BMI: Misleading or Accurate?

What is BMI?

Body Mass Index (BMI) is a person’s weight in kilograms divided by the square of height in meters. A high BMI can indicate high body fatness. It screens for weight categories that may lead to health problems, but it does not diagnose the body fatness or health of an individual.

It is a calculation of your size that takes into account your height and weight.

What is a Normal BMI?

A normal BMI is between18.5 and 25. A person with a BMI between 25 and 30 is considered overweight, and a person with a BMI over 30 is considered obese. A person is considered underweight if it is less than 18.5.

BMI range Classification Risk of poor health
less than 18.5 underweight high
18.5–24.9 normal weight low
25.0–29.9 overweight low to moderate
30.0–34.9 obese class I (Moderately obese) high
35.0–39.9 obese class II (severely obese) very high
40 or greater obese class III (extremely obese)extremely high

Should BMI be considered accurate?

Well, the answer is a big fat NO. That is mainly because BMI is not the epitome of weight and health demographics. At the population level, BMI indicates a level of risk for morbidity (disease risk) and mortality (death rates).

Differences in BMI’s between individual adults of the same age and sex are usually due to body fat. However, there are many exceptions to this rule, which is why it is a figure may not always be accurate.

BMI calculations will overestimate the amount of body fat for:

some high-performance athletes

pregnant women


The calculations will underestimate the amount of body fat for:

the elderly

people with a physical disability, who are unable to walk and may have muscle wasting.

BMI is a quick, easy, and cheap way of diagnosing overweight or obesity needing only a weight and height measurement. Since obesity carries an increased risk of disease, including heart disease, stroke, and diabetes, etc.

It can identify those at greater risk of developing health problems. It is also used to make decisions about who gets certain treatments and to evaluate how effective certain weight-loss interventions are.

But BMI alone doesn’t give a full picture of a person’s health risk, as it is simply a measure of body size. Thereby not of disease or health. It doesn’t actually measure body fat, that is a key element when establishing health risks. Although it provides a rough indication of body fat, it doesn’t distinguish between weight coming from fat versus muscle.

Also, it does not tell us anything about where body fat is distributed. Body fat stored around the abdomen poses a greater health risk than body fat stored around the hips. This is a combination of related conditions. Such as high blood pressure, high blood glucose, and high cholesterol levels – all of which increase the risk of heart disease, stroke, and type 2 diabetes.

BMI categories are also somewhat arbitrary. A study of 13,601 adults showed the prevalence of obesity was much lower when defining obesity using that instead of body fat percentage. Using its categories, fewer people were found to have obesity. Though many would have been diagnosed as such because of their body fat percentage.


Thus it can be stated that BMI is misleading to a great extent and can’t be trusted blindly in order to measure health and fitness in a person.

It needs to be used alongside other measurements to get a fuller picture of a person’s unique health risk. Lifestyle factors (such as smoking, physical activity, diet, and stress levels), and blood pressure, blood sugar, and blood cholesterol levels should all be considered alongside BMI to establish health risks.

Know more about health and fitness here.

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