Body fat percentage

The body fat percentage (also KFA ) indicates the percentage of stored fat in relation to the total mass of the body . However, it does not allow any conclusions to be drawn about the relationship between structural / abdominal fat and depot fat . The latter can lead to cardiovascular disease if it is increased and is therefore partly regarded as one of the four clinical features of the metabolic syndrome .

The body fat percentage is the basis for calculating other key figures, such as the fat-free mass index and the controversial Fels quotient .

Measurement method

The body fat percentage can be measured using different methods. Volume measurement methods and dual X-ray absorptiometry (DEXA) are considered complicated and expensive, but unsurpassed reference methods.

Mechanical process

Skin fold thickness using caliper

Caliper (pliers)

Calipometry refers to the measurement of the thickness of the skin folds with a caliper ("caliper" or "caliper pliers"), which is carried out at up to ten points on the whole body. It is important in everyday medical practice.

The disadvantage of this method is that measurements always have to be carried out by the same person, because not every examiner selects exactly the same measurement points and applies exactly the same force to the necessary manual wrinkling.

The advantage over electrical measurement methods is that coffee consumption or alcohol etc. do not play a role. It also doesn't matter whether you measure before or after a workout, as the measured subcutaneous fat tissue cannot be built up or broken down so quickly. However, after vigorous physical exertion or a sauna session, temporarily increased water retention under the skin can affect the measurement.

It is doubtful whether the Caliper is suitable as a method for the absolute determination of body fat, since it cannot measure organ fat. However, it is ideal for documenting the trend.

List of measurement methods with the caliper

There are numerous methods of measuring body fat with the Caliper. Depending on the formula, up to ten different measuring points are measured. Using the respective formula, the body fat percentage is then calculated on the basis of the measured values.

Accumeasure wrinkle measurement
Fold measurement according to Behnke & Wilmore
2-fold formula according to Sloan
3-fold formula according to Jackson & Pollock
3-fold formula according to Lohmann
4-fold formula according to Peterson
4-fold formula according to Forsythe & Sinning
4-fold formula according to Durnin & Womersly
4-fold formula according to the National Health Center of America
7-fold formula according to Jackson & Pollock
9-fold formula according to Parillo
Johnson's 10-fold formula
10-fold formula according to Parizkova

US Navy method (body size and various body girths)

With the so-called US Navy method , the body fat percentage is calculated using the following body measurements:

K: height
N: neck / neck circumference (below the larynx)
only in men:
- B: waist circumference (above navel)
only for women:
- T: waist circumference (the narrowest circumference between the lower rib and the navel)
- H: hip circumference (the widest circumference below the navel)

The formulas use the decadic logarithm , synonymous with . ${\ displaystyle \ lg}$ ${\ displaystyle \ log _ {10}}$

For men

${\ displaystyle KFA = 86.010 * \ lg (BN) -70.041 * \ lg (K) +30.30}$ (Measures in cm)

${\ displaystyle KFA = 86.010 * \ lg (BN) -70.041 * \ lg (K) +36.76}$ (Dimensions in inches )

For women

${\ displaystyle KFA = 163.205 * \ lg (T + HN) -97.684 * \ lg (K) -104.912}$ (Measures in cm)

${\ displaystyle KFA = 163.205 * \ lg (T + HN) -97.684 * \ lg (K) -78.387}$ (Dimensions in inches)

Radiation measurement method

Three-Dimensional Photonic Bodyline Scanner - imaging process using an ultrasonic scanner ; allows the measurement of the thickness of fat and muscle layers both locally and globally. This enables exact measured values - in contrast to a projection from one point to the whole body, as is the case with measurements using a caliper. Due to deviations from DEXA and hydrodensitometry, this elegant method has not yet spread widely.

Whole Body DEXA Measurement - DEXA (dual energy x-ray absorptiometry) is a radiological method that scans the body with x-rays, which can determine the body's content of fat, muscle mass, and bone. Due to the radiation exposure and the associated costs, this very precise method is not generally applicable. In Germany it is not legally permissible for young people.

⁴⁰ K measurement - A method in which the activity of the naturalradioactive isotopepotassium-40 (⁴⁰K)stored in the muscles ismeasuredusing awhole-bodycounter. From this, conclusions can be drawn about the percentage of fat in the body: the higher the mean activity per kg of body weight, the smaller the percentage of fat.

Electrical procedure

In everyday medical practice, in addition to measuring the body fat percentage with a personal body fat scale , a bioelectrical impedance analysis (BIA) is a quantitative yet relatively simple method of determining the body fat percentage. There are now body fat scales that measure the percentage of organ fat and bone mass.

In bioelectrical impedance measurement, the body fat percentage is determined by measuring the electrical resistance offered by the body. It is determined by applying a low electrical voltage to the body and measuring the resulting current flow (<1 mA). Some body fat measuring devices apply the voltage via contacts in the weighing platform only to the feet; other devices have a handpiece or handles that can be used to measure. The best measurement results are achieved with devices that have both a weighing platform and a handpiece.

Volume measurement method

Volume measurement method in air displacement plethysmography

Hydrodensitometry - This is the volumetric determination of the water displacement in a type of bathtub. The water displacement is related to body weight. The difficulty lies in correcting the volume of gas in the body, especially in the lungs. Total immersion is a nuisance for the test subject; With the necessary breath, measurement times of over half an hour usually result. Therefore, the method is not suitable for everyday use, but only serves as a reference.
Whole-body air displacement plethysmography or air displacement plethysmography (ADP) - ADP uses air displacement instead of water displacement in hydrodensitometry. This eliminates the annoyance of submerging the test subjects and the measurement time is shorter (only 10 minutes).

According to the conversion formula from Brozek or Siri, a body fat percentage of 5–40% is mapped to a density of 1.09–1.01 g / cm ³ .

Chemical measuring method

Sulfur hexafluoride dilution method - Developed and used in Japan, the method is based on changes in pressure due to the release of heat by the body. Rather unpopular due to deviations from DEXA and hydrodensitometry.

Normal and limit values

Medical recommendations and normal values for the percentage of body fat depend on age, gender and body type. Twenty year old men have an average body fat percentage of 18%, young women one of 25%. This percentage increases with age, while lean mass decreases due to the loss of muscle tissue. At the age of 45, body fat percentages of 22–24% are typical in men and around 30% in women. A healthy body fat percentage for women is usually below 30% (better below 25%), for men under 25% (better under 20%). Since larger energy reserves are required to care for the offspring during pregnancy and breastfeeding, women have a higher percentage of body fat.

Classification of body fat based on Gallagher et al., American Journal of Clinical Nutrition , Vol. 72, Sept. 2000

Age (years)	Women				Men
Age (years)	low	normal	high	very high	low	normal	high	very high
20-39	<21%	21-33%	33-39%	≥ 39%	<8%	8-20%	20-25%	≥ 25%
40-59	<23%	23-34%	34-40%	≥ 40%	<11%	11-22%	22-28%	≥ 28%
60-79	<24%	24-36%	36-42%	≥ 42%	<13%	13-25%	25-30%	≥ 30%

Since this table is aimed at a general audience, there are very likely people with a body fat percentage below the above values who are still in good health. Male professional athletes in the age group up to 30 years usually have a body fat percentage of approx. 8–12%. The body fat percentage of a male professional bodybuilder is around 5% or just below during the competition season.

A body fat percentage of at least 3 percent is essential for men and 10 percent for women.

Sources and individual references

↑ Body fat pliers - Caliper. In: Körperfett-Analyze.de. Retrieved February 16, 2017 .
↑ ^a ^b ^c ^d body fat calculator, www.bmi-rechner.net
↑ ^a ^b US Navy Method Calculator , Körperfettwaage-info.de
↑ ^a ^b Body fat evaluation method in Department of Defense Instruction , engl., Pdf, p. 15
↑ Denis M Medeiros, Robert H Friis, Denis M Medeiros, Robert EC Wildman: Advanced Human Nutrition . Jones & Bartlett Publishers, December 16, 2013, ISBN 978-1-4496-8959-9 , p. 221.

literature

Werner Hoeger : Principles and Labs for Fitness and Wellness. ISBN 0-534-59986-9
Ibrahim Elmafda, Claus Leitzmann : Human nutrition. UTB-Verlag Eugen Ulmer, Stuttgart 1998

[1] Body fat pliers - Caliper. In: Körperfett-Analyze.de. Retrieved February 16, 2017 .

[bmi-rechner-2] body fat calculator, www.bmi-rechner.net

[körperfettwaage-3] US Navy Method Calculator , Körperfettwaage-info.de

[DepartmentOfDefense-4] Body fat evaluation method in Department of Defense Instruction , engl., Pdf, p. 15

[MedeirosFriis2013-5] Denis M Medeiros, Robert H Friis, Denis M Medeiros, Robert EC Wildman: Advanced Human Nutrition . Jones & Bartlett Publishers, December 16, 2013, ISBN 978-1-4496-8959-9 , p. 221.