A bathroom scale is a good indicator of general health and weight, but it is also misleading. Scales don't consider the muscle mass a person is gaining while losing body fat. In some cases, the number on the scale may even go up as a person loses body fat, leading to discouragement and setbacks. The Body Mass Index (BMI) calculates a measurement of someone's weight in relation to her height and indicates the degree to which she is overweight or underweight.
Formula to Calculate BMI
Follow this formula to get a rating: First, convert height to inches. For example, a person who stands 6 feet 2 inches is 74 inches tall. Next, square the height in inches. (74 x 74 = 5,476). Then, divide body weight by the squared height (210 lbs./5,476 = .0383). Multiply the number by 703 to obtain your BMI rating (.0383 x 703 = 26.9 BMI).
BMI Interpretations
The Centers for Disease Control (CDC) uses weight and health standards: Any person with a BMI below 18.5 is considered underweight. Persons with a BMI between 18.5 and 24.9 are considered normal weight. Those with a BMI between 25.0 and 29.9 are considered overweight. Anyone with a BMI over 30.0 is considered obese.
BMI Reliability and Cautions
While BMI is a strong indicator of overall health based on height and weight, it is not the only factor in determining health and risk factors, according to the CDC. Other risk determinants include waist circumference and body fat, physical fitness levels, cholesterol, blood pressure and family health history. Very fit athletes tend to have a higher BMI because of large muscle load. This may erroneously put them in the "overweight" category. Women tend to have more body fat than men and older people tend to have more body fat than young adults. Also, BMI does not measure the distribution of fat in the body. Research from the American Heart Association reports that more fat in the waist is more detrimental than fat at the hips.
Other Ways to Determine Body Fat Levels
In addition to the BMI formula, other methods of measuring obesity levels include skinfold thickness measurements using calipers, underwater weighing and bio-electrical impedance. Many times, these methods aren't as readily available as the simple BMI formula. Also, results can differ based on machines and technicians administering the tests.
Considerations
Use the BMI rating as a good starting ground for overall health based on height and weight, but don't let it be the only indicator. Have regular fitness assessments and checkups from health care professionals.
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