Body Mass Index: Why is this tool not so reliable?

Body mass index (BMI) is often presented as an important indicator for identifying underweight or overweight.

Often used by doctors, it also helps detect possible eating disorders such as anorexia or bulimia.

However, this quick calculation of overall body size is not as reliable as one might think.

On the Internet, many sites allow you to easily and quickly calculate your body mass index, commonly known as BMI. Whether you’re a man or a woman, the formula is the same: just divide your weight by the square of your height. For example, if you are 1.60 meters tall and weigh 60 kg, you will get a result of 23.4 (60/2.56). Between 18.25 and 25, your build is said to be “normal”. Below that, you are underweight.

If your BMI is above 30, the index classifies you as overweight or obese. Recognized by the World Health Organization (WTO) since 1997, this calculation is used by many doctors to detect possible pathologies associated with excess weight, such as type 2 diabetes, high blood pressure and cardiovascular diseases. However, these results should be taken with a grain of salt. We explain why.

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Why is the reliability of BMI debated?

Although the WHO has used it as a reference for years to determine whether a person is overweight or not, many voices agree that BMI lacks accuracy. First, let’s remember that pregnant women are excluded from this calculation, as are athletes and even children, for whom only the growth curve in the health record should serve as a reference. Then, the tool does not take into account a high proportion of physical and morphological parameters that may explain why an individual presents results above or below BMI norms. Véronique Lisse, author of numerous books devoted to nutrition, finds a series of shortcomings. “It does not give any information about how much fat, bone, water or muscle is in the body. There are people whose body is made up of muscles and some fat.

“, she explains in Top Sente.

Given these numerous ellipses, BMI may consider people overweight who cannot yet be defined. In addition, the tool raises other criticisms from experts who claim that it does not always detect eating disorders. A person can suffer from bulimia while having a “normal” BMI, just as someone classified as overweight can eat healthily. The latter also does not consider the feelings of the patient, who may have a “good” BMI despite not being comfortable with their body.

What other tools to change BMI?

Some options make it possible to fill in the blanks in BMI, which is therefore not sufficient to diagnose the state of thinness or obesity. For a more complete analysis, the fat mass index (BMI) makes it possible to assess the amount of fat in the body. To find out, Véronique Lisse recommends weighing yourself with an impedance meter scale, “More specific and complete“. Equipped with several sensors, these commercially available scales go further than traditional bathroom scales. They provide important information, including fat, muscle, bone and water content.

As mentioned, measuring the waist circumference makes it possible to identify the presence of abdominal fat, which, when very abundant, represents a risk factor in the development of cardiovascular disorders, cholesterol, diabetes or even diabetes. Hypertension. Finally, the body volume index, for its part, takes into account many parameters such as muscle and fat mass, weight status, height, hip-waist ratio, but also stomach volume. In conclusion, it should be remembered that only a health professional has the necessary qualifications to perform a nutritional assessment.