This method is the most accurate but the most expensive measurement device. A mod pod is a chamber that is shaped like an egg. Computerized pressure sensors measures how much space your body is taking up. This device is not practical for most individuals because of the 10 to 20 thousand dollar price tag. Some gyms may have this machine and charge members $50 to $100 per test. 

Analysis (BIA) is another method of estimating body fat. BIA evaluates changes in electrical conductivity in different body tissues. This method is a safe, noninvasive, and rapid way to assess body composition. However, there are limitations to this method due to changes in the hydration and electrolyte levels of individual subjects. It is best to use other methods other than bioelectrical impedance to measure body fat percentage.

How this test works

The instrument sends a signal from one part of your body to an electrode on your hand. A slower signal indicates that your body may contain more fat. A faster signal shows that you have a higher lean muscle composition. This is due to the fact that muscle contains 70% water while fat contains much less between 5 and 13 percent.

The disadvantage of this method is the high margin of error. An extremely fat or lean individual may show a reading that’s higher or lower than the actual body fat percentage. How hydrated your body is also can affect the results since more water make the signal move faster throughout your body. It’s best to stay hydrated at the right level for the best measurement. 

The most accurate means to calculate body fat percentage is with hydrostatic or underwater weighing. This method gives you a measurement of your true body composition.  This procedure is difficult because it requires precise equipment such as a pool or large tub of water and well trained technicians to execute. This test is based on the premise that fat floats and muscles sinks. The weight that registers on the scale is plugged into a formula to find your results. All weights are measured in kilograms but you may convert it into pounds after you plugged kilograms into the formula.

How the test is preformed

1.  You are your subject sit on a scale in a tank or large body of water. It would be large enough to submerge your entire body.

2. Blow all of the air out of your lungs then bend forward until you’re completely submerged. It is important to make sure that your lungs are empty for an accurate reading.

3. Stay underwater for five seconds while the digital scale weights your body.

4. Once you get your results in kg’s, plug this into the formulas below. If you want to know your weight in pounds, simple convert it after you plug in the numbers.

Siri and Brozek formulas

Equations 

Determination of Body Density 

Body Density = dry weight / [((dry weight - wet weight) / water density)- RV - 0.1]  

Note: Units for all weights are in kg and RV is in L. The 0.1 represents an estimated volume (L) of gas in the GI tract.

Estimation of Percent Fat

The two most commonly used equations for estimating percent fat from body density are the Siri (1961) and Brozek (1963) formulae. A limitation to these formulae is that they assume the density of fat-free mass to remain a constant across the population when in fact is varies. Thus, the actual percent fat tend to be slightly higher than the measured percent fat in the lean, muscular individual and the opposite effect in obese individuals.

1 Kg = to 2.20462 pounds 

Steps to Perform The Skinfold Method

1. All measurements should be taken on the right side of the body

2. Meticulously identify the site to be measure with the thumb and forefinger of the left hand( the more subcutaneous fat a client has, the further apart your thumb and forefinger will need to be to grasp an adequate fatfold). Your left elbow should e angled up.

4. The grasp should be one centimeter (1/2 inch) above the site where the calipers will be placed to ensure that pressure from the fingers does not affect the measurement.

5. To be certain that only skin and fat has been grasped, you may, at some site, ask your client to contract the underlying muscle while you continue holding the skinfold with your left hand. If you have inadvertently pinched muscle as well as fat, the muscle tissue will separate from the rest of the skinfold as the contracts.

6. Holding the calipers in your right hand, take the measurement one centimeter (1/2 inch) below your left thumb and forefinger. The calipers should be held level and perpendicular to the direction of the skinfold. Release the jaws of the calipers completely (still holding the skinfold with your left hand) for no more than four seconds while you obtain the reading. (If the calipers remain pinching the skinfold for longer than four seconds, intracellular fluids will be forced out of the tissues and result in an inaccurate, lower value.)

7. A minimum of two measurements should be taken at each site. If your measurements vary by more than two millimeters, take a third or fourth measurement until you have obtained two measurements which vary by less than two millimeters. It is recommended that the measurements be taken in rotational order (e.g., triceps, sprailiac, thigh, then back to triceps, suprailiac, thigh), in order to avoid repeatedly compressing the tissues at the same consecutive site, resulting in smaller and smaller values. 

Standardized site for women:

Triceps – A vertical fold measured in the midline of the posterior arm over the tricep muscle. Anatomical landmarks are the lateral projection of the acromial process and the inferior border of the olecranon process with the elbow flexed at a 90 degree angle. A tape measure should be stretched between these two landmarks and the midpoint located on the lateral aspect of the arm. The actual site is at this level, only on the posterior aspect. During measurement, the right elbow should be extended and relaxed.

Suprailiac – a 45 degree angle diagonal fold immediately above the iliac crest along the anterior axillary line (this is different from the site used in the Durnin & Womersley protocol).

Thigh- a vertical fold in the midline of the anterior aspect of the thigh, midway between the inguinal crease (fold in the hip during hip flexion), and the proximal border of the patella. The body weight should be placed on the left leg so the right thigh is relaxed.

Standardized site for men:

Chest (pectoral) – a diagonal fold taken one half the distance between the anterior axillary line(underarm crease) and the nipple.

Abdomen—a vertical fold taken at the distance of two centimeters (one inch) to the right of the umbilicus. (This fold is horizontal in some other protocols.)

Thigh-same as for females

Calculating estimated percentage body fat:

1.  Carefully measure the appropriate sites two to three times each, following the directions outlined above.

2. Find the average value for each site and then add all the sites together.

3. Use the norms chart. 

Printable chart to show you what your body fat results mean.