Weight, and more specifically weight gain, is a subject of concern to many people, especially athletes. But before starting any diet and / or undergoing intense physical training in order to lose weight, the first thing to do is to establish the inventory of your fat mass to target your efforts. .

Fat meters are instruments that measure fat very accurately based on the measurement of skin folds. Their design and use are as simple as they are reliable.

Composition

An adipometer is a small manual instrument made of plastic or metal that looks like a kind of compass equipped with a protractor graduated in cm (and sometimes also in inches) to read the results. It is also called skinfold forceps. Some models are electronic with the measurement reading on a small LED screen. Others are connected to dedicated applications.

The more sophisticated professional models are fitted with a precisely calibrated spring and a pressure gauge where the measurement is reported. They are also called Harpenden clamp.

The measurement of skin folds, carried out in a rigorous and reproducible manner, makes it possible to deduce the percentage of fat mass. Four skin folds are thus measured:

• the triceps fold: vertical fold in the middle of the posterior face of the arm;
• the bicipital fold: vertical fold in the middle of the anterior face of the arm;
• the subscapular fold: oblique fold under the point of the scapula;
• the suprailiac fold: oblique fold on the stomach at the level of the iliac crest.

To these four folds can be added others which allow to refine the measurements. This may be necessary in particular in the case of a particular diet or for certain sports practiced at a high level where weight monitoring and mass distribution are subject to extremely strict control. These additional folds are:

• the umbilical fold: vertical fold about 5 centimeters from the navel;
• the quadriceps fold: vertical fold in the middle of the anterior aspect of the thigh;
• the sural fold: vertical fold on the inside face halfway up the leg;
• iliocrystal fold: almost horizontal fold above the iliac tip.

Calculate your IMG

There are several mathematical formulas that professionals use to calculate the body fat index (BMI). The choice of the formula depends on age, sex, weight, height, ethnicity, physical condition (high level athlete, occasional athlete, sedentary).

• Evans’ formula used for athletes is based on ethnicity, gender, and measurement of the triceps, quadriceps, and abdominal folds;
• Slaughter’s formula is used for children and adolescents: it depends on age, ethnicity, and measurement of the triceps and subscapular folds;
• Peterson’s formula, or 4-point method, is intended for the majority of adults with moderate physical activity: it takes into account the weight, height, age and measurement of the triceps and subscapular folds. , supraspinal and quadriceps;
• The formula conventionally used by the general public takes into account the age, sex and the sum of the triceps, bicipital, subscapular and suprailiac folds. The results are then reported in a table which makes it possible to know the corresponding percentage of fat mass.

Interpret the results

Adipometers sold to the general public are accompanied by an IMG correspondence table based on the measurement of the folds, the age and the sex of the individual.

For an individual practicing moderate regular physical activity, the average body fat percentage should be within a certain range. Below, the individual is considered too thin, and beyond, he is overweight:

Average IMG norms for an individual practicing moderate physical activity

What is the IMG for

The calculation of the IMG concerns several types of audiences:

• people wishing to follow a diet to refine their silhouette, improve their quality of life and preserve their cardiovascular capital;
• athletes to follow the development of their musculature and adapt their training and their diet accordingly. Depending on the sport practiced, the expectations on the distribution of fatty masses on the different areas of the body are not the same. The IMG of athletes is between 8 to 13%;
• bodybuilders cultivate their Herculean profile by aiming for an IMG of 4% to 6%, a figure that is very difficult to maintain for more than a few days.

The stages of operation

Despite its apparent ease of use, the measurement of skin folds must follow a fairly strict protocol so that the results are as accurate as possible.

1. The measurement should always be done by the same person;
2. the measurement of the folds must be done in a standing position;
3. the individual must be perfectly relaxed;
4. measurements are always performed on the right side of the body;
5. the fold is pinched between the thumb and forefinger then pulled and held, being careful not to pinch the underlying muscle;
6. the clamp is placed perpendicular to the axis of the fold and at a distance of 2 centimeters from the fingers;
7. the fold is released and the measurement is taken within two seconds;
8. each fold is measured 3 to 5 times to establish an average;
9. the results of the folds are noted, added together and reported in the IMG table.

Precautions to take

• It is recommended not to practice strenuous physical activity before the measurements so as not to distort the results.
• To ensure good grip of the folds, the skin must be clean and dry.

The different models

• The entry level manual adipometer is supplied with the correspondence tables. There are many variations for a price around 10 €. It can be found in sports, medical equipment or online stores.
• The connected fat meters transmit the results via Bluetooth to a dedicated smartphone application which automatically calculates and determines the IMG. Their price is higher: from 30 to 100 €.
• Some models use a tape measure instead of a clamp to make the measurements.

Other methods to measure your IMG

The impedance meter

The impedance meter works like a bathroom scale. An electric current flowing through the body helps determine the level of fat mass. However, there is a significant margin of error for the results, in particular depending on the state of hydration of the tissues.

The Deurenberg formula

You can also calculate your IMG in a very theoretical and approximate way, without any medical instrument:

IMG% = (1,2 x BMI) + (0,23 x age) – (10,8 x sex) – 5,4

with BMI (body mass index) = weight (in kg) / height²(in meters) and sex = 0 for women and 1 for men.