# Predictive Effects of Waist Circumference-Related Anthropometric Measures on Body Mass Index in South African University Students

## TL;DR

This study shows that waist measurements like waist-to-height ratio and waist circumference are better predictors of BMI and health risks than BMI alone in South African university students.

## Contribution

The study provides novel evidence from an African context on the effectiveness of central adiposity measures over BMI for health risk assessment in young adults.

## Key findings

- WHtR and WC were strong predictors of BMI across all levels, with stronger effects at higher BMI.
- Incorporating central adiposity measures improves identification of students at higher cardiometabolic risk.
- Findings suggest updating health screening practices to include waist-related indicators for better risk assessment.

## Abstract

Public health relevance—How does this work relate to a public health issue?
This study addresses the global and national public health issue of rising obesity, particularly among young adults, by highlighting the limitations of relying solely on Body Mass Index (BMI) for risk assessment.It focuses on a key demographic, that is, university students who are in a transitional life stage where early identification of unhealthy weight gain and central adiposity can inform timely public health interventions to prevent long-term cardiometabolic diseases.

This study addresses the global and national public health issue of rising obesity, particularly among young adults, by highlighting the limitations of relying solely on Body Mass Index (BMI) for risk assessment.

It focuses on a key demographic, that is, university students who are in a transitional life stage where early identification of unhealthy weight gain and central adiposity can inform timely public health interventions to prevent long-term cardiometabolic diseases.

Public health significance—Why is this work of significance to public health?
The study provides evidence from an African context, where data is often lacking, supporting the use of simple, low-cost measures like Waist-to-Height Ratio (WHtR) and Waist Circumference (WC) as more robust indicators of health risk than BMI alone.It demonstrates that these central adiposity indicators are especially predictive at higher BMI levels, offering a more precise tool for identifying individuals within the student population who are at the greatest risk for future obesity-related diseases, enabling more targeted resource allocation.

The study provides evidence from an African context, where data is often lacking, supporting the use of simple, low-cost measures like Waist-to-Height Ratio (WHtR) and Waist Circumference (WC) as more robust indicators of health risk than BMI alone.

It demonstrates that these central adiposity indicators are especially predictive at higher BMI levels, offering a more precise tool for identifying individuals within the student population who are at the greatest risk for future obesity-related diseases, enabling more targeted resource allocation.

Public health implications—What are the key implications or messages for practitioners, policy makers and/or researchers in public health?
For practitioners: Routine health assessments for young adults should incorporate WHtR or WC alongside BMI to better identify individuals with adverse fat distribution and elevated cardiometabolic risk, leading to earlier lifestyle counseling and intervention.For policy makers & researchers: Public health screening guidelines and wellness programs in higher educational institutions should be updated to include measures of central adiposity. Researchers should prioritize longitudinal studies to confirm these indicators′ power in predicting actual disease outcomes in young African populations.

For practitioners: Routine health assessments for young adults should incorporate WHtR or WC alongside BMI to better identify individuals with adverse fat distribution and elevated cardiometabolic risk, leading to earlier lifestyle counseling and intervention.

For policy makers & researchers: Public health screening guidelines and wellness programs in higher educational institutions should be updated to include measures of central adiposity. Researchers should prioritize longitudinal studies to confirm these indicators′ power in predicting actual disease outcomes in young African populations.

Background: Body mass index (BMI) is commonly used to assess obesity but does not differentiate between fat and lean mass, limiting its effectiveness to assess cardiometabolic risk. Measurements of central adiposity, such as waist circumference (WC), waist-hip ratio (WHR) and waist-to-height ratio (WHtR), are better predictors of metabolic dysfunction, especially with respect to visceral fat. Aim: To examine BMI trends and assess the association between BMI and waist-related anthropometric indicators WC, WHR, and WHtR, among university students in South Africa. Methods: A cross-sectional study involving 842 university students was conducted. Anthropometric measurements were taken according to ISAK standards. Quantile regression models supplemented by ROC curves were used to assess the predictive effects of WC, WHR, and WHtR on BMI across its distribution. Results: A total of 842 participants (63.8% female) were included, with a mean age of 21.8 ± 4.0 years. Significant differences were observed across BMI categories for all demographic and anthropometric characteristics (p < 0.001). Quantile regression analyses showed that WHtR and WC were strong and consistent predictors of BMI in all quantiles, with effect sizes increasing at higher levels of BMI. The WHR showed weaker associations overall, but these became significant in the upper BMI quantiles. Collectively, waist-related indicators, particularly WHtR and WC, exhibited robust predictive values for elevated BMI. Conclusions: Waist-related indicators, especially WHtR and WC are robust predictors of elevated BMI among university students, particularly in higher BMI ranges. These findings highlighted the value of incorporating central adiposity measures alongside BMI for more accurate health risk assessments in young adult populations.