There are several ways to determine your body
fat percent.
Metropolitan Life Insurance Height-Weight
Tables were originally developed by this insurance company to establish
recommended weight ranges for men and women. The "desirable" weights
were those associated with the lowest death rates among large population
studies of insured people. Unfortunately, these studies do not accurately
represent a cross-section of the entire American population.
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Android or "apple-shaped" obese people are more vulnerable to
disease than those who are gynic or "pear-shaped."
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Waist Measurement is an additional, independent risk factor
and can be used in conjunction with any other method. It reflects growing
evidence that excess visceral fat - surrounding the abdominal organs - on its
own increases the chance of heart disease or diabetes.
Research indicates that visceral fat (waist size) is more important in the
disease process than subcutaneous fat which is just under the skin ("love
handles," "pinchable inches"). Abdominal fat cells appear to
produce certain compounds that promote inflammation and may influence
cholesterol and glucose metabolism. In men, a waist size of >40" and in
women >35" is an indication of increased health risk.
Underwater Weighing when done accurately
is considered one of the best ways of determining body fat composition. However, it is impractical and not always
down with the precision necessary to achieve useful results. More often, in research underwater weighing
is used as the reference standard to confirm the accuracy of the technique in
question.
Bioelectrical Impedance is measured when a very small electrical signal carried by water and
fluids is passed through the body. Impedance is greatest in fat tissue, which contains
only 10-20% water, while fat-free mass, which contains 70-75% water, allows the
signal to pass much more easily. By using the impedance measurements along with
a person's height and weight, and body type (gender, age, fitness level), it is
possible to calculate the percentage of body fat, fat-free mass, hydration
level, and other body composition values.
Using BIA to estimate person's body fat assumes that the body is within normal
hydration ranges. When a person is dehydrated, the amount of fat tissue can be
overestimated. Factors that can affect hydration include not drinking enough
fluids, drinking too much caffeine or alcohol, exercising or eating just before
measuring, certain prescription drugs or diuretics, illness, or a woman's
menstrual cycle. Measuring under consistent conditions (proper hydration and
same time of day) will yield best results with this method.
We use the Quantum unit from RJL Systems, the pioneer of bioelectrical
impedance analysis (BIA) and related sciences since 1979. Since that time RJL
has delivered more than 12,000 instruments to customers throughout the world.
In addition, more than 1,000 abstracts and peer review articles have been
written about BIA using RJL Systems instruments. RJL instruments set the
standard for body composition.
The RJL Systems Quantum series assesses three compartments
of your body (fat, fat-free cells and tissue, and water) and composition with
accuracy and repeatability, which is a significant step beyond all other
analyzers. Most equipment only reports
body composition in two compartments:
fat and fat-free mass.
RJL instruments
and software assess body composition, or in other words, the different
structures or parts of your body. The BIA can measure and track changes in the
amounts of body fluids, fat, and lean body mass, which includes your muscles
and organs. The BIA distinguishes
where the water is located in your body - either intracellular or extracellular.
Functionally the BIA assesses how much of your body is acting as functioning
cells (called the body cell mass or “BCM” on the report), transport tissue
(extracellular mass or “ECM” on the report) or storage cells (fat).
- Functional Mass is where metabolic work
is done and calories are burned.
- Transport Mass is tissue that
transports nutrients and oxygen to cells and removes waste products. It has also been called mesenchyme, the
tissue matrix, etc.
- Storage Mass is the fat where energy is
stored.
Preparing for a BIA:
If you haven't had a BIA done before, it is important to be
prepared. The Quantum BIA sends a very
minute electrical current throughout your body. Although, the electrical
current is so small that it is undetectable, if you have a pacemaker or
automatic implantable cardiac defibrillator (AICD), you should not have a BIA
done with a RJL Quantum unit.
- All metal
jewelry should be removed. Although you won't feel anything, metal removal
improves accuracy.
- Avoid
exercise or other activity that would make you sweat at least 8 hours
before your test. This is important to get accurate body fluid results.
- Avoid
caffeine or alcohol in large quantities 12 hours before the test.
- Go to the
bathroom before the test to get rid of any waste products. If you have
diarrhea, it is important to tell Dr. Kaslow, as diarrhea can affect your
body fluid results.
- Your
height and weight will be measured. Your height will only be taken the
first time, but your weight will be measured each time you come in for a
BIA. Since an accurate weight is important, remember to empty out your
pockets, remove your shoes and any other heavy clothing.
- You will
be asked to remove your right shoe and sock and lie down on a table.
- Two
electrodes will be placed on your right hand and two more on your right
foot. If you have lots of hair in
these areas, you may feel some discomfort when the pads are removed.
- Once the
leads are hooked up to the electrodes, the test only takes a few seconds.
- The BIA
data will be input a computer and the results printed for review.
Understanding the BIA Results
There are several measurements
of importance that are reported in the BIA results.
¨ Phase Angle: is a measurement of your body's overall health. Phase angle is based on total
body resistance and reactance and is independent of height, weight and body
fat. Lower phase angles appear to be consistent with either cell death or a
breakdown of the cell membrane. Higher phase angles appear to be consistent
large quantities of intact cell membranes and body cell mass. All living
substances have a phase angle. In fresh
uncooked vegetables phase angle can exceed 45 degrees. In cooked vegetables
phase angle is zero because they are dead.
Phase Angle is a predictor of outcome and indicates the
course of disease or increases as the result of optimal health based on good
nutrition and consistent exercise. Usually,
a phase angle of 6 or greater is desired for men and 5 or greater is desired
for women.
As we get older our phase
angle will decrease and will be approximately 4 or less when we die. Fit
adolescents may have a phase angle greater than 10. This effect is a result of
cell integrity due to age. Low phase angles are consistent with:
- Malnutrition
- HIV/AIDS infection
- Cancer (most types)
- Abusive life style
- Chronic Alcoholism
- Old Age (80 - 100 years)
References:
M. Ott, H. Fisher, H. Polat, E.
B. Helm, M. Frenz, W. F. Caspary B. Lembcke "Bioelectrical Impedance
Analysis as a Predictor of Survival in Patient with HIV Infection" J.
of Acquired Immune Deficiency Syndromes and Human Retrovirology 9:20-25 1995
R. Liedtke "Principles of
Bioelectrical Impedance" http://rjlsystems.com
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Body Mass Index (BMI): is a ratio between weight and height. It is a
mathematical formula that correlates somewhat with body fat. If your BMI is high, you may have an increased
risk of developing certain diseases, including:
- Hypertension
- Cardiovascular Disease
- Dyslipidemia
- Adult-Onset Diabetes (Type
II)
- Sleep Apnea
- Osteoarthritis
- Female Infertility
BMI is a better predictor of disease risk than body weight
alone. However, there are certain people who should not use BMI as the basis
for estimating body fat content: competitive athletes and body builders, whose
BMI is high due to a relatively larger amount of muscle, and women who are
pregnant or lactating. Nor is it intended for use in growing children or in
frail and sedentary elderly individuals.
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The energy storage
compartment, Fat Mass
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Fat is the energy
storage mass of the body and is the total lipid mass (triglycerides) with a
density of .9 g/ml. Fat mass is equal to actual weight minus fat free mass
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The functional
compartment, Body Cell Mass
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BCM is the functional
mass of the body where work is done. All oxygen consumption, carbon dioxide
production, glucose oxidation, protein synthesis and other metabolic work
takes place within the body cell mass. The body cell mass is, in effect, the
total mass of all the cellular elements in the body, and therefore,
represents the metabolically active component of the body. In the normally
nourished individual, muscle tissue accounts for approximately 60% of the
body cell mass, organ tissue for 20% of body cell mass, with the remaining
20% made up of red cells and tissue cells. It also contains the majority of
the body's potassium, (98 - 99%).
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The support
compartment, Extracellular Mass
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ECM is the support
mass of the body and is metabolically inactive, consumes no oxygen, produces
no carbon dioxide and performs no work. The extracellular mass consists of
extracellular fluids and tissue, such as bone and cartilage, with its primary
function that of support and transport. ECM is located outside of the
cellular compartment or outside of the body cell mass. Lean body mass is the
sum of body cell mass and extracellular mass.
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Fat: this is reported both as a percentage of your total weight and your
actual body weight in pounds that is fat.
Normal values are based on age and gender. Just as you don't want too
much fat, you also want to avoid too little.
Having too little fat can cause your body to stop producing important
hormones. For men, this means testosterone.
¨ Body Cell Mass (BCM):
this is also reported as a percentage of your total weight and as the actual
pounds that make up cells that are active like your muscles and organs. The
body cell mass are the cells that create your metabolism and energy. They are what keep you healthy. When the
body cell mass goes up, you are usually putting on muscle weight. But, when it
goes down, you are losing muscle mass.
¨ ECM: stands for
extracellular mass. This number is the amount of your body weight in pounds
that is made up of your skeleton and other support structures, as well as
ECW. It is composed of tissue that is
between cells. When this number changes,
it is showing that there was a change in the ECW. This number does not show
changes in bone density.
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FFM: describes the combination of all cells and tissues that are not
fat, in other words, the Fat Free Mass.
¨ Impedance Index: is
another measurement of your general health. Normal values for both men and
women are greater than 1273. If your impedance index is more than 1273, you are
at a better level of health and fitness than if it is below 1273.
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Parallel capacitance:
All living things are made of cells. Cells are membrane bounded compartments filled
with a concentrated solution of chemicals and salts. Groups of cells perform specialized functions
and are linked by an intricate communications system. The cell membrane maintains an ion
concentration gradient between the intracellular and extracellular spaces. This gradient creates an electrical potential
difference across the membrane which is essential to cell survival. Electrical gradients are necessary to support
movement of oxygen, carbon dioxide, and nutrients. Therefore, the cell membrane has electrically
insulating qualities or capacitance.
Electrical
capacitance will increase or decrease depending on the health and the number of
cells. Damage to the cell membrane, and its functions, is as lethal to the cell
as direct damage to the nucleus itself.
The
cell membrane functions as a permeable barrier separating the intracellular
(cytoplasm) and extracellular components. The lipid membrane is transversed by
proteins, which are soluble in water thus making pores through which water,
ions and other chemicals can enter and exit the cell.
Parallel
capacitance is somewhat like phase angle, whereas it is not affected by weight
or body fat. It is a measure of cell membrane health in all living substances
and can change dramatically depending on disease or good health. A body builder, for example, would have a high
parallel capacitance and low resistance, or more cell volume, because he is
extremely muscular and fit. A malnourished AIDS patient would have a low
parallel capacitance.
¨ Basal Metabolic Rate (BMR) is how many calories are burned at
rest during the average day. The
metabolic rate is determined by how many cells are producing oxidative
energy. The more cells, the more energy,
and the higher the basal metabolic rate.
Thyroid, other hormones, medications, etc. all can affect the basal
metabolic rate. A low basal metabolic
rate means that any calories you consume above your unique basal metabolic rate
are unnecessary to supporting you and will be converted into storage (fat). A low
body temperature would occur if your rate of calorie burn is too low. If you consume a lot more calories than you
need, then you may have an excessive appetite problem, which can be due to a neurotransmitter imbalance.
Metabolism occurs in two
distinct and interdependent phases: 1.) catabolism, in which the body breaks
down food into its component parts and harvests the energy stored in its atomic
bonds, and 2.) anabolism, in which those component parts and energy are
used to build new tissues and conduct basic life functions. Basal Metabolic
Rate (BMR) is the amount of energy your body requires every day to perform its
most basic function including:
- Breathing
- Digesting
- Heart beating
- Muscle activity
- Transportation of fluids and
tissue
- Circulation of blood
This is the amount of energy you
would require if you laid in bed all day without ever moving a single muscle.
Since most of us do a bit more than that, a daily activity level must also be
factored in. This ranges from everyday activities to working out strenuously. BMR varies between the sexes. Lean body mass is a major determinant. Because women tend to have less lean muscle
mass, their BMR is lower than that of otherwise comparable males. BMR is at peak during infancy, then declines
rapidly through childhood and adolescence. It continues to fall slowly with increasing
age and decline further with old age largely due to a loss of muscle mass. However, this is not inevitable, because
weight-bearing (resistance) exercise will prevent or reverse muscle loss among
the elderly.
Fluid Assessment: is described in the section called
Total Body Water Compartments, which tells about the fluid level and
distribution in your body. The fluid is
actually primarily water. Your total
body water (TBW) is measured in liters (L) and is made up of:
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Intracellular Water (ICW): the fluid inside all of your body’s cells. The cells of your muscles and organs (liver,
kidney, brain, etc) contain more water than fat cells. The closer to ideal your ICW, the greater the
number of cells that contribute to your metabolism.
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Extracellular Water (ECW) is the fluid that circulates outside your cells
and throughout your body. This includes your blood, lymphatic tissue, and the
ECM discussed previously.
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Total Body Water (TBW): If you are
dehydrated or losing a lot of fluid, your total body water may be low. If you
are retaining fluid or have an infection, your total body water may be high.
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Water Compartmentalization is among the most valuable features of the BIA since
it tells how much water is in the cell and how much is outside of the
cell. The water content inside the cell
(“intra-cellular water”) is termed the “ICW” and the water content outside of
cells (“extra-cellular water’) is termed the “ECW.” The total body water content is called
“TBW.” These three values implicate:
1.
The functional integrity of the cell membrane,
which is responsible in part for the electro-osmotic gradient across the cell
membrane. The content of the
intracellular environment must be in balance with the surrounding tissue in
order to function properly in terms of cell nutrition and detoxification.
2.
The electrolyte content inside the cell. In order to hold the water inside the cell,
electrolytes must be in sufficient quantity to provide the osmotic pressure for
water to stay inside the cell. Potassium
is one of the major intra-cellular electrolytes whereas sodium is one of the
major extra-cellular electrolytes.
3.
The fatty acid content of the cell
membrane. If we did not have a lipid layer
around every cell in our body, all of the water would leak out. The fat repels the water (like oil and
vinegar) and helps keep water within the cell.
4.
The amount of mesenchyme or tissue that has
built up with water. Usually this
represents toxicity since normally there should be only a modest amount of
tissue separating the cells from each other and from blood vessels, nerves,
etc. Often times this reflect the amount
of ECM discussed above.
