Body mass index (BMI): an imperfect indicator?

To assess body size and likely health risks, the BMI calculation takes two factors into account: height and weight. However, the simplicity of this calculation comes at a price: BMI has its limits. Here are some of the reasons why this figure should be viewed with caution.


A classification system that does not take into account individual variations


As the different BMI cut-offs have been established based on health data from a population of European and North American adults, people under the age of 18 and pregnant or breastfeeding women should not use this classification system. In addition, there is currently no consensus regarding people with other ethnic origins. Moreover, while there are differences in the composition and body size of men and women, this classification system does not make any distinction according to the age or sex of individuals.


In short, as this system is based on population data, it does not make it possible to precisely assess the risks to an individual’s health in a personalized way. In order to specify the individual health risk, other factors such as lifestyle (diet and physical activity) and the presence of other health risk factors must be taken into account.


Some “natural” weight off intervals of “normal weight”


Since the various determinants of weight are not taken into account in estimating BMI, this classification system may underestimate or overestimate the health risks for some people. For example, adults who have strong musculature, such as elite athletes, may have a BMI in the “overweight” or even “obesity” range, whether they are in good health or not. Conversely, naturally thin people can have a BMI slightly below the “normal weight” range without necessarily being at risk for developing health problems.


Beyond BMI: The Way of Life


Although studies show that being overweight and obese are risk factors for certain diseases such as type 2 diabetes, cardiovascular disease, hypertension, sleep apnea, osteoarthritis and certain cancers, The extent to which excess weight is associated with a health risk remains unclear. In addition, these epidemiological studies rarely take into account lifestyle habits, weight fluctuations (the “yoyo” effect of drastic diets) or the socio-economic status of participants when they establish a relationship between weight and development of the patient. some diseases. However, these factors have a real influence on a person’s health risks. It is therefore difficult to define which determinant of the weight is mainly involved in the development of these diseases.


Some studies have shown that, when these factors were controlled, the risk of developing health problems diminished or disappeared completely in participants who were overweight or mildly obese. Take the example of the “yoyo” effect resulting from repeated weight loss attempts, which increases the level of inflammation and therefore the health risks. In some studies, participants who were mildly obese, but maintained a stable weight, had similar health risks to participants with a “healthy weight.” In other words, it is better to keep a slight excess weight than to see our weight fluctuate constantly over the years.


Other benchmarks for assessing health risks


The place where we accumulate excess weight makes it possible to assess the health risks even better than the number written on our scale. Indeed, an excess of adipose mass, and particularly an excess located in the abdominal region, is linked to various health problems. Thus, measuring waist circumference and knowing our body type are other useful benchmarks for assessing health risks.


All in all, even if it is imperfect, BMI remains unquestionably a useful screening tool. However, he alone cannot diagnose a health problem. If you have any concerns about your weight, see a health care professional who can do a comprehensive assessment of your condition, such as a doctor or nutritionist. 

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