Health-Related Fitness Components- Body Composition

Body composition is one of the five health-related fitness components. Body composition is defined as the proportion of fat, muscle, and bone of an individual’s body, usually expressed as percentage of body fat and percentage of lean body mass.1 Methods for obtaining body composition are categorized as direct, indirect and doubly indirect.3 Direct methods, such as a chemical analysis, are not performed on living people which makes indirect and doubly indirect methods the most common.  Indirect methods are derived from direct methods and doubly indirect methods are derived from indirect methods.

One example of an indirect method for assessing body composition is by getting a dual-energy x-ray absorptiometry (DEXA) scan.  During a DEXA scan a subject  removes all metallic objects and is then asked to lie motionless on a scanning bed and is secured with Velcro straps on the lower leg and feet.3  The subject is then scanned from head to toe for 5-25 minutes.  The advantages of a DEXA scan is that they are easy to administer and subjects have a higher comfort level compared with other techniques.  DEXA scans are very reliable and safe as they use low-level radiation.

Measuring body composition with skin-fold calipers is one example of a doubly indirect method.  Measuring skinfolds is only an estimate of percent body fat and bone density and requires a trained technician and high-quality skinfold calipers.  Analyzing body fat with this method is based on the principle that the amount of subcutaneous fat is directly proportional to the total amount of body fat.

Not only is your percent body fat important to know, but knowing where your fat is predominantly stored is a better indicator in determining a person’s risk for diabetes, heart disease, high blood pressure and stroke.2 Having just one risk factor doubles your risk for CHD. Having two risk factors increases your risk for CHD fourfold. Having three or more risk factors increases your risk for CHD more than tenfold.

People that carry excess body fat in their buttocks and thighs (pear shape) are at a lower risk for weight-related health problems than people that store excess fat in their waist.  When broken down, belly fat can increase production of bad cholesterol and triglycerides which leads to insulin resistance, blood sugar becoming unbalanced, fat and clots entering the bloodstream, which can lead to disease.  The American College of Sports Medicine’s charts below show the body fat percentage values associated with satisfactory health for both men and women.

With approximately two-thirds of Americans classified as being overweight (Body Mass Index greater or equal to 25), it is recommended that the American population gets their body composition checked on a regular basis, adopts healthy habits and lifestyles.

1.Body Compositon [Def. 1]. (n.d.) In Dictionary.com, Retrieved September 21, 2014, from http://dictionary.reference.com/browse/body+composition

2. Feature, J. (n.d.). Belly Fat Risks. Retrieved October 6, 2014, from http://www.webmd.com/diet/features/the-risks-of-belly-fat

3. Swain, D. (2014). ACSM's resource manual for Guidelines for exercise testing and prescription (7th ed., pp. 238-305). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.

4.Who Is at Risk for Heart Disease? (n.d.). Retrieved October 9, 2014, from http://www.nhlbi.nih.gov/health/health-topics/topics/hdw/atrisk.html