On Body Fat Calculators - Part 1

From the Desk of Dr Tim Lohman:

 Many of you know that I have spent many years teaching and doing research with Skinfold assessments. Skinfolds can be a very appropriate method to estimate body fat percentage, HOWEVER, they are also prone to several sources of error! Errors can easily be generated by:

• Not measuring the right ‘spot’ on the body
• Different calipers
• “Operator” error due to practitioner inexperience or knowledge
• The equations used to calculate body fat percentage

We’ll talk about several of these error factors is subsequent newsletters, but this article, I’d like to focus on the ‘Equations”.

  There are several On-Line body fat calculators available these days, and my concern is that they seem to take a “one size fits all” approach, particularly with respect to the equations they use. Thus the % fat error can range from 5 to 10% if the caliper used, the equation selected, and the measurement technique are not appropriate.

 At GHBCI, we have developed our own calculator that uses a set of different equations that are validated for the following populations:

1. Children and youth – 7-18 years of age; boys, girls, white, black
2. High school wrestlers – boys, 13-18 years of age
3. Young adults – 18-45 years of age, men and women
4. Older adults – 55-80 years of age, men and women
5. College-aged athletes, men and women

These equations have been developed in large samples and have been cross-validated in most cases. For the equations developed in children and youth, the validity of these equations came from research I and my colleagues at the University of Illinois and the University of Arizona did using the 4-component model (body density, body water and bone mineral) as the reference method. Equations with either triceps and calf skinfolds or triceps and subscapular skinfolds and the Harpenden caliper are developed on a large sample of black and white children ranging from 7 to 18 years of age (Chapter 7– ACSM’s Body Composition Assessment). The GHBCI Calculator is in final development, and will be accessible on an iPhone or Android. Percent fat will be calculated once the skinfolds are entered along with descriptive data on the person being measured.

 In our online certification course, Body Composition Practitioner Level 1, these formulas are presented and the skinfold sites are described. As our Level 2 course becomes available, it will include “In person” training which we believe is the only way to really achieve competency in accurately measuring skinfolds. The students will be mentored by an expert in both the caliper technique and the exact location of the measurement site.

 So, in summary, the equation(s) used are an absolute key to the accuracy of the result. Watch for more discussion in our next newsletter about the caliper itself, the exact measurement site and the skill level required of the “operator”!