Why and How We Do Our Research
Many facets of health and growth are closely related to body composition. The body’s mass and proportion of lean tissue, bone mineral, adipose tissue, body water and other components offer a valuable indicator of an individual’s state of health.
Accurate measurement of these parameters can be accomplished with sophisticated instrumentation that provides improved accuracy over simpler anthropometric techniques. We designed and built a state-of-the-art body composition laboratory at the Children’s Nutrition Research Center in Houston, Texas. Many of the instruments were custom designs, such as the whole-body gamma counter (WBC) used to measure total body potassium, an index of the body’s actively metabolizing cell mass. These instruments are among the best in the world for body composition assessment.
Aspects of the Body Composition Laboratory
Evaluation and Validation of Existing Technology
In addition to custom designed body composition measurement instruments, several types of commercially available technologies are being used in body composition research.
One example is dual-energy X-ray absorptiometry (DXA) for measurement of bone mineral and bone density, fat mass, and lean mass. The precision and accuracy of these instruments must be assessed before being put to practical use. We were able to test the performance of several commercial instruments, compare their results with our own instrumentation, and publish critical evaluations of the usefulness and dependability of these technologies. Our work, and the work of others, has led to either the adoption or abandonment of some of the newer instrumentation used in body composition research.
- Ellis KJ, Shypailo RJ, Pratt JA and WG Pond. Accuracy of dual energy x-ray absorptiometry for body composition studies in children. Am J Clin Nutr 1994; 60:660-665.
- Ellis KJ, Yao M, Shypailo RJ, Urlando A, Wong WW, Heird WC. Body-composition assessment in infancy: air-displacement plethysmography compared with a reference 4-compartment model. Am J Clin Nutr 2007; 85(1): 90-95.
- Shypailo RJ, Butte NF, Ellis KJ. DXA: Can It Be Used as a Criterion Reference for Body Fat Measurements in Children? Obesity (Silver Spring) 2008 Feb; 16(2):457-462
Development of Pediatric Normative Data
Body composition data, not unlike many other types of assessment data, need a frame of reference to be truly valuable. The first phase of work done by our Body Composition Laboratory was devoted mostly to establishing normative references for several growth parameters, such as total body potassium, bone mineral content, bone density, body fat mass, etc. The work was done in children in order to produce pediatric normative data against which one could compare the growth of children, the effectiveness of therapies or interventions, and to a certain extent, aid in diagnoses of diseases.
- Ellis KJ, Shypailo RJ, Abrams SA, Wong WW. The reference child and adolescent models of body composition: a contemporary comparison. Annals NY Acad Sci 2000; 904:374-382.
- Ellis KJ, Shypailo RJ, Hardin DS, Perez M.D., Motil KJ, Wong WW, Abrams SA. Z score prediction model for assessment of bone mineral content in pediatric diseases. J Bone Miner Res 2001; 16(9):1658-1664.
Software Tools Designed for Public Use
One important aim of a laboratory in a center such as the Children’s Nutrition Research Center is the dissemination of information to other investigators as well as to the general public. This pertains not only to data produced in the Body Composition Laboratory, but also to ancillary parameters closely related to body composition. One example of such a measure is body mass index (BMI), a parameter that has come into common use as an anthropometric index of weight status and obesity. Although normative data, such as for BMI, are available and in the public domain, the interpretation of such data is not always intuitive, even to trained professionals. We have designed and made available, through the Baylor College of Medicine web site, several online tools to allow users to assess Z-scores and percentiles for certain pediatric health measures. These include BMI, height, weight, blood pressure, and various DXA parameters such as bone mineral density and percent fat. The tools use data from normative national references such as NHANES – data that are available but not simple to use. These tools have been and are still being used by many investigators and by the general public.