Nutritional body mass index

| There are different methods to quantify body fat, but currently the most widely used method to express weight adequacy in adults is the Body Mass Index (BMI), also known as the Quetelet Index.

The body mass index allows to know the degree of obesity through weight and height. It is calculated by dividing the weight in kilograms (kg) by the height in meters squared (m) 2 and is valid for both sexes. For example, if a man weighs 80 kg and is 1.70 meters tall, his BMI will be: 80 / (1.70 * 1.70) = 27.68

Formula body mass index = weight / height * height

Meaning of BMI result

According to SEEDO (Spanish Society for the Study of Obesity) these are the types of results according to the BMI obtained:

• Low weight: below 18.5
• Normal weight or «normal weight»: between 18.5-24.9
• Overweight: between 25.0-29.9
• Obesity: above 30
• Morbid or severe obesity: over 40

In some people, a 25-26.9 might be thought of as "normal weight«. It would correspond to those people in whom obesity does not coexist with other risk factors such as diabetes mellitus, hypertension, established cardiovascular disease, smoking, etc.

Obesity and overweight

The values ​​of 25 and 30 to define overweight and obesity in adults, they are not valid in children and young people. To define overweight and obesity in these age groups, use age and gender specific values of the 85th and 97th percentiles of BMI, respectively.

It should be taken into account that, although obesity and overweight are associated with an increase in body weight, the weight gain is not always due to obesity or being overweight. Weight gain can be due to:

• Increased muscle mass (athletes)
• Higher Water retention in different regions of the body (in individuals with diseases that cause them to lose protein through the kidney or prevent them from making protein in the liver).

However, if we rule out these states, BMI is a good marker of fat gain, that is, of overweight and obesity because, if height remains constant, only variations (gains or losses) in weight will condition variations in weight. BMI.

Therefore, currently the BMI is the reference method as an obesity parameter used in daily clinical practice.