Health consciousness all around the world has never been higher than it is now. The importance of exercise and nutrition is well known to many, and there has been much research about the best foods, nutrients, and exercise types to become healthy. Because of this increased awareness, most of us will know what BMI or Body Mass Index is. If you are not aware, the Body Mass Index is a formula that takes your height and weight to give you points. Those points are used to measure your fitness.
When a cube's edge length is increased from 1 ft to 3 ft, its volume increases from 1 cubic foot to 27 cubic feet. However, its surface area increases from 1 square foot (per side of the cube) to 9 square feet. Volume increases much more than surface area.
If your BMI is under 18.5, you are underweight. If it is above 18.5 and below 24.9, you are in the normal weight range. If it is between 25 and 30, you are overweight. If it is above 30, you are very overweight.
The formula itself is very simple. I have given it below-
As you can see, Body Mass Index is not hard to calculate. It is a simple mathematical formula that gives us results that are very easy to use, which has contributed to its popularity. Many hospitals and nutritionists swear by it.
It is also almost completely useless.
Bear in mind that for regular human beings, BMI is usually a good indicator of your fitness. People with a BMI above 30 do usually have a lot of fat content and would definitely need to exercise more. Similarly, people with a BMI of less than 18.5 almost always need to gain some healthy weight. I'm not trying to say that BMI should be completely ignored, but the concept of BMI itself is very flawed. I'm going to explain why.
As you can see, BMI relies on taking the square of your height and dividing it with your weight. This means that BMI is a two-dimensional formula. We are three-dimensional beings. BMI thus gives us a relationship between height and weight that is not at all accurate. To understand this further, we must look into something known as the Square-Cube Law.
The Square-Cube Law is as follows: when we increase the size of an object, its area increases by squaring and its volume increases by cubing. An example is given below.
When a cube's edge length is increased from 1 ft to 3 ft, its volume increases from 1 cubic foot to 27 cubic feet. However, its surface area increases from 1 square foot (per side of the cube) to 9 square feet. Volume increases much more than surface area.
The same principle is applied to humans. Our weight depends on our volume, not our height. That is why a lot of tall people will have a very high BMI even if they are fit, and a lot of short people will have a low BMI even if they are obese. BMI will really only work for the average man. It will not work for women, children, babies, very tall people, very short people, and so on.
Another bad thing about BMI is that it does not take actual fat content into account. It only uses our weight. This is why a lot of bodybuilders will be overweight on a BMI scale, even if they don't have very much fat content.
The creator of BMI has himself admitted that his formula does not really work. It was made in the 1840s when calculators did not exist. People wanted a quick and easy way of measuring their fitness, and this mathematician gave them the BMI formula. However, he was an applied mathematician, not a doctor or scientist. He did not know that he had to also consider things such as muscle weight, bone density, and water content- all of which contribute towards someone's overall weight. Now, we understand this, and therefore we can make new and better methods of measuring fitness.
A good example of such a method is the BVI or Body Volume Index. It takes the body's actual volume into account and thus provides a much better indication of someone's fitness.
So, in the end, it is wise to take BMI with a grain of salt. If you want to become healthier, visit a dietician or a fitness trainer, start eating more healthy foods, get all your required nutrients, and exercise regularly. Health can be tracked in many other ways aside from BMI, so do not take it very seriously.
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Thank you so much for reading!
Good article Ishan. As you rightly say, in last few years the world has become more conscious of fitness and health. Easy availability of gadgets, smartwatches that measure several health indicators is also making it easy for everyone to know how “healthy “ they are and how their health is trending over a period of time. While this is good, it’s almost becoming an obsession for normal people and even for athletes to get into too many such metrics and worry about those. That’s where simple metrics like BMI help .. as long as we understand its limitations which you have clearly articulated in the article.. As a single measure, BMI is clearly not a perfect measure of health. But it’s still a useful starting point for important conditions that become more likely when a person is overweight or obese. In my view, it’s a good idea to know your BMI. But it’s also important to recognize its limitations. Nothing can beat the simple but most effective metrics like Time , Speed and most importantly “How you feel” ;)
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