If you've ever seen a chart listing the ideal weight range for someone of your height, you're probably familiar with the body mass index. Unlike the typical bathroom scale that calculates only total weight, the BMI will give you an idea of how much fat you're carrying. BMI is determined by multiplying a person's weight by 700, then dividing that figure by the individual's height in inches. The resulting number is divided a second time by height in inches to arrive at a final figure which corresponds to a chart listing ranges for underweight, healthy weight, overweight and obese people. The World Health Organization considers a BMI of 18.5 to 24.9 to be a healthy reading.
Doctors commonly use the BMI as a starting point for determining a patient's general health, so it'd be easy to assume that the BMI is the gold standard of fitness measurement. Not so. The formula was created by noted Belgium statistician Adolphe Quetelet in the mid 1800s. Much of Quetelet's work focused on determining what characterized the average man. While considered groundbreaking, the BMI or Quetelet Index has huge limitations for the individual. It doesn't differentiate lean weight from fat. That's a problem. Muscle weighs more than fat so -- using the BMI formula -- a stocky athlete would likely be categorized as overweight or obese even if he or she was truly quite lean. The body mass index also fails to address differences associated with race, sex (women need more body fat), age (lean muscle mass tends to decline over time) or bodily location of excess weight. The renowned Mayo Clinic stresses that a person with an apple-shaped body (carrying excess weight in the abdomen) is at greater risk of disease than a person with a pear-shaped body (carrying excess weight in the hips.)
Don't confuse your BMI reading with your body fat percentage. The BMI is not a percentage but, instead, a formula that can be used to arrive at a number broadly defining your physical make up.
The body mass index can be a useful tool to begin the search for your ideal body weight, but it has serious flaws. A deeper, more complex search is necessary to determine a healthy body weight with a high level of accuracy.
We'll weigh the pros and cons of other measuring tools on the next page.