Comparing Body Composition Assessments

Screening and assessment is a requisite first step in developing the needs analysis for new clients. One of the relevant components to consider in this process is body composition. It is one component of health-related fitness that should be assessed in the evaluation process as it is clearly understood that elevated levels of body fat cause negative physiological actions within the body leading to systemic low-grade inflammation and an increased risk for all-cause metabolic and cardiovascular disease. Body composition by definition is the ratio of body fat mass to fat-free mass; expressed as a percentage of body fat. There are many direct and indirect methods to assess body fat and elevated risk for disease such as (but not limited to); use of height/weight tables, measurement of body mass index (BMI), measurement of the waist-to-hip ratio, hydrostatic weighing, air displacement plethysmography (Bod Pod), dual X-ray absorptiometry (DXA) and other internal imaging mechanisms, circumference measurements, skinfold measurements, bioelectrical impedance, and near-infrared scanning. These different methods of assessment have varying degrees of accuracy and practicality. In the personal training setting three major assessments commonly employed include circumference measurements, skinfold measurements, and bioelectrical impedance. Taking a look at the pros and cons of each method can help personal trainers make prudent decisions as to which one is best to use based on their capabilities, proficiency, client needs and limitations, as well as assessment environment.

Circumference Measurements

Implementing circumference measurement protocol involves measuring the circumference of designated locations and then calculating body density based on the positive linear relationship between the circumference values. Note that simply measuring waist circumference alone has been shown to be one of the best predictors of disease risk as it examines the accumulation of visceral adipose tissue.

PROS

Circumference measurements are relatively non-invasive providing a lower psychological impact. This makes the assessment particularly useful for obese or unfit/non-athletic clients. It is also considered useful for elderly clients due to fat re-distribution during the aging process (subcutaneous to visceral). Many people think in inches and look at being able to fit into in-fashion clothing (or those that once fit), so looking at circumference values can be a tangible way to easily perceive progression and success of a program aimed at weight loss. Circumference measurements provide regional fat storage data which takes a look at disease risk, and is very easy to perform making it one of the preferred methods for larger clients and is a great option for new and inexperienced personal trainers.

CONS

Circumference measurements have a reduced level of accuracy for lean and muscular clients. The assessment will over-predict muscular individuals as the assessment does not differentiate between muscle and adipose tissue directly. A reference value such as the neck or elbow breadth is often used for genetic size prediction.

Skinfold Measurements

The sum of skinfold measurements taken at a varying number of designated sites (3, 4, or 7) based on gender is placed in a population specific regression equations to predict body density and body fat. It assumes that subcutaneous fat is predictive of overall body fat percentage.

PROS

Skinfold measurements have been shown to be fairly accurate for leaner subjects with a standard estimate of error of 3.5%. Limited and economical equipment is needed, and the assessment can be performed quickly once the trainer is proficient in the protocol in almost any environment. Even with reduced accuracy when compared to the gold standard of hydrostatic weighing, skinfold asessment can be a reliable method to look at progression of weight loss.

CONS

Skinfold measurements are not an optimal or even appropriate choice for obese clients. Accuracy of the method decreases with increasing body fat as the assessment cannot measure visceral fat. Furthermore, with obese clients the psychological impact of pinching large amounts of adipose can be very (psychologically) detrimental and is unwarranted. Consider how awkward of a situation a trainer could find themselves in if they were unable to open the calipers wide enough to assess a given skinfold, and the client is blatantly aware of it. Clients who are visibly obese know they are out of shape and need your help. They do not need to be reminded of their fatness in such an unnecessary manner. Technician expertise is required for accurate assessment, and research has shown that it takes adequate practice and repetition to even be reliable while implementing the test. Incorrect skinfold location and inadequate pinch size are two common errors with the test.

Bioelectrical Impedance

The bioelectrical impedance assessment is based on the water content of bodily tissues. A weak electrical current is run through the body to identify the speed of conductivity based on total water in the body which correlates to body fat percentage. Fat has a lower water content than muscle or connective tissues, therefore more fat will slow down, or impede, the electrical current. With more lean mass the current will progress through the body in a quicker fashion.

PROS

This modality is very easy to use and therefore limited tester expertise is required. The assessment can be performed in a very rapid fashion for all populations and both genders. The hand-held modalities commonly used in personal training make the assessment protocol virtually fool-proof. It can be a fairly reliable method for examining improvements in body composition if all conditions are equal.

CONS

Bioelectrical impedance protocol was developed in the clinical setting, and it differs greatly from the protocol implemented within the personal training setting. Assessment discrepancies though exist between the two. In the clinical setting, which correlates to a validity consistent with skinfold, electrodes are placed on the thin skin on the top of the hand and foot, and the participant is expected to lie on a non-conducted surface and in a completely resting state. With the hand-held assessment commonly used in personal training, the skin thickness of the palms can have a significant effect on validity of the test, and the participant may not be aware of guidelines necessary for the test to be valid. The test results can be negatively affected by hydration level, ambient and skin temperatures, skin permeability (location of electrodes), equation used, exercise or alcohol consumption within 24 hours prior to the test, the use of diuretics or specific medications, female menstruation, and the need to void the bowel and bladder before the assessment.