The most accurate method currently available to figure out how much weight you need to lose in order to be healthy is to calculate your personal healthy weight range, and aim for that goal. However, determining a healthy range of weight that is applicable to most people has proven to be a difficult challenge for medical and fitness science. Researchers have developed a number of equations for calculating an optimal body weight, each with advantages and limitations. There are two major systems currently in use: Body Mass Index or BMI, and Ideal Body Weight or IBW. In the 2006 issue of "Nutrition in Clinical Practice," Dr. Shah states that whereas BMI and IBW equations provide roughly equal recommendations for men, IBW provides unrealistically low goals for women as compared to BMI. For this reason, he recommends using BMI as the standard and, in large part, the medical community agrees. You can calculate your current BMI, and determine a weight loss goal if your BMI is not in an acceptable range.
Step 1
Weigh yourself using your bathroom scale or a gym scale. It is worthwhile to weigh yourself multiple times over a number of days and average those numbers. This is because multiple factors can influence your weight from day to day, such as how hydrated you are.
Step 2
Measure your height using the measuring tape or ruler. Do this with shoes off, standing flat on the ground, from the bottom of your heels to the top of your head.
Step 3
The easiest method of calculating your BMI using either British/American or metric units is to visit the National Heart Lung and Blood Institute's BMI calculator. If you're curious about the math behind it, you can calculate your current BMI using the following formula. For metric measurements the formula is (weight in kilograms)/(height in meters squared). In other words, if you weigh 80 kilograms and are 2 meters tall: (80)/(4) = BMI 20.
For British and American measurements, the easiest method is to first convert to metric. One pound = .454 kilograms and one inch = 2.54 centimeters. So (170 lbs)x(.454)=77.18 kilograms and (72 inches)x(2.54)=182.88 centimeters. Then enter these metric numbers into the above equation.
Step 4
Determine which BMI range you are currently in. Less than 18.5 is considered underweight, 18.5 to 24.9 is a healthy weight, 25.0 to 29.9 is overweight, 30 to 34.9 is obese, 35 to 39.9 is obesity class II, and 40 or greater is extreme obesity. Each rank above healthy weight is associated with a higher risk of disease.
Step 5
Calculate your ideal goal weight by multiplying your height in meters squared to a BMI of 23. For example, if you are a basketball player who is 2 meters tall, your goal weight would be (4)x(23)=92 kilograms.
Step 6
Now strive to reach that goal gradually and safely. Harrison's Principles of Internal Medicine recommends an initial weight loss goal of 10% in the first 6 months if you are in the obese BMI range.
Tips and Warnings
- An easier method of converting between units of measurement is to simply use Google. Try typing "convert 160 pounds to kilograms" in the search box. This can be done for most units.
- While the BMI scale is the current medical standard, it is not without limitations. For example, a very muscular, but fit person may find themselves with a BMI in the obese range. This is because the scale does not differentiate between pounds of fat and pounds of muscle. Bear in mind that no simple mathematical equation can be applied to all people equally.
Things You'll Need
- Body weight scale
- Measuring tape or ruler
- Calculator
References
- "Nutrition in Clinical Practice;" Comparison of Ideal Body Weight Equations and Published Height-Weight Tables With Body Mass Index Tables for Healthy Adults in the United States; Bhumika Shah, MS; Kathryn Sucher, ScD, RD; Clarie B. Hollenbeck, PhD; 2006
- "Harrison's Principles of Internal Medicine, 17e;" Anthony S. Fauci, Eugene Braunwald, Dennis L. Kasper, Stephen L. Hauser, Dan L. Longo, J. Larry Jameson, and Joseph Loscalzo, Eds.; 2008
- "CURRENT Medical Diagnosis & Treatment 2010;" Stephen J. McPhee, Maxine A. Papadakis, Eds.; 2010
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