The body mass index, or BMI, is a calculation of your health based on your height and weight. Your BMI rating will place you in a category of either underweight, healthy, overweight or obese. While many health professionals look to the BMI to provide a quick assessment of your weight, it does have its limitations.
Calculating Body Mass Index
Body mass index can be calculated two ways. The Quetelet index is the most accepted calculation of BMI, according to "Exercise Testing and Prescription" by David Nieman. To use the Quetelet index, simply divide your weight in kilograms by your height in meters squared. Another way of determining your BMI uses pounds and inches in place of metric measurements. To calculate your BMI, multiply your weight in pounds by 703, then divide by your height in inches squared.
Ranges
The body mass index helps you determine if your weight is appropriate and healthy for your height. If your BMI falls somewhere below 19, you may be considered underweight. A BMI between 19 to 24 is healthy. You are overweight if your BMI is between 25 to 29. Obesity is considered a BMI of 30 or greater.
Advantages
The greatest advantage to the body mass index is its ease of use. It is a simple, easy and free way to classify your body weight. Since BMI takes into consideration your height, it can provide a specialized way of estimating your body fat.
Limitations
The body mass index does have its disadvantages and limitations. It only takes into account height and weight, not age. Nor can it determine your body composition or where your fat is accumulating, which can also matter for health. For these reasons, the BMI may not work for the elderly or athletes. The elderly are at an increased risk for losing precious muscle mass, but may be considered to have a normal BMI. Athletes generally have a high percentage of skeletal muscle and a low percentage of body fat, but their weight may still be considered unhealthy when BMI is calculated.
References
- "Exercise Testing and Prescription"; David C. Nieman; 2007
- American Heart Association; Body Composition Tests; 2011
- Sutter Health.org: BMI Calculator
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