Find out the truth about obesity: BMI doesn't tell the whole story!
1. World Health Organization and Obesity
The World Health Organization (WHO) defines obesity as “a condition in which the percentage of body fat has increased to a degree that impairs health and well-being” and, due to the alarming increase in prevalence, has declared it a “global epidemic”.
The high prevalence of obesity is a global public health problem due to its association with several diseases and shortened lifespan.
It arises as a result of a complex interaction of genetic factors, lifestyle and above all eating habits.
Because of the endocrine and inflammatory role of fat tissue, it is necessary to classify obesity based on the composition and distribution of body fat, rather than simply on the increase in body weight.
2. Body Mass Index, What It Is and How It Is Used
Therefore, the body mass index “BMI” in English “BMI”, a ratio of a subject's weight to height squared (kg/m 2 ), used to easily approximate the percentage of body fat and stratify people into categories, leads to a large error, misclassification , and above all to the underestimation of obesity .
However, precisely because of its simplicity of use, it is used whenever one tries to classify a given population.
In fact, the obsolete BMI formula developed nearly 200 years ago by Quetelet does not measure fat, but is simply an imprecise mathematical estimate.
Its popularity stems in part from its convenience, safety, and minimal cost, and its use is widespread, even though BMI ignores several important factors that influence adiposity.
Furthermore, the error in the diagnosis of obesity generates a false belief in people that they are not at risk of developing diseases, making the error itself a further risk factor.
Especially those who have a low amount of muscle mass and an excess of lean mass, defined as “fake skinny” can easily be classified as obese with a normal BMI.
The BMI formula is only an arithmetic approximation for the relative amount of adiposity and is used to predict and assess disease risk in epidemiological studies, thus acting only as an indicator of obesity at the population level.
However, according to a WHO expert committee, “there is no consensus on the cut-off points for PBF that constitute obesity.”
3. BMI vs. Body Fat Percentage
Current research suggests that the percentage of body fat above which obesity can be defined as being between 23% and 25% in men and between 30% and 35% in women .
The clinical use of WHO BMI cutoff values, when applied for example to a population such as the Italian one, causes classification errors and a considerable number of subjects, both male and female, who are not classified as obese on the basis of body mass index alone.
The disagreement has become striking in the classification of obese women: in the 30-40 age group the percentage of obese women according to BMI is 30%, reaching approximately 82% if the classification is based on the percentage of fat.
This finding is in perfect agreement with our data collected over 25 years of body composition analysis, and with another study conducted by Prof. Braverman, presented at the American Association of Clinical Endocrinologists congress in Boston.
4. Conclusion
The actual percentage of obesity is about 3 times higher than that estimated with BMI, so about 80-90% of the world's population suffers from it.
Especially those who have a low amount of muscle mass and an excess of fat mass, defined as “falsely thin”, can easily be classified as obese with a normal BMI.
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