Is BMI the best measurement of obesity and an accurate indicator of health

weight scales

Body Mass Index (BMI) is a way of categorising how healthy our weight is when compared to our height. It was invented in 1832 by a Belgian mathematician named Lambert Adolphe Jacques Quetelet.

In certain cases, this method may be inaccurate as it doesn’t take into consideration a number of factors. For instance, It does not take into account muscle mass. As a result, if you have a bulky body, you are likely to be much heavier than without muscle mass.  Consequently, the BMI will advise that you are overweight or obese when the truth is a little different.

Why is BMI important?

Knowing your BMI is quite important because it will alert you when you approach an underweight, overweight, or obese composition of the body.
Leading to an unhealthy weight, there is a range of health risks that arise.

For example, if you are underweight you are at a higher risk of osteoporosis, weak immune system, infertility, anaemia, and premature births. On the other side of the spectrum, if you are overweight or obese, you are at a much higher risk of heart disease, type 2 diabetes, osteoarthritis, and even cancer.

Therefore, knowing your BMI will help you get a better understanding of how your body structure affects your health and whether you need to do something about it.

It’s important to note that this not a method of determining body fat. It is simply a way of finding out if you are of healthy weight, underweight, overweight, or obese.

When is BMI inaccurate?

If a person is muscular or pregnant, the BMI may be inaccurate or misleading. Things like age, sex, race, genetics, fat mass, muscle mass, and bone density are not taken into consideration. The formula does not differentiate between body fat and muscle. These factors will throw off the results.

How is BMI calculated?

It is calculated using the following formula:

BMI = kg/m2

The formula can be amended if you prefer to use pounds and inches as measurements of weight and height. In this circumstance, the formula will look like this:

BMI = (weight (lbs) / height (in2)) x 703

Otherwise, you can use the NHS healthy weight BMI calculator to do the calculations for you automatically.

Let’s do an example, but we will use the formula that includes kgs and metres as measurements. In this example, let’s assume that we have a lady who is 32 years old, she is 178cm in height and weighs 64kgs. So, we will firstly multiply her height by her height.

1.78 x 1.78 = 3.1684

Then we divide her weight in kgs by the outcome.

64/3.1684 = BMI 20.2

The results show that her BMI is 20.2. Once you have the BMI, you can place it into the correct category. Depending on the classification, it will show whether the person is underweight, healthy weight, overweight or obese. The table below shows these classifications.

Under 18.5 – Underweight18.5- 24.9 – Normal Weight
25.0-29.9 – Overweight30 or greater – Obese

As you can see, the 26-year-old woman will fall under the healthy weight BMI. As a result of these calculations, your healthcare practitioner may suggest certain lifestyle and diet changes. Nutrition2change offers great nutritional therapy programs if you’d like to improve your health and wellbeing too.

Is BMI still a relevant method for measuring health?

Despite continual criticisms of BMI, some studies show that BMI is a great and simple way of predicting a person’s health.

For instance, a 2017 study shows that a person who has been classified with a BMI of ‘underweight’ or ‘obese’ faced an increased risk of chronic disease or premature death [1]. This study successfully demonstrated that persons with a BMI of 30 or greater (obese) had a 1.5-2.7 times greater risk of dying after 30 years of age.

Other studies show that persons with a BMI of 30 or more also face a greater risk of chronic disease, type 2 diabetes, heart disease, and kidney disease [2] [3] [4].


Calculating and knowing your BMI is a great predictor of health. However, it’s important to know that it’s not always accurate as it doesn’t take age, sex, race, genetics, fat mass, muscle mass, and bone density into consideration. If you are worried about your health and BMI, take a look at our weight management and nutrition course which will help you get a thorough understanding of how to lose weight successfully and keep it off. You can use code ‘GIVEME80‘ to get 89% off at checkout.

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