Measure body fat & calculate body fat percentage

The display on the scale does not always reveal everything, because muscles and other factors can also contribute to the weight of the body. With the body fat percentage, or KFA for short, you can calculate the percentage of fat in the total body mass. But how do you measure body fat? From hydrostatic weighing to the DEXA scan: What measurement methods are there and how useful and accurate are the different methods of body fat analysis?

Measurement by hydrostatic weighing

The body fat percentage can be measured or calculated using a variety of methods. However, not all methods are equally accurate. Hydrostatic weighing is considered to be a very accurate method, in which the body weight is measured under water and the amount of water displaced is also noted. Since the method is very complex and expensive, it is only used relatively rarely.

Calipers (body fat clamps) or body fat trolleys are often used for home use or body fat determination in the gym. However, depending on the model, body fat trolleys in particular do not always provide exact values.

Measure body fat with calipers

With calipometry, the skin fold thickness is determined with the help of a caliper, the so-called caliper or caliper forceps. The thicker the skin folds, the higher the body fat percentage. To ensure that the results are as accurate as possible, the test should always be carried out by the same person. It is also advisable to measure each skin fold three times and then calculate the mean value. However, the measurement results are never completely accurate, since the body fat percentage is extrapolated from a few measurement points to the entire body.

In contrast to electrical measuring methods, a caliper offers the advantage that the consumption of beverages such as  coffee  or alcohol cannot lead to distortions. The time of the measurement – before or after the training – is also irrelevant. Because the subcutaneous fatty tissue cannot build up or break down as quickly.

The correct skinfold measurement for men and women

In order to achieve the most accurate result possible, men and women should measure their skin in at least three places with the caliper.

Men  should measure their skinfolds like this:

• Chest: Form a crease midway between chest and armpit. The crease should follow the direction of the pectoralis major.
• Belly: Form a vertical abdominal fold two to three centimeters from the navel.
• Thigh: Form a longitudinal crease on the front of the thigh, preferably in the middle.

This is the best way for women  to determine their body fat:

• Upper arm: Form a lengthwise fold on the back of the upper arm.
• Belly: Form a vertical abdominal fold two to three centimeters from the navel.
• Hip: Form a 30 degree crease over the hip bone.

Determine body fat with a body fat scale

Body fat carts determine the percentage of body fat by passing a small amount of current through the body. This procedure is called bio-impedance analysis. With the help of the electrical resistance that is measured, the body fat percentage can then be calculated. Fat is a poorer conductor of electricity than muscle, so it has a higher resistance.

With a body fat scale, the measurement result can be influenced by a wide variety of factors, such as wet feet, creamed skin or a full bladder. Since the current flows better through the body in these cases, the result can be up to 30 percent too low.

Overall, many scales do not provide accurate results because they often only measure the lower part of the body rather than the whole body. The dangerous abdominal fat is usually only recorded by scales that have two hand sensors in addition to the electrodes on the feet.

If you want to determine your body fat percentage very precisely, it is best to use other methods.

Bioelectrical Impedance Analysis (BIA)

Bioelectrical impedance analysis measures body fat percentage by passing a low-level electrical current (800 microamps) through the body. In this respect, the method is similar to the body fat scale. In contrast to this, however, a total of eight electrodes are attached to the body with BIA, two per foot and hand. Four electrodes conduct the current through the body, while the other electrodes measure changes and resistances in the electric field.

These measurements provide information about the body fat percentage, as fat tissue conducts electricity much worse than muscle tissue, which has a high water content. The water balance can therefore also influence the measurement result. Before performing a DIA, the affected person should not have eaten or drunk anything for several hours. Sport is also taboo up to twelve hours before the measurement, as this changes the water balance through sweat production.

Overall, however, the bioelectrical impedance analysis is a reliable measurement method for calculating the body fat percentage.

DEXA scan for body fat analysis

The abbreviation DEXA stands for Dual Energy X-ray Absorptiometry, also known as X-ray absorption technology. The technology is also used to  measure bone density  if osteoporosis is suspected.

With the DEXA scan, the proportion of fatty tissue, muscle mass and bones is determined very precisely using X-rays. This also makes the distribution of the fat visible.

Although this measuring method is very precise, the disadvantage is the low exposure of the body to X-rays. If possible, other methods of calculating body fat percentage should be used.

Calculate your body fat percentage yourself

It is not possible to simply calculate the body fat percentage without any measuring device. There are some formulas, but they can only be used to determine body fat relatively imprecisely. Some calculators, for example, put the waist circumference in relation to the body weight. However, the waist circumference does not allow a reliable statement about the ratio of fat and muscles in the body.

In the so-called US Navy method, the waist circumference, hip circumference, neck circumference and height are used for the calculation. The individual values ​​are determined with a measuring tape. The body fat percentage is then calculated using a special formula. Various websites offer programs for calculation here. However, body weight is not included in the calculation. Even with the US Navy method, no statements can be made about the ratio of fat and muscle through the calculation.