What is the body mass index?

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The Body Mass Index, or BMI (body mass index), is a parameter that allows you to determine if your weight is normal or if it differs. It is, therefore, a more generic and less specific to classify individuals according to their body composition, with no distinction between fat mass and lean mass, as is the case with skinfold calipers.

The body mass index is obtained by dividing the weight in kilograms, by height, expressed in meters, squared:

BMI = weight (kg)/(height (m)) 2

According to the World Health Organization, using the values ​​of BMI, the levels of adult’s weight can be mainly divided into the following four categories:

• BMI less than 18.5 = underweight

• BMI between 18.5 and 24.9 = normal weight

• BMI between 25 and 29.9 = overweight

• BMI more than 30 = obese

In the case of children and adolescents from 2 years old the calculated BMI must to be compared with specific growth curves, different for males and females, and then it is necessary consider the variability of multiple conditions.

Although BMI is calculated in the same way for both adults and children, the criteria used to interpret the result obtained for children and teens are different from those used for adults, mainly for two reasons:

• the amount of body fat changes with age

• the amount of body fat differs between girls and boys