In a society that is becoming increasingly sedentary, consumers are bombarded with reports that more people are overweight than ever before. Health-conscious people might be interested in learning how to determine whether they are overweight--and how their weight compares with their ideal healthy weight.
Body Mass Index
The body mass index, also known as the BMI, is a formula that compares height and weight. The formula gives a value that can be compared with a chart that shows users how their weight compares with their ideal healthy weight. The formula for body mass index in metric units is body weight in kilograms divided by height in meters squared. In the imperial system, it is body weight in pounds multiplied by 703, then divided by the height in inches squared.
Using the BMI
Once the BMI value has been attained, it can be compared with the chart. According to the standard used by the U.S. Department of Health and Human services, a BMI below 18.5 is considered underweight, from 18.5 to 24.9 is considered normal, 25 to 29.9 is overweight, and 30 and above is obese. For example, if a woman is 5 feet 4 and weighs 140 pounds, her BMI is 24, which makes her at the higher end of the normal range.
Limitations
The BMI is useful only as a guideline. It does not take into consideration muscle mass, bone density, gender or other factors. If you are a serious exerciser, you might have an inflated BMI even though you are healthy. Also, the BMI should be used only for people ages of 18 to 65, and it is not useful for pregnant or lactating women.
Age Considerations
Studies have shown that the BMI recommendations are not set in stone. For example, some studies have shown that the ideal BMI is 21 to 27 for people over age 35. Some evidence suggests that a slightly higher body weight is less associated with a risk of mortality in an older person if two people of the same height are compared. In general, age is not a strong determinant in ideal body weight, but older people tend to have higher body weight even if they are healthy.
Additional Considerations
There is more to measuring whether a person is healthy than simply weighing them. Factors such as body-fat percentage and hip-to-waist ratio also show whether a person is carrying a dangerous amount of fat or whether he simply is more muscular than normal for the BMI chart.
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