Materials and methods

Study design and setting

This cross-sectional analytical study was conducted at a tertiary care hospital in Maharashtra, India. The primary objective was to evaluate the correlation between the CI and VF% among overweight and obese adolescents. Participants were recruited from outpatient services using consecutive sampling on all clinic days during the study period between April 2024 and May 2025.

Study participants

Adolescents aged 10-19 years who were classified as overweight or obese were eligible for inclusion. Participants were classified according to the WHO 2007 growth reference for school-aged children and adolescents [17], using BMI-for-age and sex z-scores; overweight was defined as BMI-for-age >+1 SD and obesity as >+2 SD relative to the WHO median [17]. Adolescents were excluded if they had chronic systemic illness such as renal, hepatic, or cardiac disease; endocrine disorders affecting growth or metabolism, including hypothyroidism or Cushing syndrome; acute illness at the time of assessment; use of medications known to alter body composition, such as systemic corticosteroids, anticonvulsants, or hormonal therapy; or restrictive dietary practices likely to influence body composition.

Sample size

The assumed correlation of ρ = 0.25 was selected a priori as a conservative, minimum clinically relevant effect size, consistent with Cohen’s small-to-moderate effect-size convention, in the absence of comparable pediatric literature relating the CI to BIA-derived visceral fat at the time of study design. Assuming this correlation, a two-tailed α of 0.05, and 80% power, the minimum required sample size was 120 participants. Sample size was calculated using G*Power software (version 3.1.9.7; Heinrich Heine University Düsseldorf, Germany). A total of 120 adolescents were included, and all completed the required assessments.

Anthropometric assessment

Anthropometric measurements were performed using standardized procedures. Body weight was measured to the nearest 0.1 kg using a calibrated digital weighing scale, with participants wearing light clothing and no footwear. Height was measured to the nearest 0.1 cm using a stadiometer, with participants standing erect in the Frankfort plane. WC was measured using a non-stretchable tape at the midpoint between the lower margin of the last palpable rib and the iliac crest at the end of normal expiration. Hip circumference was measured at the level of maximum protrusion of the buttocks. All measurements were obtained twice. A third measurement was taken if the difference exceeded the predefined acceptable range, and the mean of the two closest values was used for analysis.

Derived anthropometric indices were calculated as follows:

AVI

[ AVI = \frac{2 \times WC^{2} + 0.7 \times (WC - HC)^{2}}{1000} ] where WC and HC are measured in centimeters [18].

BAI

[ BAI = \frac{HC}{\text{Height}^{1.5}} - 18 ] where HC is measured in centimeters and height in meters [19].

CI

[ CI = \frac{WC}{0.109 \sqrt{\dfrac{\text{Weight}}{\text{Height}}}} ] as described by Valdez [14], where WC and height are measured in meters and weight in kilograms.

Body composition assessment

Body-composition parameters including total body fat (BF%), subcutaneous fat (SCF), skeletal muscle mass (SMM), and VF% were estimated by BIA using the Omron Karada Scan HBF-3 device (Omron Healthcare, Inc., Kyoto, Japan) under standardized conditions, including avoidance of recent strenuous physical activity and ensuring adequate hydration. BIA is an indirect, algorithm-based method that does not measure visceral fat directly; computed tomography and magnetic resonance imaging remain the reference standards for visceral adiposity quantification, and BIA estimates may be influenced by hydration status, ethnicity, and device-specific prediction equations, which have been validated predominantly in adult populations [20].

Blood pressure assessment

Blood pressure was measured using a mercury sphygmomanometer with an appropriately sized cuff selected according to mid-arm circumference. Measurements were taken after at least five minutes of rest, with the participant seated and the arm supported at heart level. Two readings were recorded at an interval of two to three minutes. If the initial reading was elevated, a third reading was obtained, and the average of the last two readings was used [21].

Statistical analysis

Data were analyzed using jamovi software (version 2.4.1; The jamovi Project, Sydney, Australia). Continuous variables were summarized as median and interquartile range, and categorical variables as frequencies and percentages. Sex-based comparisons were performed using the Mann-Whitney U test for continuous variables and the chi-square test or Fisher’s exact test for categorical variables, as appropriate. Because several variables were not normally distributed, associations between anthropometric indices and body-composition parameters were assessed using Spearman’s rank correlation coefficient. Hierarchical multiple linear regression was used to identify independent predictors of visceral fat. Model performance was compared using R², adjusted R², Akaike information criterion, root mean square error, and change in R². A two-tailed p-value < 0.05 was considered statistically significant.

Ethical considerations

Ethical approval was obtained from the Ethics Committee for Research on Human Subjects, Mahatma Gandhi Mission (MGM) Medical College (Approval No.: MGM-ECRHS/2024/136, dated March 30th, 2024). Written informed consent was obtained from parents or legal guardians, and assent was obtained from adolescent participants.