Obesity, a global health concern, has been linked to various respiratory complications, including impaired pulmonary function.1,2 The prevalence of obesity has increased significantly over the past decades, affecting individuals across all age groups and geographical regions.3 Body mass index (BMI), a measure of body fat based on height and weight, is commonly used to classify individuals as underweight, normal weight, overweight, or obese.4

Excessive accumulation of adipose tissue in the abdominal and thoracic regions can lead to mechanical and metabolic alterations that may adversely affect respiratory function.5 The increased mass loading on the chest wall and abdomen can impair diaphragmatic excursion and lung compliance, resulting in reduced lung volumes and airflow limitation.6,7 Additionally, obesity has been associated with chronic low-grade inflammation and oxidative stress, which may contribute to the development of respiratory disorders, such as asthma and obstructive sleep apnea.8,9

Pulmonary function tests (PFTs) are widely used diagnostic tools to assess the respiratory health and functional capacity of the lungs.10 These tests measure various parameters, including forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and the FEV1/FVC ratio, which provide valuable information about lung volumes, airflow, and potential obstructive or restrictive patterns.11

Several studies have investigated the relationship between BMI and pulmonary function, highlighting the potential impact of obesity on respiratory health.12 However, the findings have been inconsistent, and further research is needed to better understand the underlying mechanisms and potential confounding factors.

The present study aimed to evaluate the effect of BMI on PFT parameters in a sample of adults aged 25-65 years. By examining the relationship between BMI categories (underweight, normal weight, overweight, and obese) and PFT measurements, this study sought to contribute to the existing body of knowledge and provide insights into the potential respiratory consequences of obesity.

This cross-sectional study aimed to evaluate the effect of body mass index (BMI) on pulmonary function test (PFT) parameters in adults. A total of 100 participants aged between 25 and 65 years were recruited for the study. All participants underwent both PFT and BMI measurements during the study period.

Based on their BMI, the participants were categorized into four groups: underweight (n=10), normal weight (n=40), overweight (n=30), and obese (n=20). The BMI cutoffs for these groups were defined according to the World Health Organization's guidelines.

Pulmonary function testing was performed on all participants using standardized protocols and equipment. The following parameters were measured and recorded: forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, and other relevant PFT parameters. The tests were conducted by trained personnel, and quality control measures were implemented to ensure accurate and reliable results.

In addition to PFT measurements and BMI calculations, demographic information such as age, gender, and smoking status was collected for each participant. This data was obtained through a structured questionnaire or interview process.

Descriptive statistics, including means and standard deviations, were calculated for the study population's age and BMI. To analyze the differences in PFT parameters across the four BMI groups, appropriate statistical tests, such as analysis of variance (ANOVA) was employed. Pearson's correlation coefficients were calculated to assess the relationship between BMI and PFT parameters, particularly FVC and FEV1. These analyses were adjusted for potential confounding variables, including age, gender, and smoking status. Furthermore, regression models were utilized to evaluate the association between BMI and PFT parameters while controlling for these confounders. All the analysis was done using SPSS version 20 t a predefined level of statistical significance, typically α = 0.05.

The study included 100 participants with a mean age of 42 years (SD = 12.5) and a mean BMI of 27.5 kg/m2 (SD = 6.2). The distribution of participants across the BMI groups was as follows: underweight (n=10), normal weight (n=40), overweight (n=30), and obese (n=20). The gender distribution was 55% females and 45% males. The prevalence of current smokers was 25%.

Significant differences in FVC, FEV1, and FEV1/FVC ratio were observed across the BMI groups (p < 0.001 for all parameters, ANOVA). Post-hoc analyses revealed that obese individuals had significantly lower FVC and FEV1 values compared to normal-weight and overweight individuals (p < 0.05). The FEV1/FVC ratio was also lower in the obese group compared to the normal-weight group (p < 0.05).[Table 1]

After adjusting for age, gender, and smoking status, BMI was inversely correlated with FVC (r = -0.32, p = 0.001) and FEV1 (r = -0.28, p = 0.005). These correlations indicate that higher BMI was associated with lower FVC and FEV1 values.Multivariate linear regression analyses were performed to further evaluate the relationship between BMI and PFT parameters. The results are presented in Table 2.

Table 1: Mean PFT Parameters across BMI Groups

Table 2: Multivariate Linear Regression Analyses for PFT Parameters

The present study investigated the effect of body mass index (BMI) on pulmonary function test (PFT) parameters in adults. The findings revealed a significant inverse relationship between BMI and PFT parameters, particularly forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). These results are consistent with previous research demonstrating the adverse impact of obesity on respiratory function.

Our study found that obese individuals had significantly lower FVC and FEV1 values compared to normal-weight and overweight individuals, suggesting a restrictive pattern of lung impairment. Similar observations have been reported in other studies. For instance, Harik-Khan et al. reported a negative association between BMI and FVC, FEV1, and other lung volumes in older adults, even after adjusting for potential confounders.12 Likewise, Saxena and Saxena observed a significant reduction in FVC and FEV1 in obese young individuals compared to their normal-weight counterparts.13

The inverse correlation between BMI and PFT parameters observed in our study is consistent with the findings of Jones and Nzekwu, who reported a decrease in lung volumes with increasing BMI.6 Additionally, Pelosi et al. demonstrated that obesity significantly affects respiratory mechanics, including lung volumes and gas exchange, during general anesthesia.7

The mechanisms underlying the detrimental effects of obesity on pulmonary function are multifactorial. Excessive accumulation of adipose tissue in the abdominal and thoracic regions can lead to mechanical compression of the lungs, diaphragmatic impairment, and reduced chest wall compliance, ultimately resulting in decreased lung volumes and airflow limitation.1,5 Furthermore, obesity is associated with chronic low-grade inflammation and oxidative stress, which may contribute to the development of respiratory disorders and impaired lung function.8,9

Interestingly, our study did not find a significant association between BMI and the FEV1/FVC ratio after adjusting for confounders, which contrasts with some previous reports. For instance, Harik-Khan et al.12 observed a decrease in the FEV1/FVC ratio with increasing BMI, suggesting an obstructive pattern of lung impairment. These discrepancies may be attributed to variations in study populations, methodologies, and the influence of potential confounding factors.

It is important to note that the relationship between BMI and pulmonary function may be influenced by age, gender, and other comorbidities. Several studies have reported age-related differences in the impact of obesity on lung function, with older adults being more susceptible to the adverse effects of obesity.14,15

The present study provides compelling evidence that higher body mass index (BMI) is associated with reduced pulmonary function, particularly decreased forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) values. Obese individuals exhibited significantly lower FVC and FEV1 values compared to normal-weight and overweight individuals, suggesting a restrictive pattern of lung impairment. These findings contribute to the growing body of evidence linking obesity to various respiratory complications and underscore the importance of maintaining a healthy body weight for optimal respiratory health. While the study did not find a significant association between BMI and the FEV1/FVC ratio after adjusting for confounders, further investigation is needed to explore potential age-related, gender-specific, and comorbidity-related differences. The results emphasize the need for effective strategies for obesity prevention and management, as well as future research into the underlying mechanisms, potential for weight loss interventions to improve respiratory outcomes, and long-term effects of obesity on lung function across different populations.

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