Visceral adiposity index and cardiorespiratory fitness: Unmasking risk of impaired fasting glucose among adolescents

Abstract

Type 2 diabetes mellitus (T2DM) is increasing among adolescents, but paediatric risk predictors are relatively underdeveloped. This study aimed to establish the associations of visceral adiposity index (VAI) and cardiorespiratory fitness (CRF) with fasting plasma glucose in 418 Nigerian adolescents aged 11 years to 19 years. Using a cross-sectional design, participants were stratified by VAI and CRF tertiles to examine variations in impaired fasting glucose (IFG) risk. The findings of this study revealed significant gender differences: In the case of boys, high VAI and low CRF is associated with IFG, while no association was present in girls. CRF, measured by the 20-meter shuttle run, was a stronger predictor of IFG than VAI, suggesting that physical fitness is a protective factor against glucose dysregulation. These findings point to VAI and CRF as useful, non-invasive predictors of risk for T2DM in youth, supporting school-based fitness programs that promote CRF and attenuate visceral adiposity, particularly in males. Future work must validate these predictors across various ethnic populations and identify other risk factors that can augment plans for early interventions aimed at the prevention of adolescent T2DM.

Key Words: Impaired fasting glucose; Visceral adiposity index; Cardiorespiratory fitness; Adolescents; Diabetes mellitus; Public health

Core Tip: The increase in type 2 diabetes mellitus among adolescents is a significant global concern. The index study aimed to establish the associations of visceral adiposity index (VAI) and cardiorespiratory fitness (CRF) with fasting plasma glucose in Nigerian adolescents. In the case of boys, high VAI and low CRF is associated with impaired fasting glucose, while no association was present in girls. CRF, measured by the 20-meter shuttle run, was a stronger predictor of impaired fasting glucose than VAI, suggesting that physical fitness is a protective factor against glucose dysregulation. These findings point to VAI and CRF as useful, non-invasive predictors of risk for type 2 diabetes mellitus in youth, supporting school-based fitness programs that promote CRF.

TO THE EDITOR

Type 2 diabetes mellitus (T2DM), a chronic metabolic disorder of significant global concern, is growing in incidence among adolescents. Worldwide, diabetes mellitus is estimated to affect over 1 in 10 adults, and nearly 90% of these cases involve T2DM[1]. This trend is now emerging in youth, with a reported 26% increase in diabetes mellitus prevalence among children and adolescents in recent decades, majority of which was contributed by T2DM[2]. Concurrently, youth with T2DM are at accelerated risk for both microvascular and macrovascular[3]. The search for reliable, specific markers of T2DM risk in the paediatric population has become increasingly important. While traditional markers such as waist circumference and body mass index are often used, they do not fully account for the complexities of visceral adiposity and its contribution to T2DM risk in adolescents.

The visceral adiposity index (VAI), a sex-specific marker calculated using waist circumference, body mass index, triglycerides, and high-density lipoprotein cholesterol, has emerged as a promising alternative. It provides a surrogate measure of visceral adiposity and has demonstrated a significant association with insulin resistance, hyperglycaemia, and cardiometabolic dysfunction in adult populations[4,5]. Additionally, cardiorespiratory fitness (CRF), an objective measure of physical fitness, has been associated with reduced insulin resistance and improved metabolic health[6]. These emerging markers offer potential as predictive tools for identifying impaired fasting glucose (IFG) in youth and could represent critical targets for T2DM prevention in at-risk adolescent populations. Despite promising results in adult studies, data on the use of VAI and CRF as T2DM risk markers in paediatric populations are limited, particularly in non-Caucasian cohorts[5].

IMPACT OF VAI AND CRF ON T2DM RISK IN ADOLESCENTS

This study aimed to investigate the independent and combined associations of VAI and CRF with fasting plasma glucose among Nigerian adolescents aged 11 to 19 and by identifying the risk markers most strongly associated with T2DM in this population. Further, it aimed to advance the development of specific, practical risk assessments for T2DM in paediatric groups[7].

Study design and methods

This cross-sectional, observational study involved 418 Nigerian adolescents aged 11 years to 19 years from secondary schools, selected using multistage cluster sampling. Participants were assessed for anthropometric measures, biochemical parameters, and physical fitness. To explore the associations between VAI, CRF, and IFG, adolescents were stratified into tertiles based on their VAI and CRF levels. This approach allowed the researchers to compare high, medium, and low levels of visceral fat dysfunction and fitness.

Means and standard deviations were used for continuous variables whereas categorical data were expressed as frequencies or percentages. The compliance rate of the study was 96% after accounting for all drop-outs. Gender differences were analyzed via independent samples t-tests or Mann-Whitney U tests as suitable. Partial correlation analysis, adjusted for age and maturity offset was used to examine the relationships between dependent and independent variables. Multivariate regression models were used to determine the associations of VAI and CRF with fasting plasma glucose and their relative importance. The ethical approval of the index study was obtained from the concerned Ethical Review Committee of the College of Health Sciences, Kogi State University, Nigeria and the details are provided in the original publication[7].

Key findings

The key findings highlighted distinct gender differences. In boys, VAI and CRF both showed significant associations with IFG, suggesting that boys with higher VAI and lower CRF were at greater risk for T2DM. However, in girls, neither VAI nor CRF showed a meaningful association with IFG, possibly due to gender-based differences in fat distribution and hormonal influences on metabolic health[8]. CRF, measured through the 20-meter shuttle run test, was found to be a better predictor of IFG than VAI (as per the standardized regression coefficients after controlling for age and maturity status), reinforcing the importance of physical fitness as a protective factor in glucose metabolism[6].

Clinical implications

These results underline the practicality of VAI and CRF as non-invasive markers for identifying IFG risk in adolescents. VAI can serve as a surrogate measure for visceral fat dysfunction, while CRF provides a reliable index of physical activity and fitness. Regular monitoring of these markers in school settings could enable early intervention and T2DM risk reduction through lifestyle modifications. However, it is important to recognize that VAI and CRF, while useful, are not definitive markers of T2DM risk. The search for improved, more specific risk indicators remains ongoing, especially for the adolescent population. The findings of this study support fitness programs that promote CRF and potentially lower VAI, especially in boys who may benefit most from increased physical activity. Public health strategies should also focus on dietary interventions from an early age to prevent visceral adiposity and its associated risks. Targeted nutritional programs in schools could help adolescents adopt healthier eating habits, further reducing T2DM risk. There is also a clear need for standardized VAI cut-offs specific to paediatric populations, which would improve the global applicability of this index for T2DM risk screening. Establishing these cut-offs could help clinicians better interpret VAI levels in adolescents and identify those who would benefit most from intervention. CRF and VAI serve as proxies for visceral adipose tissue (VAT) and overall fitness but do not replace gold-standard imaging techniques, such as magnetic resonance imaging, that directly measure VAT. However, VAI and CRF are valuable due to their practicality and low cost, making them particularly useful in low-resource settings where advanced imaging may be unavailable.

Study limitations

However, this study had certain limitations. First, the study examined the association between VAI, CRF, and IFG but did not look for all parameters for diagnosis of T2DM, a major limitation given the primary objective of preventing diabetes. Second, the cross-sectional nature of the study limits causal inference, though these findings lay an important foundation for future longitudinal research. Finally, the study’s findings would benefit from validation across diverse ethnicities to ascertain whether VAI and CRF hold universal applicability in predicting T2DM risk among adolescents. More longitudinal data is required before recommending the widespread use of these markers in day to day clinical practice.

FUTURE DIRECTIONS

Future studies should explore the potential of VAI and CRF in multi-ethnic cohorts and investigate other predictive biomarkers, ultimately leading to more robust and universally applicable T2DM risk assessment tools for adolescents. A wider and more representative population will make the data more generalizable. Moreover, prospective data on usefulness of these markers in predicting risk of T2DM is essential.

CONCLUSION

CRF and VAI serve as proxies for VAT and overall fitness. They are most relevant in resource constraint settings given its ease of measurement and cost effectiveness. The findings of this study revealed significant gender differences: In the case of boys, high VAI and low CRF is associated with IFG, while no association was present in girls. CRF, measured by the 20-meter shuttle run, was a stronger predictor of IFG than VAI, suggesting that physical fitness is a protective factor against glucose dysregulation. These findings point to VAI and CRF as useful, non-invasive predictors of risk for T2DM in youth, supporting school-based fitness programs that promote CRF and attenuate visceral adiposity, particularly in males.