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.

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.

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.

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 6,022 children aged 9–11 y 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 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.

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 .

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.

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.

Associations between sleep patterns and lifestyle behaviors in children: an international comparison

OBJECTIVES

Although evidence is accumulating on the importance of a good night's sleep for healthy eating and activity behaviors, existing research has mainly been conducted in high-income, developed countries with limited sociocultural variability. This study is the first to examine the associations between sleep patterns and lifestyle behaviors in children from 12 countries in five major geographic regions of the world.

METHODS

This observational, multinational cross-sectional study included 5777 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. Nocturnal sleep duration (hours per night), sleep efficiency (%) and bedtime (h:min) were monitored over 7 consecutive days using an accelerometer. Lifestyle behaviors included moderate-to-vigorous physical activity (MVPA), total sedentary time (SED), self-reported screen time (ST) and healthy/unhealthy diet patterns (HDP/UDP). Multilevel modeling analyses were used to account for the hierarchical nature of the data.

RESULTS

Overall, participants averaged 8.8 (s.d. 0.9) hours of sleep with 96.2% (s.d. 1.4) sleep efficiency and a mean bedtime of 2218 hours. After adjustment for age, sex, highest parental education and BMI z-score, results showed that (i) sleep duration was negatively associated with MVPA, SED and UDP score; (ii) sleep efficiency was negatively associated with MVPA and UDP score, and positively associated with SED; and (iii) later bedtime was positively associated with SED, ST and UDP score, and negatively associated with MVPA and HDP score. Results using categories of sleep patterns were consistent with the linear associations. Results also revealed that associations between sleep patterns and MVPA, SED and ST were significantly different between study sites, with stronger associations in high-income countries compared with low/middle-income countries.

CONCLUSIONS

Sleep characteristics are important correlates of lifestyle behaviors in children. Differences between countries suggest that interventions aimed at improving sleep and lifestyle behaviors should be culturally adapted.

Nocturnal sleep-related variables from 24-h free-living waist-worn accelerometry: International Study of Childhood Obesity, Lifestyle and the Environment

OBJECTIVES

We describe the process of identifying and defining nocturnal sleep-related variables (for example, movement/non-movement indicators of sleep efficiency, waking episodes, midpoint and so on) using the unique 24-h waist-worn free-living accelerometer data collected in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE).

METHODS

Seven consecutive days of 24-h waist-worn accelerometer (GT3X+, ActiGraph LLC) data were collected from over 500 children at each site. An expert subgroup of the research team with accelerometry expertize, frontline data collectors and data managers met on several occasions to categorize and operationally define nocturnal accelerometer signal data patterns. The iterative process was informed by the raw data drawn from a sub set of the US data, and culminated in a refined and replicable delineated definition for each identified nocturnal sleep-related variable. Ultimately based on 6318 participants from all 12 ISCOLE sites with valid total sleep episode time (TSET), we report average clock times for nocturnal sleep onset, offset and midpoint in addition to sleep period time, TSET and restful sleep efficiency (among other derived variables).

RESULTS

Nocturnal sleep onset occurred at 2218 hours and nocturnal sleep offset at 0707 hours. The mean midpoint was 0243 hours. The sleep period time of 529.6 min (8.8 h) was typically accumulated in a single episode, making the average TSET very similar in duration (529.0 min). The mean restful sleep efficiency ranged from 86.8% (based on absolute non-movement of 0 counts per minute) to 96.0% (based on relative non-movement of <100 counts per minute).

CONCLUSIONS

These variables extend the potential of field-based 24-h waist-worn accelerometry to distinguish and categorize the underlying robust patterns of movement/non-movement signals conveying magnitude, duration, frequency and periodicity during the nocturnal sleep period.

Associations between breakfast frequency and adiposity indicators in children from 12 countries

OBJECTIVES

Reports of inverse associations between breakfast frequency and indices of obesity are predominantly based on samples of children from high-income countries with limited socioeconomic diversity. Using data from the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE), the present study examined associations between breakfast frequency and adiposity in a sample of 9-11-year-old children from 12 countries representing a wide range of geographic and socio-cultural variability.

METHODS

Multilevel statistical models were used to examine associations between breakfast frequency (independent variable) and adiposity indicators (dependent variables: body mass index (BMI) z-score and body fat percentage (BF%)), adjusting for age, sex, and parental education in 6941 children from 12 ISCOLE study sites. Associations were also adjusted for moderate-to-vigorous physical activity, healthy and unhealthy dietary patterns and sleep time in a sub-sample (n=5710). Where interactions with site were significant, results were stratified by site.

RESULTS

Adjusted mean BMI z-score and BF% for frequent breakfast consumers were 0.45 and 20.5%, respectively. Frequent breakfast consumption was associated with lower BMI z-scores compared with occasional (P<0.0001, 95% confidence intervals (CI): 0.10-0.29) and rare (P<0.0001, 95% CI: 0.18-0.46) consumption, as well as lower BF% compared with occasional (P<0.0001, 95% CI: 0.86-1.99) and rare (P<0.0001, 95% CI: 1.07-2.76). Associations with BMI z-score varied by site (breakfast by site interaction; P=0.033): associations were non-significant in three sites (Australia, Finland and Kenya), and occasional (not rare) consumption was associated with higher BMI z-scores compared with frequent consumption in three sites (Canada, Portugal and South Africa). Sub-sample analyses adjusting for additional covariates showed similar associations between breakfast and adiposity indicators, but lacked site interactions.

CONCLUSIONS

In a multinational sample of children, more frequent breakfast consumption was associated with lower BMI z-scores and BF% compared with occasional and rare consumption. Associations were not consistent across all 12 countries. Further research is required to understand global differences in the observed associations.

Unique contributions of ISCOLE to the advancement of accelerometry in large studies

Accelerometry has become a mainstay approach for objectively monitoring children's physical activity and sedentary time in epidemiological studies. The magnitude of effort underlying successful data collection, management and treatment is prodigious and its complexity has been associated with increasingly diverse methodological choices that, while defensible relative to specific research questions, conspire to undermine the ability to compare results between studies. Although respecting widespread calls for best practices, it is also important to openly share tools and resources supporting potential improvements to research practice and study design, thus allowing others to replicate, further improve, and/or otherwise build on this foundation. The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) is a large multinational study that included accelerometer-based measures of physical activity, sedentary time and sleep. This review summarizes the unique contributions of ISCOLE to the advancement of accelerometry in large studies of children's behavior, and in particular: (1) open-access publication of the ISCOLE accelerometry Manual of Operations; (2) 24-h waist-worn accelerometry protocol; (3) identification and extraction of nocturnal total sleep episode time (with open access to editable SAS syntax); (4) development of the first interpretive infrastructure for identifying and defining an evolved list of sleep-related variables from 24-h waist-worn accelerometry; (5) provision of a detailed model for reporting accelerometer paradata (administrative data related to accelerometry); and (6) cataloging the most detailed and defensible list of accelerometry-derived physical activity and sedentary time variables to date. The novel tools and resources associated with these innovations are shared openly in an effort to support methodological harmonization and overall advancement of accelerometry in large epidemiological studies.

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.

Birth weight and childhood obesity: a 12-country study

OBJECTIVES

Few studies have investigated the association between the full range of birth weight and the risk of childhood obesity in high-, middle- and low-income countries. The aim of the present study is to assess the association between different levels of birth weight and the risk of obesity among children aged 9-11 years in 12 countries.

METHODS

A multinational, cross-sectional study of 5141 children aged 9-11 years was conducted in 12 countries. Height and weight were obtained using standardized methods. Time spent in moderate-to-vigorous physical activity (MVPA), sedentary and sleeping were objectively measured using 24-h, waist-worn accelerometer (Actigraph GT3X+) monitored for 7 days. Birth weight and other factors (regions, parental education, maternal history of gestational diabetes, children age, gender, breast feeding, gestational age, unhealthy diet scores and healthy diet scores) were collected by parental and children's questionnaires. Multilevel modeling was used to account for the nested nature of the data.

RESULTS

The overall prevalence of obesity (BMI z-score>+2 s.d.) was 15.4% for boys and 10.0% for girls. There was a positive association between birth weight and BMI z-scores. The multivariable-adjusted odds ratios (ORs) of childhood obesity were significantly higher among children whose birth weights were 3500-3999 g (OR 1.45; 95% confidence interval (CI): 1.10-1.92), and >4000 g (OR 2.08; 95% CI: 1.47-2.93), compared with the reference group (2500-2999 g). The positive association between birth weight and the odds of childhood obesity was seen in girls, whereas a U-shaped association appeared in boys.

CONCLUSIONS

High levels of birth weight, defined as birth weight ⩾3500 g, were associated with increased odds of obesity among 9-11-year-old children in 12 countries. However, sex differences in the association between birth weight and the risk of obesity need to be considered when planning interventions to reduce childhood obesity.

Are participant characteristics from ISCOLE study sites comparable to the rest of their country?

OBJECTIVES

The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) provides robust, multi-national information on physical activity, diet and weight status in 9-11-year-old children around the world. The purpose of this analysis was to examine the similarities and differences between participant characteristics from ISCOLE sites and data from nationally representative surveys from ISCOLE countries (Australia, Brazil, Canada, China, Colombia, Finland, Kenya, India, Portugal, South Africa, the United Kingdom and the United States).

METHODS

Distributions of characteristics were assessed within each ISCOLE country-level database, and compared with published data from national or regional surveys, where available. Variables of comparison were identified a priori and included body mass index (BMI), physical activity (accelerometer-determined steps per day) and screen time (child-report).

RESULTS

Of 12 countries, data on weight status (BMI) were available in 8 countries, data on measured physical activity (steps per day) were available in 5 countries and data on self-reported screen time were available in 9 countries. The five ISCOLE countries that were part of the Health Behaviour in School-aged Children Survey (that is, Canada, Finland, Portugal, the United Kingdom (England) and the United States) also provided comparable data on self-reported physical activity. Available country-specific data often used different measurement tools or cut-points, making direct comparisons difficult. Where possible, ISCOLE data were re-analyzed to match country-level data, but this step limited between-country comparisons.

CONCLUSIONS

From the analyses performed, the ISCOLE data do not seem to be systematically biased; however, owing to limitations in data availability, data from ISCOLE should be used with appropriate caution when planning country-level population health interventions. This work highlights the need for harmonized measurement tools around the world while accounting for culturally specific characteristics, and the need for collaboration across study centers and research groups.

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.

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.

Racial disparities in cardiovascular risk factor control in an underinsured population with Type 2 diabetes

AIM

To investigate the race-specific trend in attainment of the American Diabetes Association cardiovascular risk factor control goals (HbA1c <53 mmol/mol (7.0%), blood pressure <130/80 mmHg and LDL cholesterol <2.6mmol/l) by patients with Type 2 diabetes.

METHODS

The study sample included 14 946 African-American and 12 758 white patients who were newly diagnosed with Type 2 diabetes between 2001 and 2009 in the Louisiana State University Hospital system. The race-specific percentages of patients' attainment of American Diabetes Association goals were calculated using the baseline and follow-up measurements of HbA1c , blood pressure, and LDL cholesterol levels. Logistic regression was used to test the difference between African-American and white patients.

RESULTS

The percentage of patients who met all three American Diabetes Association goals increased from 8.2% in 2001 to 10.2% in 2009 (increased by 24.4%) in this cohort. Compared with African-American patients, white patients had better attainment of the following American Diabetes Association goals: HbA1c (61.4 vs. 55.1%), blood pressure (25.8 vs. 20.4%), LDL cholesterol (40.1 vs. 37.7%) and all three goals (7.3 vs. 5.1%). African-American and white patients generally had a better cardiovascular disease risk factor profile during follow-up when we assessed attainment of the American Diabetes Association goals by means of HbA1c , blood pressure and LDL cholesterol.

CONCLUSIONS

During 2001-2009, the present low-income cohort of people with Type 2 diabetes generally experienced improved control of cardiovascular disease risk factors. White patients had better attainment of the American Diabetes Association cardiovascular risk factor control goals than their African-American counterparts.

Sitting time and cardiometabolic risk in US adults: associations by sex, race, socioeconomic status and activity level

BACKGROUND

Sitting time is associated with adverse health outcomes including chronic disease and premature mortality. However, it is not known if the association of sitting time with cardiometabolic risk factors varies across sociodemographic or health factors.

METHODS

The sample included 4560 adults (≥20 years) who participated in the cross-sectional 2007-2010 US National Health and Nutrition Examination Survey. Participants self-reported typical daily sitting time. Weight, height, blood pressure, and fasting triglycerides, high-density lipoprotein-cholesterol (HDL-C), glucose and insulin were measured. Homeostatic model assessment-insulin resistance (HOMA-IR) and β cell function (HOMA-%B) were calculated. A subsample of 3727 participants underwent an oral glucose tolerance test to obtain 2 h postload glucose levels. Population-weighted linear regression analysis was used to examine the association between sitting time and each cardiometabolic risk factor, stratified by sex, race, socioeconomic status and activity level. Analyses were controlled for demographics, socioeconomic status, survey cycle, personal and family medical history, diet and physical activity.

RESULTS

Sitting time was significantly associated with adverse levels of waist circumference, body mass index, triglycerides, HDL-C, insulin, HOMA-IR, HOMA-%B and 2 h postload glucose, but not with blood pressure or glucose level. In stratified analyses, sitting time was most consistently related to cardiometabolic risk factors among low and middle socioeconomic groups and for those who reported no weekly physical activity, but there were few differences between sex or race groups.

CONCLUSIONS

Self-reported sitting time was associated with adverse cardiometabolic risk factors consistently across sex and race groups in a representative US sample, independent of other risk factors. Excessive sitting warrants a public health concern.

Ethnic and sex differences in visceral, subcutaneous, and total body fat in children and adolescents

OBJECTIVE

This study investigated ethnic and sex differences in the distribution of fat during childhood and adolescence.

DESIGN AND METHODS

A cross-sectional sample (n = 382), aged 5-18 years, included African American males (n = 84), White males (n = 96), African American females (n = 118), and White females (n = 84). Measures for total body fat (TBF) mass and abdominal adipose tissue (total volume and L4-L5 cross-sectional area) for both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots were assessed by dual-energy X-ray absorptiometry and magnetic resonance image, respectively. Analyses of covariance (ANCOVAs) were used to determine ethnic and sex differences in TBF (adjusted for age) and ethnic and sex differences in SAT and VAT (adjusted for both age and TBF).

RESULTS

Age-adjusted TBF was greater in African Americans (P = 0.017) and females (P < 0.0001) compared with Whites and males, respectively. In age- and TBF-adjusted ANCOVAs, no differences were found in the SAT. The VAT volume was, however, greater in Whites (P < 0.0001) and males (P < 0.0001) compared with African Americans and females, respectively. Similar patterns were observed in SAT and VAT area at L4-L5.

CONCLUSIONS

The demonstrated ethnic and sex differences are important confounders in the prevalence of obesity and in the assignment of disease risk in children and adolescents.

Validity assessment of a portable bioimpedance scale to estimate body fat percentage in white and African-American children and adolescents

OBJECTIVE

The objective of the study was to determine accuracy of the Tanita SC-240 body composition analyser to measure paediatric percent body fat (%BF).

METHODS

Eighty-nine African-American and white 5-18-year-olds participated in this study. %BF was estimated by dual-energy X-ray absorptiometry (DXA) and by the Tanita SC-240.

RESULTS

Overall %BF was 33.5 ± 10.5% (Tanita SC-240) vs. 34.5 ± 8.7% (DXA). There was no significant difference between the two measures (P = 0.52, average error = -1.0%, average absolute error = 3.9%). The Tanita mean %BF estimates significantly differed from the DXA mean %BF in white boys (P = 0.001, Cohen's d = 0.40) and white girls (P = 0.006, Cohen's d = 0.48), but differences were of small effect. No differences in %BF estimates were found for African-American boys or girls.

CONCLUSIONS

In this sample, the Tanita SC-240 demonstrated acceptable accuracy for estimating %BF when compared with DXA, supporting its use in field studies.

Activity related energy expenditure, appetite and energy intake: potential implications for weight management

The aim was to investigate relationships between activity related energy expenditure (AREE), appetite ratings and energy intake (EI) in a sample of 40 male (26.4years; BMI 23.5kg/m(2)) and 42 female (26.9years; BMI 22.4kg/m(2)) participants. AREE was expressed as the residual value of the regression between total daily EE (by doubly labeled water) and resting EE (by indirect calorimetry). EI was measured using an ad libitum buffet meal and visual analogue scales measured subjective appetite ratings before and after the meal. AREE was divided into low, middle and high sex-specific tertiles. General linear models were used to investigate differences in appetite ratings and EI across AREE tertiles. Before the meal, males in the high AREE tertile had significantly lower desire to eat and lower prospective food consumption and higher feelings of fullness compared to those in the low tertile. Males in the middle tertile had significantly higher satiety quotients after the meal and lower EI compared to the other tertiles. No significant differences across tertiles were found in females. Sex differences in relationships between AREE, appetite ratings and EI may lead to differing patterns of EI and subsequent weight maintenance.

Body mass index versus waist circumference as predictors of mortality in Canadian adults

BACKGROUND

Elevated body mass index (BMI) and waist circumference (WC) are associated with increased mortality risk, but it is unclear which anthropometric measurement most highly relates to mortality. We examined single and combined associations between BMI, WC, waist-hip ratio (WHR) and all-cause, cardiovascular disease (CVD) and cancer mortality.

METHODS

We used Cox proportional hazard regression models to estimate relative risks of all-cause, CVD and cancer mortality in 8061 adults (aged 18-74 years) in the Canadian Heart Health Follow-Up Study (1986-2004). Models controlled for age, sex, exam year, smoking, alcohol use and education.

RESULTS

There were 887 deaths over a mean 13 (SD 3.1) years follow-up. Increased risk of death from all-causes, CVD and cancer were associated with elevated BMI, WC and WHR (P<0.05). Risk of death was consistently higher from elevated WC versus BMI or WHR. Ascending tertiles of each anthropometric measure predicted increased CVD mortality risk. In contrast, all-cause mortality risk was only predicted by ascending WC and WHR tertiles and cancer mortality risk by ascending WC tertiles. Higher risk of all-cause death was associated with WC in overweight and obese adults and with WHR in obese adults. Compared with non-obese adults with a low WC, adults with high WC had higher all-cause mortality risk regardless of BMI status.

CONCLUSION

[corrected] BMI and WC predicted higher all-cause and cause-specific mortality, and WC predicted the highest risk for death overall and among overweight and obese adults. Elevated WC has clinical significance in predicting mortality risk beyond BMI.

Adiposity in children and adolescents: correlates and clinical consequences of fat stored in specific body depots

The 2011 Pennington Biomedical Research Center's Scientific Symposium focused on adiposity in children and adolescents. The symposium was attended by 15 speakers and other invited experts. The specific objectives of the symposium were to (i) integrate the latest published and unpublished findings on the laboratory and clinical assessment of depot-specific adiposity in children and adolescents, (ii) understand the variation in depot-specific adiposity and related health outcomes associated with age, sex, maturation, ethnicity and other factors and (iii) identify opportunities for incorporating new markers of abdominal obesity into clinical practice guidelines for obesity in children and adolescents. This symposium provided an overview of important new advances in the field and identified directions for future research. The long-term goal of the symposium is to aid in the early identification of children and adolescents who are at increased health risk because of obesity and obesity-related conditions.

Abdominal obesity and mortality: The Pennington Center Longitudinal Study

The purpose of this study was to determine the association between visceral adipose tissue (VAT) and all-cause mortality. The sample included 1089 white men and women 18–84 years of age from the Pennington Center Longitudinal Study, a prospective cohort of participants assessed between 1995 and 2008, and followed for mortality until 31 December 2009. Abdominal VAT was measured at the L4–L5 vertebral level using computed tomography. There were 27 deaths during an average of 9.1 years of follow-up. Abdominal VAT was significantly associated with mortality after adjustment for age, sex and year of examination (hazards ratio (HR) 1.46; 95% confidence interval 1.05–2.05). The association was stronger after the inclusion of abdominal subcutaneous adipose tissue (SAT), smoking status, alcohol consumption and leisure-time physical activity as additional covariates (HR 1.74; 1.17–2.59). Limiting the sample to participants who were free of stroke, heart disease and cancer at baseline reduced the strength of the relationship slightly (HR 1.62; 1.07–2.47). Abdominal SAT was not associated with mortality, either alone or in combination with VAT and other covariates. The results support the assertion that abdominal VAT is an important therapeutic target for obesity reduction efforts.

Physical activity for obese individuals: a systematic review of effects on chronic disease risk factors

The purpose of this review was to determine the effectiveness of physical activity in improving chronic disease risk factors in obese individuals. A systematic review was conducted to identify randomized physical activity intervention studies reporting changes in risk factors among obese individuals published prior to March 2010. Studies included in the review were randomized trials of at least 10 weeks in duration, with a sample mean body mass index ≥ 30 kg/m(2) at baseline, and reporting a relevant risk factor (blood pressure, blood lipids, glucose/insulin or C-reactive protein). Forty-four studies met the inclusion criteria for this review. Overall, physical activity had no more than a modest effect on chronic disease risk factors in obese individuals. There was great heterogeneity in responses of risk factors across studies. In many studies it was difficult to determine the effect of physical activity, independent of changes in body mass consequent to the intervention. Obese individuals should be encouraged to undertake physical activity following general recommendations for weight loss and health. The degree to which physical activity is effective at lowering risk factor levels among high-risk obese individuals is not known.

Comparisons of leisure-time physical activity and cardiorespiratory fitness as predictors of all-cause mortality in men and women

OBJECTIVE

To examine the combined associations and relative contributions of leisure-time physical activity (PA) and cardiorespiratory fitness (CRF) with all-cause mortality.

DESIGN

Prospective cohort study. Setting Aerobics centre longitudinal study.

PARTICIPANTS

31,818 men and 10 555 women who received a medical examination during 1978-2002. Assessment of risk factors Leisure-time PA assessed by self-reported questionnaire; CRF assessed by maximal treadmill test. Main outcome measures All-cause mortality until 31 December 2003.

RESULTS

There were 1492 (469 per 10,000) and 230 (218 per 10,000) deaths in men and women, respectively. PA and CRF were positively correlated in men (r = 0.49) and women (r = 0.47) controlling for age (p < 0.001 for both). PA was inversely associated with mortality in multivariable Cox regression analysis among men, but the association was eliminated after further adjustment for CRF. No significant association of PA with mortality was observed in women. CRF was inversely associated with mortality in men and women, and the associations remained significant after further adjustment for PA. In the PA and CRF combined analysis, compared with the reference group "not meeting the recommended PA (< 500 metabolic equivalent-minute/week) and unfit", the relative risks (95% CIs) of mortality were 0.62 (0.54 to 0.72) and 0.61 (0.44 to 0.86) in men and women "not meeting the recommended PA and fit", 0.96 (0.61 to 1.53) and 0.93 (0.33 to 2.58) in men and women "meeting the recommended PA and unfit" and 0.60 (0.51 to 0.70) and 0.56 (0.37 to 0.85) in men and women "meeting the recommended PA and fit", respectively.

CONCLUSIONS

CRF was more strongly associated with all-cause mortality than PA; therefore, improving CRF should be encouraged in unfit individuals to reduce risk of mortality and considered in the development of future PA guidelines.

Influence of overweight and obesity on physician costs in adolescents and adults in Ontario, Canada

The study purpose was to perform an obesity cost-of-illness analysis for individuals living in the province of Ontario, Canada. The participants consisted of a representative sample of 25 038 adults and 2440 adolescents (aged 12-17 years) who participated in the 2000/2001 Canadian Community Health Survey (CCHS). The CCHS data set includes measures of body mass index (BMI) (classified as normal weight, overweight or obese) and relevant covariates (age, income, smoking, alcohol, physical activity). The CCHS data set was linked to the Ontario Health Insurance Plan providers' database to obtain physician costs for 2002-2003. A two-part modelling approach was used to calculate and compare the average annual physician cost according to BMI. After adjusting for the covariates, physician costs were not significantly higher in overweight men and women compared with those with a normal weight. Physician costs were 14.7% higher in obese men and 18.2% higher in obese women than in men and women with a normal weight. Average physician costs were comparable in normal-weight and overweight/obese adolescents ($233 per year in both groups). Because Ontario operates a publicly funded healthcare system, the findings of this study have relevance for other provinces/states and countries that operate similar healthcare systems.

International prevalence of physical activity in youth and adults

Understanding population prevalences of physical activity is important to develop benchmarks for current baseline levels to monitor future changes, and for making country/regional comparisons. The purpose was to review the global prevalence of physical activity levels among youth and adults. Standardized literature searches for articles about national prevalences of physical activity were conducted in PubMed. A total of 34 studies in adults and 28 studies in youth were deemed contemporary (1996 - present) and met the inclusion criteria for this review. Wide variability was present between countries in the prevalence of physical activity (as measured and defined by individual studies). Studies with the highest reported prevalences of physical activity were for men in Sweden (77%), women in Denmark (81%), 12- to 15-year-old boys in Australia (74%) and <12-year-old girls (75%) in China. The countries with the lowest reported prevalences of physical activity were men in Brazil (4%), women in Saudi Arabia (2%) and Thailand (2%), and 17- to 18-year-old boys (0%) and 17- to 18-year-old girls (0%) in Russia. The ranges of prevalence of physical activity, mode of data collection, and determination of meeting the physical activity threshold vary greatly between countries. However, the aggregation of these data can be a useful resource to practitioners, interventionists and epidemiologists.

Does the relationship between waist circumference, morbidity and mortality depend on measurement protocol for waist circumference?

There is currently no consensus regarding the optimal protocol for measurement of waist circumference (WC), and no scientific rationale is provided for any of the WC protocols recommended by leading health authorities. A panel of experts conducted a systematic review of 120 studies (236 samples) to determine whether measurement protocol influenced the relationship of WC with morbidity of cardiovascular disease (CVD) and diabetes and with mortality from all causes and from CVD. Statistically significant associations with WC were reported for 65% (152) of the samples across all outcomes combined. Common WC protocols performed measurement at the minimal waist (33%), midpoint (26%) and umbilicus (27%). Non-significant associations were reported for 27% (64) of the samples. Most of these protocols measured WC at the midpoint (36%), umbilicus (28%) or minimal waist (25%). Significant associations were observed for 17 of the remaining 20 samples, but these were not significant when adjustment was made for covariates. For these samples, the most common WC protocols were the midpoint (35%) and umbilicus (30%). Similar patterns of association between the outcomes and all WC protocols were observed across sample size, sex, age, race and ethnicity. Our findings suggest that WC measurement protocol has no substantial influence on the association between WC, all-cause and CVD mortality, CVD and diabetes.

Adiposity, physical fitness and incident diabetes: the physical activity longitudinal study

AIMS/HYPOTHESIS

The purpose of this study was to investigate the relationships among adiposity, physical activity, physical fitness and the development of diabetes in a diverse sample of Canadians.

METHODS

The sample included 1,543 adults (709 men and 834 women) from the Canadian Physical Activity Longitudinal Study who were free of diabetes at baseline (1988). Several indicators of adiposity (BMI, waist circumference, WHR, sum of skinfold thicknesses), musculoskeletal fitness (sit-ups, push-ups, grip strength, trunk flexibility), cardiorespiratory fitness (maximal metabolic equivalents [METs]) and leisure-time physical activity levels were measured at baseline. Participants were followed until 2002-2004 for the ascertainment of new cases of diabetes.

RESULTS

The 15.5-year cumulative incidence of diabetes was 5.0% (5.2% in men, 4.9% in women). Adiposity and physical fitness, but not physical activity, were significant predictors of diabetes after adjustment for age, sex and several covariates. For each standard deviation of the indicators of adiposity, the risk of diabetes was 99-194% higher. Conversely, the risk was 70 and 61% lower for each standard deviation of maximal METs and composite musculoskeletal fitness score, respectively. Receiver operating characteristic curve analyses confirmed that neither adiposity nor physical fitness provided a superior prediction of incident diabetes.

CONCLUSIONS/INTERPRETATION

Adiposity and physical fitness were both important predictors of the development of diabetes in this cohort of Canadians.

Putative contributors to the secular increase in obesity: exploring the roads less traveled

OBJECTIVE

To investigate plausible contributors to the obesity epidemic beyond the two most commonly suggested factors, reduced physical activity and food marketing practices.

DESIGN

A narrative review of data and published materials that provide evidence of the role of additional putative factors in contributing to the increasing prevalence of obesity.

DATA

Information was drawn from ecological and epidemiological studies of humans, animal studies and studies addressing physiological mechanisms, when available.

RESULTS

For at least 10 putative additional explanations for the increased prevalence of obesity over the recent decades, we found supportive (although not conclusive) evidence that in many cases is as compelling as the evidence for more commonly discussed putative explanations.

CONCLUSION

Undue attention has been devoted to reduced physical activity and food marketing practices as postulated causes for increases in the prevalence of obesity, leading to neglect of other plausible mechanisms and well-intentioned, but potentially ill-founded proposals for reducing obesity rates.

Aerobic fitness, body mass index, and CVD risk factors among adolescents: the Québec family study

PURPOSE

The purpose of this study was to examine the association of body mass index (BMI) and aerobic fitness on cardiovascular disease (CVD) risk factors in adolescents.

METHODS

The sample included 416 boys and 345 girls 9-18 y of age from the Québec Family Study. Participants were cross-tabulated into four groups using a median split of age-adjusted physical working capacity (PWC) and body mass index (BMI). Group differences in age-adjusted CVD risk factors (blood pressures, fasting total cholesterol (CHOL), LDL -C, HDL-C, HDL/CHOL, triglycerides, glucose, and a composite risk factor score) were examined by two-way ANOVA.

RESULTS

Several CVD risk factors showed significant main effects for PWC, BMI and/or the PWC by BMI interaction. In general, low fit males and females had higher blood lipids and glucose compared to their high fit counterparts within BMI categories although none of the differences reached statistical significance. The high fit/low BMI group showed the best CVD risk factor profile while the low fit/high BMI showed a poorer profile as evidenced by several significant differences between these two groups. Other significant differences occurred for various risk factors between groups.

CONCLUSION

Both aerobic fitness and BMI show an independent association with CVD risk factors in adolescents.

Comparison of overweight and obesity prevalence in school-aged youth from 34 countries and their relationships with physical activity and dietary patterns

The purposes of this systematic review were to present and compare recent estimates of the prevalence of overweight and obesity in school-aged youth from 34 countries and to examine associations between overweight and selected dietary and physical activity patterns. Data consisted of a cross-sectional survey of 137 593 youth (10-16 years) from the 34 (primarily European) participating countries of the 2001-2002 Health Behaviour in School-Aged Children Study. The prevalence of overweight and obesity was determined based on self-reported height and weight and the international child body mass index standards. Logistic regression was employed to examine associations between overweight status with selected dietary and physical activity patterns. The two countries with the highest prevalence of overweight (pre-obese + obese) and obese youth were Malta (25.4% and 7.9%) and the United States (25.1% and 6.8%) while the two countries with the lowest prevalence were Lithuania (5.1% and 0.4%) and Latvia (5.9% and 0.5%). Overweight and obesity prevalence was particularly high in countries located in North America, Great Britain, and south-western Europe. Within most countries physical activity levels were lower and television viewing times were higher in overweight compared to normal weight youth. In 91% of the countries examined, the frequency of sweets intake was lower in overweight than normal weight youth. Overweight status was not associated with the intake of fruits, vegetables, and soft drinks or time spent on the computer. In conclusion, the adolescent obesity epidemic is a global issue. Increasing physical activity participation and decreasing television viewing should be the focus of strategies aimed at preventing and treating overweight and obesity in youth.

Application of obesity treatment algorithms to Canadian adults

OBJECTIVE

The purpose of this study was to apply obesity treatment algorithms to a representative sample of Canadians to determine their potential impact on the population.

DESIGN

The Canadian Heart Health Surveys (1986-1992) were used to describe the prevalence of adults (18-64 y) that would be eligible for weight loss treatment according to the US NIH algorithm, which uses body mass index (BMI), waist circumference (WC), and the presence of two or more cardiovascular disease (CVD) risk factors. Similar algorithms based on CVD risk factors and a single measure of either BMI or WC alone were also evaluated.

RESULTS

Using the NIH algorithm, 24% of Canadians (28% men, 19% women) would be identified for weight loss treatment. Virtually, all subjects received the same treatment recommendations when using BMI and CVD risk factors only, while 22% (23% men, 21% women) would meet the criteria for treatment using WC and CVD risk factors only.

CONCLUSIONS

Approximately one in four Canadians would be eligible for weight loss treatment using the NIH obesity treatment algorithm. However, the algorithm may be improved through the incorporation of more sensitive WC thresholds.

Waist circumference percentiles for Canadian youth 11–18 y of age

OBJECTIVE

To develop age- and sex-specific waist circumference reference data for Canadian youth.

DESIGN

Cross-sectional population survey.

SETTING

1981 Canada Fitness Survey.

SUBJECTS

Nationally representative sample of 3064 youth (1540 boys and 1524 girls) 11-18 y of age.

INTERVENTIONS

Waist circumference was measured with a flexible anthropometric tape.

MAIN OUTCOME MEASURES

Smoothed and weighted 5th, 10th, 25th, 50th, 75th, 90th, and 95th waist circumference percentiles derived from LMS regression.

RESULTS

Waist circumference increases with age in both boys and girls, and boys have higher values of waist circumference than girls at every age and percentile level.

CONCLUSIONS

These reference data can be used to identify youth with an elevated risk of developing obesity-related disorders and can serve as a baseline for future studies of temporal trends in waist circumference.

SPONSORSHIP

This research was funded by the Heart and Stroke Foundation of Ontario (Grant #T4946).

Physical inactivity, excess adiposity and premature mortality

The purpose of this report is to review the evidence that physical inactivity and excess adiposity are related to an increased risk of all-cause mortality, and to better identify the independent contributions of each to all-cause mortality rates. A variance-based method of meta-analysis was used to summarize the relationships from available studies. The summary relative risk of all-cause mortality for physical activity from the 55 analyses (31 studies) that included an index of adiposity as a covariate was 0.80 [95% confidence interval (CI) 0.78-0.821, whereas it was 0.82 [95% CI 0.80-0.84] for the 44 analyses (26 studies) that did not include an index of adiposity. Thus, physically active individuals have a lower risk of mortality by comparison to physically inactive peers, independent of level of adiposity. The summary relative risk of all-cause mortality for an elevated body mass index (BMI) from the 25 analyses (13 studies) that included physical activity as a covariate was 1.23 [95% CI 1.18-1.29], and it was 1.24 [95% CI 1.21-1.28] for the 81 analyses (36 studies) that did not include physical activity as a covariate. Studies that used a measure of adiposity other than the BMI show similar relationships with mortality, and stratified analyses indicate that both physical inactivity and adiposity are important determinants of mortality risk.

Cardiorespiratory fitness is associated with diminished total and abdominal obesity independent of body mass index

OBJECTIVE

To determine whether, for a given body mass index (BMI), men and women with high cardiorespiratory fitness (HIGH CRF) have lower waist circumference (WC), sum of trunk skinfolds (SUM2) and sum of five skinfolds (SUM5), by comparison to those with LOW CRF.

DESIGN

Observational cohort study.

SETTING

1981 Canada Fitness Survey (CFS).

PARTICIPANTS

A total of 3719 men and 3854 women 20-59 y of age from the 1981 CFS for whom anthropometric and physical fitness measures were available.

MAIN OUTCOME MEASURES

BMI, waist circumference, skinfolds, cardiorespiratory fitness.

RESULTS

For a given BMI, men and women in the HIGH CRF group had lower WC, SUM2 and SUM5 by comparison to those with LOW CRF (P<0.001). A significant main effect for CRF group remained for SUM2 in both men (P=0.0001) and women (P=0.007), after statistical control for the effects of extremity fat. In women, but not men, there were significant interaction effects for WC (P=0.0023) and SUM5 (P=0.01), indicating that the difference between the LOW CRF and HIGH CRF groups increased with increasing BMI.

CONCLUSIONS

HIGH CRF is associated with lower levels of total and abdominal obesity for a given BMI by comparison to those with LOW CRF, independent of gender. This finding suggests a mechanism by which exercise attenuates the health risks attributed to obesity as measured by BMI. It is suggested that the routine measurement of WC and CRF would substantially improve the ability to identify those at health risk.

Adiposity, adipose tissue distribution and mortality rates in the Canada Fitness Survey follow-up study

OBJECTIVE

To compare mortality rates across indicators of adiposity and relative adipose tissue distribution in the Canadian population.

SUBJECTS

The sample included 10,323 adult participants 20-69 y of age from the Canada Fitness Survey who were monitored for all-cause mortality over 13 y.

METHODS

BMI, waist circumference (WC) and the sum of five skinfolds (SF5) were indicators of adiposity, and the first principal component of skinfold residuals (PC1) represented subcutaneous adipose tissue distribution. Proportional hazards regression was used to estimate relative mortality risk from mortality rates across levels of adiposity and adipose tissue distribution, controlling for the confounding effects of age, smoking status and alcohol consumption.

RESULTS

:Significant curvilinear (J-shaped) relationships in men and linear relationships in women were observed between BMI, WC and SF5 and all-cause mortality rates. PC1 was not related to mortality rates in either men or women. In women, the inclusion of the other indicators of adiposity and adipose tissue distribution did not significantly add to the prediction of mortality rates beyond BMI; however, combinations of BMI and both WC and SF5 produced significant models in men.

CONCLUSION

The results support the hypothesis that overall level of adiposity is an important predictor of all-cause mortality, more so than the relative distribution of subcutaneous body fat, once overall level of body fatness has been accounted for.

Temporal trends in overweight and obesity in Canada, 1981-1996

OBJECTIVE

To assess changes in the prevalence of overweight and obesity among Canadian children and adults between 1981 and 1996 using recent recommendations for the classification of overweight and obesity.

DESIGN

Epidemiological study comparing the prevalence of overweight and obesity from the 1981 Canada Fitness Survey (CFS) to the 1996 National Longitudinal Survey of Children and Youth (NLSCY) and the 1996 National Population Health Survey (NPHS).

SUBJECTS

Adults 20-64 y of age and children 7-13 y of age from the CFS, NLSCY and NPHS.

MEASUREMENTS

BMI was calculated from directly measured or self-reported body mass and height. For adults 20-64 y of age, overweight and obesity were defined as BMI > or = 25 kg/m2 and BMI > or = 30 kg/m2, respectively. Age- and sex-specific cut-off points for children that correspond to the adulthood categories were used to define overweight and obesity for children 7-13 y of age.

RESULTS

The prevalence of overweight increased from 48 to 57% among men and from 30 to 35% among women, while the prevalence of obesity increased from 9 to 14% in men and from 8 to 12% in women. The corresponding increases were from 11 to 33% in boys and from 13 to 27% in girls for overweight and from 2 to 10% in boys and from 2 to 9% in girls for obesity.

CONCLUSION

The results indicate dramatic increases in the prevalence of both overweight and obesity in Canada over the last 15 y, and the problem is particularly pronounced among children.

Spousal resemblance in the Canadian population: implications for the obesity epidemic

OBJECTIVE

To determine the extent of the spousal resemblance for adiposity and leanness in the Canadian population.

DESIGN

Cross-sectional population survey.

METHODS

The sample comprised parents and offspring from 1341 families (n=4023) of the Canada Fitness Survey. Indicators of adiposity included the body mass index (BMI) and the sum of five skinfolds (SF5). Both offspring and parents were ranked by their BMI and SF5 percentile position in the population using the entire Canada Fitness Survey database (n=15 818).

RESULTS

Pearson correlations indicated significant spousal resemblance for both BMI (r=0.14; P<0.0001) and SF5 (r=0.13; P<0.0001). However, the magnitude of the spousal correlations varied by the adiposity status of the offspring, with spousal correlations tending to be stronger in parents of lean or obese children and lower among parents of 'average' children. Bivariate histograms indicated that among lean (<or=5th percentile) and obese offspring (>or=95th percentile), the parental pairs tended to cluster among the lower and higher percentiles of adiposity, respectively.

CONCLUSIONS

There are spousal similarities in adiposity, particularly among parents of lean or obese offspring in the Canadian population. The degree to which these similarities are due to a loading of spouses with genes predisposing to obesity or a shared household environment cannot be determined from the present study. However, these results are compatible with the notion that genes and mutations predisposing to obesity are more prevalent among obese parents while those for pronounced leanness are more prevalent among lean parents.

Familial aggregation of 7-year changes in musculoskeletal fitness

The purpose of this study was to determine the degree of familial resemblance in baseline and 7-year changes in musculoskeletal fitness. Data from the 1981 Canada Fitness Survey and the Campbell's Survey 7-year follow-up were used. The sample consisted of 1264 people (635 males and 629 females) between the ages of 7 and 69 years for whom measurements of musculoskeletal fitness were available at baseline. A subsample of 834 people had measurements at both baseline and 7-year follow-up. Sit-and-reach trunk flexibility, number of push-ups without time limit, number of sit-ups in 60 seconds, and hand-grip strength were used as indicators of musculoskeletal fitness. The data were adjusted for the effects of age and body mass index (and baseline level of the variable for changes) by using regression procedures, and they were standardized to zero mean and unit variance within each of the four sex-by-generation groups (fathers, mothers, sons, and daughters). Familial correlation models were fitted to the data by using the computer software SEGPATH. The results indicate significant familial resemblance for all indicators of musculoskeletal fitness for baseline measures and 7-year changes. The heritabilities, or the percentages of the total variance attributable to heredity, were 64% for trunk flexibility, 37% for push-ups, 59% for sit-ups, and 48% for grip strength. Similarly, heritabilities for the change scores were 48% for trunk flexibility, 52% for push-ups, 41% for sit-ups, and 32% for grip strength. The results suggest that familial, and perhaps genetic, factors are important in explaining the variance in musculoskeletal fitness not only cross-sectionally but also for changes over time.

Familial aggregation of seven-year changes in blood pressure in Canada

OBJECTIVE

To determine the familial resemblance for baseline and seven-year changes in blood pressure in the Canadian population.

METHODS

The study participants were 857 people from 348 families in the 1988 Campbell's Survey, which was a seven-year follow-up of the Canada Fitness Survey. Systolic and diastolic blood pressures were measured at baseline and at follow-up, and were adjusted for age and body mass index by using regression analysis. Familial correlation models were fit to the data by using path analysis, and maximal heritabilities were calculated from the most parsimonious models.

RESULTS

There was significant familial resemblance for baseline blood pressure and changes in blood pressure. In general, all classes of familial correlations (spousal, parent-offspring and sibling) were significant and were of comparable magnitude. The maximal heritabilities, which are influenced to an unknown degree by genes and shared environmental factors, were 50% and 70% for diastolic and systolic blood pressures, respectively, and 66% and 41% for seven-year changes in diastolic and systolic blood pressures, respectively.

CONCLUSIONS

There is significant familial aggregation for blood pressure and for natural changes in blood pressure in the Canadian population. Genes may be important in explaining the familial resemblance for blood pressure; however, the presence of significant spousal correlations suggests that shared lifestyle and family environments are also important factors in the familial aggregation.