Impedance scale: interpreting its results

What is an impedance scale?

The impedance meter is a type of scale. In addition to measure total weight of an individual, it also indicates the body fat percentage. Before the first weighing, three personal data must be entered into the scale: sex, age and height. The impedance meter keeps the data in memory for the following weighings. Then just step on the scale: an electric current, so weak that it goes completely unnoticed, passes through the body and measures the electrical resistance of the different types of body tissue it passes through (fat, muscle and bone tissue). The data is then displayed on the device. The ideal body fat percentage can vary a lot depending on age and gender.. It oscillates between 20 and 35% in women and between 10 and 25% in men. “The measurements made by an impedance meter scale can be influenced by many factors such as I’hydrationtemperature, time of day and food consumption“, says Agnès Couturier, nutrition practitioner. Impedance scales are commonly used in gyms, doctors’ offices, nutrition clinics and are available for home use.

Depending on the model, the impedance meter scale will measure several parameters:

• The weight (in Kg) used to measure the total body weight
• Body Mass Index (or BMI) is a measure of a person’s body mass based on their height: it is calculated by dividing the body weight in kilograms by the square of their height in meters (BMI = weight / height²). Normality is between 18.5 and 25.
• Body fat mass : this is the number of kilos of fat present in the body. It oscillates between 20 and 35% in women and between 10 and 25% in men. A high fat mass often reflects overweight problems
• body fat percentage : it is the share of fat mass in relation to the total weight of the body. The higher this rate, the greater the risk of overweight.
• muscle mass represents the weight of the muscles of the body and the water contained in them. A high lean mass rate reflects a body constitution of an athletic nature with high muscle mass.
• bone mass : it is the total weight of the bones present in the body. It is more or less important according to the constitution of the persons.
• Body water corresponds to the total amount of water contained in the body. It is expressed as a percentage of the total weight.

Body water rate in women: 45 to 60% water, in men: 50 to 65% water. A higher body water level may indicate water retention. “The whole point of weight loss is to monitor that the subject who wishes to lose weight does not lose muscle mass – only fat mass-, and regulates the problem of water retentionreturning to a correct level of hydration“, specifies the therapist. “Indeed, if we lose muscle mass, the thinning is in fact compromised because it is the muscle cells that transform the energy reserves into ATP, that is to say into energy so that we can go about our activities in full form. And if you lose more muscle mass than fat mass, the body does not firm up, the bulges persist, because the percentage of body fat mass is increasingly important“. Re water retention, it is usually due to lack of hydration or poor hydration (the person drinks but little water, or still badly). “If hydration is not correct, despite a nutritional balance that includes the required amounts of protein and reasonable amounts of carbohydrates, the person will lose muscle mass and not fat mass.

What are the normal values ​​?

The normal values ​​of a diagnostic scale can vary depending on several factors such as age, sex, height, body mass, physical activity and body composition of each person. However, the following values ​​can be considered normal for adults:
► The body mass index (BMI):

• BMI less than 18.5: underweight
• BMI between 18.5 and 24.9: healthy weight
• BMI between 25 and 29.9: overweight
• BMI between 30 and 34.9: class I obesity
• BMI between 35 and 39.9: class II obesity
• BMI greater than 40: class III obesity, or morbid.

► body fat percentage : 20 to 35% for women, 10 to 25% for men.
► Muscle mass ratio : about 30% for women, and 40% for men.
► Body water rate : 45 to 60% water for women and 50 to 65% for men.
► bone mass : between 2 and 4 kg
“The still ‘official’ standard is IMG, or fat mass index which makes it possible to estimate the proportion between the fat mass and the dry mass (muscles), resumes our interlocutor. But it is decried by many specialists. According to medical criteria, weight is considered “normal” or “ideal” when the body mass index (BMI) of a man or a woman is between 18.5 kg/m² and 25 kg/m². This range takes into account the morphology, sex, and age of each person. Except that… a heavy-duty worker or a high-level, muscular and hyper-muscled athlete could be perceived as obese according to this calculation! Many nutritionists ask that we assess the health risk based on the ratio between height and waist circumference”. Not all scales show numbers. “The scale I use shows a chart with a green area (the norm for the person), a red zone (the danger to health, obesity). The interest I see in this approach is that when the person loses their fat mass without muscle loss, the line of their measurement approaches the “norm” zone”.

“When choosing an impedance meter scale, there is several factors to consider to ensure that you are purchasing the product that best suits your needs“, specifies Agnès Couturier. Among them:

• Fonctionnalities
• The precision which varies from one model to another
• The size and the design
• Compatibility : Some body impedance scales are compatible with smartphone applications
• The cost
• The brand : favor brands known for their quality, precision and reliability

What are the most famous brands?

There are several brands in the field of impedance scales. Among the most popular and recognized:

• Tanita
• Withings
• Omron
• Fitbit
• Garmin
• Butter…

They can be found in supermarkets, in household appliance stores (Darty, Boulanger, etc.), in sports brands (Decathlon, etc.), in medical equipment stores, in certain pharmacies, online, etc.

How reliable is an impedance scale?

“From one scale to another, from one brand to another, we will often have different results.recognizes the coach. It’s important to compare the result curves on the same balance. If there is a computer error, this error will always be there. The idea is to have the progress trends and see if everything is going well. Avoid being overly focused on results“. It is recommended place the scale always horizontally or in the same place. Indeed, a few millimeters and everything changes! “And even respecting this, there is an exception: these state-of-the-art jewels are sensitive to extreme heat. Some springs will thus see their density modified. In case of heat peak, as soon as you pass 30°, forget the impedance measurement. Prefer the meter to measure the waist circumference: if we lost centimeters in the waist circumference, we lost fat, about 1 kilo for 1 centimeter “.

What dangers?

“The dangers are indicated by the manufacturers on the notices”, recalls Agnès Couturier. It should be noted that, given the electric current – ​​even weak – we do not offer impedance measurement to people who wear a electrical stimulator (pacemaker), pregnant women and children.

Thanks to Agnès Couturier, nutrition practitioner in Montgermont (35), and member of the Médoucine network.