2023-06-28 16:13:52
After half a century of honorable service, the Body Mass Index (Bmi), the most widely used mathematical formula in the world to evaluate the body weight of men and women, invented in the 1800s by the Belgian mathematician Adolphe Quetelet, could soon retire or at least be accompanied by other parameters. The experts of the Italian Society of Endocrinology (SIE) asked for the revision of the Italian guidelines, in light of the recent changes to the American guidelines, on the occasion of the national congress, on the basis of a recent American study presented at the annual meeting of the Endocrine Society just closed in Chicago.
According to research data, the exclusive use of the Bmi “would lead to the erroneous classification of millions of Americans as non-obese because basing the diagnosis of obesity only on this biometric parameter, expressed as the ratio between weight and height, leads to half of the diagnoses being wrong and underestimating weight in 53% of cases and, consequently, neglecting therapeutic interventions and changes in lifestyle necessary for health – declares Anna Maria Colao, president of Sie and full professor of Endocrinology at the Federico II University of Naples -. the specialists of the Italian Society of Endocrinology propose integrating the Bmi with other parameters, in particular with the evaluation of visceral fat through the measurement of the waistline and the estimation of body composition measured by the fat caliper”.
The limits and the enormous number of blunders of the Bmi “as the only parameter for the diagnosis of obesity – warns Sie – were highlighted by a study by Rutgers University on 9,784 adults aged between 20 and 59, classified as obese based on the results of a test called ‘dual energy x-ray absorptiometry’ (Dexa), capable of accurately estimating body composition.The results – the endocrinologists continue – showed that as many as 53% of subjects ‘escaped’ the diagnosis when assessed with the BMI alone. In practice, basing the assessment on the BMI alone, over half of the obese participants obtained a ‘false negative’ result.”
“When the researchers then added only the parameter relating to the waist circumference to the BMI assessment, the incorrect assessments were reduced by 23% – underlines Colao -. In practice, once both criteria, BMI and waist circumference, have been considered, only 31% of obese people ‘escaped’ the diagnosis.The main limitation of the BMI is that it does not distinguish between water, bone mass, muscle mass and fat tissue nor between the accumulation of visceral fat, the so-called ‘bacon’, and subcutaneous fat , thus not taking into account the influence of gender.Women, in fact – the expert points out -, have more subcutaneous fat than men, located on the hips and thighs, which is less harmful to health than abdominal fat, which males accumulate more easily in the central sections of the body.It is therefore evident that using a single parameter that does not take into account these substantial differences leads both to erroneously overestimating obesity in women and to underestimating it in men, with a dangerous distortion of understanding from part of physicians of the risk of obesity-related disease and mortality.
“For several years, experts have been wondering about the reliability and accuracy of the BMI in classifying obese people – underlines Colao -. Using Dexa as a screening tool is unrealistic because it is economically unsustainable. For this reason, scientists have long been engaged in the search for new simpler, cheaper and more reliable criteria. This does not mean that we should give up on the BMI altogether, which may have a certain degree of reliability and utility in population-based studies to screen for obesity. But it is important that specialists understand the limits of the use of the BMI in the single individual and that other parameters are added to this parameter. The BMI, together with the measurement of visceral fat and relative fat mass, could reduce errors, allowing for a more precise identification of obese people”.
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