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What Is Body Mass Index? How Is BMI Calculated?

Last update: 19 August 2017

Anyone who has ever tried to lose weight will tell you that it's not an easy game and that they want to see results and fast. There are a couple of issues, however. What should you try and how can you measure your progress? We aren't going to advise on diet tips here - there's plenty of other articles for that. So, let's take a look at the options open to you for measuring your weight loss.

Scales are a start and managing to squeeze into a certain pair of jeans is also a popular choice, but measuring your BMI is another weight management method which could be added to your health checklist.

How is BMI Calculated?

The body mass index measurement, put simply, is the calculation of someone's body weight in relation to their height. Using a BMI chart or a calculator, such as the ones on this site, you enter your weight and height details and are then told your current BMI measurement. You can also use this method to discover what your ideal weight should be for your height, a useful tool in today's climate of thin celebrities and fad diets.

In broad terms, a BMI of under 18.5 places you in the underweight category and between 18.5 to 24.9 you are deemed normal - this is what we should all be aiming for. This moves on to being overweight with a BMI of between 25 to 29.9, obese at over 30 and morbidly obese if you have a BMI of over 40.

Should you want to learn how to calculate BMI using the formula, we have an article on the BMI formula here.

To put the BMI calculations into practice, the normal weight range for a US male of average height of around 1.76m is between 130lbs and 165lbs. For a US woman with an average height of just over 1.62m, the BMI measurement for a normal weight is between 105lbs and 140lbs. Should you wish to convert this to another unit of weight, give our weight conversion tool a try.

Many do argue that the results BMI measurements provide are too general and do not consider the gender, build, age or ethnicity of a person. For example, professional athletes are often considered overweight or obese when using BMI measurements due to their muscle content, which weighs more than fat. Similarly, as people age their bone density decreases, so although they may seem to have a weight within the normal BMI range, their measurement actually needs to be scaled-down to reflect this.

Despite these hesitations there are reasons why monitoring your BMI is the path to good health. For people with a lot of weight to lose, their normal BMI weight provides them with a goal to aim for. BMI classifications also enable health professionals to recognize people with a low BMI who possibly have an eating disorder, or it can alert them to certain health problems that a person with a high BMI may have.

Most of us are not health professionals and do not have the knowledge and expertise to understand what our "true weight" should be when considering all of the factors. Therefore, the simple BMI classifications give every person the knowledge to improve their health. That's not to say that other measurements are not helpful. We list some of the alternatives in our article, 5 Alternatives To BMI.

With rising levels of obesity and obesity-related illnesses, throughout the developed world, it's fair to say anything that educates people about their weight is a good thing. BMI measurements may be a contentious issue, but with the health benefits of having a normal BMI reading being a reduced risk of diabetes, high blood pressure, heart disease, stress on your joints and overall, early death, it shouldn't be ignored and could play a important role in helping you to manage your long-term health.

Written by Soraya Ebrahimi-Calik

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