by Vera Martinella
New research indicates that BMI, used alone, “mistakes” half of diagnoses. Adding the waist measurement reduces errors. And the difference between males and females must be considered
That overweight and obesity increase the chances of getting various types of cancer is nothing new. However, several recent studies have indicated that it is not only the rising needle of the scale that is particularly dangerous, but also the enlargement of the waistline and the age during which one gained weight. In the wake of the data collected in recent years, a new one is also inserted study presented during the last congress of the Society of Endocrinology which underlines how the body mass index (or BMI, body mass index) alone is not sufficient to indicate the state of overweight or obesity of a person, so much so that more than half of the approximately 10 thousand Americans subjected to evaluation have “wrong” the diagnosis. To draw attention to the matter, proposing to review the current Italian guidelines on obesity, are the experts of the Italian Society of Endocrinology (SIE) on the occasion of their national conference.
A new US study
The body mass index is obtained by dividing the weight (expressed in kilograms) by the square of the height. A BMI value below 25 indicates a normal weight person; from 25 to 30 you are overweight; 30 to 40 indicates obesity and over 40 a severe form of obesity. In the new study, researchers from Rutgers University collected data on 9,784 adults, aged between 20 and 59 years, classified as obese based on the results of a specific test (dual energy x-ray absorptiometry, or DEXA), capable of accurately estimating body composition. The results showed that, basing the assessment on BMI alone, more than half of the obese participants had a false negative result. “According to the data, the exclusive use of the BMI would lead to erroneously classifying millions of people as non-obese because basing the diagnosis of obesity only on this parameter, expressed as the ratio between weight and height, leads to underestimating the real state in 53% of cases and, consequently, to neglecting therapeutic interventions and lifestyle changes necessary for health – clarifies Anna Maria Colao, president of the and full professor of Endocrinology at the Federico II University of Naples -. For this reason, 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”.
I limit the BMI
After half a century of honorable service, the body mass index, the most 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 therefore retire or at least be joined by other parameters. Experts have long emphasized that the BMI represents an approximate index since it does not take into account the type of physical constitution, the location of fat and muscle mass. Another value to consider is the waist circumference (measured at navel height), which is an index of abdominal adipose tissue in relation to the risk of cardiovascular and dysmetabolic diseases and which should not exceed 80 centimetres. «When the researchers added to the evaluation with the BMI even only the parameter relating to the waist circumference, the incorrect evaluations were reduced by 23% – underlines Colao -. In practice, once both criteria, BMI and waist circumference are 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».
Differences between males and females
Many researches are still open, but the information available so far leaves no room for doubts: obesity and overweight are among the known risk factors for at least six different types of cancer: endometrium, colorectal, oesophagus, kidney, pancreas and breast, especially among post-menopausal women. «Women – concludes the expert -, 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 clear that using a single parameter that does not take into account these substantial differences leads both to erroneously overestimating obesity in women and underestimating it in men, with a dangerous distortion of doctors’ understanding of the risk of obesity-related disease and mortality.
July 21, 2023 (change July 21, 2023 | 09:14)
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