The Body Mass Index (BMI) is a formula that gives us data about our ideal weight. It is widely used, but usually leads to errors since it is usually wrong in many casesespecially in athletes. In this article we will tell you a brief description of the BMI and why its use is not recommended.
What is the Body Mass Index (BMI)?
The BMI is a number that is obtained by performing a calculation whose variables are the person’s weight and height. To calculate it we need divide our body weight by our height squared (in meters).
If we weigh 80 kg and measure 1.80m we can obtain our BMI by dividing 80 (kg) by 1.80 (m) squared. The result tells us that our BMI is 24.7 kg/m2. To find out what that number means, we will use a category table according to our BMI.
BMI | CATEGORY |
---|---|
Below 18.5 | Below ideal weight |
18.5 to 24.9 | Healthy |
25.0 to 29.9 | With overweight |
over 40 | Extreme or high-risk obesity |
In the example of a person weighing 80kg and 1.80m tall, we can see according to his BMI of 24.7 that he is in the “healthy” category, although very close to being overweight. Can you calculate your BMI easily with the commented calculation and assess which category you fall into.
An BMI above 25 and below 18.5 are associated with increased risk of disease, and thus morbidity and mortality. Until recently it has been used by almost all professionals, but relatively recently other more reliable indicators have been preferred.
body fat percentage
The really important data is not our body weight, but the amount of fat we have at that weight, since it is the accumulated body fat that does increase the risk of diseases. That fat can accumulate in different areas, which is why we talk about different types of fat.
The more dangerous is visceral fat that is found surrounding our organs, such as the heart. There are others such as subcutaneous fat that are also indicators of poor health when it accumulates in excess, but with a somewhat lower risk than visceral fat.
BMI tells us nothing about these types of fat. They only relate weight and height, without going into more detail. That is why it can be a general indicator in some populations, but very unreliable in other people.
Why shouldn’t we use BMI as the “ideal” indicator?
For my height my ideal weight is 70kg. That is one of the most heard phrases in people who use scales like the ones in pharmacies that issue a ticket with a section that shows both the BMI and the ideal weight.
However, they can be guided by wrong data and start working towards the wrong goal. The following reasons are the main reasons why the use of BMI is misleading and is preferable based on our amount of fat and not on this index.
Muscle mass weighs, but it is healthy
Our body has different components that weigh and are more or less essential. Fat is dispensable (up to a percentage that we must have for our vital functions), but muscle mass is essential.
Muscle mass will make us be independent when we grow up because we can get up from the sofa, walk and avoid falls. Throughout life, it provides us with aesthetic support, which is why it also helps our self-esteem.
And the most important thing is that muscle is an active tissue that gives us health. A greater muscle mass our BMI will also be greater since we will weigh more. An athletic person with very little body fat may fall into the category of “overweight” or “obese” to the contrary.
One of the classic examples is Roberto Carlos, a Real Madrid soccer player a few years ago. His height did not exceed 1.70m, but his muscular build made his BMI mark him as “obese”. Therefore, BMI should not be used on people who train because it doesn’t make sense.
In older adults it is something different
As we age and begins a physical decline it is preferable to have a somewhat higher BMI, since it is associated with a better survival rate than lower BMI. In this case, we will be interested in being in values above 25 in the BMI, despite being in categories of excess weight.
not in children
Each child has a completely opposite growth rate, with large differences between measurements. In children, the BMI goes by percentiles according to age, so It can easily give wrong data.
Does not provide any information
The BMI is just data that does not tell us how the cholesterol or blood sugar levels are. We don’t know if the blood pressure and triglycerides They are within healthy ranges.
active or sedentary
A healthy BMI for a sedentary person could be worse than a BMI in the overweight category for an active person. When comparing the lifestyle of different people it is important to take into account the amount of accumulated fat, but also if the person is active or notsince a sedentary lifestyle can be more dangerous than a BMI outside healthy ranges.
Why should we take into account the BMI?
For the whole non-special population (sedentary adults) is fine as a general measure of obesity. It is a quick measure that can give some information about the person’s status, as long as they are not within those special populations.
If we do not have another measure, or we need to evaluate an entire educational center, it can serve as a guide. Yes indeed, with all the limitations that we have commented previously. We must leave it as a last resort, but knowing that it exists and that its reliability is limited.
Alternatives to BMI
The best option we have is to perform a DEXA to see exactly the number of compartments we have: how much fat, how much muscle mass, bone weight… We add a blood test to delve into our state of health and we have the perfect formula.
The problem is that it is very difficult to be able to do a DEXA due to the availability of the machine in the medical center and due to its high cost. There are other alternatives to the BMI such as measuring the skinfolds at different points, and using a formula to calculate how much fat we have accumulated.
It is a much cheaper method and can be done by anyone certified in skinfold calculation. If we are not convinced either, we can simply make the mirror our BMI. To the see ourselves in the mirror we know if the amount of accumulated fat is excessive or not, in very broad strokes.
To accompany this visual measurement, we can use the measurement of our waist and hips, obtaining data that we can compare with different tables and that we can use as a guide when losing weight.
In Vitónica | Body fat percentage: how to know if you are in an optimal percentage
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