Understanding Body Fat Analysis

Tanita Duo User Body Fat Scale

This Tanita scale uses advanced technology to detect body fat% in 0.5% increments found in the prof. body composition analyzers used by medical centers, weighs upto 300 lbs in 0.2 lb increments, and has duo memory (ADDITIONAL S/H RATES APPLY)

Product Home Page Features & Benefits Symptoms & Conditions Body Fat FAQs TBF Series FAQs Product FAQs Health Links Body Fat Analysis BIA Explained Determining Body Fat Diet & Excercise More Info Newsletters About Body Fat User Modes Why Measure? Female Body Fat

Other Body Fat Monitors

Test Medical Symptoms Home Page

$43.00/scale

Understanding Body Fat Analysis

Recently, a student asked me what benefits I get from my personal exercise program besides putting in miles on my bicycle...

I was tempted to say that exercising outside in the fresh air always makes me feel good, but instead, I replied: In addition to the cardiovascular benefits I've gained in the last six months, I've lost eight pounds of fat--I've reduced my body fat level from 18% of my total weight to 14%.

This is the kind of definitive statement you can make after adding body composition analysis to your exercise and diet program as I have. If weight loss or maintenance is your goal, accurate body fat testing is a terrific and more precise way to monitor your progress while you're making slow but gradual gains. It can be a valuable tool--if you understand it.

This may sound like a contradiction, but you can be overfat but not overweight; or overweight and not overfat. And when you exercise and diet properly, you can lose fat without changing your weight measurement on a scale. With strength training or intense aerobic exercise, you can actually gain a few pounds of muscle while at the same time losing pounds of fat. Most individuals never know this kind of information because they simply measure weight. I believe that the more information and biofeedback you have on improvements to your health and fitness, the more likely you are to stay motivated toward your goals.

Everyone needs some body fat and there are recommended healthy ranges. The ranges for men and women are different because women are anatomically designed to have about 5% more fat than men of equal fitness.

For both sexes, however, being severely overfat or obese can lead to health problems. Obesity is linked to increased risk of diabetes, hypertension, heart disease, stroke, certain cancers, and other debilitating conditions.

If you're an athlete carrying excess pounds, it's going to slow you down. But excessive thinness can also lead to trouble. While a lean body may improve your appearance, strength and speed, many athletes lower their body fat levels to such an extreme that they become susceptible to illness. Many athletes that I have worked with tell me that when they drop below a certain weight and percent body fat they often experience chronic fatigue. Female athletes face an additional problem in that too low a percentage of body fat (12% or under) can disrupt their menstrual cycles. So remember, the thinnest and leanest athletes are not always the strongest. The body needs an adequate amount of fat to be healthy and to use as an energy source during hard exercise.

When participating in any exercise and diet program you probably know that exercise increases metabolism or your body's ability to burn calories for energy. Weight control is a question of balancing how much food we eat against how much energy we expend; and weight loss requires taking in fewer calories and burning off even more. Dieting alone slows down your metabolism, while eating the right foods plus a program of exercise will help you burn off calories--even when you're resting.

As measuring body fat becomes easier and cheaper, and the results of tests more accurate, naturally more people want to know their measurements. And, as I have successfully learned, keeping tabs on my body composition can be an important index of my health and state of fitness. Personally, I measure my weight and body fat twice a week, and use these measurements in addition to my training mileage as tools to help me reach and maintain my fitness goals.

Before you put yourself to the test, understand the principles of body fat testing. There is more than one way to measure body fat, and each method has its strengths and weaknesses. Choose one that feels right for you and, more importantly, one that you can use on a regular basis. While conclusions on the best test for body composition may differ, remember that it is more important to use the same one consistently--over time.

Edmund R. Burke, Ph.D.
Professor and
Director of the Exercise Science Program
University of Colorado at Colorado Springs

Dr. Burke is the author of "Getting in Shape: Programs for Men and Women" and the "Complete Home Fitness Handbook"; as well as a regular contributor to numerous scientific journals and publications, including "Bicycling Magazine" and "Nutritional Science News." Dr Burke's research interests include sports nutrition, cycling performance, fitness and adaptations to training. Personally, he enjoys cycling and hiking and is an experienced international competitor He is a Fellow of the American College of Sports Medicine and a Certified Strength and Conditioning Specialist (CSCS).

Scientists have been studying body composition since the beginning of the 20th century, but research has increased dramatically in the last 25 years as methods for measuring and analyzing the body have grown in accuracy.

There is growing evidence that clearly links body composition with health risks and the development of certain diseases. New research indicates that fat loss, not weight loss, can extend human longevity.

Adding further to the acceptance of this practice is the importance of body composition in athletic performance and its move from being a laboratory-only procedure to one used in ordinary medical practice and now health clubs or at home. By measuring body composition, a person's health status can be more accurately assessed and the effects of both dietary and physical activity programs better directed.

Most people don't realize that there is only one "direct" method of measuring body composition that is close to 100% accurate, and that is an autopsy-performed Post Mortem. All other current methods for measuring body composition rely on "indirect" measurement techniques and are called In Vivo methods--meaning they are performed on a living body.

In Vivo methods give estimates of percentage of body fat, lean mass, or other body components. in each case, whatever methodology used is combined with standard equation formulas derived from large research studies to predict body composition.

According to the National Institutes of Health (NIH) National Heart, Lung and Blood Institute, no trial data exist to indicate that one method of measuring body fat is better than any other for following overweight and obese patients during treatment. Good results can be obtained only when the measurement is done accurately and the equation used is based on an adequate scientifically derived data base. Every measurement method has strengths as well as defined sources of error. The "gold standard" for body composition may not be a single method but actually a combination of measurement methods together with a highly specific equation formula for the type of person being measured.

Body composition equipment manufacturers should have scientific studies available to support accuracy claims, but often companies fail to explain the problems encountered in day-to-day use outside of the controlled environment of a research lab. Tanita feels it is very important for people to fully understand the benefits--and limitations--of body composition analysis. This information will enable people to make better decisions about which method is the best or most appropriate for their particular needs.

Measurements of body composition are based on theoretical body composition models.

The more traditional methods are based on a two-component model that simply divides the body into fat and fat-free mass. Newer, more sophisticated techniques measure the body as multiple compartments consisting of water, protein, bone mineral, and fat. This approach improves the accuracy of the calculation for determining the real density of fat-free mass.

Equation Formulas
The equations used in predicting body composition have been developed using regression models that take into account data from many different research projects. Known as regression equations, these can be population-specific (developed for specific types of people including such categories as gender, age, ethnicity, fitness level, etc.) or generalized to cover a wide range of people types.

Generally speaking, the more components a body composition model consists of, the more specifically written the regression equations can be.

All body composition methods have an underlying mathematical basis summarized according to a simple formula. C = f (Q). C is an unknown component; Q is a measurable quantity; and f is the mathematical function that links Q to C. For example, calipers measure skinfolds in millimeters and use that measurement to estimate body fat percentage according to a mathematical equation; BIA measures electrical impedance or resistance in ohms to then produce a body fat percentage reading according to another equation.

Height-Weight Tables were originally developed by insurance companies to establish recommended weight ranges for men and women. The "desirable" weights were those associated with the lowest mortality among large population studies of insured people. Unfortunately, these studies do not accurately represent a cross-section of the entire American population.

Body Mass Index (BMI) is a simple calculation that determines height to weight ratio. BMI is obtained by multiplying weight in pounds by 700 and dividing the result by the square of height in inches. This index correlates a person's physical stature with mortality ratios based on actuarial studies. According to National Institutes of Health (NIH) and World Health Organization (WHO) guidelines, overweight is defined as a BMI of 25-29.9, and obesity as a BMI equal to or greater than 30. A person with a BMI of 30 is about 30 lbs. overweight/overfat.

While BMI is widely accepted, it can be misleading. Current guidelines do not differentiate for gender, ethnicity or age, and do not distinguish obesity or leanness for individuals who are extremely muscular. It is, however, more precise than height/weight tables and allows comparisons of population groups. Studies have confirmed that obesity-related health risks start in the BMI range of 25-30.

Waist Measurement Waist size 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.

Android or "apple-shaped" obese people are more vulnerable to disease than those who are gynoid or "pear-shaped".

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 may influence cholesterol and glucose metabolism. A waist size of 35 inches or more is deemed a risk for people who have a BMI over 25.

Recommended Body Fat Ranges:
For Normal Adults
Body fat percentage ranges differ for men and women and include an allowance for age.

Anthropometry (Skinfold Measurements)
Using hand-held calipers that exert a standard pressure, the skinfold thickness is measured at various body locations (3-7 test sites are common). Then a calculation is used to derive a body fat percentage based on the sum of the measurements. Different prediction equations are needed for children and specific ethnic groups (over 3,500 equations have been validated). This approach usually uses underwater weighing as a reference method. The caliper method is based upon the assumption that the thickness of the subcutaneous fat (found just under the skin) reflects a constant proportion of the total body fat (contained in the body cavities ), and that the sites selected for measurement represent the average thickness of the subcutaneous fat.

Skinfold measurements are made by grasping the skin and underlying tissue, shaking it to exclude any muscle and pinching it between the jaws of the caliper. Duplicate readings are often made at each site to improve the accuracy and reproducibility of the measurements. Often to save time in large population studies, a single skinfold site measurement is made to reduce the time involved. Such a test should be used only for a rough estimate of obesity.

Generally speaking, skinfold measurements are easy to do, inexpensive and the method is portable. Overall, results can be very subjective as precision ultimately depends on the skill of the technician and the site measured. The quality of the calipers is also a factor; they should be accurately calibrated and have a constant specified pressure. Inexpensive models sold for home use are usually less accurate than those used by an accredited caliper technician. The more obese the subject, the more difficult to "pinch" the skinfold correctly, requiring even more skill to obtain an accurate measurement.

This method measures whole body density by determining body volume according to Archimedes' principle, which states that an object submerged in water is kept afloat by the weight of the water it displaced. This technique first requires weighing a person outside the tank then immersing them totally in a tank of water. The densities of bone and muscles are higher than water, and fat is less dense than water. So a person with more bone and muscle will weigh more in water, meaning they have a higher bone density and lower percentage of body fat. The body volume and density is calculated by using standard formulas (Siri or Brozek). Body fat percentage is then calculated from body density.

The underwater weighing system uses strain gauges mounted under the water on the floor of a stainless steel tank. A person kneels or sits on a cot or stool placed on these gauges which allows the body mass to be suspended in water. This method is not practical for testing large numbers of people because it requires a lot of cooperation from each individual. It is difficult for people who are not comfortable with swimming, or apprehensive about submersion, or who simply have difficulty expelling all the air in their lungs (a requirement for the test), and may take from 15 minutes to an hour to obtain valid results. The system requires a number of pieces of special equipment and experienced technicians, thereby limiting the method to clinics and sophisticated health clubs.

Another consideration is measuring the amount of air left in a person's lungs. This should be measured directly. If estimated according to existing formulas, the body fat measurement is subject to a certain degree of error.

New research shows that body density can vary because of changes in hydration or the proportion of bone minerals from person to person. Work is under way to develop multi-component body models to replace the two-compartment model (fat and fat-free mass) on which underwater weighing is currently based. This could lead to more refined prediction equations.

Bioelectrical Impedance
Body impedance is measured when a small, safe amount of current, is passed through the body, carried by water and fluids. The greater the amount of water in the person's body, the easier it is for the current to pass; the less water, the higher the resistance or impedance, By entering impedance measurements, along with a person's height, weight and gender into mathematical equations, it is possible to estimate the values of water, lean mass, and fat content, Lean body tissue (fat-free mass) is composed of 70-75% water, fat tissue only 10-15% water. The more lean tissue a person has, the more water their body can hold. Once the person's impedance is known, the amount of lean and fat tissue can be estimated. BIA usually uses underwater weighing as its method of reference.

Estimating the amount of lean tissue, however, assumes that the person is normally hydrated. If the muscles are dehydrated, the amount of fat tissue will measure greater. Factors such as not drinking enough fluids, too much caffeine or alcohol, exercising or eating close to measuring time, use of prescription drugs, menstrual cycle, etc. can alter a person's state of hydration, thereby affecting total body resistance and the estimate of fat-free mass.

In the traditional BIA method, a person lies on a cot and spot electrodes are placed on the hands and bare feet. Electrolyte gel is applied first, and then a current of 50 kHz is introduced. BIA has emerged as a promising technique because of its simplicity, low cost, high reproducibility and non-invasiveness. BIA prediction equations can be either generalized or population-specific, allowing this method to be potentially very accurate. Selecting the appropriate equation is important in determining the quality of the results. To minimize variables caused by a person's hydration level, measurements should always be taken under constant and controlled conditions.

As BIA research improves, scientists are leaning toward developing a multi-frequency method that will further improve BIAs ability to predict a person's hydration level and increase the over-all accuracy of the measurement. New segmental BIA methodologies will use more electrodes leading to more precise measurements of specific sections of the body.

Tanita has developed a simplified version of BIA that uses leg-to-leg bioimpedance analysis. In this system, two footpad electrodes (pressure contact) are incorporated into the platform of a precision electronic scale. A person's measurements are taken while in a standing position with the electrodes in contact with bare feet. The body fat monitor/analyzer automatically measures weight and and then impedance. Computer software (a microprocessor) imbedded in the product uses the measured resistance, the subject's gender and height, and in some cases age, (which have been pre-programmed and the weight to determine body fat percentage based on equation formulas. Tanita's reference method is DEXA.
	Tanita's footpad design sends a safe, low level electrical signal through the body. As easy as stepping on a traditional scale, it measures weight and body fat percentage within 30 seconds.

	A person's measurements are taken while in a standing position with the electrodes in contact with bare feet.

Through multiple regression analysis, Tanita has derived standard formulas to determine body fat percentage. Tanita's equations are generalized for standard adults, athletes, and children. The Tanita method has all the advantages of traditional BIA as well as greater ease of use, speed, and portability. Professional versions of the product can be found in hospitals, health clubs, and research labs and include computer printouts of comprehensive data such as BMI, fat percent, fat weight, total body water, fat-free mass, and BMR. The concept has been adapted for use as an affordable home monitoring device. Now ordinary people along with fitness enthusiasts and patients with health risks can measure body fat as part of a regular healthy lifestyle. The same variables apply with regard to hydration levels, and measuring should be done under consistent conditions.

Near-infrared Interactance
A fiber optic probe is connected to a digital analyzer that indirectly measures the tissue composition (fat and water) at various sites on the body. This method is based on studies that show optical densities are linearly related to subcutaneous and total body fat. The biceps is the most often used single site for estimating body fat using the NIR method. The NIR light penetrates the tissues and is reflected off the bone back to the detector. The NIR data is entered into a prediction equation with the person's height, weight, frame size, and level of activity to estimate the percent body fat.

This method has become popular outside of the laboratory because it is simple, fast, noninvasive, and the equipment is relatively inexpensive. However, the amount of pressure applied to the fiber optic probe during measurement may affect the values of optical densities, and skin color and hydration level may be potential sources of error. To date, studies conducted with this method have produced mixed results; a high degree of error has occurred with very lean and very obese people; and the validity of a single-site measurement at the biceps is questionable. Numerous sources report that more research is needed to substantiate the validity, accuracy and applicability of this method.

Duan Energy X-ray Absorptiometry
A relatively new technology that is very accurate and precise, DEXA is based on a three-compartment model that divides the body into total body mineral, fat-free soft (lean) mass, and fat tissue mass. The principle of this technique is based on the assumption that bone mineral content is directly proportional to the amount of photon energy absorbed by the bone being studied. Graphics (p.1-3)

DEXA uses a whole body scanner that has two low-dose X-rays at different sources that read bone and soft tissue mass simultaneously. The sources are mounted beneath a table with a detector overhead. The scanner passes across a person's reclining body with data collected at 0.5 cm intervals. A scan takes between 10-20 minutes. It is safe and noninvasive with little burden to the individual, although a person must lie still throughout the procedure.

Although DEXA is not as accurate in measuring the extremely obese and initial costs are high, this method is quickly moving from the laboratory setting into clinical studies. DEXA allows fat distribution throughout the entire body to be read in a single scan, it is extremely reliable, and provides a higher degree of precision in only one measurement.

Magnetic Resonance Imaging (MRI)
An X-ray based method in which a magnetic field "excites" water and fat molecules in the body, producing a measurable signal. A person lies within the magnet as a computer scans the body. High-quality images show the amount of fat and where it is distributed.

MRI takes about 30 minutes and is very safe as it uses no ionizing radiation, but use is limited due to the high cost of equipment and analysis.

Total Body Electrical Conductivity (TOBEC)
This method is based on lean tissue being a better conductor of electricity than fat. A person lies in a cylinder that generates a very weak electromagnetic field. The strength of the field depends on the electrolytes found in the person's body water. In about 10 seconds, TOBEC makes 10 conductivity readings that estimate lean body mass. Although very accurate, its use is limited due to the high cost of the equipment.

Computed Tomography (CT)
CT produces cross-sectional scans of the body. An X-ray tube sends a beam of photons toward a detector. As the beam rotates around a person, data is collected, stored, and applied to complex algorithms to build images that determine body composition. CT is particularly useful in giving a ratio of intra-abdominal fat to extra-abdominal fat. It is noninvasive, but potential is limited by exposure to radiation and high equipment cost.

BOD POD� (Air Displacement)
Based on the same principle as underwater weighing, the BOD POD uses computerized sensors to measure how much air is displaced while a person sits for 20 seconds in a capsule. It uses a calculation to determine body density, then estimates body fat. The equipment is very expensive and limited in availability.

At Tanita Corporation, we recognize the importance of education in helping to make the concept of body composition analysis understandable.

We believe people should know what methods of measurement exist and how these techniques work in order to decide which operation is right for their particular needs.

As body composition, rather than body weight, becomes an integral part of a person's health and fitness evaluation, we predict that analytical methods will be driven by scientific research and practical application--each with their own objectives.

Scientifically, body composition analysis will become more complex and precise with prediction equations capable of greater individualization. Various techniques may be combined to create a multi-faceted view of the body where body fat and its distribution is just part of a person's fitness profile.

In terms of practical applications, body composition analysis will become simpler, more accessible, and easily affordable. It will redefine the traditional scale and re-shape how people measure and monitor their bodies.

At Tanita Corporation we are developing products to meet all these objectives. Tanita's goal is to provide people--whether they are medical researchers or consumers--more information about the human body.

Women Have More Body Fat Than Men
By nature, a woman's body is developed to protect her and a potential fetus. As a result, women have more enzymes for storing fat and fewer enzymes for burning fat. Additionally, the estrogen women have activates fat storing enzymes and causes them to multiply.

It's Possible to Have Too Little Body Fat
Women athletes involved in high performance sports that emphasize low body weight and extremely low body fat percentage often experience a decrease in hormones that causes an interruption in the menstrual cycle. The same condition can occur when a woman is anorexic and her body goes into a semi-starvation mode. Over an extended period of time, this can lead to other health risks such as the loss of bone mass.

Hydration Levels
Women experience more changes in hydration levels than men because of their menstrual cycle, and this can affect body fat measuring, particularly using the BIA method, Retaining fluid may also cause weight to fluctuate day-to-day during this period.

And, because weight is one of the components in determining body fat, it may cause additional variation in the measured body fat percentage.

Female users of BIA products should be aware of their natural monthly body cycles. To establish a baseline for body fat, many women find it useful to monitor and chart their readings daily for a month. Afterward, a monitoring program done at regular intervals can anticipate monthly fluctuations.

Hormonal changes due to pregnancy or menopause may also cause water retention and variations in measuring. Changes in hydration levels can also be due to food, caffeine or alcohol consumption, strenuous exercise, stress or illness, or the taking of prescription drugs, etc.

Remember
To monitor progress, compare weight and body fat percentage measurements taken under the same conditions over a period of time. Pay attention to fluctuations caused by menstruation. Stay within the Women's--not the Men's--Healthy Body Fat Range!

Bibliography
Bioelectrical impedance analysis in body composition measurement. National Institutes of Health Technology Assessment Conference Statement. (1996). American Journal of Clinical Nutrition.

Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. (1998). National Heart, Lung, and Blood Institute and National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Eating and Body Image. (Dec.1995, Vol. III, #4). Harvard Women's Health Watch.

Heymsfield, S. B. (1998). Lecture on Body Composition. Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, NY, NY.

Heyward, V.H. (Sept. 1996). Evaluation of Body Composition. Sports Medicine. Adis Intl. Ltd.

Heyward, V.H, and Stolarczyk, L.M. (1996). Applied Body Composition Assessment. Human Kinetics.

Jebb, Susan A. (1998). Measuring Body Composition from the Laboratory to the Clinic. Clinical Obesity (18-49). Blackwelll Science Ltd.

Kushner, Kunigk, Alspaugh, Leitch, Schoeller (Aug. 1990). Validation of BIA as a measurement of change in body composition in obesity. American Journal of Clinical Nutrition.

Lohman, T.C. (1992, Monograph #3). Advances in Body Composition Assessment. Current Issues in Exercise Science. Human Kinetics.

Lukaski, H.C. (1987). Methods for the assessment of human body composition: traditional and new. American Journal of Clinical Nutrition.

Margolis, S., Cheskin, L.J. (1997, 1998). Weight Control. Johns Hopkins White Papers. The Johns Hopkins Medical Institutions.

Nieman, D.C. (1986). Fitness and Sports Medicine: A Health Related Approach. 3rd Edition, Mayfield Publishing Company.

Nunez, C., Gallagher, D., Visser, M., Pi-Sunyer, F.X., Wang, Z., Heymsfield, S.B. (1997). Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact footpad electrodes. Medicine and Science in Sports and Exercise. American College of Sports Medicine.

Pi-Sunyer, F.X. (Oct. 993, Vol. 119, #7). Medical Hazards of Obesity. Annals of Internal Medicine. American College of Physicians.

Tsui, E.Y.L., Gao, X.J., Zinman, B. (Mar 1998). Bioelectrical Impedance Analysis (BIA) Using Bipolar Foot Electrodes in Assessment of Body Composition in Type 2 Diabetes Mellitus. Diabetic Medicine.

Williams, D.P., Going, S.B., Milliken, L.A., Hall, M.C., Lohman, T.G. (1995). Practical techniques for assessing body composition in middle-aged and older adults. Medicine and Science in Sports and Exercise. American College of Sports Medicine.

Yet Another Word on Weight (Aug. 1998, Vol. V, #12). Harvard Women's Health Watch.

* Same day and next day shipments are normally the case with the exception of any out-of-stock items.
** Lifetime member discounts are subject to member terms & conditions. Also, use of this site & products sales that result from this site are subject to our company's policies & disclaimers

Weight	refers to the total weight of the body including bones, muscle, fat, water, etc.
Overweight	is defined as a body weight that exceeds the acceptable weight for a particular person, based on individual height and/or frame size. Standards are usually determined solely on the basis of population averages that can and do change over time. Standards may also vary with gender and ethnicity. An overweight person does not necessarily have too much fat nor increased health risks, if the excess weight is due to an above-average amount of muscle.
Obesity (Overfat)	is the condition where the individual has an excessive amount of body fat. There is general agreement that men with body fat percentages over 25 and women over 35 are overfat, and that fat values of over 30 percent in men and 40 percent in women is considered obese.
Percentage Body Fat	is the percentage of total body weight that is fat.
Fat Mass	means the actual fat mass (in pounds or kilos) in the body.
Body Fat	functions as insulation, protection and energy reserve. When the percentage is too high, fat increases a person's risk of high blood pressure, elevated cholesterol, diabetes, heart disease, and some forms of cancer. It can also interfere with the immune system, prevent heat loss, stress the musculoskeletal system, cause sleep problems, and may affect self-esteem.
Basal Metabolic Rate (BMR)	diet alone will usually result in a loss of muscle, and this will slow your metabolic rate, making it more difficult to keep the weight off. Exercise, however, increases your metabolic rate, for hours even after exercise, and can increase the amount of muscle you have.
Weight Versus Body Fat	Weight measurement alone cannot always accurately determine the body fat status of a person because it does not differentiate between the fat-free mass and fat mass in the body. The relationship between three categories of body weight and body fat can be described according to five different people categories.