3.31.08 Body Composition

Describes the makeup of the human body into 2 components: FM and FFM.

FM
Must have a certain amount of fat on the body-essential fat: for the brain, mylin sheath, cells, etc. And stored fat.

FFM
Protein/muscle (21%)

Water (72%)
Mineral (7%)

The nutrient and health status of an individual can be estimated by the individual's body composition.

Obesity

1. A body wt. that exceeds by more than 20% the desirable level for a given age, gender, and skeletal frame. (NIH, 1985).

2. Overfat: An excess of body fat at which health risks begin to increase (HHS, 1988).
No #s associated with this definition.

3. Males > or = 25%
Females > or = 32%

Overweight

Body wt. above some standard of acceptable weight (10-20%) that is usually defined by relations to height, age, gender, and skeletal frame.

Obesity and Health Risks

1. Inc. risk of CVD (Heart disease and stroke)
2. Inc. risk of HBP (2.9 X more likely)
3. Inc. risk for High blood cholesterol (2.1 X)
4. Inc. risk of Type II diabetes (2.9 X)
5. Inc. risk of obstructive pulmonary disease (COPD, asthma, etc.)
6. Inc. risk of osteoarthritis in weight bearing and non-weight bearing parts.
7. Inc. risk of certain cancers.

Types of Obesity

1. Hyperplastic: creating additional fat cells.
2. Hypertrophic: existing fat cells get bigger.

1 function of a fat cell-store more fat/get bigger.

5 pts. that we see #1.

Infancy 0-1 year (F&M)
Puberty (F&M)
Pregnancy (F)
Menopause (F)
Morbid obesity (>70%) (F&M)
*Genetic potential of a fat cell to hold a certain amount of fat
*Cells split off and then get bigger.

Only lose fat by cells getting smaller-you keep the same # of fat cells.


Methods of Body Fatness &/or Health Risks

1. Weight-for-height tables
* Metropolitan Life Insurance Co. Tables
* 1959; revised 1983
*based on gender, height, weight, and skeletal frame size.
*frame size via
a. elbow breadth
b. ht.-wrist circumference ratio

r= height (cm)/ wrist cir. (cm)

ht. inches x 2.54

See Met Life table

Actual weight/upper # on your range = % you are over

<10% is normal risk

2. Body Mass Index:
(NOT % BF!!)

BMI: Weight (kg)/(height m)^2

Associated health risk:

BMI Vs. Health risk
<18.5% / Malnutrition, serious disease
18.5-24.9 / Healthy
25-30 / Overweight
>30 / Obese
>35-40 / Morbid Obesity

*Inc. risk for CVD
if:
Males: > or = 25
Females: > or = 25

Not accurate w/athletes
- muscle mass
-but for average American it is a good indicator of health

3. Waist to Hip Ratio (WHR)
Identify whether you tend to carry fat androidally or gynoidally

a. android
*male pattern
*apple
*abdominal fat
*assoc. with diabetes, CVD, HBP

b. gynoid
*female pattern
*pear shape
*hip, buttock, thigh fat
*No additional risk associated that android does
*very stable fat stores

Waist measured @ smallest circumferance
hip measured @ greatest circ. including buttocks
WHR: Waist/hip
*Inc. risk
Males: > or = .86
Females: > or = .95

4. Hydrostatic/Underwater weighing
*"Gold Standard" of BC

Assumed: Density of FFM= 1.1g/ml (not true)
Density of FM= .901g/ml (true)
Density of Water= 1 g/ml (true except in temperature changes)
Standard error= +/- 2-2.5%

5.BIA (Bioelectrical Impedence Analysis)
*Introduces electrical current through body from hand to foot, foot to foot, or hand to hand.

Muscle= 70% water (faster current, electrolyte full)
Adipose = 10% water (slower current, electrolyte empty)

Can estimate % BF based on speed of conduction
*Standard error = +/- 3-4% only if you adhere to the following:

No food or drink (including water) within 4 hours
No mod or vig exercise within 12 hours
No alcohol within 48 hours
No diuretics/caffine prior

6. Skinfold Measurements (SKF)
Estimates subcutaneous fat to extrapolate visceral stores
33% subcu
67% visceral
SKF formulas are specific to gender, ethnicity, and age
*Standard error = +/- 3%

Contraindications: Bloated female, pregnant female, after aggressive exercise.

7. Near infrared Reactance (NIR)
Introduce NI light to different body sites.

This light is absorbed differently depending on chemical composition (muscle vs. fat) can estimate % BF

All 9 sites used
*bicept was found to be most representative for both males and females
*correction factor for skin color (color wheel to match to bicept color)
*Standard error of >5%
Pg. 68 pkt. Body comp norms - KNOW THESE!!

Prevalence of Obesity:

35% of female adults
31% of male adults

~60% of US adults >25% BMI
33.4% of US adults are >20% ideal wt. (obese)

1962= 24.4%

Classified as Obese:
Anglo women: 32%
Hispanic: 47%
Black: 49%
This phenomenon is not seen in males

Causes of Obesity:

1. Genetics- 80% chance of being obese if both parents are (even in adopted children)
40% chance if one is obese
<10% chance if neither are

2. Energy Imbalance

Isocaloric diet
then + 100kcals of extra fat
97% will be stored as fat
3 used to convert dietary fat to adipose

+ 100kcals of extra CHO
74% stored as fat
26% used to convert dietary to adipose

+ 100kcals of extra Protein
24% used for digestion and absorption
? used to convert dietary protein into adipose
Rest stored