Fitness Measures and Health Outcomes in Youth (2012) / Chapter Skim
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4 Health-Related Fitness Measures for Youth: Body Composition
4 Health-Related Fitness Measures for Youth: Body Composition
Pages 79-110
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From page 79... ...
, an indicator of weight-for-height; waist circumference, an indicator of abdominal adiposity; and skinfolds, an indicator of subcutaneous adipose tissue. These three recommended field indicators of body composition for a national youth fitness survey uniquely measure different elements, and each can be linked to health markers and outcomes in both youth and adults.
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From page 80... ...
This approach should be used until evidence becomes available to support establishing waist circumference and skinfold cut-points by associating those measures with cardiometabolic risk factors. B ody weight (mass)
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From page 81... ...
. A variety of models and methods -- developed largely in adults -- have been used to partition body mass into several elements: fat-free mass, fat mass, total body water, fat-free dry mass, and bone mineral.
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From page 82... ...
is used for classification of weight status (underweight, normal, overweight, obese) , although it does not accurately predict percent body fat (Moreno et al., 2006)
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From page 83... ...
· Waist circumference increasingly is used as an indicator of central or abdominal adiposity rather than percent body fat, which can vary greatly among individuals with a similar BMI. Located in the abdominal region, abdominal fat is composed of three elements: visceral, retroperitoneal, and subcutaneous.
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From page 84... ...
BODY COMPOSITION IN YOUTH In addition to age, energy intake, and other factors, individual differences in biological maturation, gender, and race/ethnicity affect elements of body composition such as fat mass and fat-free mass, subcutaneous fat, and fat distribution. The following discussion is based on trends described in Malina (1996, 2005)
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From page 85... ...
. Fat mass as a percentage of body mass (percent body fat)
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From page 86... ...
. Ratios of skinfolds measured on the trunk to those measured on the extremities are commonly used to estimate relative subcutaneous fat distribution.
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From page 87... ...
African Americans have greater total bone mineral content during childhood, adolescence, and adulthood than whites. Comparisons between Mexican Americans and whites show small differences in fat-free mass and bone mineral content, although Mexican Americans tend to have greater adiposity.
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From page 88... ...
Fat-free mass also is highly correlated with height in children and adolescents. Fat mass and percent body fat are more variable, but excess fatness (absolute and relative)
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From page 89... ...
; with percent body fat, percent abdominal fat, and waist circumference in 8-year-old boys and girls (Stigman et al., 2009) ; and with BMI, skinfolds, and predicted percent body fat in obese children of both sexes aged 6-13 (Nassis et al., 2005)
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From page 90... ...
. The Bogalusa Heart Study, a longitudinal study investigating the risk factors for cardiovascular disease since 1972, provides many insights into the relationship between different measures of body composition and cardiovascular health in a biracial population (African American and white)
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From page 91... ...
Among children aged 9 and 15 from Denmark, Estonia, and Portugal, waist circumference and the sum of skinfolds were associated with clustered cardiovascular disease risk, determined by a composite score of systolic blood pressure, triglycerides, insulin resistance (using the homeostasic model assessment-insulin resistance [HOMA-IR] level)
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From page 92... ...
VALIDITY AND RELIABILITY OF SELECTED BODY COMPOSITION MEASURES By definition, field-based measurements such as skinfolds, BMI, and waist circumference are, to a large extent, indirect estimates of body composition. The advantages of field measures include minimal subject burden, adequate reliability in the hands of trained technicians (see more on quality control in Annex 4-1)
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From page 93... ...
Among youth aged 8-18 in the Fels Longitudinal Study, age-specific correlations between BMI and components of body composition ranged from 0.37 to 0.78 for percent body fat, 0.67 to 0.90 for fat mass, and 0.39 to 0.72 for fat-free mass in girls, and from 0.64 to 0.85 for percent body fat, 0.83 to 0.94 for fat mass, and 0.25 to 0.78 for fat-free mass in boys (Maynard et al., 2001)
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From page 94... ...
. Unlike other field measures, waist circumference may not be a good indicator of percent body fat or fatness in youth.
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From page 95... ...
A key is standard definition and location of the sites and proper marking of the sites prior to application of the skinfold calipers. As noted earlier, ratios of skinfolds measured on the trunk to those measured on the extremities are commonly used to estimate relative subcutaneous fat distribution, which has been related to chronic disease risk factors in youth.
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From page 96... ...
, identification of the correct level for measuring waist circumference, and identification of the correct sites for measuring the triceps and subscapular skinfolds. The level for measuring waist circumference and the sites for each skinfold measurement should be marked on the skin.
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From page 97... ...
This approach may be appropriate when test administrators must select one measure of body composition from multiple alternatives, such as when a battery of tests is applied in schools and other educational settings. Body Mass Index Cut-points for BMI have been calculated by age and gender from percentiles developed using the CDC growth charts based on data from large national surveys.
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From page 98... ...
, which are widely used internationally.2 Skinfolds The same U.S. national data used to develop growth charts for body weight and BMI were used to develop reference curves for the triceps and subscapular skinfolds for youth through age 19 (Addo and Himes, 2010)
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From page 99... ...
. A report describing suggested percentiles for British youth indicates that waist circumference was measured midway between the tenth rib and the iliac crest, but later in the paper, the authors indicate it was measured at the "natural waist" (McCarthy et al., 2001)
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From page 100... ...
This approach should be used until the necessary evidence becomes available to support establishing waist circumference and skinfold cut-points by associating those measures with cardiometabolic risk factors. The committee's full recommendation for including body composition in a national youth fitness survey is presented in Chapter 8.
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From page 101... ...
The height, weight, waist circumference, and triceps and subscapular skinfold measurement techniques described below are provided as examples from the commonly used NHANES Anthropometry Procedures Manual.5 Stature and Weight Stature, or standing height, is the linear distance from the floor or standing surface to the top (vertex) of the skull.
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From page 102... ...
Height and weight are used to derive body mass index (BMI)
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From page 103... ...
2008. Fitness, fatness and clustering of cardiovascular risk factors in children from Den mark, Estonia and Portugal: The European Youth Heart Study.
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From page 104... ...
2009. Risk factors and adult body mass index among overweight children: The Bogalusa Heart Study.
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From page 105... ...
2004. Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents.
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From page 106... ...
2009. Prevalence of pre-diabetes and its asso ciation with clustering of cardiometabolic risk factors and hyperinsulinemia among U.S.
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From page 107... ...
2002. Validity of body mass index compared with other body-composition screening indexes for the assessment of body fatness in children and adolescents.
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From page 108... ...
2004. Body fatness and clustering of cardiovascular disease risk factors in Portuguese children and adolescents.
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From page 109... ...
2000. Waist circumference and waist-to-height ratio are better predictors of cardiovascular disease risk factors in children than body mass index.
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From page 110... ...
1992. Body fatness and risk for elevated blood-pressure, total cholesterol, and serum-lipoprotein ratios in children and adolescents.
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