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Increasing obesity prevalence among children and
adolescence is one of the most important public health problems (1). The number of children who are
overweight has doubled in the last two to three decades, and currently one child in five is overweight in
the United States (2). The increase has been presented in both children and adolescents, and in all age,
race and gender groups. Progress toward reducing
the national prevalence of overweight and obesity is
monitored using data from the National Health and
Nutrition Examination Survey (NHANES). Data from
two NHANES surveys (1976-1980 and 2003-2004)
show that the prevalence of overweight is increasing:
for children aged 2–5 years, prevalence increased from
5.0% to 13.9%; for those aged 6-11 years, prevalence
increased from 6.5% to 18.8%; and for those aged 12-
19 years, prevalence increased from 5.0% to 17.4% (1).
Being overweight is the result of caloric imbalance
(too few calories expended for the amount of calories
consumed) and mediated by both genetic and environmental factors. An estimated 61% of overweight young
people have at least one additional risk factor for heart
disease, such as high cholesterol or high blood pressure
(2,3). In addition, children who are overweight are at
greater risk for bone and joint problems, sleep apnea,
and social and psychological problems such as stigmatization and poor self-esteem (2). Overweight young
people are more likely to become overweight or obese
adults than children of normal weight, and therefore more at risk for associated adult health problems,
including heart disease, type 2 diabetes, stroke, several types of cancer, and osteoarthritis. Healthy lifestyle
habits, including healthy eating and physical activity,
can lower the risk of becoming overweight, underweight and developing related diseases (2,3).
Because of their public health importance, the trends
in childhood obesity should be closely monitored (3).
Classifications of overweight for children and adolescents are age and sex-specific because children’s body
composition varies as they age and varies between boys
and girls (4). While BMI is an accepted screening tool
for the initial assessment of body fatness in children
and adolescents, it is not a diagnostic measure because
BMI is not a direct measure of body fatness. Recent
studies have shown that obesity, especially the central
type obesity, increases the risk of developing metabolic
syndrome in adults (3). The severity of central obesity
is determined by taking waist and hip measurements.
Waist circumference (WC) is the anthropometric indicator of fat distribution which are most closely related
to cardiovascular disease (CVD) risk factors (3). The
prevalence of the metabolic syndrome in the pediatric
age group was 27.2% among Turkish children identified as obese (5). Each country must have its own reference values to identify obesity within the country.
Bundak et al. reported data and curves for body mass
index values in healthy Turkish children aged 6-18 years in 2006 (6).
Since WC is a highly sensitive and specific measure of upper body fat in childhood and adolescence,
to identify overweight and obese children at risk of
developing metabolic complications, it should be
used routinely (7). Early identification and treatment
of children with central adiposity is very important
due to metabolic complications. WC percentiles have
been developed for children and adolescents in several countries. Hatipoglu et al. reported data and smoothed percentile curves for waist circumference of
healthy Turkish children aged 7-17 years in 2007 (8).
WC is a marker for central body fat accumulation;
a large WC is linked to an increased risk of metabolic
complications (9). In this study, we aimed to evaluate whether the waist circumference may clinically be
useful as a predictor of obesity/underweight in children or not.
Material and Methods
Subject selection: This descriptive and cross-sectional
study was carried out between October 2007 and May
2008. The universe of this study constituted 2572 cases who were educated at the 6 primary and high schools in Konya. Konya Province which has more than
1.500.000 inhabitants is a leading industry and trade
center in Turkey. Before beginning this research, ethical consideration was approved by the ethical committee of Meram Medical Faculty of Selcuk University. For
this research, first approval was obtained from governorship and then second approval was obtained from
National Education Administration. In the first step,
6 primary and high schools located in the center of
Konya where the research was performed were selected
by the cluster sampling method. In the second step,
children and adolescents aged 7-18 years were selected randomly from school enrollments. Among these,
students with growth retardation such as acondroplasia, pituitary gland dwarfism and students who refused
to participate in this study and the ones who could
not be found at school were excluded from the study.
This research was started with the official permission
and cooperation of the directors of the selected schools. All of the participants were all volunteers and healthy school children. Initially, we aimed to include
3000 children and adolescents in this research. In this
study, 2572 participants has been reached (85.7%)
(2572/3000). A standardized questionnaire was applied to determine the sociodemographic characteristics.
The participants’names, surnames, the chronological
ages, genders, grade and parents’education levels were
recorded on this paper.
Measurements: The chronological age was calculated
as the decimal age by subtracting the birth date from
the observation date. Each year elapsed from their
birthday was noted as one age (8). WC, height, weight, and hip were measured by a well- trained research assistant. WC was measured in the standing position at the level of the umbilicus (halfway between
the lower border of the ribs, and the iliac crest in a
horizontal plane) to the nearest 0.1 cm with a flexible
anthropometrical tape. Hip was measured with a flexible anthropometrical tape by taking reference of the
participant’s hip circumference that passes through
the middle of gluteal region transversely (the widest
point over the buttocks). For each of waist and hip circumference, two measurements to the nearest 0.5 cm
were recorded. Weight was measured after removal of
shoes and with light clothes only by using a stadiometer and was recorded to the nearest 0.1 kg. Height
was measured to the nearest 0.5 cm without shoes by
using the Height Measuring Scale, and the cases stood
still on the middle of the scale without leaning or holding on anything. While the height of a schoolchild
is measured standing straight, without shoes, heels together, back against the wall and looking straight ahead. The research assistant put a ruler horizontally on
top of her/his head to mark off the corresponding spot
on the chart or measuring stick. All measurements
were taken twice. If the variation between the measurements was greater than 2 cm, a third measurement
was taken. The mean of the two closest measurements
was calculated. Body mass index (BMI) was calculated
as weight (kg)/(height (m)
2
) (10).
Cole et al. defined the internationally acceptable
criteria of childhood overweight and obesity. In that
study, the resulting curves were averaged to provideage- and sex-specific cut off points from 2-18 years. For
each of the surveys, centile curves determined at the
age of 18 years were widely used as cut off points of
25 and 30 kg/m2
for adult overweight and obesity (4).
Bundak et al. reported data and curves for body mass
index values in healthy Turkish children aged 6-18 years in 2006 in Turkey (6).
In children, we focused on the specific percentile of
the WC according to age and gender. WC percentiles indicate the following: WC-for-age less than the
5th percentile means underweight, WC-for-age 5th
to 85th percentile means the child is healthy weight
(normal), WC-for-age 85th to 95th percentile means
the child is overweight, WC-for-age greater than 95th
percentile means the child is obese (11).
Ethical considerations: The study protocol was approved by the Ethics Committee of Meram Medical Faculty
of Selcuk University and a written informed consent
was taken from parents of all included subjects.
Statistical analysis: The SPSS 13.0 statistical software package was used in data entry and analysis. The
statistical analysis and evaluations were conducted by
the authors. The variables were described by mean, frequency and standard deviation (SD). To compare the
statistical significance between groups, Chi-square and
Student T tests were used. Statistical significance was
defined as p<0.05.
Results
Of all 2572 students, 1381 (53.7%) were male, 1191
(46.3%) were female, mean age was 13.28±2.59 (min:
7, median: 13, max: 18), mean number of sibling
was 2.41±1.44 (min: 0, median: 2, max: 10). When
we evaluated the fathers’ occupation, we found that
45.3% (n=1165) were tradesmen, 25.7% (n=660) civil
servants, 20.7% (n=532) workers. For women, we found that 89.9% (n=2310) were housewives and 7.9%
(n=203) were civil servants. We found that WC increased with age in both genders. The mean value of
WC in boys at the age of 8, 10, 11, 15, 16, 17 and 18
was statistically greater than that of girls. The boys
had usually higher WC values than the girls except
for the age group of 12-14 years. The prevalence of
obesity was 7.7% in 8-year-old female students and
5.3% in 9- and 14-year-old male students. The prevalence of overweight was 10.9% in 13-year-old
female students and 11.6% in 8-year-old male students. The prevalence of underweight was 17.9% in
18-year-old female students and 20.0% in 7-year-old
male students. Table I presents the means and standard deviations of WC according to age and sex of
the participants. In this study, smoothed percentile
values for the 3rd, 5th, 10th, 25th, 50th, 75th, 85th,
90th, 95th and 97th percentiles were calculated for
boys and girls separately by the authors. At the age
of 18 years, BMI was used as cut off points of 25 and
30 kg/m2
for adult overweight and obesity. Table II
Table I. Mean values of waist circumference (cm) according to
age and sex
Ages* Boys Girls Total
n Mean (SD) n Mean (SD) n %
7 20 58.25 (8.55) 22 59.46 (4.39) 42 1.6
8 26 58.39 (5.22) 26 57.88 (5.17) 52 2.0
9 19 61.58 (7.29) 19 61.58 (7.29) 38 1.5
10 156 64.31 (8.10) 126 62.33 (7.32) 282 11.0
11 168 63.14 (8.19) 143 61.97 (6.02) 311 12.1
12 162 64.13 (7.16) 151 64.64 (8.01) 313 12.2
13 123 67.15 (8.51) 138 69.25 (9.07) 261 10.1
14 188 69.10 (8.27) 205 69.33 (8.39) 393 15.3
15 171 69.74 (6.83) 119 68.91 (7.28) 290 11.3
16 166 73.49 (7.79) 91 70.11 (8.27) 257 10.0
17 123 73.90 (7.91) 113 68.85 (6.79) 236 9.2
18 58 75.09 (7.92) 39 66.64 (6.69) 97 3.8
Total 1381 1191 2572 100.0
*: Age indicates the whole age group, e.g. 8.0 to 8.99 years
Table II. Waist circumference percentile values (cm) of study group for boys in the age groups of 7-17 years
Ages* 3rd 5rd 10rd 25rd 50rd 75rd 85rd 90rd 95rd 97rd
7 50.0 50.0 50.0 51.5 56.0 60.0 71.5 76.6 77.9 78.0
8 49.0 49.4 52.1 54.8 57.5 61.3 64.9 65.0 69.6 72.0
9 56.0 56.0 56.0 57.0 62.0 66.0 70.0 72.0 80.0 80.0
10 51.7 54.0 55.0 59.0 63.0 68.0 72.0 76.0 82.0 85.0
11 52.1 53.0 54.0 57.2 61.0 67.8 71.0 73.1 79.0 83.8
12 52.9 54.1 57.0 59.0 63.0 69.2 73.0 74.0 77.0 80.0
13 54.7 55.2 58.0 61.0 66.0 72.0 77.0 78.0 81.6 83.8
14 56.6 58.0 60.0 64.0 68.0 74.0 78.0 80.0 83.6 88.4
15 58.0 60.0 63.0 65.0 69.0 73.0 77.0 79.6 82.4 86.4
16 61.0 62.4 65.0 69.9 72.0 77.0 80.0 83.6 89.7 93.9
17 61.7 64.0 65.0 68.0 73.0 78.0 81.0 86.0 91.8 94.0presents smoothed age-specific WC percentile values (cm) for boys at 7-17 years. Table III presents the
smoothed age-specific WC percentile values (cm) for
girls at 7-17 years. Table IV presents the differences
of WC according to age and gender among children
and adolescents. Table V presents the comparison ofBMI according to age and gender among children
and adolescents. Table VI and VII present the weight
classifications based on an age- and sex-specific percentiles for Turkish boys and girls at 7-17 years.
Discussion
In this study, the mean values of WC by age and
sex, smoothed age-specific WC percentile values (cm)
for Turkish children aged 7–18 years, the differences
of WC between age and gender, the comparison of
BMI according to age and gender were presented.
The weight classifications based on an age- and sexspecific percentile were computed. In our study, we
found that the mean values of WC were more frequently higher in males than females. Particularly,
there were statistically significant differences between
females and males at the age of 8, 10, 11, 15, 16, 17
and 18. Overweight in childhood and adolescence is
an important public health issue because of its rapidly
increasing prevalence and associated adverse medical and social consequences. Recent studies have estimated that 15 percent of children in the United States
are at risk of overweight. Important predictors of overweight include age, sex, race/ethnicity, and parental
weight status (12). Chinn and Rona reported that from
1984 to 1994 overweight increased from 5.4% to 9.0%
in English boys (increase 3.6%, 95% confidence interval 2.3% to 5.0%) and from 6.4% to 10.0% in Scottish
boys (3.6%, 1.9% to 5.4%) (13). These rising trends are
likely to be reflected in increases in adult obesity and
associated morbidity. Overweight in children is a serious public health problem in Britain (13). In another
study, WC in British youth has increased over the past
10-20 years at a greater rate than BMI, the increase
being greatest in females (9). In our study, increasing
obesity/overweight prevalence among children has
Table VI. Weight classifications based on an age-specific waist circumference percentile values (cm) in the male cases
Age
Underweight Healthy weight (Normal) Overweight Obese
Range n % Range n % Range n % Range n %
7 <50.00 4 20.00 50.00-71.49 13 65.0 71.50-77.95 2 10.0 >77.95 1 5.0
8 <49.40 1 3.8 49.40-64.90 21 80.8 64.90-69.60 3 11.6 >69.60 1 3.8
9 <56.00 2 10.5 56.00-70.00 15 78.9 70.00-80.00 1 5.3 >80.00 1 5.3
10 <54.00 9 5.8 54.00-72.00 125 80.1 72.00-82.00 16 10.3 >82.00 6 3.8
11 <53.00 11 6.5 53.00-71.00 136 81.0 71.00-79.00 14 8.3 >79.00 7 4.2
12 <54.10 8 4.9 54.10-73.00 134 82.7 73.00-77.00 14 8.6 >77.00 6 3.8
13 <55.20 6 4.9 55.20-77.00 101 82.1 77.00-81.60 10 8.1 >81.60 6 4.9
14 <58.00 11 5.9 58.00-78.00 153 81.4 78.00-83.60 14 7.4 >83.60 10 5.3
15 <60.00 9 5.3 60.00-77.00 138 80.7 77.00-82.40 16 9.3 >82.40 8 4.7
16 <62.40 8 4.8 62.40-80.00 134 80.7 80.00-89.70 16 9.6 >89.70 8 4.9
17 <64.00 7 5.7 64.00-81.00 100 81.3 81.00-91.80 10 8.1 >91.80 6 4.9
Table VII. Weight classifications based on an age-specific waist circumference percentile values (cm) in the female cases
Age
Underweight Healthy weight (Normal) Overweight Obese
Range n % Range n % Range n % Range n %
7 <49.05 1 4.50 49.05-65.00 19 86.5 65.01-66.85 1 4.5 >66.85 1 4.5
8 <49.70 1 3.8 49.70-64.90 21 80.0 64.90-68.60 2 7.7 >65.30 2 7.7
9 <52.00 --- --- 52.00-66.00 17 89.5 66.00-86.01 1 5.3 >66.01 1 5.3
10 <52.30 6 4.8 52.30-68.00 104 82.5 68.00-76.00 11 8.7 >76.00 5 4.0
11 <54.00 10 7.0 54.00-68.00 113 79.0 68.00-72.80 13 9.1 >72.80 7 4.9
12 <54.00 8 5.3 54.00-73.00 122 80.8 73.00-81.00 16 10.6 >81.00 5 3.3
13 <56.90 6 4.3 56.90-79.00 113 81.9 79.00-88.00 15 10.9 >88.00 4 2.9
14 <58.00 11 5.4 58.00-77.10 164 80.0 77.10-86.00 21 10.2 >86.00 9 4.4
15 <60.00 9 7.6 60.00-76.00 97 81.5 76.00-81.00 8 6.7 >81.00 5 4.2
16 <61.00 7 7.7 61.00-78.00 73 80.2 78.00-88.00 8 8.8 >88.00 3 3.3been determined. This can be attributed to social, economical and traditional customs in this province.
McCarthy and Ashwell have reported that the values
of the waist: height ratios (WHtR) during the past 10-
20 years have increased greatly showing that central
fatness in children has risen dramatically (14). WHtR
is more closely linked to childhood morbidity than
body mass index (BMI) and they suggest it should be
used as an additional or alternative measure to BMI in
children as well as adults. Consequently, they declared
a simple public health message that is the same for
adults and children of both sexes and all ages could be
stated as “keep your waist circumference to less than
half your height” (14). This slogan might be the starting point of reducing the spread rate of obesity together with the protective measures.
Savva et al. also reported that visceral adipose tissue
was associated with increased risk for cardiovascular
disease risk factors and morbidity from cardiovascular
diseases (15). They used the waist measurement and
WHtR as proxy measures of visceral adipose tissue. In
their study, they validated the BMI, WC and WHtR
as predictors for the presence of cardiovascular disease risk factors in children of Greek-Cypriot origin.
Consequently, they have declared that waist circumference and WHtR are better predictors of cardiovascular disease risk factors in children than BMI (15).
While BMI according to age and sex was different at
the age of 18, WC differences for age and sex at the
ages of 8, 10, 11, 15, 16, 17 and 18 were more important in our study.
Moreno et al. presented that WC showed higher values in boys than in girls, especially after 11.5 y, and
waist values increased with age both in 1360 males
and females Spanish children (16). WC tended to
be higher in males than females and this difference
was significant after 11.5 y. In general, hip circumference was higher in females than in males (statistically
significant differences at 7.5, 10.5, 12.5 and 13.5 y).
These findings justify the use of age and gender specific reference standards (16). Generally, the mean WC
values in our study were higher in males than females.
Especially it was statistically greater in males than
females at the ages of 10, 16, 17 and 18. As a result,
young female adolescents seem to tend to be thinner
to have an aesthetic look.
Katzmarzyk presented the age- and sex-specific WC
reference data for 3064 Canadian youth 11-18 y of
age. WC increased with age in both boys and girls,
and boys had higher values of WC than girls at every
age and percentile level. In conclusion, these reference
data can be used to identify those who have an elevated risk of developing obesity-related disorders and can
serve as a baseline for future studies of temporal trends
in WC (17). In our study, WC values of males were
generally higher than those of females, and they were
in the tendency of increasing with age.
In another study, overweight was a serious health
concern for children and adolescents. Recently redefined BMI classifications are not appropriate for children, because BMI shows profound changes from birth
through to early adulthood. WC seems to be the best
predictor of children with the metabolic syndrome
in pediatric clinical settings (18). Pouliot et al. have
presented that central obesity is associated with a statistically higher risk of heart disease, hypertension,
dyslipidemia, insulin resistance, and diabetes mellitus
type 2 (3). We emphasize in our study that WC is an
important predictor of obesity during the childhood.
Eisenmann has presented that mean WC increases
in both males and females, with the values being similar between Australian males and females prior to age
11 y, after which values are slightly higher in males
(19). In our study, WC values increased with age in
both sexes. The mean value of WC in boys at the age
of 10, 16, 17 and 18 was statistically greater than girls.
Garnett et al. have reported that BMI may not indicate the level of central adiposity associated with the
clustering of cardiovascular disease (CVD) risk factors.
Hence, it has been recommended that waist circumference be used as an alternative measure (20). In our
study, BMI was statistically greater in boys than girls in
18 age group (p=0.037).
Taheri et al. presented that the prevalence rates of
overweight and obesity were 4.8% and 1.8% in 7- to
18-year-old children in Iran, respectively. These rates
are lower than our results (21).
The study of Hatipoğlu et al. from Kayseri is important as it can be a reference to other studies. These
data can be added to the existing international reference values for WC of children and adolescents (8).
Obesity prevalence among children is an important
public health problem (22,23). In this study, we aimed
to evaluate whether the WC may clinically be useful as
a predictor of obesity/underweight in children or not.
The limitations of our study should be considered.
Although the overall sample was relatively large, we
reached a small group. In addition, although a quite
close match, this study group is not entirely representative of the Turkish population. The study includes
only the province of Konya. It should not be disregarded the possibility of the side effects of nutrition
habits of Central Anatolia Region on the results since
the main nutrition of the region is based on cereals.
Smoothed percentile values for the 3rd, 5th, 10th,
25th, 50th, 75th, 85th, 90th, 95th and 97th percentiles were calculated for boys and girls separately (23).
In conclusion, WC values increased with age in both
sexes in our study. The mean value of WC in boys at
the ages of 8, 10, 11, 15, 16, 17 and 18 was statistically greater than girls. Current and future morbidity in Turkish youth may be seriously affected due
to accumulation of excess central fat. We emphasize
in our study that WC is an important predictor of
obesity during the childhood. We expect that our
study will contribute to Turkish literature for age and
sex-specific reference values for WC. These findings
deserve further prospective study and highlight the
importance of early recognition and improved treatment models for children and adolescents with overweight and obese
Acknowledgements
The authors acknowledge the Director of National
Education Administration, the teachers of the selected schools for their efforts in collecting information.
The authors thank to Mustafa Tasbent for supports to
English review. We thank to all of the participants.