Upper Arm Composition as an Indicator of Body Composition and Nutritional Status of Adolescent Boys Aged 10-18 Years

Introduction: The upper arm composition is usually assessed based on total upper arm area (TUA), upper arm muscle area (UMA), upper arm fat area (UFA) and arm fat index (AFI). It is closely associated with assessment of body composition and nutritional status. The present study aims to determine the age specific variations in upper arm composition and its usefulness in the assessment of body composition and nutritional status among adolescent boys. Materials and Methods: The study was conducted among 964 boys (aged 10 – 18 years) and belonging to the indigenous Rajbanshi population of West Bengal, India. The boys were selected from five different sub-urban government secondary schools located under Siliguri subdivision of Darjeeling district, West Bengal, India. The anthropometric measurements of height, weight, MUAC and TSF were recorded and upper arm composition was estimated based on TUA, UMA, UFA and AFI using standard procedures. The overall body composition was evaluated using body mass index (BMI). Results: There appears to be existence of significant age-specific variations in BMI, UMA and UFA as the boys approached higher ages. The age specific means of TUA, UMA and UFA increased with age. The adolescent boys were observed to be well below the 50th percentiles of the reference population in BMI, TUA, UMA, UFA and AFI. Age and sex-specific smooth percentile curves were derived for height, weight, TSF, BMI, UMA and UFA using the L, M and S modelling approach for further evaluation of body composition. Conclusion: The present study recommends the assessment of body composition and nutritional status to improve screening of nutritional status using upper arm composition, especially in community settings so as to accurately identify the risk of lower or greater adiposity and muscularity, and thereby proposing a major opportunity to improve health through proper intervention programmes. J Nepal Paediatr Soc 2015;35(2):152-161


Introduction
B ody composi on is strongly associated with nutri onal status, specifi c diet, physical exercise, disease and gene cs.
The determina on of body composi on allows for the quan ta ve assessment of muscle mass and adiposity changes that refl ects nutri onal intake, losses and expenses over a me period (1,2,3,4).Thus, changes in body composi on are very important in clinical and epidemiological inves ga ons.Poor body composi on and nutri onal status can lead to increased morbidity, poor physical ac vity and performances.So the evalua on of body composi on of nutri onally vulnerable segments of a popula on becomes a priority for the researcher.It is quite diffi cult to assess body composi on with fair accuracy and several techniques have been developed only in the last decade for an accurate es ma on and distribu on of body adiposity (2,3,5,6).These methods include underwater weighing, air displacement plethysmography, bioelectrical impedance analysis and dual-energy X-ray absorp ometry.However, anthropometric measurements s ll cons tute an important method of choice of researchers for such assessments in clinical and epidemiological inves ga ons.The indirect assessment of muscularity and adiposity are widely being done using skinfolds thickness, body mass index (BMI) and circumference measurements (4)(5)(6)(7).Several researchers have u lized these anthropometric measurements and BMI to es mate body composi on varia ons in children (1,3,4,6,8).
The upper arm composi on has received considerable a en on during the last few decades, but has not been widely adopted for rou ne assessments of body composi on among children and adolescents.Recently several studies have reported direct associa ons of disease, bio-chemical changes, clinical symptoms and nutri onal status with upper arm composi on among children (9,10).Upper arm composi on is usually assessed using total upper arm area (TUA), upper arm muscle area (UMA), upper arm fat area (UFA) and arm fat index (AFI).These are determined from mid-upper-arm circumference (MUAC) and triceps (TSF) skinfold thickness (5,7).However, few studies have u lized upper arm composi on to determine nutri onal status of children, adolescents and adults (8,(11)(12)(13)(14)(15)(16)(17).Studies are also scarce in the domain of standard growth references for school-aged children and adolescents related to upper arm composi on (7,12,13,15).
The adolescent period is a very important phase in the life span of an individual.It is defi ned as the period of transi on between childhood and adulthood and is characterized by an excep onally rapid rate of growth (1,6).During the period of adolescence, the nutrient requirements of the body are high and as such the nutri onal status of these individuals needs to be monitored closely as they cons tute the next genera on of parents.Undernutri on among adolescents cons tutes a major focus of nutri onal research in India.There also appears a need to develop a database on the nutri onal status of adolescents from diff erent parts of the country.This will enable the government and non-governmental agencies to formulate policies and ini ate strategies for well-being of the adolescents.But such a database for the country is lacking at the moment.There is li le available informa on on the nutri onal status of adolescents from India, although some important scien fi c papers are men onable (18)(19)(20)(21)(22).A few compara ve studies have reported that adolescents were observed to have poor growth a ainment, late sexual maturity and body composi on than their reference counterparts, especially among boys (21)(22)(23).The current literature shows a paucity of literature in the fi eld of body composi on, nutri onal assessment vis-à-vis upper arm composi on among children and adolescents belonging to various Indian popula ons (8,14,15,16).Given the above, the objec ves of this present study were to determine the age specifi c varia ons in upper arm composi on and its usefulness in the assessment of body composi on among adolescent boys aged 10-18 years.

Material and Methods
Nature of the popula on and subjects: Popularly known as North Bengal, the northern part of the state of West Bengal, India, comprises of seven districts and is the home to a number of tribal and indigenous popula ons (such as Lepcha, Rabha, Meche, Toto, Oraon, Santal and Munda) and non-tribal popula ons (such as Rajbanshi, Bengali Caste and Bengali Muslim).Given the region's general backwardness in health care, educa onal and medical facili es, these popula ons remain very vulnerable to undernutri on (8,19,20).Although there are some studies on the assessment of body composi on and nutri onal status among individuals belonging to these popula ons, there is a lack of such studies among adolescents of the same.As far as the la er is concerned, a detailed literature search has yielded just two studies in this regard and here those of Mondal and Sen (4) Sen et al. ( 8) may be cited.
The most widely distributed indigenous popula on in North Bengal is the Rajbanshi.According to the Na onal Census 2001, they cons tute the largest and the number of the Scheduled Caste popula on of West Bengal (18.40% and nearly 3.4 million, respec vely).It is generally agreed that the Rajbanshi shows resemblances with the Koch popula on of the neighboring state of Assam and it is been conjectured that they belong to a mixed ethnicity of Austroasian/ Dravidian and Mongolian (19).Researchers have opined that they belong to a Dravidian stock that came in contact with the heterogeneous Mongoloid popula ons.A study on gene c markers among the popula ons of north-eastern India has reported that the Rajbanshi was a semi-Hinduized caste group located in-between the clusters comprising the Caucasoid caste and Mongoloid tribal popula ons (24).
The data for the present study were collected from adolescent Rajbanshi boys (aged 10 -18 years).The boys were the students of fi ve diff erent sub-urban government secondary schools located under the subdivision of Siliguri, district Darjeeling of the region.The schools were iden fi ed and selected based on iden cal subject strength, easy accessibility by road and homogeneity using a purposive sampling method.The predominance of Rajbanshi boys was the sole criterion behind the selec on of the schools.The boys were selected using a mul -stage stra fi ed sampling method.The physical features and surnames were u lized to iden fy the subjects and subsequently their ethnicity was verifi ed from the offi cial records.A total of 1127 Rajbanshi boys were ini ally iden fi ed and approached to voluntarily par cipate in the study.Of them, 111 boys refused to take part in the study.Out of the remaining 1016 boys who agreed to par cipate, 52 were excluded as their dates of birth could not be verifi ed from the governmental records.Hence, the fi nal sample consisted of 964 boys (subjects) aged from 10 years to 18 years.Special care was taken so that each age had a minimum of 100 boys.All the subjects were free from any physical deformity and not suff ering from any form of disease at the me of examina on.Necessary consents and permissions were obtained from the local and school authori es prior to commencement of the study.A verbal consent was also taken from each subject and their parents before ini a ng the phase of data collec on.The study was conducted in accordance with the ethical guidelines of human experiments as laid down in the Helsinki Declara on of 2000 (25).
Socio-economic data recorded: Parents of the boys were interviewed on the basis of a structured schedule so as to ascertain their socio-economic status.Relevant data on socio-economic and demographic variables (ethnic group, family size, parents' educa on, occupa on, family income and dependent children in family) were recorded for this purpose.A modifi ed scale of Kuppuswamy was used to ascertain the socio-economic status (SES) (26).It was subsequently observed that the boys belonged to a lower to a middle SES as ascertained by the using modifi ed socioeconomic scale men oned above.A er determining the SES, socio-economic and demographic variables were not taken into considera on in further sta s cal analysis.

Anthropometric measurements obtained:
The anthropometric measurements of height, weight, midupper arm circumference (MUAC) and triceps skin fold (TSF) were recorded following standard anthropometric procedures (27).The subjects wore minimum clothing and were without any footwear at the me of recording the measurements.Height of the subjects was recorded with the help of an anthropometer rod, with the head held in the Frankfurt Horizontal plane.Height was measured to the nearest 0.10 cm.Weight of the subjects was recorded using a portable weighing scale to the nearest 100 g.The MUAC was taken at the point midway between the acromion and the radiale of the upper arm using a plas c coated non-stretchable measuring tape on the le side of each subject to the nearest 0.10 cm.The skin fold measurement of TSF was made using a Holtein skinfold caliper calibrated to exert a constant pressure of 10 g/mm 2 on the le side of each subject to the nearest 0.20 mm.
The intra-observer and inter-observer technical error measurements (TEM) were calculated to improve the precision of anthropometric measurements by u lizing the standard procedure of Ulijaszek and Kerr (28).The TEM was calculated using the following equa on: TEM=√(ΣD 2 /2N), D=diff erence between the measurements, N=number of individuals.
The co-effi cient of reliability (R) was calculated from TEM using the following equa on: R={1−(TEM) 2 /SD 2 }, SD= standard devia on of the measurements.
Height, weight, MUAC and TSF were recorded from 50 adolescent boys other than those selected for the study by two of the authors (PG and NM) for the calcula on of TEM.Very high values of R (>0.975) were obtained for all the four measurements and these values were observed to be within the acceptable limits of R=0.95 (28).Hence, the measurements recorded by PG and NM were considered to be reliable and reproducible.All the measurements in course of the present study were subsequently recorded by both the authors (PG and NM).

Assessment of body composi on:
The upper arm composi on was es mated from MUAC and TSF by the standard equa ons (7).These equa ons are appended below: The overall body composi on was evaluated using BMI.The BMI was calculated by the following standard equa on: BMI (kg/m 2 ) = weight (kg)/ height (m 2 ).

Sta s cal analysis:
The sta s cal analysis was done using Sta s cal Package for Social Sciences (version 17.0).The one-sample Kolmogorov-Smirnov test was used to compare the observed cumula ve distribu on func ons for each of the anthropometric variables with respect to a specifi ed theore cal distribu on (p>0.05).One way analysis of variance (ANOVA) was u lized to iden fy the mean diff erences among the anthropometric variables with respect to the diff erent ages.A post-hoc test using Scheff e procedure was done to compare the mul ple comparisons of mean between the anthropometric variables when applicable within the ages.The least median square (LMS) model analysis was used by taking into the account the degree of skewness (L), central tendency (M: Median) and dispersion or the generalized coeffi cient of varia on (S) for the calcula on of reference percen les curves.This model is a concept of an age varying adjustment for skewness based on the Box-Cox transforma on.The method converts the measurements for a subject of known age and sex to evaluate percen le and standard devia on score or z-score (29,30).The LMS method so ware computer program fi ts smooth percen le curves to the reference data using the LMS method as described by Cole and Green (29).The age-specifi c height, weight, BMI, TSF, UMA and UFA percen le curves with 3 rd , 10 th , 15 th , 25 th , 50 th , 75 th , 90 th and 97 th smoothed percen le lines for the boys were plo ed separately for further evalua on of nutri onal status.The results were considered to be signifi cant at p<0.05 level.

Results
The age-wise distribu on of the means (±S.D.) of the anthropometric variables among the Rajbanshi boys is depicted in Table 1.The age specifi c mean height and weight increased with age from early adolescence but height decreased in the ages from 17 to 18 years.Boys belonging to the age groups of 10 to 14 years have showed accelera on in growth pa erns in height and weight.The age specifi c mean MUAC was also increased with age but no such age specifi c trend was observed in TSF.The mean TSF values ranged from 5.57 mm (in 10 years) to 6.97 mm (in 18 years).Using ANOVA, sta s cally signifi cant (p<0.05)diff erences were observed in weight (F-value=138.10;d.f.: 8, 963), height (F-value=165.19;d.f.: 8, 963), TSF (F-value=5.31;d.f.: 8, 963) and MUAC (F-value=47.48;d.f.: 8, 963) variables with respect to age (Table 1).

Assessment of upper arm and body composi on:
The age specifi c means (± S.D.) of the derived anthropometric body composi on characteris cs among the adolescent boys are presented in Table 1.There appears to be an existence of signifi cant age specifi c varia on in height, weight, BMI, UMA and UFA as the boys approached to higher ages.The BMI gradually increased with age from 10 years to 14 years, followed by a slight decrease in 16 years (17.48 kg/ m 2 ) and then con nued to rise reaching its highest peak in the age of 18 years (20.21 kg/m 2 ).The age specifi c means of TUA and UFA increased with age, with excep ons in 15 years (36.10 cm 2 ) and 14 years (6.11cm 2 ).The age specifi c mean values of UMA increased with age in the later ages (14 years to 18 years) but AFI did not show any trend with respect to age.The age specifi c mean AFI was observed to be lower in 17 years (16.91) and higher in 13 years (19.86)The age specifi c mean diff erences were observed to be sta s cally signifi cant (p<0.05) in BMI (F-Value= 21.49; d.f.: 8, 963), TUA (F-Value= 49.18; d.f.: 8, 963), UMA (F-Value=41.73;d.f.: 8, 963), UFA (F-Value=19.65;d.f.: 8, 963), and AFI (F-Value=6.22;d.f.: 8, 963), using ANOVA (Table 1).Age specifi c smooth percen le curves were also derived using LMS procedures for height, weight, BMI, TSF, UMA and UFA among Rajbanshi boys and are depicted in Figure 1.

Comparison with the Reference Popula on:
The comparison of age specifi c mean height and BMI values obtained in the present study with the Na onal Health and Nutri onal Examina on Survey (NHANES-III) (31), Centres for Disease Control and Preven on (CDC) (32) and World Health Organiza on (WHO) (33) reference popula on has been depicted in Figure 2. The lower a ainment of height and BMI respect to age is generally considered as long term linear growth retarda on (i.e., stun ng) and chronic energy defi ciency (i.e., thinness), respec vely (33).The age specifi c mean height were below the 25 th percen le of the all considered growth reference popula ons and the boys who reached the higher ages of 13 to 18 years and 15 to 18 years were found to be below the 5 th percen le for NHAHES (31), and both CDC (32) and WHO (33) indicates chronic linear growth retarda on, respec vely.The age specifi c mean values of BMI were observed to be below the 50 th percen le of NHANES (31), whereas the age specifi c mean BMI values were below the 25 th percen le in ages 10 years, 11 years, 13 years, 14 years to 16 years of CDC (32).The comparison with WHO (33) reference popula on showed that age specifi c mean BMI values were well above the 50 th percen les with excep on observed in 10 years, 11 years, 16 years and 17 years but the values were observed to be below the 25 th percen le (Figure 2).
The comparison of age specifi c mean upper arm composi on variables of TUA, UMA, UFA and AFI values obtained in the present study with the NHANES-III (31) reference popula on for further evalua on of body composi on and nutri onal status has been depicted in Figure 3.The age specifi c mean values of TUA and UFA were found to below the 25 th percen le of NHANES reference, but the only excep on was observed for 17 years (i.e., TUA, <5 th percen le) and 15 years (i.e., UFA, <50 th percen le).The age specifi c mean values of UMA were observed to be below the 5 th percen les values in 12 years and 15 to 18 years boys.The age specifi c mean values of UMA were also observed to be below the 25 th percen les in 11 years, 13 years and 14 years ages while the value was below the 50 th percen les in 10 years.The age specifi c mean values of AFI were observed to be below the 25 th percen les for the age specifi c mean values of 10 to 13 years boys.Age specifi c mean values of AFI varied with the age and it was observed well within the 50 th to 75 th percen les in the age groups of 14 to 18 years ages of NHANES-III reference popula on data (Figure 3).

Discussion
Body composi on assessment using anthropometric measurements is s ll an important technique of preference and proving increasingly important in epidemiological and clinical inves ga ons (4,5,8,16,17).Several studies have used the skinfolds measurements to quan fy the amount of muscularity and adiposity in children and adolescents (4,8,11,(14)(15)(16)(17).They have also advocated that these measures are very useful to monitor body-composi on, nutri onal status and for evalua ng the eff ects of target specifi c interven on and supplementary programmes.
Changes in body composi on characteris cs have been evaluated among Rajbanshi adolescent boys in the present study, especially when they approached the stage of puberty.Several studies have reported similar changes in upper arm composi on related to sexual characteris cs a ainment during puberty (8,14,15).The results of the present study suggest that adolescent boys were observed to be well below the 50 th percen les of the reference popula ons (31)(32)(33) in height, BMI (Figure 2) and TUA, UMA, UFA and AFI of the NHANES-III reference (31) (Figure 3).Similar studies have already reported body composi on a ainment as compared to their reference counterparts among Indian children and adolescents from Bengalee Muslim (8), Santal (14), Khasi (15) and Sonowal Kachari (16) popula ons.Therefore, the results of the present study are consistent with those previously reported studies sugges ng a poor caloric and protein reserve among the adolescents.Therefore, the assessment of body composi on allows a quan ta ve assessment of muscle-mass and adiposity changes that refl ects nutri onal intake, losses and expenses over me period in children and adolescents (2,3,6).This achievement of unsa sfactory nutri onal status may be a ributed due to their poor living condi ons and lower SES.The socio-economic scale of Kuppuswamy's (26) used in the present study has shown that the boys belonged to a lower to middle SES group.It has been reported that poor living condi ons and environmental varia ons can infl uence physical growth a ainment pa erns among adolescents (8,18) and these could be determinant factors in the present study.Furthermore, these diff erences can be ini ally a ributed to the diff erent related factors such as age-sex, genotype, diet and ea ng habits, physical exercise, SES and environmental condi ons during childhood and adolescence (1,(4)(5)(6)14).
The poor upper arm composi on among the Rajbanshi adolescent boys is probably a ributed to lower-SES and higher early age undernutri on that are prevalent in the vulnerable segments in Indian popula ons (4,8,16,34).Furthermore, early life experiences involving adverse environmental condi on, intrauterine growth retarda on, poor physical growth in early childhood and subsequent catch-up growth can also have an impact on growth a ainment, poor body composi on, and health related outcomes later in adulthood (35,36).Moreover, this unsa sfactory body composi on largely refl ects the inadequate nutri on during early-childhood and is likely to be a consequence of well-known phenomenon of prolonged breas eeding combined with inadequate weaning food of low energy-density among Indian children (34).
Possibly the poor physical growth a ainment among the nutri onally vulnerable segments in developing countries such as India is probably because of the more pronounced infl uence of specifi c non-gene c factors such as infec ous disease and undernutri on (35)(36).Moreover, researchers have already observed a signifi cant associa on between poor nutri onal status and upper arm composi on with disease related morbidity and mortality among children and adolescents (37)(38).Therefore, body composi on assessment and evalua on and monitoring of nutri onal status should be integrated into rou ne epidemiological and clinical prac ces for ini al assessment and sequen al follow-up of health and nutri onal status assessment studies.However, it needs to kept in mind that upper arm composi on can provide a be er assessment of muscularity and adiposity over conven onal anthropometric measures, but it is s ll rela vely insensi ve to short-term altera ons in body-composi on (8,14,16).The main limita on of the present study that has determined the age specifi c trends of upper arm composi on using a set of simple anthropometric measurements of a homogenous sample and a cross-sec onal study design is that it would be diffi cult to draw a major conclusion.A longitudinal design and heterogeneous popula on in clinical and/or epidemiological se ngs could be more useful to explain the possible associa on of upper arm composi on with undernutri on and disease related mortality and morbidity.

Conclusion
Upper arm composi on is very useful to monitor nutri onal status and evalua ng the eff ects of target specifi c interven on and supplementary programmes.Moreover, currently recommended anthropometric measures (i.e., stun ng and thinness) are unable evaluate the body composi on.Therefore, the measures of upper arm composi on should be used with conven onal anthropometric measures for a comprehensive es ma on of nutri onal status and body composi on.Future inves ga ons are necessary to understand the rela onship between upper arm adiposity measures with body fat percent, central and regional body adiposity measures.The present study recommends assessment of body composi on and nutri onal status to improve screening of undernutri on using upper arm composi on, especially in epidemiological and clinical inves ga ons so as to accurately iden fy the rela ve risk of lower or greater adiposity and muscularity, and thereby propose a major opportunity to improve health through proper interven on programmes and to reduce the subsequent manifesta ons in popula on.

Fig 1 :
Fig 1: Percen le curves of age specifi c mean height, weight, BMI, TSF, UMA and UFA among the Rajbanshi boys

Fig 3 :
Fig 3: Age specifi c mean upper arm composi on variables of TUA, UMA, UFA and AFI of the Rajbanshi boys as compared with 5 th , 25 th , 50 th , 75 th and 95 th percen les of NHANES-III (33) Reference popula ons.

Table 1 :
Age-specifi c subject distribu on, descrip ve sta s cs (mean ± SD) of the anthropometric and body composi on variables and within age diff erences among the Rajbanshi boys