The Role of Energy Intake on Fitness-Adjusted Racial/Ethnic Differences in Central Adiposity Using Quantile Regression.

BACKGROUND: Energy intake (EI) is suggested to be associated with adiposity and may explain previously observed fitness-adjusted racial disparities in waist circumference (WC). OBJECTIVE: The purpose of this study was to comprehensively evaluate the role of EI on the fitness-adjusted racial/ethnic disparities in WC in a nationally representative sample of females using quantile regression. METHODS: Our sample consisted of 3874 female participants (aged 12 to 49 years) from the 1999-2004 National Health and Nutrition Examination Survey. The role of EI was assessed in separate analyses via estimation using a 24-hour dietary recall (DR) and the Institute of Medicine total daily energy expenditure equations. Age-stratified quantile regression models were used to estimate the differences in WC between minority groups and non-Hispanic (NH) white, adjusting for EI, CRF, age, and height. RESULTS: Results from the quantile regression analyses adjusting for EI via DR showed significant differences in WC between NH black and NH white at the 25th-90th WC percentiles (5.9-11.1 cm) for females 20-49 and at the 90th WC percentile (10.1 cm) for females 16-19. For females 12-15, no significant differences were observed between NH black and NH white. Analyses adjusting for EI via IOM showed significant differences in WC between NH black and NH white only for females aged 20-49 years, at the 50th and 75th percentile (1.7-3.6 cm). Compared to NH White, Mexican American females, in all age groups, tended to have significantly greater WC. CONCLUSIONS: These results highlight the importance of rigor in energy intake assessments, suggesting that EI, if adequately assessed, may explain a substantial part of the racial/ethnic differences in WC between NH black and NH white females. Additionally, the observed persistence of estimated differences in WC with advancing age suggests other factors (e.g., hormones) may play a role.

Physical and Social Contexts of Physical Activity Behaviors of Fifth and Seventh Grade Youth.

BACKGROUND: The purpose of this study was to characterize the temporal, social, and physical contexts for physical activities commonly reported in a diverse cohort of 753 boys and girls from fifth to seventh grade. METHODS: Data were obtained from a multilevel longitudinal study, the Transitions and Activity Changes in Kids. The Physical Activity Choices instrument assessed previous 5-day participation in specific physical activities and their temporal, social, and physical contexts. Mixed model repeated measure analyses of variance and multinomial analyses examined sex differences and change over time. RESULTS: Fifth grade boys and girls reported participation in similar activities at similar frequencies, which declined significantly by seventh grade. One temporal pattern, playing with younger children, changed over time from "both inside/outside" to "outside" school. Boys and females reported more activities performed in class/team groups over time. Most activities took place primarily at home for all participants in both grades. CONCLUSIONS: Boys and girls reported declines in the variety and frequency of activities from fifth to seventh grade. There were sex-specific patterns in physical activities and groups; however, all participants reported home as the primary location and a shift to class/team groups over time. Schools are well-positioned to provide additional physical activity opportunities.

Maternal inactivity: 45-year trends in mothers' use of time.

OBJECTIVE: To examine 45-year trends in time use and physical activity energy expenditure (PAEE) in a nationally representative sample of US mothers. PARTICIPANTS AND METHODS: We quantified time allocation to physical activity (PA), sedentary behaviors (SED), and PAEE from 1965 to 2010 in mothers with older children (MOC) (>5 to ≤18 years) and mothers with younger children (MYC) (≤5 years). Physical activity was the sum of time allocated to housework, child care, laundry, food preparation, postmeal cleanup, and exercise. Sedentary behavior was the sum of time spent in a vehicle and using screen-based media. Physical activity energy expenditure was calculated using body weights from national surveys and metabolic equivalents. RESULTS: From 1965 to 2010, the time allocated to PA decreased by 11.1 h/wk (from 32.0 to 20.9 h/wk) in MOC and by 13.9 h/wk (from 43.6 to 29.7 h/wk) in MYC. The time spent in SED increased by 7.0 h/wk in MOC (from 17.7 to 24.7 h/wk) and increased by 5.7 h/wk in MYC (from 17.0 to 22.7 h/wk). Physical activity energy expenditure decreased by 1237.6 kcal/wk (176.8 kcal/d) in MOC (from 5835.3 to 4597.7 kcal/wk), and in MYC, PAEE decreased by 1572.5 kcal/wk (224.6 kcal/d), from 7690.5 to 6118.0 kcal/wk. CONCLUSION: There was a significant reallocation of time by mothers from PA (eg, housework) to SED (eg, watching television) between 1965 and 2010. Given the essential role of PA for health and the potential for the intergenerational transmission of obesity and obesogenic behaviors, these results suggest that maternal inactivity may be an important target for the primary prevention of chronic noncommunicable diseases and obesity.