What is Body Mass Index (BMI) And How To Calculate It?


Earlier, whenever we used to go to a doctor, he used to check our weight as well. But over time, checking and keeping a tab on the weight became a daily habit. The reason being your weight can act as a great determiner of how healthy you are! But it is not just the weight but your body mass index (BMI) which can say a lot about your health and your risk of health problems. This is what we will be explaining in today’s know your numbers.

What is BMI?

BMI is a measure of a person’s body fat as a result of the weight in relation to the height. It is commonly used to classify adult men and women as underweight, overweight or obese. It applies to men and women over 20 years of age; for teens and children aged 2 and above[2]  BMI percentile is the best measure to assess body fat. In children, BMI varies with age, gender and pubertal stage.

How to calculate BMI?

The BMI is calculated as:

BMI = body weight (in kgs)/[height (meters)] squared

What is Normal BMI?

According to the World Health Organization (WHO), Body mass index is classified into four major categories:

Underweight: 15 – 19.9

Normal: 20 – 24.9

Overweight: 25 – 29.9

Obese: Greater than or equal to 30

For example, an individual with a BMI in the range of 15 – 19.9 would be considered as underweight and normal if the BMI is in the range of 20 – 24.9.

Obesity was further classified into three major classes with values as follows:

Class I obesity: 30 – 34.9

Class II obesity: 35 – 39.9

Class III obesity: greater than or equal to 40

However, there is a suggestion for diagnosing overweight and obesity using Body Mass Index (BMI) cut-offs of 23 kg/m2 and 25 kg/m2, respectively, for Indians as per the Consensus Guidelines for Asian Indians (2009).  

Also, according to a study in the American Diabetes Association the BMI cut-off point for screening overweight or obese Asian Americans for prediabetes and type 2 diabetes was changed to 23 kg/m2 (vs. 25 kg/m2 ) because this population is at an increased risk for diabetes at lower BMI levels relative to the general population.

Therefore, we recommend that you follow the stringent BMI guidelines recommended by your physician, especially if you are at risk for diabetes.

As per a 2015 study published in the Journal Nutrition Today, there has been an increase in BMI in the general population over the past several decades. As the mortality rates increase with increasing degrees of overweight and obesity, it is important to keep a close tab on your BMI & weight.

The higher the body mass index, the higher the risk of various metabolic diseases such as:

-High cholesterol

-High blood pressure

-Type 2 diabetes

-Heart disease

-Metabolic syndrome

-Coronary artery disease



-Breathing problems

-Gallbladder disease


-Polycystic Ovarian Syndrome (PCOS)


The body mass index is considered as a poor indicator of percent of body fat, however it is commonly used as a risk factor for various health problems.

Recommended Reads:

7 Easy Ways To Lose Weight At Your Workplace

Unable To Achieve Your Fitness Goals? Try Body Weight Training


Nuttall FQ. Body Mass Index: Obesity, BMI, and Health: A Critical Review. Nutr Today. 2015 May;50(3):117-128.

BMI Table. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report.

Consensus Statement for Diagnosis of Obesity, Abdominal Obesity and the Metabolic Syndrome for Asian Indians and Recommendations for Physical Activity, Medical and Surgical Management

American Diabetes Association: Standards for medical care in diabetes—2015. Diabetes Care 2015;38(Suppl 1):S1–S94.

Misra A. Ethnic-Specific Criteria for Classification of Body Mass Index: A Perspective for Asian Indians and American Diabetes Association Position Statement. Diabetes Technol Ther. 2015; 669p

Aziz N, Kallur SD, Nirmala PK.Implications of the revised consensus body mass indices for Asian Indians on clinical obstetric practice.J Clin Diagn Res.2014;8(5):OC01–OC03.

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