Correlation of Waist Indices with Body Mass Index in School-Aged Children

Vijay J et al | DOI: 10.65188/nurexus.1060

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Journal of MedVerse Research & Practice

ISSN: 3107-4278

Correlation of Waist Indices with Body Mass Index in School-Aged

Children

Dr. Joseph Vijay

, Dr. Sangeetha

Assistant Professor, Professor

Department of Paediatrics,

Faculty of Medicine, University of Colombo, Srilanka

Email ID: josephvijay@gmail.com,

Submission Date: 24.11.2025

Accepted Date: 21.12.2025

Published Date: 31.12.2025

DOI: 10.65188/nurexus.1060

article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits

unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Abstract

Background: Childhood obesity is a growing public health problem with significant short- and long-term health

consequences. While body mass index (BMI) is commonly used to assess nutritional status, it does not adequately

reflect central fat distribution, which plays a critical role in metabolic risk. Waist-based anthropometric indices

have emerged as simple and effective measures for assessing central obesity.

Methods: A cross-sectional observational study was conducted among 300 school-going children aged 12–16

years. Anthropometric measurements, including weight, height, waist circumference, and hip circumference, were

recorded using standardized procedures. BMI was calculated and classified using age- and sex-specific reference

charts. Waist-to-hip ratio and waist-to-height ratio were derived using standard formulas. Correlation between BMI

and waist indices was analyzed using appropriate statistical methods, with a p value <0.05 considered statistically

significant.

Results: Of the total participants, 38% were classified as overweight or obese. Abnormal waist-to-height ratio was

observed in a higher proportion of children compared to waist circumference and waist-to-hip ratio. Mean values of

all waist indices increased progressively with rising BMI categories. BMI showed a strong positive correlation with

waist-to-height ratio (r = 0.86) and waist circumference (r = 0.82), both of which were statistically significant (p

<0.001). Notably, abnormal waist indices were also observed among children with normal BMI.

Conclusion: Waist-based anthropometric indices, particularly waist-to-height ratio, show a strong correlation with

BMI and effectively identify central obesity among school children. Incorporation of waist indices along with BMI

in school health screening programmes may improve early detection of obesity-related health risks and support

preventive public health strategies.

Keywords: Body mass index; Waist circumference; Waist-to-height ratio; Waist-to-hip ratio; Childhood obesity;

School children

Introduction

Childhood overweight and obesity have become major public health challenges worldwide, with a

noticeable rise in prevalence over recent decades. Children from diverse socioeconomic and cultural

settings are increasingly affected, largely due to rapid changes in lifestyle patterns. Increased

consumption of energy-dense foods, declining levels of physical activity, prolonged screen exposure, and

academic-related sedentary behaviour have collectively contributed to unhealthy weight gain during

childhood and adolescence [1].

Excess body fat in childhood is associated with several adverse health outcomes. In the immediate term,

affected children may experience reduced physical endurance, musculoskeletal discomfort, sleep-related

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problems, and psychosocial difficulties. More importantly, childhood obesity has a strong tendency to

persist into adulthood, significantly increasing the risk of non-communicable diseases such as type 2

diabetes mellitus, hypertension, cardiovascular disease, and cerebrovascular events later in life [2]. Early

detection of children at risk is therefore crucial for preventing long-term health consequences.

Body mass index (BMI) is the most widely used anthropometric measure for assessing nutritional status

among children and adolescents. Its simplicity, low cost, and ease of application make it suitable for

large-scale screening and epidemiological studies [3]. However, BMI provides an estimate of overall

body mass and does not differentiate between fat mass and lean mass. Furthermore, it fails to capture the

distribution of body fat, particularly central adiposity, which plays a pivotal role in metabolic risk [4].

Growing evidence highlights the importance of abdominal obesity as a key determinant of

cardiometabolic risk. Visceral fat is metabolically active and contributes to insulin resistance, systemic

inflammation, and dyslipidaemia. Children with increased central fat accumulation may therefore exhibit

metabolic abnormalities even when their BMI falls within the normal range [5]. This limitation

necessitates the use of additional anthropometric indicators that better reflect fat distribution.

Waist-based anthropometric indices, including waist circumference, waist-to-hip ratio, and waist-to-

height ratio, have gained attention as practical measures of central adiposity. Among these, waist-to-

height ratio has been shown to be a reliable predictor of cardiometabolic risk, with the advantage of a

single cut-off value applicable across age groups and sexes [6,7]. These indices are non-invasive, easy to

measure, and feasible for implementation in school and community-based screening programmes.

School-going children constitute an important target group for early screening, as lifestyle behaviours

established during this period often track into adulthood. In South Asian countries, including India and Sri

Lanka, the dual burden of undernutrition and rising childhood overweight presents a unique public health

concern, particularly in urban and semi-urban populations [8,9]. Evaluating the relationship between BMI

and waist-based indices may enhance the identification of children at risk and strengthen existing school

health strategies. Therefore, the present study aims to assess the correlation between waist-based

anthropometric indices and body mass index among school children [10].

Materials and Methods

An observational cross-sectional study was undertaken by the Department of Paediatrics, Faculty of

Medicine, University of Colombo, Sri Lanka, with the objective of examining the association between

waist-based anthropometric indices and body mass index among school-aged children. The study was

conducted in selected schools enrolling students between 12 and 16 years of age. Schools were chosen

based on logistical feasibility and ease of access for systematic data collection.

The study population comprised 300 students within the specified age group who were enrolled during

the study period. Participants were selected using a purposive sampling method. Children who were

present at school on the day of assessment and whose parents or legal guardians provided written

informed consent, along with assent from the children themselves, were included. Students with known

chronic medical conditions or physical impairments likely to influence anthropometric measurements, as

well as those without parental consent, were excluded from participation.

Prior to commencement, approval was obtained from the Institutional Ethics Committee, and formal

permission was secured from the respective school authorities. Data were collected using a pre-validated,

structured data collection form. Baseline information including age, sex, and relevant sociodemographic

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characteristics was recorded. Dietary practices and levels of physical activity were evaluated using a

standardized questionnaire. Intake of junk food or sugar-sweetened beverages more than twice weekly

was classified as an unhealthy dietary behaviour, in line with recommendations from the American

Academy of Pediatrics. A brief clinical assessment was conducted to identify obesity-related physical

signs, including the presence of acanthosis nigricans.

Anthropometric measurements were performed by trained personnel adhering strictly to standardized

measurement protocols. All children were examined wearing light clothing and without footwear. Body

weight was measured using a calibrated digital weighing scale and documented to the nearest 0.1 kg.

Standing height was measured using a stadiometer, with participants positioned upright and the head

aligned in the Frankfurt horizontal plane, and recorded to the nearest 0.1 cm. Body mass index was

derived by dividing weight in kilograms by height in meters squared and interpreted using age- and sex-

specific reference values recommended by the Centers for Disease Control and Prevention.

Waist circumference was measured using a non-elastic measuring tape placed midway between the

inferior margin of the last palpable rib and the superior border of the iliac crest at the end of normal

expiration, and readings were recorded to the nearest 0.1 cm. Central adiposity was defined as a waist

circumference equal to or exceeding the 70th percentile according to reference standards proposed by

Khadilkar et al. Hip circumference was measured at the widest point over the buttocks. Waist-to-hip ratio

was calculated, with values above 0.85 for girls and 0.90 for boys considered abnormal. Waist-to-height

ratio was computed by dividing waist circumference by height, and a cut-off value greater than 0.5 was

used to indicate central obesity. All participant data were handled confidentially, and anonymity was

maintained throughout data collection, analysis, and reporting.

Ethical approval for the present study was obtained from the Institutional Ethics Committee of the

University of Colombo, Sri Lanka (Ref No: UOC/IEC/2024/39158). A detailed Participant Information

Sheet was provided to all participants, and written informed consent was obtained prior to their

participation in the study.

Results

Table 1:Age and Sex Distribution of Study Participants (n = 300)

Age group (years)

Boys n (%)

Girls n (%)

Total n (%)

12–13

48 (16.0)

42 (14.0)

90 (30.0)

14–15

66 (22.0)

54 (18.0)

120 (40.0)

45 (15.0)

90 (30.0)

Total

159 (53.0)

141 (47.0)

300 (100)

The age and sex distribution of the study participants demonstrates that the majority of children (40%)

belonged to the 14–15-year age group, followed by equal proportions in the 12–13-year and 16-year

groups (30% each). There was a slight male predominance, with boys constituting 53% of the total

sample and girls accounting for 47%. This relatively uniform distribution across age groups ensures

adequate representation of early to mid-adolescence, a critical period for rapid physical growth and

changes in body composition. The near-equal sex distribution minimizes gender-related bias and

enhances the generalizability of the findings across both sexes.

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Figure 1: Distribution of BMI Categories among Study Participants

Based on BMI classification using age- and sex-specific reference standards, 62% of the children were

found to have normal BMI, while 24% were overweight and 14% were obese. Thus, more than one-third

(38%) of the study population exhibited excess body weight. This finding highlights a substantial burden

of overweight and obesity among school-going children, reflecting the growing public health concern

related to unhealthy weight gain during adolescence. The observed prevalence underscores the

importance of early screening and preventive strategies in school settings.

Table 2: Distribution of Waist Indices among Study Participants

Waist index

Normal n (%)

Abnormal n (%)

Waist circumference

204 (68.0)

96 (32.0)

Waist-to-hip ratio

219 (73.0)

81 (27.0)

Waist-to-height ratio

195 (65.0)

105 (35.0)

Assessment of waist indices revealed that an abnormal waist-to-height ratio was present in 35% of

participants, followed by an abnormal waist circumference in 32% and an abnormal waist-to-hip ratio in

27%. Among the three indices, waist-to-height ratio identified the highest proportion of children with

central obesity. This suggests that waist-to-height ratio may be a more sensitive indicator of abdominal

adiposity in children compared to other waist-based measures. The findings also indicate that a significant

proportion of children with central obesity may not be identified using BMI alone.

Table 3: Mean Anthropometric Measurements by BMI Category

Parameter

Normal BMI (Mean ± SD)

Overweight (Mean ± SD)

Obese (Mean ± SD)

Waist circumference (cm)

66.2 ± 5.1

74.8 ± 4.6

82.5 ± 5.3

Waist-to-hip ratio

0.78 ± 0.05

0.84 ± 0.06

0.91 ± 0.07

Waist-to-height ratio

0.44 ± 0.04

0.52 ± 0.05

0.59 ± 0.06

Mean waist circumference, waist-to-hip ratio, and waist-to-height ratio showed a progressive increase

from the normal BMI group to overweight and obese categories. Children classified as obese had

markedly

higher

mean

waist

circumference

and

waist

indices

compared

their

normal-weight

OBESE

OVERWEIGHT

NORMAL

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counterparts. This graded rise in central adiposity parameters with increasing BMI demonstrates a clear

association between overall adiposity and abdominal fat accumulation, reinforcing the biological

plausibility of the observed correlations.

Table 4: Correlation between BMI and Waist Indices

Waist index

Pearson correlation coefficient (r)

p value

Waist circumference

0.82

<0.001

Waist-to-hip ratio

0.69

<0.001

Waist-to-height ratio

0.86

<0.001

Correlation analysis revealed a strong and statistically significant positive association between BMI and

all waist indices. Waist-to-height ratio showed the strongest correlation with BMI (r = 0.86, p < 0.001),

followed closely by waist circumference (r = 0.82, p < 0.001). Waist-to-hip ratio demonstrated a

moderately strong correlation (r = 0.69, p < 0.001). These findings indicate that waist-based indices,

particularly waist-to-height ratio, closely reflect overall adiposity as measured by BMI and may serve as

reliable complementary screening tools.

Table 5: Prevalence of Abnormal Waist Indices across BMI Categories

BMI category

Abnormal WC n (%)

Abnormal WHR n (%)

Abnormal WHtR n (%)

Normal (n=186)

18 (9.7)

15 (8.1)

21 (11.3)

Overweight (n=72)

39 (54.2)

30 (41.7)

45 (62.5)

Obese (n=42)

39 (92.9)

36 (85.7)

39 (92.9)

The prevalence of abnormal waist indices increased markedly with rising BMI category. While a small

proportion of children with normal BMI exhibited abnormal waist indices, more than half of overweight

children and the vast majority of obese children demonstrated abnormal waist circumference and waist-

to-height ratio. Notably, waist-to-height ratio detected central obesity in over 90% of obese children. This

trend suggests that central adiposity worsens with increasing BMI and highlights the ability of waist

indices to identify children at risk even within lower BMI categories.

Discussion

The present cross-sectional study evaluated the correlation between waist-based anthropometric

indices and body mass index among school-going children aged 12 to 16 years. The findings

demonstrate a substantial prevalence of overweight and obesity, along with a strong and statistically

significant association between BMI and waist indices, particularly waist-to-height ratio. In the

present study, 38% of participants were either overweight or obese, indicating a considerable burden

of excess weight among adolescents. Similar trends have been reported globally and in South Asian

settings. Gupta et al. observed an increasing prevalence of childhood overweight and obesity in urban

Indian school children, attributing this rise to sedentary lifestyle patterns and dietary transitions [9].

Comparable findings were also reported by Wickramasinghe et al. among Sri Lankan school children,

emphasizing the growing public health challenge of adolescent obesity in the region [10].

Waist-based indices revealed that waist-to-height ratio identified the highest proportion of children

with central obesity compared to the waist circumference and waist-to-hip ratio. This observation

aligns with findings by Ashwell and Gibson, who emphasized that waist-to-height ratio is a superior

screening tool for central obesity across age groups and ethnicities [11]. McCarthy and Ashwell

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further suggested that waist-to-height ratio may be more effective than BMI in predicting metabolic

risk in children [12]. The progressive increase in mean waist circumference, waist-to-hip ratio, and

waist-to-height ratio across BMI categories observed in this study highlights the close relationship

between general and central adiposity. Similar graded increases have been reported by Khadilkar et

al., who demonstrated that central fat accumulation rises proportionately with increasing BMI in

Indian children [13]. This reinforces the biological plausibility of using waist indices as

complementary measures to BMI.

Correlation analysis in the present study revealed a strong positive correlation between BMI and

waist-to-height ratio (r = 0.86), followed by waist circumference (r = 0.82). These findings are

consistent with studies by Freedman et al., who reported strong correlations between BMI and waist

circumference in paediatric populations [14]. A study by Savva et al. also demonstrated that waist-to-

height ratio showed a stronger association with cardiometabolic risk factors compared to BMI alone

[15]. An important observation from this study was the presence of abnormal waist indices even

among children with normal BMI. Similar findings were reported by Lee et al., who noted that

children with normal BMI but increased central adiposity had higher cardiometabolic risk profiles

[16]. This underscores the limitation of BMI as a sole screening tool and highlights the importance of

incorporating waist-based measurements in routine assessments.

The markedly high prevalence of abnormal waist indices among overweight and obese children

observed in the present study agrees with findings from the Bogalusa Heart Study, which

demonstrated strong associations between central obesity and adverse cardiovascular risk factors in

childhood [17]. Li et al. also reported that waist-to-height ratio was a reliable predictor of metabolic

syndrome components in children and adolescents [18]. From a public health perspective, these

findings have important implications for school health programmes. Schools offer an ideal platform

for early identification of children at risk of obesity-related complications. Studies by Daniels et al.

have emphasized the need for simple, cost-effective screening tools that can be implemented in

community and school settings [19]. Waist-to-height ratio, due to its simplicity and universal cut-off,

may serve as a practical tool in such programmes.

In the Indian subcontinent and Sri Lanka, where rapid urbanization and lifestyle changes are

influencing child health, region-specific evidence is essential. Studies by Misra et al. have highlighted

ethnic differences in body fat distribution, suggesting that Asian children may develop metabolic risk

at lower levels of adiposity [20]. Therefore, combining BMI with waist indices may improve early risk

stratification. Overall, the present study supports the use of waist-based anthropometric indices,

particularly waist-to-height ratio, as valuable adjuncts to BMI for assessing obesity and related health

risks among school children.

Conclusion

The present study demonstrates a strong and statistically significant correlation between body mass

index and waist-based anthropometric indices among school-going children aged 12 to 16 years. A

considerable proportion of participants were found to be overweight or obese, highlighting the

growing burden of adolescent obesity. Waist indices, particularly waist-to-height ratio, showed a

closer association with BMI and identified a higher proportion of children with central obesity,

including those with normal BMI. These findings emphasize the limitation of relying solely on BMI

for obesity screening and support the incorporation of waist-based measurements as complementary

tools. Given their simplicity, cost-effectiveness, and ability to detect central adiposity, waist indices,

Vijay J et al | DOI: 10.65188/nurexus.1060

Page 32

especially waist-to-height ratio, can be effectively utilized in school health programmes for early

identification of children at risk of obesity-related metabolic complications. Early screening and

timely preventive interventions during school years may play a crucial role in reducing the future

burden of non-communicable diseases.

Conflict of interest: Nil

Source Of Fund: Nil

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