All you need to know about BMI


Body mass index (BMI) is a standard statistic used by healthcare facilities to assess the health of their patients. It has been used for decades as the standard for the evaluation of health based on body size, but it has repeatedly come under fire for its simplification of what being healthy truly requires.

In reality, many individuals contend that BMI should not be used in medical or fitness situations since it is out-of-date and inaccurate.

This blog tells you all you need to know about BMI, including its origins and its propensity to properly predict health.

Background Of BMI

The term “BMI” refers to body mass index. It was invented in 1832 by a mathematician from Belgium named Lambert Adolphe Jacques Quetelet.

He developed the BMI scale to help governments quickly assess a population’s degree of being overweight and obesity. This helped them allocate resources for health and money.

Curiously, Quetelet asserted that using BMI to study a single individual was inferior to using it to assess the general health of a community. It is, nevertheless, commonly used to evaluate people’s health.

Is BMI a Valid Indicator Of Health?

Despite worries that BMI doesn’t accurately identify whether a person is healthy, the majority of research shows that a person’s risk of chronic illness and early death does increase with a BMI lower than 18.5 (“underweight”) or 30.0 or over (“obesity”).

For example, a 2017 retrospective study of 103,218 deaths revealed that those with a BMI of 30.0 or above (referred to as “obesity”) had a 1.5–2.7-fold increased risk of passing away after a 30-year follow-up.

Those with an “obese” BMI had a 20% greater risk of dying from any cause including heart disease than those with a “normal” BMI, according to a second study involving 16,868 people.

Furthermore, the researchers found that, compared to those with “normal” BMI, those with “underweight” and “severely obese” or “extremely obese” BMIs died, respectively, 6.7 and 3.7 years earlier. Other studies have shown that having a BMI above 30.0 significantly increased the risk of suffering from chronic illnesses such as type 2 diabetes, heart disease, breathing issues, renal sickness, non-alcoholic fatty liver diseases, and mobility issues.

Additionally, a 5–10% decrease in BMI has been associated with a decreased risk of type 2 diabetes, metabolic syndrome, and heart disease.

Since most studies show that people who are obese have a higher risk of acquiring chronic illnesses, many health practitioners can utilize BMI as a general indication of health.

How To Calculate BMI?

The BMI scale is based on a mathematical formula that compares a person’s height in meters squared to their weight in kilograms to determine if they have a “healthy” weight 

Height / Weight (kg) = BMI (m2)

Alternately, you may determine BMI by multiplying 703 by the product of your weight in pounds and your height in square inches:

Weight (lbs) x Height (in2) x 703 equals BMI.

A BMI calculator that is available online, such as the one from the National Institutes of Health, is another option. If you fall within the “normal” weight range, your BMI is computed and then compared to the BMI scale.

Problems With BMI

Despite evidence connecting low (below 18.5) and high (over 30) BMI with increased health risks, there are significant issues with BMI usage.

Assumes that all weights are equal.

Even though 1 pound or kilogram of muscle weighs the same as 1 pound or kilogram of fat, muscle is denser and takes up less space. Therefore, a person who is thin yet has a lot of muscle may weigh more than a normal person.

For instance, someone who weighs 200 pounds (97 kilograms) and is 5 feet 9 inches (175 cm) tall, and has a BMI of 29.5 is regarded as “overweight.”

If BMI is the only factor considered, it is quite easy to mistakenly label someone as “overweight” or “obese” despite their low-fat mass.

As a result, in addition to weight, it is crucial to take into account a person’s muscle, fat, and bone mass.

Possible weight bias

Medical professionals are expected to apply their best judgment, which means that they will take the BMI result and treat each patient as an individual.

However, some medical practitioners simply utilize BMI to assess a patient’s health before making recommendations, which can result in weight prejudice and subpar medical care.

Higher BMI patients more frequently claim that their doctors only address their BMI during appointments for unrelated issues.

Serious medical conditions frequently go undiagnosed or are misdiagnosed as weight-related disorders.

In reality, research has shown that those with higher BMIs are less likely to have frequent health checks because of anxiety about being assessed and mistrust of the medical system. 

Other unaddressed health issues

Without taking into account a person’s age, sex, genetics, lifestyle, medical history, or any other factors, BMI simply states whether or not they are a “normal” weight.

One may overstate or underestimate their true health by disregarding other important health indicators including cholesterol, blood sugar, heart rate, blood pressure, and inflammatory levels, such as BMI.

Additionally, even though men and women have different body compositions, BMI uses the same calculation for both sexes (men having higher muscle mass and less fat mass than women)

Also, as a person ages, their muscle mass gradually declines and their body fat mass naturally increases. Numerous studies have shown that a BMI range of 23.0-29.9 can be protective against illness and premature mortality in older adults.

Last but not least, using BMI alone to judge someone’s health ignores other aspects of health including mental health and intricate societal problems.


A person’s risk for bad health and body fat is assessed using the widely contested body mass index (BMI) method.

Most research indicates that the risk of acquiring a chronic illness increases as BMI exceeds the “normal” range. A low BMI (below 18.5) has also been linked to detrimental health impacts.

BMI, however, disregards other elements that may impact health, such as age, sex, fat mass, muscle mass, race, genetics, and medical history.

BMI has also been shown to exacerbate weight bias and health inequities when used as the only predictor of health. Although BMI is a great place to start, it shouldn’t be your major health indicator.

Author: Zainab Cutlerywala (INFS Faculty)


  • Klatsky, A. L., Zhang, J., Udaltsova, N., Li, Y., & Tran, H. N. (2017). Body Mass Index and Mortality in a Very Large Cohort: Is It Really Healthier to Be Overweight? The Permanente Journal, 21, 16–142. 


  • Aune, D., Sen, A., Prasad, M., Norat, T., Janszky, I., Tonstad, S., Romundstad, P., & Vatten, L. J. (2016). BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants. The BMJ, 353.


  • Borrell, L. N., & Samuel, L. (2014). Body Mass Index Categories and Mortality Risk in US Adults: The Effect of Overweight and Obesity on Advancing Death. American Journal of Public Health, 104(3), 512. 


  • Abdelaal, M., le Roux, C. W., & Docherty, N. G. (2017). Morbidity and mortality associated with obesity. Annals of Translational Medicine, 5(7). 


  • Han, T. S., & Lean, M. E. (2016). A clinical perspective of obesity, metabolic syndrome and cardiovascular disease. JRSM Cardiovascular Disease, 5, 204800401663337. 


  • Ye, M., Robson, P. J., Eurich, D. T., Vena, J. E., Xu, J. Y., & Johnson, J. A. (2018). Changes in body mass index and incidence of diabetes: A longitudinal study of Alberta’s Tomorrow Project Cohort. Preventive Medicine, 106, 157–163.


  • Brown, J. D., Buscemi, J., Milsom, V., Malcolm, R., & O’Neil, P. M. (2016). Effects on cardiovascular risk factors of weight losses limited to 5–10 %. Translational Behavioral Medicine, 6(3), 339. 


  • Grier, T., Canham-Chervak, M., Sharp, M., & Jones, B. H. (2015). Does body mass index misclassify physically active young men. Preventive Medicine Reports, 2, 483. 


  • Jayedi, A., Soltani, S., Zargar, M. S., Khan, T. A., & Shab-Bidar, S. (2020). Central fatness and risk of all cause mortality: systematic review and dose-response meta-analysis of 72 prospective cohort studies. BMJ (Clinical Research Ed.), 370


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