Body Fat Testing

BODY COMPOSITION TESTS

Body composition refers primarily to the distribution of muscle and fat in the body, and its measurement plays an important role in both sports and health. Excess body fat may lead to obesity and increases the risk of getting many diseases. In sports, excess fat hinders performance as it does not contribute to muscular force production, and it is additional weight that requires energy to move about.

Body composition is often represented as a two compartment system; lean body weight and fat weight. The fat weight is then expressed as a percentage of total body weight, where percent body fat = (fat weight / total body weight) x 100. The table below gives general guidelines for body fat percentage levels. 

Many training or exercise programs are geared solely to modify body size and composition in some way. The tests described below provide a way of measuring current levels and determining changes over time. 

Listed below you will find different ways to test your Body Composition

Body Mass Index (BMI)

BMI stands for Body Mass Index. It takes a person's weight in kilograms and divides it by their height in meters squared. For instance, if your height is 1.82 meters, the divisor of the calculation will be (1.82 * 1.82) = 3.3124. If your weight is 70.5 kilograms, then your BMI is 21.3 (70.5 / 3.3124) (see calculator links below).

The higher the figure the more overweight you are.  Like any of these types of measures it is only an indication and other issues such as body type and shape have a bearing as well. Remember, BMI is just a guide - it does not apply to elderly populations, pregnant women or very muscular athletes.

Calculate your own BMI!
If you are from the US, use this calculator . 

note: if you are exactly 5 feet or 6 feet tall, put a 0 in the inches box.

• Description / procedure: BMI is calculated from body mass (M) and height (H). BMI = M / (H x H), where M = body mass in kilograms and H = height in meters. The higher the score usually indicating higher levels of body fat

• Scoring:

• Equipment required: scales and stadiometer as for weight and height.

• Target population: BMI is often used to determine the level of health risk associated with obesity.

• Advantages: simple calculation from standard measurements

• Disadvantages: BMI can be inaccurate, for example with large and muscular though lean athletes scoring high BMI levels which incorrectly rates them as obese.

• Other comments: Other measures of body composition would be preferable if available.

 

Skinfold Measurement

• Description / procedure: Estimation of body fat by skinfold thickness measurement. Measurement can use from 3 to 9 different standard anatomical sites around the body. The right side is usually only measured. The tester pinches the skin at the appropriate site to raise a double layer of skin and the underlying adipose tissue, but not the muscle. The calipers are then applied 1 cm below and at right angles to the pinch, and a reading taken 2 seconds later. The mean of two measurements should be taken. If the two measurements differ greatly, a third should then be done, then the median value taken.

• The sites: the following descriptions are for the common sites at which the skinfold pinch is taken. The caliper is then applied 1 cm below and at right angles to the pinch. I have added some lay terms (in brackets) that may help the non-medical users to find the correct sites for taking the skinfold measurements.

TRICEPS	A vertical pinch at the level of the mid-point between acromial process (boney tip of shoulder) and proximal end of the radius bone (elbow joint), on the posterior (back) surface of the arm.
BICEPS	The pinch position is at the same level as for triceps, though on the anterior (front) surface of arm.
SUBSCAPULA	The pinch is made 2 cm below the lower angle of the scapula (bottom point of shoulder blade) on a line running laterally (away from the body) and downwards (at about 45 degrees). The fold is lifted in this direction.
AXILLA	The pinch is made at the intersection of a horizontal line level with the bottom edge of the xiphoid process (lowest point of the breast bone), and a vertical line from the mid axilla (middle of armpit).
ILIAC CREST	The pinch is made at a site immediately above the iliac crest (top of hip bone), at the mid-axillary line. The fold is directed anteriorly and downward.
SUPRASPINALE	The pinch is made at the intersection of a line joining the spinale (front part of iliac crest) and the anterior (front) part of the axilla (armpit), and a horizontal line at the level of the iliac crest. The pinch is directed anteriorly and downward
ABDOMINAL	The vertical pinch is made 5 cm adjacent to the umbilicus (belly-button)
FRONT THIGH	A vertical pinch is made at the mid-point of the anterior surface of the thigh, midway between patella (knee cap) and inguinal fold (crease at top of thigh).
MEDIAL CALF	A vertical pinch is made at the point of largest circumference on medial (inside) surface of the calf.
CHEST	A diagonal pinch is made between the axilla and nipple as high as possible on the anterior axillary fold (males only).

• Results: Because of the increased errors involved, it is not appropriate to convert skinfold measures to percentage body fat (%BF). It is best to use the sum of several sites to monitor and compare body fat measures. In order to satisfy many of you who want a percentage body fat measure, I have included a couple of equations for calculating this. There are hundreds of equations available, and it is best to use one that is based on a sample that most closely resemble you. Use them at your own risk.. You will find that you get different results depending on which equation you use.

Some of the following equations give a measure of body density (D), which then needs to be converted to %BF using the Siri equation: %BF = (495/D) - 450.

MALES :

D = 1.10938 - (0.0008267 x sum of chest, abdominal, thigh) + (0.0000016 x square of the sum of chest, abdominal, thigh) - (0.0002574 x age), based on a sample aged 18-61.
Jackson, A.S. & Pollock, M.L. (1978) Generalized equations for predicting body density of men . British J of Nutrition, 40: p497-504.

D = 1.1043  - (0.001327 x thigh)  - (0.00131 x subscapular), based on a sample aged 18-26.
Sloan AW: Estimation of body fat in young men ., J Appl. Physiol. (1967);23:p311-315.

%BF = (0.1051 x sum of triceps, subscapular, supraspinale, abdominal,  thigh,  calf) + 2.585, based on a sample of college students.
Yuhasz, M.S.: Physical Fitness Manual, London Ontario, University of Western Ontario, (1974).

FEMALES : 

D = 1.0994921 - (0.0009929 x sum of triceps, suprailiac, thigh) + (0.0000023 x square of the sum of triceps, suprailiac, thigh) - (0.0001392 x age), based on a sample aged 18-55.
Jackson, et al. (1980) Generalized equations for predicting body density of women . Medicine and Science in Sports and Exercise, 12:p175-182.

D = 1.0764 - (0.0008 x iliac crest)  - (0.00088 x tricep), based on a sample aged 17-25. 
Sloan, A.W., Burt A.J., Blyth C.S.: Estimating body fat in young women., J. Appl. Physiol. (1962);17:p967-970.

%BF = (0.1548 x sum of triceps, subscpular, supraspinale, abdominal,  thigh,  calf) + 3.580, based on a sample of college students.
Yuhasz, M.S.: Physical Fitness Manual, London Ontario,University of Western Ontario, (1974).

• Equipment required: skinfold calipers (e.g. Harpenden, Holtain, Slimglide, Lange). These should be calibrated for correct  jaw tension and gap width. 

• Target population: suitable for all populations, though it is sometimes difficult to get reliable measurements with obese people.

• Validity: using skinfold measurements is not a valid predictor of percent body fat, however they can be used as a monitoring device to indicate changes in body composition over time.

• Reliability: can vary from tester to tester depending on the skill and experience of the tester.

• Advantages: Skinfold measurements are widely utilised to assess body composition. It is a lot simpler than hydrostatic weighing. After the outlay for callipers, the tests costs are minimal.

Waist to Hip Ratio

• Description / procedure: A simple calculation of the measurements of the waist girth divided by the hip girth.
• Scoring: The table below gives general guidelines for acceptable levels for hip to waist ratio. You can use any units for the measurements (e.g. cm or inches), as it is only the ratio that is important.

Hydrostatic Weighing Description / procedure: The dry weight of the subject is first determined. The subject, in minimal clothing, then sits on a special seat, expels all air from the lungs and is lowered into the tank until all body parts are emerged. Underwater weight is then determined. Scoring: Body density = Wa/(((Wa-Ww)/Dw)-(RV + 100cc)), where Wa=body weight in air (kg), Ww=body weight in water (kg), Dw=density of water, RV=residual lung volume, and 100cc is the correction for air trapped in the gastrointestinal tract. Equipment required: Hydrostatic weighing tank, including scale, weighted belt, nose clip. Advantages: Underwater weighing is the most widely used test of body density and is the criterion measure for other indirect measures. Disadvantages: The equipment required to do underwater weighing is expensive. The tanks are mostly located at university or other research institutions, and there is generally not easy access for the general population. Other comments: Residual lung volume is required for the calculatiosn. For more accuracy it should be measured, though there are calculation for RV estimation. One estimation of residual volume is one third of forced vital capacity (FVC).

Bioelectric Impedance

• Description / procedure: The subject lies on their back on a non conducting surface, with legs apart and arms away from the body. A pair of electrodes are placed on the hand and wrist, and another pair placed on the ankle and foot (usually opposite sides of the body).
• Equipment required: Bioelectric Impedance Analyser.
• Advantages: very simple and quick to perform
• Disadvantages: The equipment is relatively expensive (units on the low end of the scale are available for about $100), with prices ranging up to thousands of dollars. The impedance measure  is affected by body hydration status, body temperature, time of day, and therefore requires well controlled conditions to get accurate and reliable measurements.
• Other comments: Bioelectric impedance analysis is based on the principle that the resistance to an applied electric current is inversely related to the amount of fat-free mass within the body.

Dual-Energy X-Ray Absorptiometry (DEXA)

• Description / procedure: The DEXA instruments differentiate body weight into the components of lean soft tissue, fat soft tissue and bone, based on the differential attenuation by tissues of two levels of x-rays.
• Equipment required: DEXA machine.
• Advantages: DEXA measurements are based on a three compartmental model rather than two compartment as in most other methods. It can also distinguish regional as well as whole body parameters of body composition.
• Disadvantages: The equipment is expensive, and often requires trained radiology personnel to operate.
• Other comments: If not for the limiting price of measurement, DEXA would be considered the criterion method of body composition analysis.