Chapter 6- Body Composition

Android obesity

individuals who store fat in the trunk or abdominal area ("apple" shaped)

Fat In the Human Body is Classified Into

Two groups: essential and nonessential fat

Underweight

BMI less than 18.5 (also has increased disease risk)

Air Displacement

Calculates body volume from the air displaced by an individual sitting inside a small chamber (Bod Pod) Body Volume is calculated by subtracting the air volume with the person inside the chamber from the volume of the empty chamber. Body density & body fat are then calculated from Body Volume. Standard Error of Estimate:+/- 2.2% and may be higher Considerations Takes about 15 minutes Consistently overestimates percent body fat More research required to determine accuracy

Techniques to Measure Body Composition

Dual-Energy X-ray Absorptiometry Hydrostatic weighing Air displacement Skinfold thickness Girth measurements Bioelectrical Impedance * It is important to use the same method(s) to assess changes in body composition for pre-test & post-test comparisons (different techniques may yield slightly different values).

Obese

Excessive accumulation of body fat and can be defined as a more serious degree of being overweight. BMI of 30+ FM greater than 39% and 25% in females and males ages 20-39, respectively.

Nonessential Fat

Fat above the minimal amount 10-22 percent for men, and 20-32 percent for women is considered satisfactory for good health. Functions: Insulator to retain body heat Energy substrate for metabolism Padding against physical trauma to the body Types/Locations: Visceral fat= wraps around inner organs (stored in upper body) Subcutaneous fat= below skin, distributed in hips & thighs Intramuscular fat= marble throughout muscles (like a steak)

Skinfold Thickness

Measures a double-thickness of skin at specific sites on the body (using skinfold calipers). A three-site procedure is commonly used: Women: triceps, suprailium and thigh Men: chest, abdomen and thigh Standard Error of Estimate: +/- 3.5% Considerations: Training is necessary to perform assessment accurately Measurements should be taken at the same time of day (a.m. is best) More research required to determine accuracy

Girth Measurements

Measures the circumference of specific body sites Women: upper arm, hip and wrist Men: waist, wrist Standard Error of Estimate:+/- 4.0% Considerations May not be valid for athletic individuals or those who appear visually thin or obese

Dual-Energy X-ray Absorptiometry (DXA)

Measures total body fat mass, fat distribution pattern & bone density. Uses very low-dose beams of x-ray. Standard of Error: +/- 1.8% Considered by many exercise scientists to be the standard technique for assessing body comp. Considerations: Is expensive & is not readily available to fitness participants. Takes less than 15 minutes to administer.

Bioelectrical Impedance

Sensors are applied to the skin and run a weak electrical current through the body to measure electrical resistance Used to estimate body fat, lean body mass, & body water Based on the principle that fatty tissue is a less-efficient conductor of an electrical current The easier the conductance, the leaner the individual Standard Error of Estimate: Percent body fat may be off by 10 percentage points or more Considerations: Accuracy of equations is questionable Hydration and body temperature affect results More research required to determine accuracy

Body Mass Index

Technique used to determine the thinness and excessive fatness that incorporates height and weight to estimate critical fat values at which the risk for disease increases Serves as a screening tool for disease risk Does not include actual fat and lean mass percentages Fairly reliable indicator of fatness for most, with exception of those with greater lean mass, bone density, & more muscle (e.g., some athletes) Second measure of fatness (e.g., Waist Circumference) provides greater clarity of risks BMI = Body Weight (lbs) x 705 ÷ (height in inches)2 Example Body Weight = 172 lbs Height = 67 inches BMI = 172 x 705 ÷ (67)2 BMI = 27

Overweight

The accumulation of non-essential body fat to the point that it adversely affects health BMI (body mass index) of 25 - 29.9 FM greater than 32% and for females and 19% males, aged 20-39, respectively.

Body Composition

The body's relative amount of fat-free mass (FFM) and fat mass (FM) and is generally expressed as a percentage of total body weight. FFM includes bones, muscles, ligaments, body fluids and other organs FM is limited to fat tissue

Essential fat

The minimal amount of fat necessary for normal physiological function 3% of total fat in Males 12% for females (sex specific fat required for energy requirements of pregnancy and lactation) Location (found within tissues): Muscles Nerve cells Bone marrow Intestines Heart Liver Lungs

Hydrostatic Weighing

Underwater weighing Most common technique used Most accurate technique available in fitness labs A person's "regular" weight is compared with underwater weight Fat is more buoyant than lean tissue, so comparing the two weights can determine body fat Almost all other indirect techniques have been validated against hydrostatic weighing Standard of Error: +/- 0.5% Considerations: Requires up to 30 minutes per person Residual lung volume should also be considered May be difficult for people who are aquaphobic.

Gynoid obesity

people who store fat primarily around the hips or thighs ("pear" shaped