C h a p t e r 1 0
Disorders of Nutritional Status
229
multiple sites. They can provide information about the
location of the fat and can be used together with equa-
tions and tables to estimate the percentage of lean body
mass and fat tissue. However, these measurements often
are difficult to perform, are subject to considerable vari-
ation between clinicians, and do not provide informa-
tion about abdominal and intramuscular fat.
Bioelectrical impedance involves the use of electrodes
attached to the wrists and ankles to send a harmless cur-
rent through the body. The flow of the current is affected
by the amount of water in the body. Because fat-free tis-
sue contains virtually all the water and current-conduct-
ing electrolytes, measurements of the resistance (i.e.,
impedance) can be used to estimate the percentage of
body fat present.
Computed tomography and MRI can be used to pro-
vide quantitative pictures from which the thickness of fat
can be determined. Computed tomography scans also can
be used to provide quantitative estimates of regional fat
and give a ratio of intra-abdominal to extra-abdominal
fat. Another novel way of measuring body composition
is the BOD POD. The subject sits inside the device, and
air displacement is measured to determine body compo-
sition (i.e., fat vs. lean tissue). Because these methods are
costly, they usually are reserved for research studies.
Laboratory Studies
Various laboratory tests can aid in evaluating nutritional
status. Some of the most commonly performed tests are
serum albumin and prealbumin to assess the protein sta-
tus, total lymphocyte count and delayed hypersensitivity
reaction to assess cellular immunity, and creatinine–
height index to assess skeletal muscle protein. Vitamin
and mineral deficiencies can be determined by measure-
ments of their levels in blood, saliva, and other body tis-
sues or by measuring nutrient-specific chemical reactions.
TABLE 10-2
Classification of Overweight and Obesity by BMI,Waist Circumference, and Associated
Disease Risk
*
Disease Risk
*
Relative to Normal Weight and
Waist Circumference
BMI (kg/m
2
)
Obesity Class
Men
≤
102 cm (
≤
40 in.)
Women
≤
88 cm (
≤
35 in.)
Men
>
102 cm (
>
40 in.)
Women
>
88 cm (
>
35 in.)
Underweight
<18.5
—
—
Normal
†
18.5–24.9
—
—
Overweight
25.0–29.9
Increased
High
Obesity
30.0–34.9
I
High
Very high
35.0–39.9
II
Very high
Very high
Extreme obesity
≥
40
III
Extremely high
Extremely high
BMI, body mass index.
*Disease risk for type 2 diabetes, hypertension, and cardiovascular disease.
†
Increased waist circumference also can be a marker for increased risk, even in persons of normal weight.
Pi-Sunyer FX, DietzWH, Becker DM, et al., for the NHLBI Obesity Education Initiative Expert Panel on the
Identification, Evaluation, andTreatment of Overweight and Obesity in Adults. Clinical Guidelines on the
Identification, Evaluation, andTreatment of Overweight and Obesity in Adults. 1998. NIH Publication No.
98–4083. Available at:
SUMMARY CONCEPTS
■■
Nutritional status describes the condition of
the body related to the availability and use of
nutrients, which provide the energy and materials
necessary for performing the activities of daily
living and for the growth and repair of body
tissues.
■■
Metabolism is the organized process whereby
nutrients such as carbohydrates, fats, and
proteins are broken down, transformed,
or otherwise converted to cellular energy,
measured in kilocalories (kcal or C).
Carbohydrates are the body’s primary source
of immediate energy. They supply 4 kcal/g,
are stored in limited quantities as glycogen
and can be converted to fatty acids. Fats are a
concentrated water-free energy source. They
contain 9 kcal/g and are stored in fat cells as
triglycerides. Proteins, which are broken down
into amino acids, generate 4 kcal/g. However,
their main role is in building functional and
structural body proteins. Excesses of any of the
macronutrients will be stored as triglycerides in
adipose tissue. Water, vitamins, and minerals are
other essential nutrients.
■■
Nutritional status can be assessed by evaluation
of dietary intake; anthropometric measurements
such as measurements of height and weight,
body circumference, and skinfold thickness; and
laboratory tests.
