Written by Tiffany Esmat, Ph.D.
What does the number on the weight scale really mean? In regard to overall health, weight is not nearly as important as the composition of that weight. More important, rather than tracking weight, we should be aware of our body composition. Stepping on a weight scale simply tells us the combined weight of all our body’s tissues. That weight may fluctuate throughout the day depending on the time of day, hydration status or what we are wearing. In contrast, body composition reveals the relative proportions of fat and lean mass in the body. Fat mass consist of two types of fat: essential and nonessential fat. The second component of body composition, lean mass, refers to bones, tissues, organs and muscle.
Essential fat is the minimal amount of fat necessary for normal physiological function. For males and females, essential fat values are typically considered to be 3% and 12%, respectively. Fat above the minimal amount is referred to as nonessential fat. It is generally accepted that a range of 10-22 percent for men and 20-32 percent for women is considered satisfactory for good health.
A body composition within the recommended range suggests you have less risk of developing obesity-related diseases such as diabetes, high blood pressure, and even some cancers. In addition, although we face risks when our body composition is too high, we face another set of risks when our body composition is too low. When we drop below the minimal recommended levels of essential fat, we negatively affect the delivery of vitamins to the organs, the ability of the reproductive system to function, and overall well-being.
How can you determine your body composition? Body composition can be estimated through various techniques from field-based tests requiring only a calculator or tape measure to advanced tests conducted in a clinical or laboratory setting performed by a trained technician. Common methods of exploring the levels of adiposity include body mass index (BMI), waist circumference, skinfolds, bioelectrical impedance analysis, and the BOD POD.
Two techniques that do not assess body fat percentage but that can be useful are BMI and waist circumference. BMI is used to assess weight relative to height and is calculated by dividing weight in kilograms (kg) by height in meters squared (kg m-2). A BMI of 25 or higher is classified as overweight while a BMI of 30 or greater is classified as obese. While BMI may give an individual a general idea of increased risk for obesity-related health problems, it fails to distinguish the composition of that weight. The measurement of waist circumference provides insight to increased risk of obesity-related illness due to the location of excess fat. Waist circumference can be measured by placing a cloth tape measure around the smallest part of the waist while standing relaxed. Waist circumference should be at or below 40 inches for men and 35 inches for women. Android obesity, classified as excess weight located in the trunk area, places an individual at greater risk for high blood pressure, metabolic syndrome, type 2 diabetes, high cholesterol, coronary artery disease and premature death.
Body fat percentage can be estimated via many techniques, some simple while others are more complex. This article describes three common techniques you may encounter: skinfold measurements, BOD POD measurements, and bioelectrical impedance analysis (BIA). Percent body fat can be estimated by using calipers to measure skinfold thickness at various body sites on the body. The sum of the skinfolds taken at various sites can then be converted to calculate percent body fat. This technique is fairly quick and can be accurate. However, it is important to find a trained technician to make the measurements. If the measurements are not taken correctly or an incorrect formula is applied, erroneous values can result. A fairly new and “high-tech” approach to assessment of body composition is the BOD POD. These fiberglass units are designed to measure body weight and body volume (i.e., the body’s total size). Because fat is less dense than lean tissue, the weight-to-volume ratio can be used to predict percent body fat. Another technique that is frequently used in fitness facilities is BIA. The principle behind this technique is that fat contains little water; most of the body’s water is in the lean compartment. Therefore, when an electrical current encounters fat, there is more resistance. By measuring how easily currents move through the body, body fat can be estimated.
Calculation of percent body fat through any of these techniques is best done by a trained health and fitness professional. These individuals will not only be able to make accurate assessments but will also be able to explain the results to you. Check with your local fitness facility to see what methods of assessment are available to you.
What can you do with your results? The results from your body composition assessment can be used to identify risks, personalize your exercise program or evaluate how well your current exercise and nutrition program is working for you. If you find that you are within a healthy range, continue your exercise and dietary behaviors. If you find that your body composition has room for improvement, take a closer look at what you can do to make positive changes to your current level of activity and diet. Use more than just the scale to assess body composition. Remember, it is possible for the number on the scale to remain constant but experience changes in fat mass and lean mass. Changes in body composition take time and a dedicated effort, but the positive impact on health and quality of life is worth the effort. Participation in regular exercise and physical activity along with a healthy balanced diet are the key to reaching and maintaining a healthy body composition.
View the full summer 2010 issue of the ACSM Fit Society® Page online.