BODY COMPOSITION: FACTS AND FALLACIES By: Nanna L. Meyer, Sport Dietitian US Speed Skating and United States Olympic Committee
Have you ever wondered whether the numbers you get on a body composi- tion test are accurate? Are they a true reflection of your percent body fat or is there an error? How precise are the measurements – in other words, would you get the same number if you tested it twice or multiple times within a short time? Is leaner always faster or is there a limit? And should we all be a bit more careful not to over-emphasize weight and body composition in our athletes? Much of our body weight and compo-
sition (fat and fat free mass) is geneti- cally determined. However, there are factors, such as nutrition and exercise training that can influence body weight and composition significantly. Also, en- vironmental factors (e.g., altitude, heat, cold) among others can affect resting energy expenditure, and could lead to changes in body weight and composi- tion over time, especially if energy in- take from food is not adequate. While a lean physique is important for skating performance (short and long track), speed skating is an extremely demanding sport that requires long hours and multiple training sessions focusing on ice and dry-land training. Energy (calorie) expenditure is high in both long and short track skating. Meeting these physiological demands, while staying lean is a challenging bal- ancing act. Chronic energy deficits, as a result of weight and fat loss attempts, can quickly run down the athlete and lead to a host of problems. While body weight is easily assessed
using a scale, body composition test- ing is more complex. There are direct, indirect, and doubly indirect methods. We wish we could always use the direct methods but these are generally done with cadavers (yes, dead people!) or us- ing sophisticated lab equipment (e.g., CT Scans, MRI, Dual Energy-X Ray Absorp- tiometry, DXA; Air Displacement Pleth- ysmography, BodPod; or Hydrodensi-
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tometry/underwater weighing to name a few). Obviously, there are ethical, practical, and cost-prohibitive issues with this. Thus, we are reliant on indirect (e.g., skinfolds measuring total sum of skinfolds in millimeters; Bioelectrical Impedance, BIA) or doubly indirect (e.g., skinfolds using equations to calculate % body fat – most common) methods. Un- fortunately, even among direct methods, there is currently no ‘gold standard’ for measurement, and the more field-based or indirect the technique, the less accu- rate and precise it will likely be. In terms of the standard error of estimate (this is the error related to estimating body fat from any method), even the most ac- curate method can only estimate to the nearest 1% (this means that a percent body fat of 14% could actually fall any- where between 13 and 15%). Unfortu- nately, using the most common indirect and doubly indirect field techniques leave us with a standard error of estimate of 3-4%, even if the test is performed under standardized conditions (e.g., calibrated equipment, well-experienced tester, normal hydration status etc). Thus, a body fat level of a male athlete measured at 7%, could be 10-11% or the unlikely 3-4%. Under less standardized condition, the error easily exceeds 3-4%, and thus, athletes and clinicians should do every- thing to ensure maximal control prior to and during testing. With that said, there are ways to keep the errors involved with body composition testing as low as possible. The following points constitute a
thorough standardization: 1. Always do your body weight and composition assessment at the same time of the day (preferably morning)
2. Eat a standard breakfast prior to testing (always the same)
3. Maintain normal hydration status prior to testing; test urine specific gravity to ensure normal hydration
status or check your urine color (should be lightly yellow but not dark)
4. Do not exercise in the hours before the test
5. Get tested by the same clinician each time
6. Make sure you select a clinician who is well trained and experienced (if they don’t use a tape and mark you up they are probably not trained)
7. Select the same field method each time you get tested to maintain consistency as numbers may vary greatly from method to method (Note: you can add direct laboratory methods to
complement your field techniques) Important is that coaches and health
care providers understand why they want body composition assessed in their athletes and what else might be measured at the same time that could provide useful information regarding training adaptation. Reasons for body composition testing should be well grounded in a monitoring/tracking sys- tem that is performed throughout the annual training/competition plan. Body composition tracking is probably then most useful if packaged into a weight loss intervention plan developed and supported by a sports dietitian. This also appears to be the best justification to assess body composition more fre- quently. However, research shows that body composition methods may not be able to detect any changes in body fat if weight gain or loss is within 2kg (~4.4 lbs). Again, this goes back to the under- lying lack of accuracy and precision in body composition methods. When try- ing to pick up changes, direct methods show errors of 2-3% in estimating % fat changes. Thus, if the change is less than 3%, the method cannot accurately estimate it! This is why performance
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