Body mass index (BMI) is a measure of body fat based on your weight in relation to your height, and applies to most adult men and women aged 20 and over. For children aged 2 and over, BMI percentile is the best assessment of body fat.
BMI does not measure body fat directly. However, research indicates that BMI correlates to direct measures of body fat such as underwater weighing and dual-energy X-ray absorptiometry (DXA), and is considered an inexpensive and easy-to-perform alternative for these.1,2,4
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Fast facts on BMI
Here are some key points about BMI. More detail and supporting information is in the main article.
BMI is used as a screening tool to indicate whether a person is underweight, overweight, obese or a healthy weight for their height.
If a person's BMI is out of the healthy BMI range, their health risks may increase significantly.3
BMI values are age-independent and the same for both sexes. However, BMI may not correspond to the same degree of fatness in different populations due to different body proportions.
The health risks associated with an increasing BMI are continuous, and the interpretation of BMI grading in relation to risk may differ for different populations.6
There are two ways to check your BMI:
The benefits of maintaining a healthy weight include:4
Excess weight increases how hard the heart has to work, it also raises blood pressure, blood cholesterol and triglyceride levels and lowers HDL (good) cholesterol levels. Excess weight can make a person more likely to develop diabetes.
Lifestyle changes that help you maintain a 3-5% weight loss are likely to result in clinically meaningful improvements in blood glucose, triglycerides and risk of developing type 2 diabetes. Greater weight loss can also help reduce blood pressure and improve blood cholesterol.4
BMI is not accurate enough to be used as a diagnostic tool. However, it is used as a screening tool to identify potential weight problems in adults.
A person may have a high BMI, yet to determine if this excess weight is a health risk, a health care provider would need to complete further assessments such as:2
Belgium Statistician Adolphe Quetelet developed the BMI formula approximately 150 years ago.
The calculation of BMI is based on the following formulas:
Weight (kg) / Height (m)2
With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared (kg/m2). Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters.
(Weight (lbs.) * 703) / Height (inches)2
When using pounds and inches, the formula needs to be altered slightly. Multiply your weight in pounds by 703. Divide that by your height in inches, squared.
Follow us to the next page to work out your BMI with our BMI calculators and charts.
Disclaimer: This informational section on Medical News Today is regularly reviewed and updated, and provided for general information purposes only. The materials contained within this guide do not constitute medical or pharmaceutical advice, which should be sought from qualified medical and pharmaceutical advisers.
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