Percent Body Fat: Estimation and Interpretation

Michelle N. Kuperminc, MD Developmental and Behavioral Pediatrician

Naval Medical Center Portsmouth Portsmouth, Virginia

This presentation does not represent opinions or views of the US Government

Overview

•  Estimate percent body fat

– Slaughter method

– Gurka method

•  Interpretation of percentages

Rationale •  Growth/nutritional status linked to health, participation, life

expectancy in individuals with CP

•  Due to differences in body composition, simple anthropometric measures used in other populations not predictive of nutritional status in individuals with CP (weight/height, BMI, arm circumference, single skinfold measurement)

•  Complex methods of body composition assessment not always feasible in clinical setting (underwater weighing, D2O dilution, DEXA, BIA)

•  Additive skinfold equations developed to predict percent body fat Stevenson et al, 2006 Kuperminc et al, 2010

Brooks et al, 2012 Brooks et al, 2014

Triceps skinfold

Subscapular skinfold

Slaughter Equations •  Estimate percent body fat from skinfolds

•  Prior equations by Lohman et al. not adequate for children (change in body composition over time and pubertal status)

•  Developed from classic methods used to measure body composition (underwater weighing, D20 dilution method)

Slaughter et al, 1998

Gurka Equations •  Estimate percent body fat from skinfolds

•  Slaughter equations underestimate percent body fat in children with CP

•  Specific to individuals with CP

•  Developed correction factors to Slaughter equations

•  Based on DEXA

•  Externally validated in ambulatory population

•  May overestimate percent body fat in children with higher percent body fat

Kuperminc et. al, 2010 Gurka et al, 2010 Rieken et al, 2011

Gurka Equations

Two skinfolds: subscapular and triceps

1.  Slaughter method to calculate percent body

fat.

2.  Correct for CP, gender, pubertal status,

severity of motor impairment (GMFCS 3-5)

Example

•  11 year old prepubertal white male with CP GMFCS 4

•  TSF=10

•  SSF=11

Percent body fat by Slaughter method

•  TSF=10, SSSF=11

•  %BF Slaughter=1.21 (TSF+SSSF)-.008 (TSF+SSSF)2-1.7

•  %BF Slaughter=1.21 (21) – 0.008 (441) – 1.7

•  %BF Slaughter= 25.42 – 3.528 - 1.7

•  % BF Slaughter=23.6%

Percent Body Fat by Gurka Method

•  % BF Gurka =% BF Slaughter (corrected) •  CP +12.2

•  Male -5

•  Level of motor impairment +5.1 •  % BF Gurka =23.5 + 12.2 – 5 + 5.1

•  % BF Gurka = 35.8%

Interpretation

•  Published, population based reference curves are descriptive rather than prescriptive

•  Published, population based accepted cutoffs (may or may not be relevant

to children/adolescents with CP) are prescriptive

–  Based on percentiles (random?)

–  Based on health indicators (outcomes, metabolic studies)

•  Emerging health indicators in population of individuals with CP

–  Overall growth relationship with health and participation (Stevenson et al, 2006)

–  Body weight relationship with mortality (Brooks et al, 2012)

–  No published indicators linked to percent body fat in this population

McCarthy et al, 2006

Reference Curve Percentiles for Percent Body Fat: US Boys Ages 5-19 NHANES IV

Laurson et al, 2011

Gurka

Slaughter

Recommended cutoffs: UK Boys Ages 5-18

McCarthy et al, 2006

Gurka

Slaughter

References •  Brooks et al. Low weight, morbidity, and mortality in children with cerebral palsy: New clinical growth charts.

Pediatrics, 2011.

•  Chumlea et al. Prediction of stature from knee height for black and white adults and children with application to mobility-impaired or handicapped persons. Juornal of the American Dietetic Association, 1994.

•  Gurka et al. Assessment and correction of skinfolld thickness equations in estimating body fat in children with cerebral palsy, Developmental Medicine and Child Neurology, 2010.

•  Kuperminc et al. Anthropometric measures: poor predictors for body fat in children with moderate to severe cerebral palsy, Developmental Medicine and Child Neurology, 2010.

•  Laurson et al. Body Percentile Curves for US Adolescents and Children, American Journal of Preventative Medicine, 2011.

•  Oeffinger et al. Accuracy of Skinfold and Bioelectrical Impedance assessments of body fat percentage in

ambulatory individuals with cerebral palsy. Developmental Medicine and Child Neurology, 2013.

•  Rieken et al. Measuring body composition and energy expenditure in children with severe neurologic impairment

and intellectual disability. American Journal of Clinical Nutrition 2011.

•  Slaughter et al. Skinfold equations for estimation of body fatness in children and youth. Human Biology, 1984

•  Stevenson. Use of segmental measures to estimate stature in children with cerebral palsy. Archives of Pediatric and Adolescent Medicine, 1995.