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BUCHANAN: Measuring and evaluating body fat

Perry Buchanan

Perry Buchanan

As I’m writing this week’s article, I’m thinking about my high school reunion coming up this weekend. Like a lot of my classmates, I will be curious to see how others have changed over the past 35 years. Wow, yes, 35 years! Certain events like reunions and holidays do tend to make us focus more on our weight, especially this time of year. From Halloween to New Year we can become overly obsessed with the scale.

But, what does the number on the weight scale really mean? It simply tells us how much we weigh, not how many of those pounds are actually fat. Body Mass Index (BMI), used to assess weight relative to height, and waist circumference give us a general idea of our condition, but also fail to distinguish the composition of that weight. A BMI of 25 or higher is classified as overweight, while 30 or greater is classified as obese. The measurement of your waist provides a little better insight due to the location of excess fat. A waist above 40 inches for men and 35 inches for women places you at a greater health risk.

In contrast to weighing and measuring, body composition testing reveals what that weight actually consists of. What’s a good amount of body fat to have? For males, essential fat values are typically considered to be 3 to 5 percent and for females, 8 to 12 percent. Essential fat is the minimal amount of fat necessary for normal physiological function. Generally, a range of 10 to 22 percent for men and 20 to 32 percent for women is considered satisfactory for good health. Within this range, you have less risk of developing obesity-related diseases such as type-2 diabetes, high blood pressure, coronary artery disease and even some cancers.

If you are interested in getting that coveted six pack, you will probably need to drop your body fat down to 8-12% for men and 15-17% range for women. If you are an athlete and interested in optimal athletic performance, a body fat percentage around 15% for men or 20% for women is probably best for most sports. Body fat percentage can be estimated with many techniques. Except for DEXA scanning, I have either tested, observed or been tested by each of the following methods.

DEXA Scanning is considered the most accurate method, as it actually takes a full dual X-ray of your body composition.

Hydrostatic weighing is based on the principle of water displacement. The person is submerged under water and weighed while exhaling as much air as possible.

Air Displacement testing performed in a fiberglass chamber called a BOD POD, works on a similar principle as underwater weighing. It gauges air displacement to measure your body mass, volume, and density.

Bioelectric impedance analysis (BIA) is the most popular method used to test body fat. The first three methods I listed are usually performed in hospital or clinical settings. BIA uses either specially designed weight scales or hand held devices to pass a low intensity electric current through the body and measure its resistance. The principle behind BIA is that fat contains little water while muscle contains up to 70% water. I prefer to use BIA to test most people since it is simple and less intimidating than pinching. Pregnant women and those with implantable pacemakers or defibrillators should avoid BIA.

Near-infrared interactance (NIR) uses a specialized probe placed against an area of the body, emitting infrared light that passes through muscle and fat. Research has shown NIR to be less accurate than other methods, overestimating body fatness in lean people and underestimating it in those overweight.

Skin fold analysis uses calipers to measure skin fold thickness at various sites. The sum of the skin folds can then be converted to calculate percent body fat. A relationship exists between subcutaneous (under the skin) fat and the total amount of body fat. When used by a skilled tester and with high quality calipers, I find it to be one of the more accurate body fat testing methods, especially for those that are leaner.

Calculation of percent body fat through any of these techniques is best done by a trained health and fitness professional who can make accurate assessments and explain the results to you. 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. Participation in regular exercise along with a healthy balanced diet is the key to reaching and maintaining a healthy body composition, and to hopefully impress those at your next class reunion!

Perry Buchanan, owner of PT Gym, is certified as Health Fitness Specialist through the American College of Sports Medicine, and Fitness Nutrition Specialist through the National Academy of Sports Medicine. He has been in the fitness industry for more than 35 years.