Written and Medically Reviewed by Dr Benjamin George, MBBch, BAO, LRCP & SI, FRCS, AM, ISAPS, CMTP. Updated as of May 15, 2021.
Table of contents
What is Body Mass Index?
The body mass index is the measure of body size. It combines height and weight to give a depiction of a healthy body for a given height.
Your body mass index is your weight in kilograms divided by the square of height in meters. Confusing? Essentially, BMI is a measure to screening if you are underweight, at a healthy weight, overweight, or obese. It is a screening tool and should not be used to determine or diagnose the health of an individual or body fat.
How do I calculate my BMI?
For example, if a person is 70 kg and 165 cm (or 1.65m) tall, to calculate the person's BMI simply do 70kg / (1.65m)2 = 25.71.
|18.5 – 24.9||Normal or Healthy Weight|
|25.0 – 29.9||Overweight|
|30.0 and Above||Obese|
The BMI takes into account natural variations in body shape, giving a healthy weight range for a particular height. Often BMIs are used in coordination with other factors to assess an individual's healthy weight.
However, BMI as an independent measure is no conclusive enough. For example, an avid gym-goer with muscles may be considered obese despite being at a healthy weight because muscle is denser than fat.
Furthermore, ethnicity plays a role in some health conditions, which could make BMI incorrect. For example, Indians have a higher propensity for heart problems and diabetes but can still have a healthy BMI.
BMI does not measure body fat, and it does not account for age, sex, ethnicity, or muscle mass in adults.
Health Benefits of Being A Healthy Weight
In addition to reducing the risks of developing or having greater difficulty managing health conditions, maintaining a healthy weight offers additional benefits:
- fewer joint and muscle pains;
- increased energy and ability;
- improved regulation of bodily fluids and blood pressure;
- reduced burden on the heart and circulatory system; or
- improved sleep patterns.
Health Risks of Extra Weight
An overweight or obese person may have the following effect on their body:
- It raises how hard the heart works;
- It increases blood pressure, blood cholesterol, and triglyceride levels;
- It lowers high-density lipoprotein (HDL), or good cholesterol levels; or
- It can make diabetes and other health problems more probable.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), carrying extra weight can increase the risk of the following conditions:
- hypertension, or high blood pressure
- dyslipidemia, which involves high LDL cholesterol, low HDL cholesterol, or high levels of triglycerides
- type 2 diabetes
- coronary heart disease
- gallbladder disease
- sleep apnea and respiratory problems
- some cancers, including endometrial, breast, and colon cancer.