The Impact of Self-Reported Physical Activity Levels on the Prediction of Body Fatness from BMI in White and Black College Students

The purpose of this study was to test the hypothesis that self-reported physical activity (PA) levels quantified from the International Physical Activity Questionnaire (IPAQ) could be used to improve the prediction of percent body fat (%BF) measured by dual-energy X-ray absorptiometry (DXA) from body mass index (BMI), gender, and race in White and Black college students. A total of 278 students, aged 18 – 24 yr, volunteered to participate. There were 133 males (85 White and 48 Black) and 145 females (77 White and 68 Black). Total activity levels were quantified in MET-hours per week (MET-hrs•wk-1) using the IPAQ short form. Height and weight were measured and BMI values calculated (kg•m-2). Percent fat was assessed using DXA. Regression analysis was used to determine the impact of MET-hrs•wk-1 on the relationship between %BF and BMI, taking gender and race into account. The prediction sum of squares (PRESS) statistic was used to cross-validate the models. Mean (± SD) values were as follows: MET-hrs•wk-1 37.4 ± 21.9, %BF 24.5 ± 9.3%, and BMI 24.4 ± 4.1 kg•m-2. Percent body fat was significantly correlated with MET-hrs•wk-1 (r = -0.44, p \u3c 0.0001) and BMI (r = 0.38, p \u3c 0.0001). Stepwise regression analysis of a reduced model with BMI, gender and race produced an R2 value of 0.81 (root mean square error [RMSE] = 4.07). The full model with MET-hrs•wk-1 marginally improved the prediction of %BF (R2 = 0.83, RMSE = 3.87). When cross-validated, the corresponding PRESS statistic for the reduced and full model was 4.10 and 3.90, respectively. These results suggest that %BF can be predicted with greater precision and accuracy in a college-aged population when MET-hrs•wk-1 are included in addition to BMI, gender, and race

Development and Comparison of Two Field-Based Body Fat Prediction Equations: NHANES 1999-2004

International Journal of Exercise Science 5(3) : 223-231, 2012. Clinical guidelines define obesity in terms of excess body weight adjusted for height (i.e., bodymass index [BMI] categories) and/or gender-specific waist circumference (WC) cut-point values. Since body composition, particularly fat mass, is the most variable among individuals due to differences by gender, age, and race, and total percent body fat (%BF) can be estimated accurately using dual-energy X-ray absorptiometry (DXA), the purpose of this study was to develop and compare two field-based body fat prediction equations suitable for a nationally representative sample of the US adult population. Data were analyzed from subjects 20+ years of age (n = 11,907) with BMI and WC values, and that participated in DXA scans as part of the 1999-2004 National Health and Nutrition Examination Survey (NHANES). Multiple linear regression was used to develop and compare DXA-estimated %BF as the dependent variable versus BMI or WC, gender, age, and race as predictor variables. Mean values for age, BMI, WC, and %BF among the sample were 46.84 ± 0.30 years, 28.17 ± 0.11 kg/m2, 96.69 ± 0.27 cm, and 34.19 ± 0.14 %, respectively. Both equations were similar in terms of explained variance, with R2 values of 0.82 for the BMI and WC equations, respectively. Both equations are easy to use, and could easily be developed as an application on a smartphone or other handheld device, or simply integrated into a spreadsheet for use as an additional tool for health professionals to assess the current health status of individuals based on predicted body fat from BMI, WC, and demographics

Diet quality is positively associated with 100% fruit juice consumption in children and adults in the United States: NHANES 2003-2006

<p>Abstract</p> <p>Background</p> <p>One hundred percent fruit juice (100% FJ) has been viewed by some as a sweetened beverage with concerns about its effect on weight. Little regard has been given to the contribution of 100% FJ to diet quality.</p> <p>Methods</p> <p>In this study data from the 2003-2006 National Health and Nutrition Examination Survey were used to examine the association of 100% FJ consumption with diet quality in participants 2-5 years of age (y) (n = 1665), 6-12 y (n = 2446), 13-18 y (n = 3139), and 19+y (n = 8861). Two 24-hour dietary recalls were used to determine usual intake using the National Cancer Institute method. Usual intake, standard errors, and regression analyses (juice independent variable and Healthy Eating Index-2005 [HEI-2005] components were dependent variables), using appropriate covariates, were determined using sample weights.</p> <p>Results</p> <p>The percentage of participants 2-5 y, 6-12 y, 13-18 y, and 19+y that consumed 100% FJ was 71%, 57%, 45%, and 62%, respectively. Usual intake of 100% FJ (ounce [oz]/day) among the four age groups was: 5.8 ± 0.6, 2.6 ± 0.4, 3.7 ± 0.4, and 2.4 ± 0.2 for those in age groups 2-5 y, 6-12 y, 13-18 y, and 19+y, respectively. Consumption of 100% FJ was associated with higher energy intake in 6-12 y, 13-18 y, and 19+y; and higher total, saturated, and discretionary fats in 13-18 y participants. Consumption of 100% FJ was associated with higher total HEI-2005 scores in all age groups (< 0.0001). In 100% FJ consumers, total and whole fruit consumption was higher and intake of added sugars was lower in all age groups.</p> <p>Conclusions</p> <p>Usual intake of 100% FJ consumption exceeded MyPyramid recommendations for children 2-5 y, but was associated with better diet quality in all age groups and should be encouraged in moderation as part of a healthy diet.</p

Physical Activity is Associated with Percent Body Fat and Body Composition but not BMI in White and Black College Students

The objective of this study was to examine the association of self-reported physical activity (PA) with body composition in 290 college students (49% male, 60% White) 18-25 years of age. Outcome measures included: self-reported PA levels calculated in MET-hrs·wk-1 from the International Physical Activity Questionnaire (IPAQ); body mass index (BMI; in kg·m-2); and body composition variables estimated by dual-energy X-ray absorptiometry (DXA). Mean activity levels of the sample were 39.8 ± 23.8 MET-hrs·wk-1. Participants were divided into quartiles of PA levels: ≥0 to \u3c24.0, ≥24.0 to \u3c34.0, ≥34.0 to \u3c51.25, and ≥51.25 MET-hrs·wk-1 and body composition variables were compared by group. Chi-square analyses revealed a significant difference for gender by PA quartile [χ2 (3, N=290) = 32.42, p \u3c 0.0001], and for gender by race by PA quartile [χ2 (9, N=290) = 37.82, p \u3c 0.0001]. MET-hrs·wk-1 was inversely correlated with %BF (r = -0.40, p \u3c 0.0001) but not BMI (r = 0.05, p = 0.43). When comparing body composition variables across PA quartiles, no significant differences were observed for BMI; however, subjects in the highest quartile of PA had a lower percent body fat (%BF) and fat mass (FM), and a higher lean-tissue mass (LTM) compared to subjects in the other three groups. In this cohort of young adults, participants in the highest activity group had a more fit body composition profile (e.g., lower %BF, lower FM, and higher LTM) which was not reflected in BMI and was independent of gender and race

Endurance and Resistance Training Lowers C-Reactive Protein in Young, Healthy Females

The purpose of this study was to determine whether endurance (E) or endurance + resistance (ER) training affects C-reactive protein (CRP) and if these changes are related to alterations in fitness and (or) body composition in young females. Thirty-eight females (aged 18-24 years) were assigned to 1 of 3 groups: (1) E, (2) ER or (3) active control (AC). The E and ER groups completed 15 weeks of marathon training. The ER group performed additional resistance training and the AC group maintained their usual exercise routine. Primary outcomes were measured pre- and post-training and included anthropometric indices, dual-energy x-ray absorption metry, plasma CRP, time to complete 1.5 miles (in minutes), and upper and lower body strength tests (i.e., 8 repetition max on bench and leg press (ER group only)). There were no differences in any variable among the groups at baseline. After training, the E group decreased time to complete 1.5 miles (p \u3c 0.05). The AC group decreased percent and absolute body fat while the E group decreased percent body fat, absolute body fat, and android and gynoid body fat (p \u3c 0.05). The ER group significantly improved strength (p \u3c 0.001) and reduced plasma CRP from 2.0 ± 1.1 to 0.8 ± 0.3 mg ·L -1 (p = 0.03). No significant associations were observed between CRP and measures of body composition or aerobic capacity. Combined endurance and resistance training may be an effective modality for reducing plasma CRP in young adult females independent of changes in aerobic capacity or body composition