Impact of Body Mass Index and Anthropometric Measures on Cardiorespiratory Fitness in Non-obese Adult Males: A Cross-Sectional Observational Study.

Introduction Cardiorespiratory fitness (CRF) is a key health indicator for assessing optimal physical function and overall well-being. Exploring the early impact of body mass index (BMI) and anthropometric measures on CRF in non-obese individuals is essential for identifying risk factors and guiding preventive strategies to address weight-related health challenges. This study aims to investigate the impact of BMI and anthropometric measures on CRF, focusing on maximal oxygen uptake (VO2max) and metabolic equivalents (METs) in non-obese adult males.  Methods This cross-sectional study included 108 non-obese male participants aged 18-40 years, categorized by BMI into three groups: underweight, normal weight, and overweight. Anthropometric assessments, including height, weight, waist circumference, hip circumference, and skinfold thickness, were conducted. CRF was evaluated by measuring VO2max and METs. Statistical analysis was performed using one-way analysis of variance (ANOVA) for between-group comparisons, followed by Tukey's post hoc test for pairwise analysis and Pearson's correlation to examine associations between anthropometric measures and fitness parameters. Results Significant differences in VO2max (p < 0.001) and METs (p = 0.013) were found across the BMI categories. Fair negative correlations were observed between BMI and both VO2max (r = -0.382, p < 0.001) and METs (r = -0.384, p < 0.001). Additionally, waist circumference and waist-to-hip ratio showed significant poor negative correlations with these fitness measures, while body density exhibited a fair positive correlation with VO2max (r = 0.37, p < 0.001). Conclusion The findings suggest that higher BMI is associated with reduced CRF, as indicated by lower VO2max and MET values, even within the non-obese category. Additionally, waist circumference, waist-to-hip ratio, and body density significantly influence these measures. These results highlight the importance of incorporating these crucial anthropometric factors into health strategies aimed at improving CRF in those with higher BMI, regardless of obesity status.