Stephanie T. Broyles

The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE): design and methods

BackgroundThe primary aim of the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) was to determine the relationships between lifestyle behaviours and obesity in a multi-national study of children, and to investigate the influence of higher-order characteristics such as behavioural settings, and the physical, social and policy environments, on the observed relationships within and between countries.Methods/designThe targeted sample included 6000 10-year old children from 12 countries in five major geographic regions of the world (Europe, Africa, the Americas, South-East Asia, and the Western Pacific). The protocol included procedures to collect data at the individual level (lifestyle, diet and physical activity questionnaires, accelerometry), family and neighborhood level (parental questionnaires), and the school environment (school administrator questionnaire and school audit tool). A standard study protocol was developed for implementation in all regions of the world. A rigorous system of training and certification of study personnel was developed and implemented, including web-based training modules and regional in-person training meetings.DiscussionThe results of this study will provide a robust examination of the correlates of adiposity and obesity in children, focusing on both sides of the energy balance equation. The results will also provide important new information that will inform the development of lifestyle, environmental, and policy interventions to address and prevent childhood obesity that may be culturally adapted for implementation around the world. ISCOLE represents a multi-national collaboration among all world regions, and represents a global effort to increase research understanding, capacity and infrastructure in childhood obesity.

The Pediatric Obesity Epidemic Continues Unabated in Bogalusa, Louisiana

OBJECTIVES: To examine 35-year trends in the prevalence of overweight and obesity among children and adolescents from Bogalusa, Louisiana. PATIENTS AND METHODS: Height and weight were measured for 11653 children and adolescents between 5 and 17 years of age in 8 cross-sectional surveys. The Bogalusa Heart Study contributed data from 1973–1994, and routine school screening provided 2008–2009 data. Trends in mean BMI, mean gender-specific BMI-for-age z scores, prevalence of overweight/obesity (BMI ≥ 85th percentile), and prevalence of obesity (BMI ≥ 95th percentile) according to age, race, and gender were examined. RESULTS: Since 1973–1974, the proportion of children and adolescents aged 5 to 17 years who are overweight (overweight plus obese) has more than tripled, from 14.2% to 48.4% in 2008–2009. Similarly, the proportion of obese children and adolescents has increased more than fivefold from 5.6% in 1973–1974 to 30.8% in 2008–2009. The prevalence of overweight or obesity, and secular changes, were similar among black and white boys and girls. CONCLUSIONS: In semirural Bogalusa, the childhood obesity epidemic has not plateaued, and nearly half of the children are now overweight or obese.

Screen time, physical activity, and overweight in U.S. youth: national survey of children's health 2003.

The purpose was to examine screen-based leisure time sedentary behavior and physical activity and overweight in a national sample of children. Boys and girls who engage in low physical activity and high leisure time sedentary behavior are two times more likely to be overweight than more active, less sedentary children.

Physical Activity, Sedentary Time, and Obesity in an International Sample of Children

PURPOSE To determine the relationships between moderate-to-vigorous physical activity (MVPA), vigorous physical activity (VPA), sedentary time, and obesity in children from 12 countries representing a wide range of human development. METHODS The sample included 6539 children age 9-11 yr. Times in MVPA, VPA, and sedentary behaviors were assessed by accelerometry. The body mass index (BMI; kg·m) was used to classify children as obese based on z-scores (> +2 SD) from World Health Organization reference data. RESULTS The mean (SD) times spent in MVPA, VPA, and sedentary behavior were 60 (25) min·d, 18 (11) min·d, and 513 (69) min·d, respectively. The overall proportion of the sample that was obese ranged from 5.2% to 24.6% across sites. The odds ratios for obesity were significant for MVPA (0.49; 95% CI, 0.44-0.55), VPA (0.41; 0.37-0.46), and sedentary time (1.19; 1.08-1.30) in the overall sample. The associations of MVPA and VPA with obesity were significant in all 12 sites, whereas the association between sedentary time and obesity was significant in five of the 12 sites. There was a significant difference in BMI z-scores across tertiles of MVPA (P < 0.001) but not across tertiles of sedentary time in a mutually adjusted model. The results of receiver operating characteristic curve analyses for obesity indicated that the optimal thresholds for MVPA (area under the curve [AUC], 0.64), VPA (AUC, 0.67) and sedentary behavior (AUC, 0.57) were 55 (95% CI, 50-64) min·d, 14 (11-16) min·d, and 482 (455-535) min·d, respectively. CONCLUSIONS Greater MVPA and VPA were both associated with lower odds of obesity independent of sedentary behavior. Sedentary time was positively associated with obesity, but not independent of MVPA. Attaining at least 55 min·d of MVPA is associated with lower obesity in this multinational sample of children, which supports current guidelines.

Correlates of Total Sedentary Time and Screen Time in 9–11 Year-Old Children around the World: The International Study of Childhood Obesity, Lifestyle and the Environment

Purpose Previously, studies examining correlates of sedentary behavior have been limited by small sample size, restricted geographic area, and little socio-cultural variability. Further, few studies have examined correlates of total sedentary time (SED) and screen time (ST) in the same population. This study aimed to investigate correlates of SED and ST in children around the world. Methods The sample included 5,844 children (45.6% boys, mean age = 10.4 years) from study sites in Australia, Brazil, Canada, China, Colombia, Finland, India, Kenya, Portugal, South Africa, the United Kingdom, and the United States. Child- and parent-reported behavioral, household, and neighborhood characteristics and directly measured anthropometric and accelerometer data were obtained. Twenty-one potential correlates of SED and ST were examined using multilevel models, adjusting for sex, age, and highest parental education, with school and study site as random effects. Variables that were moderately associated with SED and/or ST in univariate analyses (p<0.10) were included in the final models. Variables that remained significant in the final models (p<0.05) were considered correlates of SED and/or ST. Results Children averaged 8.6 hours of daily SED, and 54.2% of children failed to meet ST guidelines. In all study sites, boys reported higher ST, were less likely to meet ST guidelines, and had higher BMI z-scores than girls. In 9 of 12 sites, girls engaged in significantly more SED than boys. Common correlates of higher SED and ST included poor weight status, not meeting physical activity guidelines, and having a TV or a computer in the bedroom. Conclusions In this global sample many common correlates of SED and ST were identified, some of which are easily modifiable (e.g., removing TV from the bedroom), and others that may require more intense behavioral interventions (e.g., increasing physical activity). Future work should incorporate these findings into the development of culturally meaningful public health messages.

Dietary Intakes Associated with Successful Weight Loss and Maintenance during the Weight Loss Maintenance Trial

BACKGROUND Dietary components effective in weight maintenance efforts have not been adequately identified. OBJECTIVE To determine the effects of changes in dietary consumption on weight loss and maintenance during the Weight Loss Maintenance clinical trial. DESIGN Weight Loss Maintenance was a randomized controlled trial. Successful weight loss participants who completed Phase I of the trial and lost 4 kg were randomized to one of three maintenance intervention arms in Phase II and followed for an additional 30 months. PARTICIPANTS/SETTING The multicenter trial was conducted from 2003 through 2007. This substudy included 828 successful weight loss participants. METHODS The Block Food Frequency Questionnaire (FFQ) was used to assess nutrient intake levels and food group servings. Carbohydrates, proteins, fats, dietary fiber, fruit/vegetable, and dairy servings were utilized as predictor variables. The FFQ was collected on all participants at study entry (beginning of Phase I). Those randomized to Phase II completed the FFQ at three additional time points: randomization (beginning of Phase II), 12 months, and 30 months. INTERVENTION The main intervention focused on long-term maintenance of weight loss using the Dietary Approaches to Hypertension diet. This substudy examined if changes to specific dietary variables were associated with weight loss and maintenance. STATISTICAL ANALYSES PERFORMED Linear regression models that adjusted for change in total energy examined the relationship between changes in dietary intake and weight for each time period. Site, age, race, sex, and a race-sex interaction were included as covariates. RESULTS Participants who substituted protein for fat lost, on average, 0.33 kg per 6 months during Phase I (P<0.0001) and 0.07 kg per 6 months during Phase II (P<0.0001) per 1% increase in protein. Increased intake of fruits and vegetables was associated with weight loss in Phases I and II: 0.29 kg per 6 months (P<0.0001) and 0.04 kg per 6 months (P=0.0062), respectively, per 1-serving increase. Substitution of carbohydrates for fat and protein for carbohydrates were associated with weight loss during both phases. Increasing dairy intake was associated with significant weight loss during Phase II (-0.17 kg per 6 months per 1-serving increase, P=0.0002), but not during Phase I. Dietary fiber revealed no significant findings. CONCLUSIONS Increasing fruits, vegetables, and low-fat dairy may help achieve weight loss and maintenance.

TVs in the bedrooms of children: does it impact health and behavior?

OBJECTIVES To (1) determine socio-demographic characteristics associated with a TV in the bedroom (BTV) and (2) examine relationship of BTV, independent of total viewing time, with social and behavioral characteristics. METHODS Children 6-17 years from the 2007 US National Survey of Childrens Health were included (n=48,687). BTV, daily TV viewing time, demographic, behavioral and social outcomes (community involvement, social skills, health habits and status, and family) were examined using logistic regression, and adjusted for total viewing time. RESULTS Overall prevalence of BTV was 49.3% in American children. Older age, non-Hispanic Black (71.3%), Hispanics (56.3%), higher level of poverty (>56.2%), non two-parent biological family structure (>62.6%), Midwest (47.1%), Northeast (46.7%), South Atlantic (56.4%) and South Central (59.8%) region of the country were associated with higher odds of BTV. Female gender (52.7%) and residence in Alaska (33.0%) were associated with lower prevalence of BTV. BTV was associated with higher prevalence of exhibiting problematic social behaviors (29%) and overweight status (44%). BTV was significantly associated with lower prevalence of regular family meals (13%), engagement in school (16%), participation in extracurricular activities (31%), regularly sleeping enough (20%), and participation in community service (25%) after adjustment for total viewing time. CONCLUSIONS BTV appears associated with more social and behavioral indices than previously reported, in addition to total viewing time.

Relationship between lifestyle behaviors and obesity in children ages 9–11: Results from a 12‐country study

The aim was to assess associations between lifestyle behaviors and obesity in a multinational study of children from 12 countries representing a wide range of human development.

Impact of small group size on neighbourhood influences in multilevel models

Background Given the growing availability of multilevel data from national surveys, researchers interested in contextual effects may find themselves with a small number of individuals per group. Although there is a growing body of literature on sample size in multilevel modelling, few have explored the impact of group sizes of less than five. Methods In a simulated analysis of real data, the impact of a group size of less than five was examined on both a continuous and dichotomous outcome in a simple two-level multilevel model. Models with group sizes one to five were compared with models with complete data. Four different linear and logistic models were examined: empty models; models with a group-level covariate; models with an individual-level covariate and models with an aggregated group-level covariate. The study evaluated further whether the impact of small group size differed depending on the total number of groups. Results When the number of groups was large (N=459), neither fixed nor random components were affected by small group size, even when 90% of tracts had only one individual per tract and even when an aggregated group-level covariate was examined. As the number of groups decreased, the SE estimates of both fixed and random effects were inflated. Furthermore, group-level variance estimates were more affected than were fixed components. Conclusions Datasets in which there is a small to moderate number of groups, with the majority of very small group size (n<5), size may fail to find or even consider a group-level effect when one may exist and also may be underpowered to detect fixed effects.

Television, Reading, and Computer Time: Correlates of School-Day Leisure-Time Sedentary Behavior and Relationship With Overweight in Children in the U.S.

BACKGROUND The purposes were 1) to determine if different leisure-time sedentary behaviors (LTSB), such as TV/video/video game viewing/playing (TV), reading for pleasure (reading), and nonschool computer usage, were associated with childhood overweight status, and 2) to assess the social-ecological correlates of LTSB. METHODS The analytic sample was 33,117 (16,952 boys and 16,165 girls) participants from the 2003 National Survey of Childrens Health. The cut-point for excessive TV and nonschool computer usage was ≥ 2 hr/day. High quantities of daily reading for pleasure were classified as ≥ 31 min/day. Weighted descriptive characteristics were calculated on the sample (means ± SE or frequency). Logistic regression models were used to determine if the LTSB were associated with overweight status and to examine social-ecological correlates. RESULTS Over 35% of the sample was overweight. Odds of being overweight were higher in the 2 to 3 hr/day (OR: 1.48, 95% CI: 1.24, 1.76) and ≥ 4 hr/day (OR: 1.52, 95% CI: 1.22, 1.91) daily TV groups compared with none. Reading and nonschool computer usage was not associated with being overweight. CONCLUSIONS TV was associated with overweight classification; however, nonschool computer usage and reading were not. Several individual, family, and community correlates were associated with high volumes of daily TV viewing.