# Assessment of the Predictive Potential of Pediatric Relative Fat Mass Compared to Alternative Measures of Obesity for Cardiorespiratory Fitness in Children: Longitudinal Associations During Two-Year Follow-Up

## TL;DR

This study found that the relative fat mass pediatric index (RFMp) is a better predictor of cardiorespiratory fitness in children over two years than other common obesity measures like BMI.

## Contribution

The study demonstrates that RFMp outperforms alternative obesity indices in predicting long-term cardiorespiratory fitness in children.

## Key findings

- Over 40% of girls and boys had a BMI above the norm.
- RFMp was the best predictor of cardiorespiratory fitness over two years for both genders.
- RFMp outperformed BMI, %BF, WC, WHtR, WHR, TMI, and waist-BMI ratio in predictive power.

## Abstract

Background/Objectives: Relative Fat Mass (RFM) is an anthropometric index estimating whole-body fat percentage. Though RFM is analyzed in scientific articles in various contexts, the research on the association between RFM and cardiorespiratory fitness (CRF) level is extremely limited. The aim of this study was to investigate the prognostic value of the relative fat mass pediatric index (RFMp) in predicting CRF results over a two-year period among school-age children, in comparison with alternative indices. Methods: Based on data comprising student measurements collected previously, in the years 2017–2019, a multiple regression analysis was conducted. Predictive models for CRF were constructed over a two-year period, separately for each of the eight indicators associated with obesity assessment. The models were prepared for boys and for girls separately. Results: over 40% of girls and boys have a BMI above the norm. In the case of both girls and boys, RFMp turned out to be the best CRF predictor over a two-year period. It proved to be better in terms of its predictive power than body mass index (BMI), body fat percentage (%BF), waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), tri-ponderal mass index (TMI) and waist-BMI ratio. Conclusions: RFMp demonstrated a certain advantage in terms of predictive ability compared to alternative indicators. This indicates its potential for implementation in the general pediatric population and clinical practice for the prediction of CRF. However, this needs to be confirmed in further studies involving a larger and more diverse population.