The impedance scale is a device for measuring weight but also defining body composition, by measuring the body’s resistance to the passage of a low-intensity electric current. It thus makes it possible to provide various information such as the percentage of fat mass, the percentage of water retention, the percentage of bone mass or even nutritional needs.

The impedancemeter scale is a scale, equipped with sensors, making it possible to measure the weight but also to analyze the basal metabolism by displaying:

• body mass index (BMI);
• the percentage of body fat;
• the rate of visceral fat;
• muscle mass;
• healthy bone mass;
• bone mineral mass;
• the water mass in% or in kg, etc.

It uses impedancemetry, a technique used to define body composition, by measuring the body’s resistance to the passage of a low-intensity electric current.

Concretely, the sensors send an electric current, which passes through the most conductive compartments of the body – those containing water – and avoids the most insulating compartments, that is to say those containing fat. The electrical measurements obtained are then interpreted according to the age, weight, sex, level of physical activity and height of the subject, and translated as a percentage relative to the overall body mass.

The impedance scale is generally used:

• as part of a medico-sporting follow-up, by high-level athletes but also as part of the physical preparation of astronauts: to monitor and control the development of their muscle mass and their fat mass. This makes it possible to assess the impact of physical preparation programs on the body and to adapt diet or training;
• in a fitness center or in an establishment specializing in the treatment of overweight and obesity, to document the variation of the different masses over the course of the consultations and thus allow the impact of hygiene and dietetic measures to be assessed and better support the patient. patient in stabilization or in weight loss. The stake in this case is to reduce the fat mass, without having too much impact on the muscle mass, too great a loss of muscle which can cause generalized fatigue and pain contravening the treatment;
• within the framework of medical monitoring, it can allow the monitoring of a diet specific to a chronic disease, or the monitoring of a protocol of undernutrition, renutrition or even hydration. It can also help to detect and follow the evolution of diseases such as water retention, sarcopenia (muscle wasting due to aging or a neurological disease) or osteoporosis.

The use of an impedance scale is simple. Simply :

• step on the scale, barefoot;
• place your feet at the level of the electrodes (one or two on each side);
• enter their age, size, sex, and even their level of physical activity;
• the current is then emitted by the left sensor (s), and recovered by the right sensor (s) (or vice versa), after having crossed the entire body mass.

Precautions for use

• always weigh yourself under the same conditions: at the same time of the day (rather in the late afternoon or early evening because that is when the hydration level is most stable), in the same outfit, on the same type of floor;
• avoid too intense efforts just before weighing yourself;
• avoid weighing yourself when leaving the bath to avoid damaging the sensors. Better to wait until you are really dry;
• hydrate as usual;
• avoid having a full bladder;
• spread your arms and legs slightly so as not to obstruct the flow of current.

Cons-indications

It is recommended to avoid using an impedance scale when wearing a pacemaker or other electronic medical device. In this case, do not hesitate to seek the advice of a doctor to know the best way to lose weight.

Furthermore, the use of this device is strictly prohibited in pregnant women. Although the current intensity used is minimal, the fetus is sensitive to it.

Initially intended for healthcare professionals, the impedance meter scale has become a very common accessory available online, in pharmacies or in supermarkets.

There are different models of impedance meter scales. The main selection criteria include:

• the reach, that is to say the maximum weight that the scale can support;
• the precision, that is to say the error threshold. In general, this type of device is accurate to within 100 g;
• Memory : Can the scale record the data of several people? for how long ? ;
• the operating mode of the device: battery or mains? ;
• the functions of the scale and their compatibility with your equipment (mobile phone / iOS and Android systems) : is it a simple impedance meter or an impedance meter connected by Bluetooth? ;
• display: choose it adapted to its sight in order to obtain the best possible visibility.

It should be noted that the most reliable devices have sensors in the feet but also in the hands, allowing the current to pass through the whole body, and not just the legs. This type of device, called segmental, is also more interesting because it allows to obtain targeted data on the arms, trunk and legs.