Chapter
6
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What Is Body Composition and Why Is It Important?
 Assessing Body Mass Index,
Body Composition, and Body Fat
 Setting Body Composition Goals
 Making Changes in Body Composition

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
The human body is
divided into fat-free
mass and body fat
 Fat-free mass is body’s
nonfat tissues
▪ Bone, water, muscle,
connective tissue, organ
tissues, and teeth
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
Body fat includes essential
and adipose tissues
 Essential fat: Fats incorporated in
various tissues of the body, critical
for normal body functioning
 Adipose tissue: Tissue in which fat is stored
 Subcutaneous fat: Fat
located under the skin
 Visceral fat: Fat located around major
organs; also called intra-abdominal fat
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SOURCE: Adapted from Brooks, G A, et al
2005 Exercise Physiology: Human
Bioenergetics and Its Applications, 4th ed New
York: McGraw-Hill
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
Most important consideration: proportion
of body’s total weight that is fat
 Percent body fat: The percentage of
total body weight that is composed of fat
 Overweight: Body weight that falls
above the recommended range for
good health; sometimes defined as a
body mass index between 25 and 299
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 Obesity: Severely overweight,
characterized by an excessive accumulation
of body fat; may also be defined in
terms of some measure of total body
weight or a body mass index of 30 or more
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
Prevalence of obesity increased
from 13% in 1960 to 35% today
 68% of adult Americans overweight
 About 35.5% of men and 35.8% of women
obese, according to the latest statistics
 By 2015, estimates are that 75% of adults
will be overweight and 41% will be obese
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
Possible explanations:
 More sedentary work and leisure activities
 Fewer short trips on




foot and more by automobile
Fewer daily gym classes for students
More meals eaten outside the home
Greater consumption of fast food
Increased portion sizes, and
more soft drinks and convenience foods
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SOURCE: Centers for Disease Control and Prevention and the National: enter for
Health Statistics 2011 2007–2010 National Health and Nutrition Examination Survey
(NHANES) Hyattsville, Md: National Center for Health Statistics
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SOURCE: Flegal, K M, et al 2012
Prevalence of obesity and trends in
the distribution of body mass index
among US adults, 1999–2010
Journal of the American Medical
Association 307(5): 491–497
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
Metabolic syndrome: Cluster of
symptoms present in many overweight
and obese people that greatly increases
their risk of heart disease, diabetes, and
other chronic illnesses; symptoms include
insulin resistance, abnormal blood fats,
abdominal fat deposition, type 2
diabetes, high blood pressure, high blood
glucose, and chronic inflammation
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
Chronic inflammation: A
response of blood vessels to
such harmful substances as germs,
damaged cells, or irritants;
can lead to heart disease, cancer,
allergies, and muscle degeneration
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
Distribution of body fat is an
important indicator of health
 Apple shape versus pear shape
 Abdominal fat is more easily mobilized and
sent into bloodstream, increasing diseaserelated blood fat levels
 Waist circumference helps assess risks
of unhealthy body fat distribution
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Too much body fat makes physical
activity difficult
 Overfat people are less fit than others
and lack muscular strength,
endurance, and flexibility that make
normal activity easy

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Being perceived as
fat can be a source of
ridicule, ostracism and
can contribute to
psychological problems
 The popular image
of the “ideal” body
has changed greatly
in the past 50 years

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
Health experts
generally view too
little body fat as a
threat to health
 Too little for women:
less than 8 to 12%
 Too little for men: less
than 3 to 5%
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 Amenorrhea: Absent or infrequent
menstruation, sometimes related
to low levels of body fat and excessive
quantity or intensity of exercise
 Female athlete triad: A condition
consisting of three interrelated disorders:
abnormal eating patterns (and excessive
exercising) followed by lack of menstrual
periods (amenorrhea) and decreased
bone density (premature osteoporosis)
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
Body mass index (BMI): Measure
of relative body weight correlating
highly with more direct measures of
body fat, calculated by dividing
total body weight (in kilograms) by
the square of body height (in meters)
 BMI between 18.5 and
24.9 considered healthy
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
Underwater Weighing
 Individual submerged
and weighed under water
 Percentage of fat and fat-free
weight calculated from body density

The Bod Pod
 Small chamber containing
computerized sensors measures
body composition by air displacement
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
Skinfold Measurements
 Typically involves measuring thickness of
skinfolds at different places on the body
 Caliper: A pressure-sensitive measuring
instrument with two jaws that can be
adjusted to determine thickness
 Important to test exact sites, to
measure several different times,
and to take measurements at
approximately the same time of day
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
Bioelectrical Impedance Analysis (BIA)
 Works by sending a small electrical
current through the body and
measuring the body’s resistance to it

Advanced Techniques: DEXA and TOBEC
 DEXA works by measuring
tissue absorption of highand low-energy X-ray beams
 TOBEC estimates lean body mass by
passing a body through a magnetic field
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Waist circumference
measurement and waist-to-hip
ratio calculation easiest to perform
 Total waist measurement more than
40 inches for men and 35 inches for
women and a waist-to-hip ratio above
0.94 for young men and 0.82 for young
women are associated with increased
risk of heart disease and diabetes

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Endomorphs are round and pear
shaped, with wide hips and shoulders
 Mesomorphs are lean and muscular
and respond well to exercise
 Ectomorphs are thin and linear,
with narrow hips and shoulders

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If assessment tests indicate that
fat loss would be beneficial, first
step is to establish a realistic goal
 Be sure your goal is realistic
and will ensure good health

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
If you are overfat or have known
risk factors, consult a physician to
determine a body composition goal
for your individual risk profile
 Decide whether the body weight
the formulas suggest is realistic,
meets your goals, is healthy,
and is reasonable to maintain
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Focus on lifestyle
 Track progress
 Reassess your
body composition
occasionally during
the program

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