Pediatric Fatness Measurement: A Completely Different Approach To Define Obesity From Adults!

Monday, 17 August 2009 00:00

Children are not small adults.

     The prevalence of pediatric obesity is increasing in the United States and in European countries (JAMA 2002; 288: 1728-32; JAMA 2008; 299: 2401-05). This rising obesity prevalence is a major concern given the health risks associated with pediatric obesity (J Endocrinol Invest 2008; 31 (11): 979-84). A reliable and accurate estimate of body fatness is extremely needed when studying the various health correlates of pediatric obesity (Int J Obes 2005; 29: S97-100).
     Better understanding of body composition and factors influencing its development can improve the prediction of adult status and help to create strategies for reducing the risk factors of various diseases. Whatever the reason of assessing body composition, nutritionists and clinicians in health-related fields should have a general understanding of the most commonly used techniques for assessing body composition in pediatric subjects. However, body composition techniques used in adults are not directly applicable to the pediatric population (Pediatric body composition methods, in: Human Body Composition, Human Kinetics, 2005, 129-141- no link).
     Compared with adults children have much greater variation in body composition attributable to growth and development from infancy to adolescence. Throughout infancy, childhood and adolescence, there is a change in the chemical composition of the fat free mass. The two-compartment model, which divides the body into fat-free mass (FFM) and fat mass (FM), is influenced by age and maturation (Ann Rev Nutr 2002; 22: 1-17). Growth during pediatric age is consequence of increasing cell size and number; body composition undergoes changes in absolute amounts and relative proportions of water, lipid, protein and mineral mass (Acta Paediatrica 2005; 94: 8-13). It is important to know that boys and girls grow differently, and it is fundamental to assess this natural aspect when we measure children (Am J Clin Nutr 1982; 35: 1169-75).
     On the other hand clinician adherence to obesity screening guidelines remains suboptimal (BMC Pediatrics 2009; 9: 19). In the largest study evaluating pediatricians’ weight perceptions of children and their weight assessment and management practices, less than half of surveyed pediatricians (3633 pediatricians in total) knew definitions for pediatric overweight and obesity and a minority of physicians reported calculation of body mass index on a routine basis (either at well child care visit or at all visits (Obesity 2007; 15: 225-32; Arch Pediatr Adolesc Med 2005; 159: 632-38).  
     Obesity is defined as an excessively high amount of body fat or adipose tissue in relation to lean body mass (J Pediatrics 1998; 132: 204-10). Body mass index (BMI) is a common measure expressing the relationship (or ratio) of weight in kilograms to height squared in meters. Adults with a BMI of 25 to 29.9 are considered overweight, while those with a BMI of 30 or more are considered obese. Children with a BMI at or above the 95th percentile for their age are considered obese, and children with a BMI at or above the 85th percentile but below the 95th percentile are considered overweight (CDC, 2000), www.cdc.org).
     In daily clinical practice family pediatricians could use in their office anthropometry and circumferences as well as bioimpedance analysis (BIA).
     We briefly discuss measurement techniques with  the pros and cons. of each one.

     Anthropometry
     Anthropometry is an inexpensive, non invasive method of assessing size, shape and composition of the human body. Body weight and stature are measures of body size, and ratios of body weight to height can be used to represent body proportion.

     Body Mass Index (BMI)
     Body Mass Index (BMI), is an expression of relative weight to height. The BMI curve increases during infancy, with a peak at approximately 9 mo of age, then decreased until about age of 6 y and then increases again, which lasts until adulthood (BMJ 2000; 320: 1240-43). In pediatric age the interdependence between weight, height, BMI and body fat is not well understood and sometimes controversial. We need to take into account that BMI does not measure adiposity directly. BMI is safe, simple, inexpensive to obtain and widely used to characterize childhood in epidemiological studies (J Pediatrics 1998; 132: 204-10). However, BMI cannot predict a specific individual’s body fat (Am J Epidemiol 1999; 150: 939-46) because it is not able to disentangle FFM from FM (Acta Paediatrica 2005; 94: 8-13) and it could define a surrogate measure of fatness at individual level.

     Skinfold
     A long-standing method for evaluating growth and body composition is measurement of skinfold thickness. This technique uses special calipers to grasp a skinfold held between the tester’s thumb and fingers to provide measurement, in millimeters, for a double fold of skin and subcutaneous fat. It is a method of estimating body density. Total FFM, FM and %FM can be estimated from prediction equations that use skinfold measurements. The most often used skinfolds in pediatric age groups are triceps, biceps and sub-scapular skinfolds. Although this method is not so useful when measuring overweight and obese subjects (Acta Paediatrica 2005; 94: 8-13).

     Circumferences
     Circumferences at the waist, hip and thigh are used to predict body fat distribution and waist in particular is a very good predictors of intra-abdominal fat (Int J Obes 2006; 30 (1): 23-30). A flexible plastic tape measure with a local-loaded handle enables the operator to produce the tension on the end of the tape measure used for the measurement. Waist circumference is an early indicator of the risk of maintaining excess adiposity, as well as its metabolic complications (Obes Res 2001; 9: 179-87). Fernandez and colleagues provided the distribution of waist circumferences among children age 2 to 18 y in nationally representative samples of three major ethnic groups (African American, Caucasian and Hispanic) in terms of percentile at 10th, 25th, 50th and 90th percentiles (J Pediatr 2004; 145: 439-44).     

     Bioimpedance Analysis (BIA)
     Bioimpedance Analysis (BIA) is based on a simple concept: tissue rich in water and electrolytes is much more resistant to the passage of on electrical current than adipose tissue. BIA measures the impedance of a low-energy electrical signal as it passes through the body, which is proportional to the length of the conductor (a function of height) and inversely proportional to the cross-sectional area (volume) (Int J Body Comp Res, 2009, in press – no link). Usually, four electrodes are attached to the pediatric subject during the measurement, one each to the ankle and foot, and one each to the wrist and back of the hand. BIA provides an estimate of total water, which is then transformed into FFM. It is important to note that measurement conditions are fundamental for obtaining correct body composition estimates (Acta Diabetol 2003, 40(S1):270-73 – no link).

     Conclusions
     Although not reviewed in this paper, it is important to consider nutritional factors, energy intake, diet, composition, hormonal status, food preferences, and other behavioral factors that influence pediatric body composition. When these are taken together with an accurate and precise body composition assessment it may be possible to evaluate more effectively the growth process and disease risk.

     Final remark/statement
     In daily clinical practice the use of at least two body composition measurements is fundamental.
Keeping in mind that in pediatric age BMI is a surrogate measurement of fatness, we could suggest the routinely use of waist circumference as a reliable measurement of visceral fat longitudinally. We can associate the use of BIA for assessment of total body water in which, using appropriate equations, could estimate FMM and FM in a short medium and long term period follow-up.     

August 17, 2009

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Prof. Angelo Pietrobelli, MD
Pediatric Unit
Verona University Medical School
Policlinic GB Rossi
P.le LA Scuro, 1
37134 Verona (ITALY)
Phone: ++ 39 045 8124390
FAX:  ++ 39 045 8124746
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
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Re:Pediatric Fatness Measurement: A Completely Dif Roya Kelishadi 2009-09-13 21:03:17 Childhood obesity has been increasing globally, and its impact on public health is marked in developing countries under rapid economic and nutrition transitions ( Epidemiol Rev 2007;29:62-76). Usually, Asians are less obese but more susceptible to metabolic disorders than other ethnicities; they may have larger visceral adipose tissue than other ethnic groups at similar levels of obesity. Recent observations have documented adverse health hazards of abnormal central body fat deposition even in childhood, e.g. abdominal obesity, but not generalized obesity, is found to be associated with markers of inflammation and oxidative stress (Clin Chem 2007;53(3):456-64), moreover, it is shown that among obese adolescents, the odds ratio for increasing the risk of insulin resistance and non-alcoholic fatty liver disease is higher for waist circumference than body mass index ( Atherosclerosis. 2009 ;204(2):538-43). However, waist circumference and body mass index have strong correlation among children and adolescents, and in different age groups of children and adolescents, different anthropometric indexes as waist-to-hip ratio and waist-to-height ratio are correlated with cardio-metabolic risk factors ( Int J Cardiol. 2007;117(3):340-8 ; Acta Paediatr 2006 ;95(12):1625-34 ). Furthermore, the hypertriglyceridemic-waist phenotype can be used as an accurate and easy tool for screening children at metabolic risk in population-based studies ( J Trop Pediatr 2008;54(3):169-77 ). The first reference curves of waist and hip circumferences in Asian children and adolescents (J Trop Pediatr. 2007 ;53(3):158-64) had marked differences with other ethnicities ( World J Pediatr 2008 ;4(4):259-66). In addition to ethnic predisposition, modifiable lifestyle and environmental factors are associated with body fat deposition and its cardiometabolic consequences (Atherosclerosis. 2009 ;203(1):311-9; Nutr Metab Cardiovasc Dis 2008 ;18(7):461-70), which warrants establishment of healthy lifestyle from early life. Uniform, universally acceptable criteria for abdominal obesity in children and adolescents need to be defined for this emerging public health concern. Given that waist circumference and waist-to- height ratio are shown to have the strongest association with cardiometabolic risk factors , it may be clinically useful to routinely measure waist circumference in the pediatric population as a screening tool to identify high-risk youths. Roya Kelishadi, MD Associate Professor of Pediatrics Pediatric Preventive Cardiology Department Isfahan Cardiovascular Research Center Isfahan University of Medical Sciences Isfahan,Iran

angelo pietrobelli 2009-09-18 13:17:06 What Dr. Kelishadi wrote is completely correct and I can drive a conclusion that is quite good: - waist circumference must be used in the daily clinical practice to "screen" subject at risk, in particular during adolescence. Angelo Pietrobelli

MD, Prof. em. Peter Schwandt 2009-10-03 23:08:12 Comment: The suboptimal adherence of clinicians to the guidelines (BMC Pediatrics 2009; 19) is of much concern. One reason could be the poor motivation of physicians, parents and children. Some answers to the question “Why” might help. 1. Screening children for overweight and abdominal obesity allows early detection of cardio-metabolic risk by additional assessment of the conventional risk profile. This should include detection of silent risk factors in young parents (Atherosclerosis 2009; 205: 626-631) 2. Adverse anthropometric constellations in youth might predict overweight and obesity in later life. 3. Awareness of adiposity mediated risk often is an effective step to lifestyle change in the whole family (J Clin Epidemiol 1999; 52: 791-800; Int J Obesity 2001;25: 830- 837). 4. All the measurement techniques are easy to perform, inexexpensive, non invasive and reproducible. Globalization of risk also needs uniform definitions for children and adolescents with special concern of ethnic disparities (WJOP 2008; 4:259-266; Metabolic Syndrome and related disorders 2009; in press). Because the International Diabetes Federation recommends ethnicity specific cut-off values for waist circumference in adults only (Lancet 2007; 369: 20059-2061) national age- and gender-specific percentile values are needed eventually completed by corresponding curves for waist-to-height-ratio and skinfold thickness. Peter Schwandt , MD Professor em. Arteriosklerose – Praeventions - Institut Wilbrechtstr. 95 D-81477 München Phone ++49 89 7904191 Telefax ++49 89 74994941 E-mail: API.Schwandt.Haas@t-online.de pep-family-hear t@t-online.de

Reply to Prof. Schwandt Prof. Angelo Pietrobelli 2009-10-07 17:19:05 Prof. Schwandt comments are right into the point. It is fundamental to support and suggest adherence of clinicians to the guidelines. On the other hand, body composition measurement is the main point to promote and the follow-up the second step to strongly recommend. This could prevent diseases later in life. Angelo Pietrobelli, MD

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