Calories & Weight Loss

Below is an excerpt from Part Two of

The 2004 Multi-Diet

by Anderson A. Anonymous, M.D., Ph.D.

The Body Mass Index

Another useful number to know is your Body Mass Index (BMI). BMI is a formula that gives approximately the same results as the desirable weight table.[1]

However, the BMI (Body Mass Index) extends the value of the IBW tables by allowing a determination of how much overweight you are compared to other people of different heights. In other words, a BMI of (e.g.) 25 represents approximately the same degree of body fatness in a person 5’2” (157 cm) as it does in a person who is 6’2” (188 cm) or any other height.

How accurate is the BMI? When tested against the underwater weighing technique (which is considered to be very accurate), it shows a high degree of correlation. But obviously no general formula can account for all individual variation.

The BMI formula is most accurate in adults between 19 and 70 years of age. It is less accurate in competitive athletes and body builders (i.e., people with a large muscle mass). It is also less accurate in women who are pregnant. The BMI is not useful for growing children or in elderly patients who are both frail and sedentary.

The Body Mass Index (BMI) is becoming the standard scientific way of talking about obesity for two reasons:

1. It is an easy way to compare the body fat level of people of different heights.
2. When researchers know this body fat level they can more easily connect it to the person’s general level of health and to specific diseases likely to develop.

The mid-point of the desirable weight range for each height on the Metropolitan Desirable Weight Table falls at a BMI of between 21 and 22. In other words, a BMI of 21–22 probably represents your “ideal” (i.e., healthiest), weight.

The 1998 reclassification of terms by the National Institutes of Health (U.S.) now defines a BMI of 25 or higher as “overweight” and a BMI of 30 or higher as “obese”. This means that clinically observable health problems typically begin to emerge when BMI rises over 25.

Calculating Your BMI (Metric System)

If you would like to know your BMI, you can calculate it most directly using the formula BMI=Kg/M². That is, BMI = your weight in kilograms divided by your height in meters squared. (You’ll need a calculator.)

Calculating Your BMI (English System)

For Americans and others who typically use traditional English measurements instead of the metric system, the following is a mathematical adaptation of the above metric formula. (You’ll still need a calculator.)

To calculate your BMI:

(1) multiply your weight in pounds by 703.

(2) Divide the number you got in step 1 by your height in inches.

(3) Divide the number you got in step 2 by your height in inches again. The result is your BMI.

If you don’t like formulas or don’t have a calculator handy, the four BMI tables below will make your life easier.

To use these tables:

(1) Select the table that contains both your height and your weight in the heading.

(2) From the first column, select the row with your height.

(3) Then find the column in that row that contains your weight.

(4) Then look at the bottom of that column to find your BMI.