Body Composition

Why isn't hydrostatic weighing a gold standard now?

-Density of nonfat compartment varies as a function of age, sex and racial group. - So a nonfat density of 1.10 g/ml is not universally applicable.

Criticism of BMI. What is a better predictor?

-Doesn't differentiate body composition. -Waist circumference / Waist-Hip ratio.

What is the four-component model?

-Fat -Protein -Minerals -Water

Define essential fat.

-Fat that is required for normal physiological functioning - structural components of cell membranes, required for the synthesis of certain hormones, transport of fat-soluble vitamins,etc.

Define storage fat.

-Fat that is stored in adipose tissue for energy supply purposes. It is located underneath the skin, in the abdominal cavity, and around certain organs.

Define fat-free mass.

-Fat-free mass is primarily composed of bone, muscle, vital organs, and connective tissue.

What is NEAT?

-Non-exercise activity thermogenesis. -Energy expended by physical activities other than planned exercise.

What are the causes of the obesity epidemic?(6 points)

-Too much food, too little activity. The human body is set up to deal with scarcity. -Decreased physical activity. -Increased consumption of calories. -Social environment (advertising). -Biology (genetics). -Possibly Viruses, still being researched.

Bioelectrical Impedance Analysis (2 points).

-Used to measure the electrical resistance of the body, and through that, fatness. -Impedance is greater in adipose tissue (14 - 22% water) than in bone and muscle (71 - 75% water).

What are the changes associated with aging in a prosperous, industrialized society? (3 points)

-increased fat mass -decreased muscle mass - sarcopenia -decreased bone mass

Near-Infared Interactance (2 points).

-the degree of infrared light absorbed and reflected is related to the composition of the tissues. Optical densities are linearly related to subcutaneous and total body fat. -The biceps is the best single site for estimating body fat using this method.

Other procedures for body composition (6 points).

1. Dual energy X-ray absorptiometry - widely used for performing bone mineral density measurements 2. Total body water - hydrometry 3. Ultrasound 4. Magnetic resonance imaging 5. Computerized tomography 6. Total body potassium

Describe the O-Scale system. (3 points)

A-Rating - Adiposity or "fatness" rating W-Rating - Proportional weight rating used as an indicator of musculoskeletal development. Stanine Scale - A and W ratings are made by comparing the sum of skinfolds/proportional weight to a normalized distribution using this scale.

What are the two common techniques for assessing body composition?

Direct methods - chemical analysis of human cadavers Indirect methods - noninvasive techniques used on living persons

Define Body composition.

-Body composition - two-component model - the amount of fat and fat-free mass of which the body is composed.

Define male and female type obesity.

"Male type" obesity - excess fat is deposited on the upper torso and around the abdomen. Male type obesity is associated with higher health risks (apple shape). "Female type" obesity - excess fat is deposited below the waist in the thighs, hips, and buttocks (ie) pear shape. After menopause females begin depositing more fat in the abdominal area

CPAFLA Method requires the consideration of what 3 indicators (body weight, adiposity and fat distibution)?

(1) Body mass index - is the subject overweight? (2) Sum of 5 skinfolds - triceps, biceps, subscapular, iliac crest, and medial calf. Is the subject over-fat? (3) Waist girth - is the subject high in visceral adiposity - male type obesity?

Assumptions using skinfold measurements?(5 points)

(1) Constant densities in a two-compartment model (2) Proper identification of measurement site and proper measurement technique (3) Constant compressibility of the skinfold (4) Fixed adipose tissue patterning (5) Fixed proportion of internal to external fat

What are the two types of body composition prediction equations?

(1) Population specific equations - developed from relatively small, homogeneous (age, sex, state of training, fatness) samples. Their application is limited to that subsample. Example - Sloan, Yuhasz (2) Generalized equations - developed from large, heterogeneous samples. These equations have a wider application in terms of age, and fatness. Example - Jackson and Pollock, Durnin & Womersley, Peterson, Wang

What do the assumptions the percent body fat equations make? (2 points)

(1) The human body has two compartments - fat and nonfat (2) Each of these compartments has densities which are known constants.

What are the criticisms of height-weight tables?

(1) These tables do not consider body composition. (2) Most of the data in the 1983 Metropolitan Life Insurance Height-Weight tables comes from white, middle-class, U.S. adults age 25 to 59 years. This is not a representative sample of the general North American population. (3) No accepted method has been devised for determining frame size.

What are the two ways to use fatfolds?

(1) Use the sum of a number of skinfolds as an indication of relative fatness among individuals. Also compare "before" and "after" in the same individual. (2) Use fatfolds in conjunction with equations or tables to predict percent body fat.

Define Anthropometry.

- Quantitative measures of selected human landmarks.

Why assess body composition? (5 points)

- Suitable body composition is important for health. - Establish reasonable fatness ranges for athletes in various sports - Accurate measures of body composition are needed to develop sound weight reduction programs - Knowledge of bone mineral content in women and children is important. - Monitor changes in body composition associated with disease.

Define BMI.

Body Mass Index (BMI) - used as an indicator of obesity. This index uses the body mass (kg) divided by the height (meters) squared. BMI less than 18.5 = underweight BMI of 25.0 to 29.9 = overweight BMI of 30 or higher = obese

Average male vs. average female

The average male is taller, heavier, has a larger muscle mass, and a lower total body fat content. Female has sex specific fat depots in the breasts, pelvic and thigh regions, and probably other areas.

What is the rationale behind skinfold measurements?

a relationship exists between the fat located in the depots directly beneath the skin and internal body fat and body density.

What are the functions of adipose tissue?

adipose tissue is not simply a passive storehouse for fat, but an endocrine organ that secretes more than a dozen peptide and non-peptide compounds that trigger changes throughout the body. When fat cells expand they release more of some of these compounds and less of others. ex. leptin