Deirdre M. Harrington

Anthropometric Correlates of Total Body Fat, Abdominal Adiposity, and Cardiovascular Disease Risk Factors in a Biracial Sample of Men and Women

OBJECTIVE To investigate associations between anthropometric measurements and total body fat, abdominal adipose tissue, and cardiovascular disease risk factors in a large biracial sample. PATIENTS AND METHODS This study is limited to cross-sectional analyses of data from participants attending a baseline visit between January 26, 1996, and February 1, 2011. The sample included 2037 individuals aged 18 to 69 years: 488 African American women (24%), 686 white women (34%), 196 African American men (9%), and 667 white men (33%). Anthropometry included weight; hip circumference; waist circumference; waist-hip, waist-height, and weight-height ratios; body adiposity index; and body mass index. Body fat and percentage of fat were measured by dual-energy x-ray absorptiometry, and abdominal visceral and subcutaneous adipose tissue were measured by computed tomography. Bivariate correlations, logistic regression models, and receiver operator characteristic curves were used, and analyses were stratified by sex and race. RESULTS In each sex-by-race group, all anthropometric measures were highly correlated with percentage of fat, fat mass, and subcutaneous adipose tissue and moderately correlated with visceral adipose tissue, with the exception of the waist-hip ratio. The odds of having an elevated cardiometabolic risk were increased more than 2-fold per SD increase for most anthropometric variables, and the areas under the curve for each anthropometric measure were significantly greater than 0.5. CONCLUSION Several common anthropometric measures were moderately to highly correlated with total body fat, abdominal fat, and cardiovascular disease risk factors in a biracial sample of women and men. This comprehensive analysis provides evidence of the linkage between simple anthropometric measurements and the purported pathways between adiposity and health.

Validation of MET estimates and step measurement using the ActivPAL physical activity logger

Abstract The purpose of this study was to determine the validity of the metabolic equivalent (MET) equation and step rate function of the ActivPAL™ physical activity logger in a group of females. Using a standard treadmill protocol, 62 females aged 15–25 years walked on a treadmill at speeds between 3.2 and 7.0 km · h−1 while wearing an ActivPAL. Oxygen consumption was measured using expired gas analysis at each speed and METs for each speed were estimated based on each participants own resting metabolic rate. A sub-set of 18 participants also wore an Actigraph. Results showed that the in-built equation in the ActivPAL significantly underestimated (P < 0.001) METs under treadmill conditions at higher intensities. The ActivPAL equation is based on step rate yet the relationship between counts and measured METs (r = 0.76; P < 0.001) is stronger than that between steps and measured METs (r = 0.59; P < 0.001). Both the ActivPAL and Actigraph step functions showed no significant difference (P > 0.05) to video recorded step rate except at the slowest walking speed where the Actigraph significantly underestimated steps (P < 0.05). The development of a new equation based on the counts–METs relationship that includes a variety of speeds and activities would be useful. The ActivPAL step function performs better than the Actigraph at the slowest walking speed under treadmill conditions.

The independent and combined associations of physical activity and sedentary behavior with obesity in adults: NHANES 2003‐06

To examine the combined influence of moderate‐to‐vigorous physical activity (MVPA) and sedentary behavior on obesity in US adults.

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.

Body adiposity index, body mass index, and body fat in white and black adults.

To the Editor: Body mass index (BMI) is widely used as a proxy for body fat and has been shown to correlate with other measures of adiposity.1 However, its use is limited by differences in body fatness for a given BMI across age, sex, and race.2–3 To address this limitation, Bergman et al. developed the body adiposity index (BAI) in samples of Mexican-Americans and blacks.4 However, no sex-specific information was provided, and it is unknown how well BAI performs in whites. We investigated the sex-specific relationship between both BMI and BAI and body fat in white and black adults.

Criterion and Concurrent Validity of the activPAL™ Professional Physical Activity Monitor in Adolescent Females

Background The activPAL has been identified as an accurate and reliable measure of sedentary behaviour. However, only limited information is available on the accuracy of the activPAL activity count function as a measure of physical activity, while no unit calibration of the activPAL has been completed to date. This study aimed to investigate the criterion validity of the activPAL, examine the concurrent validity of the activPAL, and perform and validate a value calibration of the activPAL in an adolescent female population. The performance of the activPAL in estimating posture was also compared with sedentary thresholds used with the ActiGraph accelerometer. Methodologies Thirty adolescent females (15 developmental; 15 cross-validation) aged 15–18 years performed 5 activities while wearing the activPAL, ActiGraph GT3X, and the Cosmed K4B2. A random coefficient statistics model examined the relationship between metabolic equivalent (MET) values and activPAL counts. Receiver operating characteristic analysis was used to determine activity thresholds and for cross-validation. The random coefficient statistics model showed a concordance correlation coefficient of 0.93 (standard error of the estimate = 1.13). An optimal moderate threshold of 2997 was determined using mixed regression, while an optimal vigorous threshold of 8229 was determined using receiver operating statistics. The activPAL count function demonstrated very high concurrent validity (r = 0.96, p<0.01) with the ActiGraph count function. Levels of agreement for sitting, standing, and stepping between direct observation and the activPAL and ActiGraph were 100%, 98.1%, 99.2% and 100%, 0%, 100%, respectively. Conclusions These findings suggest that the activPAL is a valid, objective measurement tool that can be used for both the measurement of physical activity and sedentary behaviours in an adolescent female population.

Television, adiposity, and cardiometabolic risk in children and adolescents.

BACKGROUND It is largely unknown how TV use relates to depot-specific adiposity or cardiometabolic risk in children. PURPOSE To examine relationships between having a TV in the bedroom and TV viewing time with total fat mass, abdominal subcutaneous and visceral adiposity, and cardiometabolic risk in children and adolescents. METHODS A cross-sectional study of 369 children and adolescents aged 5-18 years was conducted (2010-2011; analysis 2011-2012). Waist circumference; resting blood pressure; fasting triglycerides, high-density lipoprotein cholesterol [HDL-C] and glucose; fat mass by dual-energy x-ray absorptiometry; and abdominal subcutaneous and visceral adiposity by MRI were assessed. Cardiometabolic risk was defined as three or more risk factors including adverse levels of waist circumference, blood pressure, triglycerides, HDL-C, and glucose. Logistic regression analysis was used to compute ORs of high fat mass; subcutaneous and visceral adipose tissue mass (top age-adjusted quartile); and cardiometabolic risk, based on self-reported TV present in the bedroom and TV viewing time, controlling for age, gender, ethnicity, moderate-to-vigorous physical activity level, and unhealthy diet. RESULTS In multivariable models, presence of a TV in the bedroom and TV viewing time were associated with (p<0.05) higher odds of high waist circumference (OR=1.9-2.1); fat mass (OR=2.0-2.5); and subcutaneous adiposity (OR=2.1-2.9), whereas viewing TV ≥5 hours/day was associated with high visceral adiposity (OR=2.0). Having a TV in the bedroom was associated with elevated cardiometabolic risk (OR=2.9) and high triglycerides (OR=2.0). CONCLUSIONS Having a bedroom TV and TV viewing time were related to high waist circumference, fat mass, and abdominal subcutaneous adiposity. TV viewing time was related to visceral adiposity, and bedroom TV was related to cardiometabolic risk in children, controlling for moderate-to-vigorous physical activity and an unhealthy diet. REGISTRATION This study is registered at Clinicaltrials.govNCT01595100.

Cross-Sectional analysis of levels and patterns of objectively measured sedentary time in adolescent females

BackgroundAdolescent females have been highlighted as a particularly sedentary population and the possible negative effects of a sedentary lifestyle are being uncovered. However, much of the past sedentary research is based on self-report or uses indirect methods to quantity sedentary time. Total time spent sedentary and the possible intricate sedentary patterns of adolescent females have not been described using objective and direct measure of body inclination. The objectives of this article are to examine the sedentary levels and patterns of a group of adolescent females using the ActivPAL™ and to highlight possible differences in sedentary levels and patterns across the week and within the school day. A full methodological description of how the data was analyzed is also presented.MethodsOne hundred and eleven adolescent females, age 15-18 yrs, were recruited from urban and rural areas in the Republic of Ireland. Participants wore an ActivPAL physical activity monitor for a 7.5 day period. The ActivPAL directly reports total time spent sitting/lying every 15 seconds and accumulation (frequency and duration) of sedentary activity was examined using a customized MATLAB® computer software programme.ResultsWhile no significant difference was found in the total time spent sitting/lying over the full 24 hour day between weekday and weekend day (18.8 vs. 18.9 hours; p = .911), significantly more sedentary bouts of 1 to 5 minutes and 21 to 40 minutes in duration were accumulated on weekdays compared to weekend days (p < .001). The mean length of each sedentary bout was also longer (9.8 vs. 8.8 minutes; p < .001). When school hours (9 am-3 pm) and after school hours (4 pm-10 pm) were compared, there was no difference in total time spent sedentary (3.9 hours; p = .796) but the pattern of accumulation of the sedentary time differed. There were a greater number of bouts of > 20 minutes duration during school hours than after school hours (4.7 vs. 3.5 bouts; p < .001) while after school time consisted of shorter bouts < 20 minutes.ConclusionsSchool is highlighted as a particularly sedentary setting for adolescent females. Interventions to decrease sedentary time at school and the use of wearable devices which distinguish posture should be encouraged when examining sedentary patterns and behaviors in this population.

Relationship between abdominal fat and bone mineral density in white and African American adults

Several studies have documented relationships between adipose tissue and bone mineral density (BMD); however, the degree to which there are racial differences in this relationship is not known. The purpose of this study was to examine the relationships between abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) and BMD among white and African American adults. The sample included 330 white women, 328 African American women, 307 white men, and 116 African American men 18-74 years of age. Dual-energy X-ray absorptiometry scans were used to measure BMD and computed tomography scans were used to measure abdominal VAT and SAT. Linear regression was used to assess the relationships between abdominal adiposity and BMD and to explore possible sex and race differences in the associations. In the total sample as well as in all sex-by-race groups, VAT and SAT were negatively related to BMD, after adjustment for lean body mass (LBM) and several covariates. The VAT model (including covariates) explained 33.3% of the variance in BMD and the SAT model (including covariates) explained 32.7% of the variance in BMD. Being African American, being male, and having high LBM were all associated with higher BMD. Race and sex interactions were not significant, indicating that the relationships were similar across race and sex groups. In conclusion, BMD was inversely related to abdominal VAT and SAT in white and African American adults after adjustment for LBM.

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.