aged 9-11 years. MUAC may be a promising screening tool for obesity in resource-limited settings.

Comparison of the heart failure risk stratification performance of the CKD-EPI equation and the MDRD equation for estimated glomerular filtration rate in patients with Type 2 diabetes.

AIMS: To investigate the risk prediction and the risk stratification performances of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and the Modification of Diet in Renal Disease (MDRD) equation for estimated glomerular filtration rate (eGFRCKD - EPI vs. eGFRMDRD ) on heart failure in patients with Type 2 diabetes. METHODS: The study cohort included 12 258 White and 16 886 African American low-income patients with Type 2 diabetes who were 30-90 years old at baseline. Heart failure risk according to different eGFRCKD - EPI and eGFRMDRD categories was prospectively assessed. RESULTS: During a mean follow-up of 6.5 years, 5043 incident heart failure cases were identified. Multivariable-adjusted hazard ratios (HRs) of heart failure associated with the eGFRCKD - EPI categories [≥ 90 (reference group), 75-89, 60-74, 30-59 and < 30 ml/min/1.73 m(2) ] were 1.00, 1.11, 1.31, 1.75 and 2.93 (Ptrend < 0.001) for African American patients, and 1.00, 1.11, 1.08, 1.59 and 2.92 (Ptrend < 0.001) for White patients, respectively. The model with eGFRCKD - EPI and the other risk factors had significantly higher Harrell's C than the model with eGFRMDRD and other risk factors. Patients reclassified downward from eGFRMDRD 60-74 to eGFRCKD - EPI 30-59 and from eGFRMDRD 30-59 to eGFRCKD - EPI < 30 ml/min/1.73 m(2) showed higher heart failure risk than those who were not reclassified. CONCLUSIONS: Impaired kidney function (i.e. GFR < 60 ml/min/1.73 m(2) ), and even mildly decreased GFR (60-74 ml/min/1.73 m(2) ) estimated by both equations is associated with an increased risk of heart failure. Compared with GFR estimated using the MDRD equation, GFR estimated using the CKD-EPI equation added more predictive power to the model with the other risk factors. Also, eGFRCKD - EPI provided more accurate heart failure risk stratification than eGFRMDRD .

Prospective association between body composition, physical activity and energy intake in young adults.

BACKGROUND/OBJECTIVES: Despite considerable research on the association between physical activity (PA) and body composition, there remains limited information on the directionality of the relationship. The present study examined the prospective associations among objectively measured PA, energy intake (EI) and body composition. SUBJECTS/METHODS: A convenience sample of 430 adults (49% male) between 21 and 35 years of age was followed over 1 year with repeated measurements taken every 3 months. BMI (kg/m(2)) and percent body fat (%BF) were calculated based on anthropometric measurements and dual energy X-ray absorptiometry. A multi-sensor device was worn over a period of 10 days to estimate total daily energy expenditure and time spent in different intensities. EI was calculated based on change in body composition and total daily energy expenditure. RESULTS: A total of 379 participants provided valid data. On average, participants experienced a significant weight gain of 1.2±4.3 kg during the 12-month observation period, which was associated with an increase in %BF (0.8±3.2 %). Average time spent in moderate-to-vigorous PA (MVPA) decreased significantly, whereas EI remained constant. Optimal linear mixed models, adjusting for age and sex, showed an inverse effect of MVPA on BMI and %BF, whereas EI only directly affected BMI (P<0.001). There was also a significant inverse effect of BMI and %BF on MVPA (P<0.001). CONCLUSIONS: Results of this study indicate an inverse reciprocal association between MVPA and measures of adiposity. Thus, primary preventive actions are warranted to avoid excess weight gain, which may result in a vicious cycle of weight gain and low PA.

Pattern changes in step count accumulation and peak cadence due to a physical activity intervention.

OBJECTIVES: The purpose was to determine if a 12-week weight loss intervention with a physical activity (PA) component would lead to changes in steps/day, step count accumulation patterns, and peak cadence. DESIGN: Randomized clinical trial. METHODS: Overall, 121 overweight/obese White and African-American adults (ages 35-64yrs) were randomized to a diet education plus PA education and behavior change intervention group (DE+PA) or diet education and behavior change group (DE). The DE+PA intervention was designed to increase steps/day, and steps at moderate-to-vigorous intensity. The Actigraph GT3X+ accelerometer was used to measure steps accumulated in different cadence bands (1-19, 20-39, 40-59, 60-79, 80-99, 100-119, 120+ steps/min), and peak 1-min, 30-min and 60-min cadence. Pre- to post-intervention changes in steps/day, step count within each cadence band, and peak cadences were compared within groups using paired sample t-test and between groups after adjustment for baseline values of the same variable using ANCOVA. RESULTS: Ninety participants had valid data (44 in the DE+PA group). Change in steps/day was not significantly different between the groups. However, participants in the DE+PA group accumulated significantly more steps at post-intervention in the 80-99, 100-119, and 120+ cadence bands, all p<0.02. The DE+PA group increased step counts accumulated within the 100-119 (463±1092 vs 56±546 step counts; p=0.01) and 120+ (390±999 vs 34±321 step counts; p=0.03) cadence bands, as well as peak 60-min cadence when compared to the DE group. CONCLUSIONS: Non-significant changes in steps/day following a PA intervention may mask changes in steps accumulated at moderate-to-vigorous intensity cadences.

Body mass index, cardiorespiratory fitness and cardiometabolic risk factors in youth from Portugal and Mozambique.

OBJECTIVES: The objectives of this study are to examine differences in cardiometabolic risk indicators, as well as their prevalences, in Portuguese and Mozambican youth, and to investigate the associations between weight status and cardiorespiratory fitness levels with cardiometabolic risk. METHODS: The sample comprises 721 adolescents (323 Mozambican and 398 Portuguese), aged 10-15 years. Anthropometry (height, sitting height, weight and waist circumference), blood pressure, serum-fasting triglycerides, high-density lipoprotein cholesterol and glucose, and cardiorespiratory fitness were measured. Maturity offset was estimated and a cardiometabolic risk score adjusted for sex, age and biological maturity was computed. Adolescents were classified as normal weight and overweight/obese as well as fit or unfit (cardiorespiratory fitness). RESULTS: Portuguese youth have better cardiometabolic and cardiorespiratory fitness profiles. About 32% and 30% of Portuguese boys and girls, respectively, are overweight/obese; in Mozambicans, these prevalences are 7.5% for boys and 21% for girls; in addition, 81.6% of Portuguese boys and 77.7% of Portuguese girls were classified as cardiorespiratory fit, against 54% and 44.4% of Mozambican boys and girls, respectively. No statistically significant differences (P>0.05) were found between Mozambicans and Portuguese for the cluster of three or more cardiometabolic risk indicators. A positive relationship (P<0.001) was found between weight status and cardiometabolic risk in adolescents from both countries; however, a negative association (P<0.001) between cardiorespiratory fitness and cardiometabolic risk was only found among Portuguese youth. CONCLUSIONS: Portuguese and Mozambican youth differ in their cardiometabolic risk profiles, body weight and cardiorespiratory fitness, favoring Portuguese. Overweight/obesity and low cardiorespiratory fitness levels are related to a worse cardiometabolic risk profile, being relevant to design public health intervention strategies to reduce excess weight and increase cardiorespiratory fitness.

Active school transport and weekday physical activity in 9-11-year-old children from 12 countries.

OBJECTIVES: Active school transport (AST) may increase the time that children spend in physical activity (PA). This study examined relationships between AST and weekday moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), sedentary time (SED) and total activity during naturally organized time periods (daily, before school, during school and after school) in a sample of children from 12 countries. METHODS: The sample included 6224 children aged 9-11 years. PA and sedentary time were objectively measured using Actigraph accelerometers. AST was self-reported by participants. Multilevel generalized linear and logistic regression statistical models were used to determine associations between PA, SED and AST across and within study sites. RESULTS: After adjustment for age, highest parental educational attainment, BMI z-score and accelerometer wear time, children who engaged in AST accumulated significantly more weekday MVPA during all studied time periods and significantly less time in LPA before school compared with children who used motorized transport to school. AST was unrelated to time spent in sedentary behaviors. Across all study sites, AST was associated with 6.0 min (95% confidence interval (CI): 4.7-7.3; P<0.0001) more of weekday MVPA; however, there was some evidence that this differed across study sites (P for interaction=0.06). Significant positive associations were identified within 7 of 12 study sites, with differences ranging from 4.6 min (95% CI: 0.3-8.9; P=0.04, in Canada) to 10.2 min (95% CI: 5.9-14.4; P<0.0001, in Brazil) more of daily MVPA among children who engaged in AST compared with motorized transport. CONCLUSIONS: The present study demonstrated that AST was associated with children spending more time engaged in MVPA throughout the day and less time in LPA before school. AST represents a good behavioral target to increase levels of PA in children.

Relationships between active school transport and adiposity indicators in school-age children from low-, middle- and high-income countries.

OBJECTIVES: Within the global context of the nutrition and physical activity transition it is important to determine the relationship between adiposity and active school transport (AST) across different environmental and socio-cultural settings. The present study assessed the association between adiposity (that is, body mass index z-score (BMIz), obesity, percentage body fat (PBF), waist circumference) and AST in 12 country sites, in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE). METHODS: The analytical sample included 6797 children aged 9-11 years. Adiposity indicators included, BMIz calculated using reference data from the World Health Organization, obesity (BMIz ⩾+2 s.d.), PBF measured using bioelectrical impedance and waist circumference. School travel mode was assessed by questionnaire and categorized as active travel versus motorized travel. Multilevel linear and non-linear models were used to estimate the magnitude of the associations between adiposity indicators and AST by country site and sex. RESULTS: After adjusting for age, sex, parental education and motorized vehicle availability, children who reported AST were less likely to be obese (odds ratio=0.72, 95% confidence interval (0.60-0.87), P<0.001) and had a lower BMIz (-0.09, s.e.m.=0.04, P=0.013), PBF (least square means (LSM) 20.57 versus 21.23% difference -0.66, s.e.m.=0.22, P=0.002) and waist circumference (LSM 63.73 cm versus 64.63 cm difference -0.90, s.e.m.=0.26, P=0.001) compared with those who reported motorized travel. Overall, associations between obesity and AST did not differ by country (P=0.279) or by sex (P=0.571). CONCLUSIONS: AST was associated with lower measures of adiposity in this multinational sample of children. Such findings could inform global efforts to prevent obesity among school-age children.

An international comparison of dietary patterns in 9-11-year-old children.

OBJECTIVES: Dietary pattern is defined as a combination of foods and drinks and the frequency of consumption within a population. Dietary patterns are changing on a global level, which may be linked to an increased incidence of chronic diseases. The aim of this study was to identify and compare the dietary patterns among 9-11-year-old children living in urban regions in different parts of the world. METHODS: Participants were 7199 children (54% girls), aged 9-11 years, from 12 countries situated in all major world regions. Food consumption was assessed using a 23-item Food Frequency Questionnaire (FFQ). To identify dietary patterns, principal components analyses (PCA) were carried out using weekly portions as input variables. RESULTS: Both site-specific and pooled PCA resulted in two strong components. Component 1 ('unhealthy diet pattern') included fast foods, ice cream, fried food, French fries, potato chips, cakes and sugar-sweetened sodas with >0.6 loadings. The loadings for component 2 ('healthy diet pattern') were slightly weaker with only dark-green vegetables, orange vegetables, vegetables in general, and fruits and berries reaching a >0.6 loading. The site-specific diet pattern scores had very strong correlations with the pattern scores from the pooled data: r=0.82 and 0.94 for components 1 and 2, respectively. CONCULSIONS: The results suggest that the same 'healthier' and 'unhealthier' foods tend to be consumed in similar combinations among 9-11-year-old children in different countries, despite variation in food culture, geographical location, ethnic background and economic development.

The reliability and validity of a short food frequency questionnaire among 9-11-year olds: a multinational study on three middle-income and high-income countries.

OBJECTIVE: The main aim of this study was to assess the reliability and validity of a food frequency questionnaire with 23 food groups (I-FFQ) among a sample of 9-11-year-old children from three different countries that differ on economical development and income distribution, and to assess differences between country sites. Furthermore, we assessed factors associated with I-FFQ's performance. METHODS: This was an ancillary study of the International Study of Childhood Obesity, Lifestyle and the Environment. Reliability (n=321) and validity (n=282) components of this study had the same participants. Participation rates were 95% and 70%, respectively. Participants completed two I-FFQs with a mean interval of 4.9 weeks to assess reliability. A 3-day pre-coded food diary (PFD) was used as the reference method in the validity analyses. Wilcoxon signed-rank tests, intraclass correlation coefficients and cross-classifications were used to assess the reliability of I-FFQ. Spearman correlation coefficients, percentage difference and cross-classifications were used to assess the validity of I-FFQ. A logistic regression model was used to assess the relation of selected variables with the estimate of validity. Analyses based on information in the PFDs were performed to assess how participants interpreted food groups. RESULTS: Reliability correlation coefficients ranged from 0.37 to 0.78 and gross misclassification for all food groups was <5%. Validity correlation coefficients were below 0.5 for 22/23 food groups, and they differed among country sites. For validity, gross misclassification was <5% for 22/23 food groups. Over- or underestimation did not appear for 19/23 food groups. Logistic regression showed that country of participation and parental education were associated (P⩽0.05) with the validity of I-FFQ. Analyses of children's interpretation of food groups suggested that the meaning of most food groups was understood by the children. CONCLUSION: I-FFQ is a moderately reliable method and its validity ranged from low to moderate, depending on food group and country site.

Reliability of accelerometer-determined physical activity and sedentary behavior in school-aged children: a 12-country study.

OBJECTIVES: Focused on the accelerometer-determined physical activity and sedentary time metrics in 9-11-year-old children, we sought to determine the following: (i) number of days that are necessary to achieve reliable estimates (G⩾0.8); (ii) proportion of variance attributed to different facets (participants and days) of reliability estimates; and (iii) actual reliability of data as collected in The International Study of Childhood Obesity, Lifestyle and Environment (ISCOLE). METHODS: The analytical sample consisted of 6025 children (55% girls) from sites in 12 countries. Physical activity and sedentary time metrics measures were assessed for up to 7 consecutive days for 24 h per day with a waist-worn ActiGraph GT3X+. Generalizability theory using R software was used to investigate the objectives i and ii. Intra-class correlation coefficients (ICC) were computed using SAS PROC GLM to inform objective iii. RESULTS: The estimated minimum number of days required to achieve a reliability estimate of G⩾0.8 ranged from 5 to 9 for boys and 3 to 11 for girls for light physical activity (LPA); 5 to 9 and 3 to 10, for moderate-to-vigorous physical activity (MVPA); 5 to 10 and 4 to 10 for total activity counts; and 7 to 11 and 6 to 11 for sedentary time, respectively. For all variables investigated, the 'participant' facet accounted for 30-50% of the variability, whereas the 'days' facet accounted for ⩽5%, and the interaction (P × D) accounted for 50-70% of the variability. The actual reliability for boys in ISCOLE ranged from ICCs of 0.78 to 0.86, 0.73 to 0.85 and 0.72 to 0.86 for LPA, MVPA and total activity counts, respectively, and 0.67 to 0.79 for sedentary time. The corresponding values for girls were 0.80-0.88, 0.70-0.89, 0.74-0.86 and 0.64-0.80. CONCLUSIONS: It was rare that only 4 days from all participants would be enough to achieve desirable reliability estimates. However, asking participants to wear the device for 7 days and requiring ⩾4 days of data to include the participant in the analysis might be an appropriate approach to achieve reliable estimates for most accelerometer-derived metrics.

The epidemiological transition and the global childhood obesity epidemic.

OBJECTIVES: Childhood obesity is now recognized as a global public health issue. Social patterning of obesity, consistent with the theory of epidemiologic transition, has not been well described in children, and the limited research has focused on developed settings. The aim of this study was to describe the relationship between childhood obesity and household income using objective measures of adiposity and to explore how this relationship differs across levels of country human development. METHODS: The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) was a multi-national cross-sectional study conducted in 12 urban/suburban study sites that represented all inhabited continents and wide ranges of development. ISCOLE collected objectively measured height, body mass and percentage body fat in 7341 10-year-old children. Multi-level random-effects models were used to examine income gradients in several obesity measures. RESULTS: The mean age of the children was 10.4 years, and 12.6% were obese, ranging from 5.4% (Finland) to 23.8% (China). For both boys and girls, obesity prevalence, body fat percentage and body mass index (BMI) z-score increased linearly with higher income at lower levels of development (all P for trend ⩽0.0012), but decreased linearly with higher income at higher levels of development (all P for trend ⩽0.0003). Country human development explained 75% of the variation in the country-specific income-obesity relationships (r=-0.87, P=0.0003). CONCLUSIONS: Results are consistent with the theory of epidemiologic transition. Global efforts to control obesity must account for socioeconomic factors within a country's context. Future research should seek to understand global socioeconomic patterns in obesity-related lifestyle behaviors.

Development and reliability of an audit tool to assess the school physical activity environment across 12 countries.

OBJECTIVES: Schools are an important setting to enable and promote physical activity. Researchers have created a variety of tools to perform objective environmental assessments (or 'audits') of other settings, such as neighborhoods and parks; yet, methods to assess the school physical activity environment are less common. The purpose of this study is to describe the approach used to objectively measure the school physical activity environment across 12 countries representing all inhabited continents, and to report on the reliability and feasibility of this methodology across these diverse settings. METHODS: The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) school audit tool (ISAT) data collection required an in-depth training (including field practice and certification) and was facilitated by various supporting materials. Certified data collectors used the ISAT to assess the environment of all schools enrolled in ISCOLE. Sites completed a reliability audit (simultaneous audits by two independent, certified data collectors) for a minimum of two schools or at least 5% of their school sample. Item-level agreement between data collectors was assessed with both the kappa statistic and percent agreement. Inter-rater reliability of school summary scores was measured using the intraclass correlation coefficient. RESULTS: Across the 12 sites, 256 schools participated in ISCOLE. Reliability audits were conducted at 53 schools (20.7% of the sample). For the assessed environmental features, inter-rater reliability (kappa) ranged from 0.37 to 0.96; 18 items (42%) were assessed with almost perfect reliability (κ=0.80-0.96), and a further 24 items (56%) were assessed with substantial reliability (κ=0.61-0.79). Likewise, scores that summarized a school's support for physical activity were highly reliable, with the exception of scores assessing aesthetics and perceived suitability of the school grounds for sport, informal games and general play. CONCLUSIONS: This study suggests that the ISAT can be used to conduct reliable objective audits of the school physical activity environment across diverse, international school settings.

Association between body mass index and body fat in 9-11-year-old children from countries spanning a range of human development.

The purpose was to assess associations between body mass index (BMI) and body fat in a multinational sample of 9-11-year-old children. The sample included 7265 children from countries ranging in human development. Total body fat (TBF) and percentage body fat (PBF) were measured with a Tanita SC-240 scale and BMI z-scores (BMIz) and percentiles were computed using reference data from the World Health Organization and the U.S. Centers for Disease Control and Prevention, respectively. Mean PBF at BMIz values of -1, 0 and +1 were estimated using multilevel models. Correlations between BMI and TBF were >0.90 in all countries, and correlations between BMI and PBF ranged from 0.76 to 0.96. Boys from India had higher PBF than boys from several other countries at all levels of BMIz. Kenyan girls had lower levels of PBF than girls from several other countries at all levels of BMIz. Boys and girls from Colombia had higher values of PBF at BMIz=-1, whereas Colombian boys at BMIz 0 and +1 also had higher values of PBF than boys in other countries. Our results show a consistently high correlation between BMI and adiposity in children from countries representing a wide range of human development.