Chapter4

Body CompositionBody Composition

Chapter 4

ObjectivesObjectives Define body composition and understand its relationship to

assessment of recommended body weight. Explain the difference between essential fat and storage fat. Describe various techniques used to assess body

composition. Be able to assess body composition using skinfold thickness

and girth measurements. Understand the importance of body mass index (BMI) and

waist circumference in the assessment of risk for disease. Be able to determine recommended weight according to

recommended percent body fat values and BMI. Learn how to measure body composition. Assess your risks for potential disease.

IntroductionIntroduction Body composition

Fat component Percent body fat

Nonfat component Lean body mass

Recommended body weight A fat distribution pattern that is not

associated with higher risk for illness. Best determined based on the percent of

body fat and lean tissue

IntroductionIntroduction Recommended body weight

A fat distribution pattern that is not associated with higher risk for illness.

Obesity Excess body fat, not based on

total weight. Some individuals are heavy

because of a large amount of muscle.

Some individuals are light but have a substantial amount of body fat.

Essential and Storage FatEssential and Storage Fat Total fat is determined by:

Essential fat Needed for normal physiologic function.

Found in muscles, nerve cells, bone marrow, intestines, heart, liver, and lungs.

Constitutes about 3% of body weight in men and about 12% of body weight in women

Storage fat Stored in Adipose tissue under skin and

around organs An insulator to retain heat. An energy substrate for metabolism. Padding against physical trauma to the body.

Typical Body Composition of Typical Body Composition of an Adult Man and Womanan Adult Man and Woman

Similar amounts of storage fat in men and women:

Men tend to store fat around the waist (“android").

Women tend to store fat around the hips and thighs (“gynoid").

Techniques to Assess Body Techniques to Assess Body CompositionComposition

Dual Energy X-ray Absorptiometry (DEXA) Uses very low-

dose beams of X-ray energy

Research and medical facilities

SEE ± 1.8 percent


Hydrostatic weighing Most common

technique A person's "regular"

weight is compared with a weight taken underwater

Drawbacks? SEE ± 0.5 percent


Air displacement Bod Pod Computerized

pressure sensors determine the amount of air displaced by the person inside the chamber.

Not population specific SEE ± 2.2 percent


Skinfold thickness Relation of

subcutaneous fat and total body fat

SEE ± 3.5 percent Should be taken by

the same technician and at the same time of day


Girth measurements Administered using a measuring tape to

assess the circumference of various body parts.

Women—the upper arm, hip, and wrist Men—the waist and wrist

May not be valid for athletic individuals or for people who can be classified visually as thin or obese.

SEE ± 4 percent

Body Fat Assessment Body Fat Assessment According to Girth According to Girth Measurements Measurements


Bioelectrical impedance Based on the principle that fat tissue is a

less efficient conductor than lean tissue of electrical current.

Accuracy is questionable 10 percentage points

Hydration and body temp can affect the results

Body Mass Index (BMI)Body Mass Index (BMI) Determine thinness and excessive

fatness Height and weight to estimate fat values

Most widely used measure to determine obesity and overweight Weight (lb.) x 705 ÷ Height (in.)2

Disease risk Lowest risk 22-25 range

Mortality Risk Versus Body Mortality Risk Versus Body Mass Index (BMI)Mass Index (BMI)

Body Mass Index (BMI)Body Mass Index (BMI) Compared with a BMI between 22-25:

Mortality rates for those with a BMI between 25 and 30 (overweight) are up to 25 percent higher.

Mortality rates for those with a BMI above 30 (obese) are 50 to 100 percent higher.

The risk for premature illness and death increases for individuals who are underweight.

Weakness of BMI cannot differentiate between muscle and fat

therefore doesn’t work well with athletes

Disease Risk According to Disease Risk According to Body Mass Index (BMI)Body Mass Index (BMI)

Overweight & Obesity Trends Overweight & Obesity Trends in the U.S., 1960-2006in the U.S., 1960-2006

Waist CircumferenceWaist Circumference Storage of fat affects disease risk

Android obesity Apple shape Fat around organs Higher risk for Heart disease,

Hypertension, Type 2 diabetes, and stroke

Gynoid obesity Pear shape

Measured at the level of the umbilicus

Visceral Fat Compared to Visceral Fat Compared to SBC or RTP Fat for Disease SBC or RTP Fat for Disease Risk Risk

Disease Risk from WC and Disease Risk from WC and BMIBMI

Body Composition Body Composition Classifications According to Classifications According to Percent Body FatPercent Body Fat

Determining Recommended Determining Recommended Body Weight Body Weight

EXAMPLE:Sex: Female FP: 30% (.30)Age: 19 years DFP: 22% (.22)

BW: 160 lbs.

1. FW = BW x %F FW = 160 x .30 = 48 lbs.

2. LBM = BW - FW LBM = 160 – 48 = 112 lbs.

Determining Recommended Determining Recommended Body Weight Body Weight FW: 48 lbs. BW: 160 lbs.LBM: 112 lbs. DFP: 22% (.22)

3. RBW = LBM ÷ (1.0 – DFP) RBW = 112 ÷ (1.0 - .22) RBW = 112 ÷ .78 = 144 lbs.

4. Desired Weight Loss (DWL) DWL = BW - RBW

DWL = 160 – 144 = 16 lbs.

Importance of Regular Body Importance of Regular Body Composition AssessmentComposition Assessment

Fat gain after 25 yrs 1 to 2 lbs weight

gain per year ½ lb lean tissue lost

per year Body composition

reassessment periodically because of the effects of negative caloric balance on lean body mass.

Real Life StoriesReal Life Stories

Real Life Stories Real Life Stories Critical Thinking Critical Thinking QuestionsQuestions

1. Can you identify what got Camille started on her weight-loss program? Was the starting point self- or environmentally determined? Discuss the pros or cons that got her going on her weight-loss program. How was the end point of the weight loss determined? List the benefits of her long-term approach to weight loss.

2. What weight-loss programs are likely to end up being just another “yo-yo diet”? Have you had any experiences with some of these methods; and if so, what were the results? What strategies are more likely to lead to permanent and sustainable weight loss?

3. Discuss the roles of aerobic exercise and strength training on weight management. Do you think strength training is a good idea for those who are trying to lose weight? Is it as important for women as for men?

Education

Chapter4