Nutrition woman measuring BMI

Published on October 24th, 2013 | by Joe Starks


Fitness Jargonbuster: BMI

The idea that there is an ideal range of body weight for each of us dates back to the 19th century. It is only recently that we have used the term BMI to describe this weight range. BMI is more than just an indicator of what weight we should be. It can also show us how far away we are from having that weight and how dangerous our weight is for our well-being. Let’s take things from the beginning and look into this matter from a scientific perspective. BMI has been abused by many magazines and diet franchises to achieve some monetary gain from. This is why we should look at things as simply as possible.

What is BMI?

BMI is actually a formula called Quetelet index. Only recently in 1972 has this formula been named BMI and the science that proved which BMIs are normal is quite recent too. This formula takes your height and current weight into account and gives you a number as an answer. If that number falls between specific ranges you know just about how healthy you are.

To have a better perspective here is a list of various BMI ranges:

  • Less than 18.5 is the BMI of an underweight person
  • From 18.5-24.9 is the normal BMI range
  • From 25-29.9 is slightly overweight
  • From 30 and up is the BMI of an obese person

For instance if you find out that you have a BMI of 23 then you know you are a healthy weight, no matter what that weight is and what your height is. Taller people need to be heavier to be healthy.

What happens when your BMI is too high?

This is sadly too often the case in our days. Many people are far above the upper limit. If you are in the slightly overweight category chances are the worst thing you’ll experience is a lack of self-esteem and a difficulty finding clothes you like. There are no good studies that show that slightly overweight people have any great health risks. There are some health problems that do get worse the more overweight you are, so a person with a BMI of 26 will probably have less strong symptoms than a person with a BMI of 29 is they have a disease that is affected by weight.

Obesity on the other hand brings with it devastating diseases that have created great troubles for healthcare organizations worldwide. Once you have reached a certain weight and have a BMI above 30 you can expect you life expectancy to be shortened and your quality of life to drop dramatically.

There are two sides to this problem, the psychological and the physical ones. Psychological obesity can ruin lives because it is linked to loss of libido, lack of self-esteem and social problems, which may not always stem from the weight itself but other people’s reaction to it. Physically you have far higher chances to become ill.

What happens if your BMI is too low?

It might come as a surprise, but having a BMI beneath 18.5 can be far more life threatening than obesity. Being underweight comes with a horde of very serious health risks. First of all the lack of good nutrition often leads to malnutrition and all the symptoms that might bring. If you lack certain vitamins, minerals and macronutrients for a long while then you might even have a cardiac arrest and instantly die.

Of course the closer you are to 18.5 the smaller the chances are you will have any problems at all. A woman at 17 BMI might be perfectly healthy, but that is almost never the case with a person with a BMI of 15.

Can BMI be wrong?

Yes of course it can. People are very versatile and there are great examples of that. Usually when the BMI system is wrong one of these things is happening:

  • The person is extremely muscular. Very fit people are heavy because muscles are heavier than fat, but they look lean. These people can have the BMI of a slightly overweight person, yet still look muscular and fit.
  • The person has a very flattering body type. When it comes to the slightly overweight BMIS close to 25 a person with a flattering figure might not look overweight at all. This of course is impossible at very high BMIs.
  • At extreme heights, either very short or very tall, BMI seems to be working less good. That happens because these people end up having a different limb-core ratio. Tall people often have comparatively longer limbs than shorter people, they aren’t just taller copies. This is why BMI might sometimes be wrong in those cases.

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