Illinois State University Introduction to Body Composition Chapter 1

Illinois State University Exercise and Body Composition l Body composition refers to the substances that make up the body. l This includes more than just fat.

Illinois State University Exercise and Body Composition l The major components of the body for this class are: –Muscle mass (protein) –Bone mass (mineral) –Fat mass –Water volume –Known as the 4-C molecular level model

Illinois State University Why do we measure body composition? l Health l Performance l Insurance

Illinois State University Reasons for Assessing Body Composition* l To identify a client’s health risk associated with excessively low or high levels of total body fat. l To promote a client’s understanding of health risks associated with too little or too much body fat.

Illinois State University Reasons for Assessing Body Composition l To monitor changes in body composition that are associated with certain diseases. l To assess the effectiveness of nutrition and exercise interventions in altering body composition.

Illinois State University Reasons for Assessing Body Composition l To estimate a healthy body weight for a client. l To formulate dietary recommendations and exercise programs.

Illinois State University Reasons for Assessing Body Composition l To monitor growth, development, maturation, and age-related changes in body composition. (Heyward and Wagner, 2004)

Illinois State University Why we do not measure BC? l Grading purposes l Stereotyping l Labeling l Criticism

Illinois State University Key Terms l Adipose tissue l Body density l Body mass l Body volume l Densitometry l Dual-energy X-ray absorptiometry l Essential lipids l Fat-free body density l Fat-free mass l Fat mass l Healthy body weight l Hydrometry l Lean body mass l Nonessential lipids

Illinois State University Key Terms l Reference method l Percent body fat l Total body bone mineral l Total body mineral l Total body water

Illinois State University Exercise and Body Composition l Key terms related to fatness: –Overweight and underweight –Weight loss and fat loss –Overfat and underfat –Obese

Illinois State University Key Terms l Obesity may be defined as an excessive amount of body fat relative to body weight.

Illinois State University Assessment of Body Composition l Mirror l Fit of Clothes l Social Feedback l Weight

Illinois State University Anthropometric Techniques l Height vs Weight l Body mass index (BMI) = kg/m 2 l Girth and breadth - circumferences l Skinfold measurements

Illinois State University Body Comp Assessment l Hydrostatic (underwater) weighing. l Bioelectrical Impedance Analysis l Air-Displacement Plythesmography (Bod Pod).

Illinois State University Body Comp Assessment l Computer assisted tomography

Illinois State University Body Composition l Most methods estimate percent body fat from body density. l Most body density estimations are drawn from a relatively small population of cadavers.

Illinois State University Exercise and Body Composition l Metropolitan Life Insurance Tables –Used to establish insurance premium –Based on relationship between height and weight.

Illinois State University Body Composition Models l See Fig 1.1

Illinois State University Exercise and Body Composition l The traditional two-component model of body composition defines the body in terms of its adipose tissue (AT) and lean body mass (LBM).

Illinois State University Exercise and Body Composition l The LBM includes essential lipids associated with the brain, nerves, membranes, etc.

Illinois State University Exercise and Body Composition l This model was refined into another two-component model based on fat mass (FM) and fat free mass (FFM). –Referred to as 2-C molecular level model

Illinois State University Exercise and Body Composition l The fat includes all extractable lipids contained in both adipose tissue and the other tissues, and the residual is the fat free mass.

Illinois State University Exercise and Body Composition l A three-component model was then developed with the added component being total body water. –Referred to as the 3-C water molecular level model.

Illinois State University Exercise and Body Composition l A problem with all of these models was that one had to make assumptions about bone mineral and protein stores in the body.

Illinois State University Exercise and Body Composition l These assumptions included that bone has a density of about 3.0 gm/ml, compared with about 1.0 gm/ml for body water, about 1.34 for body protein, and about 0.9 for fat.

Illinois State University Exercise and Body Composition l Potential problems?

Illinois State University Models l This has led to the 4-C molecular level model being the desired model for research purposes –Fat –Mineral (Bone) –Protein (Muscle) –Water

Illinois State University Models l However, most assessment still rely on the 2-C molecular level model because it is difficult to measure the components of the 4-C model.

Illinois State University 2-C Model l The two most common 2-C models rely on estimating percent fat from body density.

Illinois State University 2-C Models l The 1963 Brozek model uses: %BF = (4.57/Db ) x 100

Illinois State University 2-C Models l The 1956 Siri model uses: %BF = (4.95/Db ) x 100

Illinois State University 2-C Models l The major difference between the models is: –In the Brozek model, any variation in measured Db from the reference body density is assumed to be due to a difference in obesity (adipose tissue).

Illinois State University 2-C Models l In the Siri model, any variation in measured Db from the reference body is due to a difference in triglyceride content instead of adipose tissue.

Illinois State University 2-C Models l However, they both yield nearly identical %BF estimates (varying by only % BF) for densities ranging from to g/cc.

Illinois State University 2-C Models l For individuals with more than 30% BF, the Siri equation gives relatively higher body fat estimates than the Brozek equation.

Illinois State University 2-C Models l Both rely on the following assumptions: –The densities of the fat and the fat-free body components (water, mineral, and protein) are additive and are the same for all individuals –The proportions of water, mineral, and protein in the LBM or reference body are constant within and between individuals

Illinois State University Assumptions l The individual being measured differs from the reference body only in the amount of body fat (triglyceride) or obesity (adipose) tissue.

Illinois State University Fat-Free Body Composition ComponentDensity Fat-free body Reference body (g/cc) (%) (%) Water Mineral Protein Fat-free body Fat Reference body From Table 1.3

Illinois State University Body Density l Density has traditionally been defined as 1.10 gm/ml. l In young African American males, some studies have shown it to be gm/ml. l 8-10 yr old ~ gm/ml.

Illinois State University 2-C Model Problems l If you deviated from the reference cadaver, the ability to predict your percent body fat diminished. See Table 1.4 (p. 9) for specific equations

Illinois State University Which technique should be used? l Purpose of assessment. l Accuracy required. l Time required. l Availability of equipment. l Training of personnel. l Expense.

Illinois State University Which technique should be used? l At present, experts agree that a multi- component approach should be used whenever possible, especially for development and validation of body composition methods and prediction equations.

Illinois State University Standards for Comparison l Vary greatly depending on the source l See Table 1.2 for percent body fat standards for adults, children, and physically active adults.

Illinois State University Overweight and Obesity (BMI) III> 40 II I Obesity Overweight Normal Weight <18.5Underweight Obesity ClassBMI (kg/m 2 ) WHO 1998

Illinois State University Standards of Fatness MenWomen Underfatness<3<12 Essential Fat312 Optimal Health Overfatness Obesity>25>35

Illinois State University Current Body Wt Goal % Fat* Goal % LBM* Current % Fat* Current Fat Wt Current LBM Target Body Wt 1 * % is expressed as a decimal. Divide by 100 before entering the data. X  by minus Computing Target Wt assuming all wt. Loss is fat Fill in boxes with double lines and compute others