Evaluating the Impact of Body Mass Index on Respiratory Muscle Strength and Peak Expiratory Flow Rates in Tertiary Healthcare Settings

Background: Body mass index (BMI) determines pulmonary mechanics, and changes in body mass index can cause changes in respiratory muscle strength and peak expiratory flow. These differences are significant in assessment of respiratory functioning in healthy adults. The proposed study aims to determine the effect of BMI on respiratory muscle strength measured by Maximal Inspiratory Pressure (MIP) and Maximal Expiratory Pressure (MEP) and peak Expiratory Flow Rate (PEFR) in various BMI groups. Methods: This cross-sectional study (September 2024 to April 2025) included 180 healthy adults who were underweight (n=32), normal weight (n=74), overweight (n=46) and obese (n=28). Largely demographic variables, BMI, MIP, MEP, and PEFR were noted. Continuous variables were analyzed by statistical comparison between BMI categories using ANOVA, whereas categorical variables were tested with Chi-square methods, wherein p<0.05 was considered as significant. Results: The BMI groups differed significantly in terms of MIP (F=11.52, p<0.001), MEP (F=10.34, p<0.001) and PEFR (F=14.08, p<0.001). The participants with normal weight had the highest MIP (78.5 ± 14.3 cmH2O), MEP (89.6 ± 16.1 cmH2O) and PEFR (410.7 ± 52.9 L/min). The lowest values were observed among underweight individuals and obese participants also exhibited lower performance as compared to the normal-weight group. Conclusion: BMI plays a significant role in determining the respiratory muscle strength and expiratory airflow in healthy adults. Normal weight individuals show better MIP, MEP and PEFR values, underweight as well as obese individuals show lower respiratory performance.