Natl. J. Physiol. Pharm. Pharmacol.(2025), Vol. 15(4): 272-280

Research Article

10.5455/NJPPP.2025.v15.i4.3

A study on the assessment of role of BMI on immediate exercise impact on peak expiratory flow rate (PEFR) among undergraduate students at one of the medical colleges of Ahmadabad

Jahnavi Upadhyay^* and Anand Mistry

Department of Physiology, GCS Medical College, Hospital and Research Center, Shahibaug, Ahmadabad

*Corresponding Author: Jahnavi Upadhyay. Department of Physiology, GCS Medical College, Hospital and Research Center, Ahmadabad. Email: jahnavi271996 [at] gmail.com

Submitted: 17/2/2025 Accepted: 10/4/2025 Published: 30/04/2025

---

ABSTRACT

Background: In India, obesity is a rapidly growing health concern across all age groups. Obesity has significant effects on pulmonary function. The peak expiratory flow rate (PEFR) demonstrates the caliber of the airways and is widely recognized as an objective indicator of respiratory efficiency. This indicator is useful for the diagnosis and management of respiratory disorders.

Aim: This study aimed to determine the relationship between BMI and immediate post-exercise changes in PEFR among medical undergraduate students.

Methods: A cross-sectional study was conducted among 120 healthy undergraduate medical college students. Baseline anthropometric data, including height and weight, were collected for the assessment of body mass index (BMI). BMI was calculated using the Quetelet index. PEFR was measured using a Wright Peak Flow Meter. PEFR measurements were taken before and after performing a 5-minute moderate-intensity Harvard Step Test by the participants.

Results: The results showed that individuals with a normal BMI had the highest mean increase in PEFR (mean difference: 27.85 ± 7.97, p < 0.0001), followed by the overweight group (mean difference: 15.23 ± 12.04, p < 0.0001). The obese group exhibited the least improvement (mean difference: 5.49 ± 11.82, p < 0.0001). The P values in all three groups for PEFR before and after exercise were low (<0.0001) indicating a statistically significant difference in PEFR across BMI categories.

Conclusion: This study assessed the impact of BMI on immediate post-exercise changes in PEFR among young medical students. A significant negative association was observed between BMI and PEFR. This relationship was present both before and after exercise. The study found that students with a normal BMI group demonstrated the most substantial improvement in PEFR after exercise, followed by the overweight group. The obese group exhibited the least improvement in PEFR. These findings suggest that excess weight has a direct impact on PEFR. Further research is warranted to explore the underlying mechanisms.

Keywords Peak expiratory flow rate (PEFR), body mass index (BMI), Harvard step exercise, obesity

---

Introduction

Obesity is a medical condition involving an excessive amount of body fat. A reliable indicator of body fat content is the body mass index (BMI). Obesity is not merely a cosmetic concern; it is also a medical problem that increases the risk of many other diseases and health problems. These can include heart disease, respiratory disorders, diabetes, high blood pressure, high cholesterol, liver disease, obstructive sleep apnea (OSA), and certain cancers. Among these, the impact of obesity on respiratory function is of particular concern because of its role in altered lung mechanics, increased airway resistance, and impaired gas exchange (Jain, 2023). As society has become more urbanized and rich, dietary patterns have shifted. The consumption of complex carbohydrates has declined, whereas the intake of saturated fats and sugars has increased. At the same time, physical activity has decreased because of a shift toward less physically demanding jobs and more sedentary lifestyles. Consuming excessive carbohydrate calories is particularly problematic for those with insulin resistance. Every calorie matters. For example, drinking just one soda (150 calories) daily for a year can lead to an additional 15 pounds of weight gain (Richardson, 2016). Rates of overweight and obesity continue to increase in adults and children. From 1990 to 2022, the percentage of children and adolescents aged 5–19 years living with obesity increased four-fold from 2% to 8% globally, whereas the percentage of adults aged 18 years and older living with obesity more than doubled from 7% to 16%. Modern lifestyle is a potent risk factor for obesity (World Health Organization, 2023). Obesity occurs when individuals take more calories than they burn through normal daily activities, and these extra calories are stored in the body as fat (Jain, 2023).

Obesity is associated with numerous structural and functional changes in the cardiovascular and respiratory systems, even in the absence of cardiovascular and respiratory disorders (Richardson, 2016). Obesity is a significant and common cause of respiratory compromise. It leads to decreased static and dynamic pulmonary volumes. It is associated with reduced airflow and increased airway hyperresponsiveness. Obesity increases the risk of developing pulmonary hypertension, pulmonary embolism, respiratory tract infection, and OSA (Haslam, 2007). Obese and overweight individuals, even without diagnosed pulmonary illness, may experience shortness of breath during exercise because of increased respiratory effort and oxygen demand (Patil et al., 2019). Rochester and Enson (1974) et al. reported that obesity impaired the strength of the respiratory muscles, especially the diaphragm. This makes breathing less efficient.

Peak expiratory flow rate (PEFR) is the maximum rate (peak rate) in litters per minute with which air is expelled with maximum force after deep inspiration. The normal range is 350 to 600 l/minutes or 6–101/seconds. This assessment is valuable for distinguishing between reversible (asthma) and irreversible disease (COPD). Factors contributing to an increase in PEFR are as follows: males have higher PEFR than females, upright posture (standing or sitting), breathing in pollution-free air, using bronchodilators, quitting smoking, losing excess weight, regular physical activity and exercise such as running, swimming, walking, and cycling, and improving PEFR. It can be reduced due to various physiological, environmental, and pathological factors such as PEFR declines with age, females generally have lower PEFR, slouching or lying down posture, obstructive lung diseases (e.g., asthma, chronic obstructive pulmonary disease), restrictive lung diseases (e.g., pulmonary fibrosis), obesity-related hypoventilation, neuromuscular disorders (e.g., muscular dystrophy, myasthenia gravis), lack of exercise, smoking and passive smoke exposure, obesity, and excess weight leading to lower PEFR (Varshney and Bedi, 2023). The peak expiratory flow rate is measured by the pulmonary capacity, respiratory passage, elastic recoil of the lung, and exercise tolerance (Shenoy et al., 2014). This monitoring device can be used at any time when the patient needs to measure their peak expiratory flow rate. It is intended for adults and children. The normal peak flow value can range from person to person and is dependent on factors such as sex, age, and height. It is a reliable indicator of ventilation adequacy and airflow obstruction. Its measurement has a very simple procedure, and a peak flow meter can be carried out in one’s pocket anywhere, even outside the laboratory for PEFR measurement. This approach provides insight into bronchial tree airflow and respiratory efficiency (Das et al., 2017).

Normal BMI individuals generally exhibit optimal lung compliance, efficient diaphragm function, and balanced oxygen uptake. A higher BMI is associated with reduced PEFR, particularly in overweight and obese individuals. Fat accumulation around the neck and chest wall compresses the upper airways. This leads to a turbulent airflow that makes breathing less efficient. Moreover, it increased airway resistance, which further restricted the airflow. This narrowing of the airways leads to reduced PEFR (Jones and Nzek, 2006). Additionally, obese individuals are more prone to airway hyperresponsiveness, which can further worsen respiratory conditions such as asthma and OSA. Deposition of subcutaneous adipose tissue causes a decrease in total respiratory compliance. Lung compliance refers to the lung’s ability to expand and recoil tendency during breathing. In individuals with obesity, excessive fat accumulation in the thoracic and abdominal regions restricts diaphragmatic movement and limits lung expansion. In addition, excess weight around the chest wall reduces rib cage mobility, making inhalation more difficult. As a result, lung volume is significantly affected. The association between high BMI and low PEFR may indicate that obesity is an important risk factor for lung function and reduced airflow (Melo et al., 2014). Another study by Dr Kalpojit Saikia and Dr Shrabani Barman also observed an inverse correlation between BMI and PEFR (Saikia and Barman, 2017).

Regular exercise in the category of physical games, cardiac workout, or strength training, when performed routinely has a positive influence on the various physiological systems of the body. Any type of physical activity is considered exercise. It could be a planned sport such as running, swimming, tennis, or bowling, an exercise training program, or a hobby such as cycling or walking. The advantage of performing such exercises routinely is that they enhance blood circulation to vital organs, promoting better oxygenation and nutrient distribution and ultimately improving lung function (Freedman, 1992). Gibson et al. suggested that pulmonary function is a key determinant of overall survival rates in both male and female sexes and highlighted the need for maintaining optimal respiratory health (Gibson, 2000). Exercise induces notable changes in body functions due to its intense nature, and the lungs are not exception. On the contrary, a sedentary lifestyle can lead to decreased pulmonary efficiency (Jaakkola et al., 2019). Coelho et al. (2018) suggested that exercise improves lung function by strengthening the respiratory muscle, increasing respiratory compliance, and decreasing airway resistance.

It is possible that enhanced lung function is linked to exercise-induced bronchodilation. Such dilatory effects are more pronounced during short episodes and at moderate levels of physical exercise in everyday life. Regular exercise leads to multiple physiological benefits, ultimately enhancing quality of life. In general, pulmonary function is influenced by the strength of the respiratory muscles, flexibility of the thoracic cavity, airway resistance, and elastic recoil of the lungs (Mansfield et al., 1979).

While previous studies have examined the effects of obesity on lung function, few have focused on the immediate impact of exercise on the PEFR across different BMI categories. Most existing studies focused on long-term respiratory changes rather than short-term variations followed by physical activity. Understanding these acute effects is essential, particularly in young adults, because it may provide valuable insights into the influence of BMI on respiratory adaptability during exercise. This study addresses this gap by evaluating the immediate changes in PEFR among medical students with different BMI levels and by providing a more detailed perspective on the relationship between BMI and pulmonary function.

Aims and objectives

The aim of this study was to examine the influence of BMI on the immediate effect of exercise on peak expiratory flow rate among undergraduate students at one of the medical colleges in Ahmadabad.

The specific objectives of the study are as follows:

1. To assess the relationship between BMI and the PEFR of undergraduate medical students with obesity, overweight, and normal weight at one of the medical colleges in Ahmadabad.

2. To assess the relationship between BMI and PEFR in response to immediate exercise.

3. To assess acute changes in the peak expiratory flow rate following immediate exercise among undergraduate students with different BMI categories.

4. To identify potential differences in respiratory adaptation to immediate exercise across different weight groups.

---

Materials and Methods

The study was conducted among 120 apparently healthy 18–25 years undergraduate students at one of the medical colleges in Ahmadabad. The sample size was derived using post hoc power analysis for the paired T test. This study was approved by the Institutional Ethics Committee of GCS Medical College, Hospital and Research Center. The ethical approval number of the study was GCSMC/EC/Project/APPROVE/2024/690. Informed written consent was obtained from all participants after explaining the study’s purpose, procedures, potential risks, and their right to withdraw from the study at any time.

Before participation, all subjects underwent a routine health examination. The following parameters were assessed: height, weight, BMI, and PEFR.

Study design: A cross-sectional observational study.

Sampling method: The convenience sampling method

Sample size: 120 participants were calculated from the previous study.

The subjects were divided into three groups according to their BMI: normal BMI, overweight, and obese. The comparison group considered 40 students with a BMI between 18.5 and 24.9 kg/m² (non-obese), and the study group included a total of 80 students who were further divided into two groups according to their BMI. Those with a BMI of 25–29.9 kg/m² (overweight) were considered Study Group 1 and those with a BMI of ≥30kg/m² (obese) were considered Study Group 2. To maintain a balanced representation, participants were first categorized into BMI-based strata (normal, overweight, and obese). Within each stratum, 15 students were chosen from each academic year of MBBS (Phase I, Phase II, Phase III Part I, and Phase III Part II) for Study Group 1, Study Group 2, and the Comparison Group. Each group consisted of 40 students, to make a totaling 120 participants.

The normality of the data was assessed using the Shapiro–Wilk test. Because the data were normally distributed, a paired t-test was used to compare pre- and post-exercise PEFR values among all three groups. The results are expressed as mean ± SD. A p value of < 0.05 was considered statistically significant. Anthropometric measurements include height, which was measured using a wall-fixed stadiometer. The students were asked to stand without shoes, with heels together, and with their head in a straight position against a wall-fixed stadiometer to measure height. The measurement was performed near 0.1 cm. The weight of the students was measured with light clothing and without shoes on a weighting scale (Boldfit weight machine).

For adults, underweight (BMI≤18.5kg/m²), normal (BMI=18.5–24.99 kg/m²), overweight (BMI=25–29.99 kg/m²), and obese (BMI=>30 kg/m²) are defined according to the latest WHO criteria (World Health Organization, 2003).

Wright peak flow meter

B. M. Wright introduced the peak flow meter in 1959. In 1969, a more affordable, simple, and portable version of the instrument, the miniature Wright peak flow meter was developed (Bora et al., 2017).

The peak flow meter is a handheld monitoring device that measures the PEFR generated by the patient during a forced exhalation maneuver. It can be used to objectively measure PEFR by tracking day-to-day changes in breathing patterns. The mini-Wright peak flow meter is a short cylinder made of plastic. An indicator moves in a slot alongside a scale with a number on it, which indicates l/min (litters per minute). There is a handle near the mouthpiece. The end opposite the mouthpiece has holes in it for allowing air to exit the apparatus. It has a diameter of 5.0 cm and a length of 15 cm. This instrument weighs 75 g. The three zones help patients comply with treatment regimens. The color-coded indicators can be adjusted to delineate a patient’s green, yellow, and red zones based on the personal best peak flow (Varshney and Bedi, 2023; Sandhu et al., 2017) (Fig. 1).

Figure 1 shows the peak expiratory flow meter used for PEFR measurement.

Function and usage of the peak flow meter

PEFR was measured using Wright’s peak flow meter, and all subjects were comfortably seated. Readings were consistently taken at the same time of day to maintain accuracy.

Each participant was asked to sit in a relaxed posture and hold the instrument horizontally. The subject was asked to hold the peak flow meter by its handle, ensuring that the fingers were clear of the scale and the slot and did not obstruct the holes at the end of the apparatus. Make sure that the indicator is at the bottom of the scale. The subject was asked to take a deep breath and firmly put their lips around the mouthpiece to make a tight seal. Then, they were asked to blow out as hard and fast as they could in a single blow. Their first burst of air is the most important, so blowing for a longer time will not affect your result. Read the peak flow value next to the indicator and write down that reading. Then, the indicator was dragged back down and the measuring process was repeated three times at intervals of 1 minute, and the maximum value indicated by the cursor was recorded for the report. Write down the highest of the three readings along with the date and time.

Each subject was encouraged to exert maximum effort (blowing as hard and as fast as possible) while being closely monitored to ensure an airtight seal between their lips and the mouthpiece.

Fig. 1. Mini-Wright peak flow meter.

Fig. 2. Harvard step test.

Fig. 3. Self-designed representation based on study findings. Green dots: normal BMI; Blue dots: overweight; Red dots: obese.

Precautions taken during that study:

1. The subject should be instructed to blow out rapidly, completely, and forcefully into the mouthpiece.

2. The mouthpiece should not leak.

Harvard step test

Brouha et al. (1943) introduced this test in Harvard Fatigue Laboratories during WWII. It is designed to be easy to understand and requires only a minimal apparatus. The step height used in the test was 30 cm for women and 40 cm for men, following the standard protocol. A metronome was used to maintain a 30-step pace, ensuring consistency in exercise intensity across participants. Participants ascend and descend at a rhythm of 30 steps per minute for a duration of 5 minutes or until they reach exhaustion. Exhaustion was defined as reaching ≥85% of the maximum heart rate (HRmax), a Borg rating of perceived exertion (RPE) of 17 or higher, or voluntary cessation due to fatigue. Initially, this assessment was developed for military personnel to evaluate fitness levels, but it was later adapted for use by the general public. The test can be administered to children, teenagers, and adult athletes. It is used to assess physical fitness and serves as a predictive tool for determining a person’s VO2max. Additionally, it evaluates cardiovascular endurance and indicates the body’s general ability to adapt to increased physical exertion and recover afterward (Pal and Pal, 2003; Ismail, 2011; Parmar and Modh, 2013).

Equipment

Equipment required: Harvard step or raised platform (Fig. 2),

Inclusion criteria

• Age range: 18–25 years.

• Health status: generally healthy without any known chronic or systemic disease.

• Physical activity: individuals capable of performing Harvard step exercise.

Exclusion criteria

• Students with BMI <18.5 kg/m² (classified as an underweight).

• Respiratory disorders: history of COPD, asthma, or any other diagnosed chronic respiratory conditions. Regular medication use affects lung function (bronchodilators)

• Recent respiratory tract infection (within or past 2 weeks).

• History of cardiovascular disease (hypertension and ischemic heart disease) irrespective of type of severity.

• Smoking history (regular or occasional within past 6 month).

• Pregnancy (maintain uniform physiological response).

• Diabetes mellitus (potential effects on lung and cardiovascular functions, which influenced PEFR measurements).

• Obesity-related comorbidities (sleep apnea).

• Chest deformities (scoliosis).

---

Procedure

All the students were informed about the objectives and methodology of the study. Written informed consent was obtained from all participants. Basic details such as age, health history, and past history were collected using surveys to determine eligibility based on inclusion and exclusion criteria. The height and weight of the participants were measured using a stadiometer and digital weighting machine (Boldfit weight machine). BMI was determined by using the following equation:

BMI=WEIGHT (KG)/HEIGHT (M²)

All students were classified into three categories based on their BMI

Normal (BMI=18.5–24.99 kg/m²), overweight (BMI=25–29.99 kg/m²), and obese (BMI=≥30 kg/m²) are defined according to the latest WHO criteria (World Health Organization, 2023).

First, PEFR was measured at rest; PEFR was recorded using Wright’s peak flow meter for all subjects. They were seated comfortably and then instructed to take a deep breath. Place the mouthpiece of the peak flow meter inside the mouth between the teeth and lips, and then blow out the air as rapidly, completely, and forcefully as possible with a close nostril in a single breath. Each subject then held the instrument and performed three trials of blows, and the highest value was taken for the study as the baseline PEFR. After measuring PEFR at rest by all the participants: they were asked to perform moderate-intensity Harvard step exercise. The participant stepped up and down from the platform at a rate of 30 completed steps per minute (1 second up, 1 second down) for 5 minutes. Exhaustion was defined as the student being unable to maintain the stepping rate for 15 seconds. This procedure was carefully monitored to ensure the safety of participants and the uniformity of the study. Immediately after exercise, the participants sat down, and PEFR was measured again using the same method with the help of Wright’s peak flow meter.

---

Results

• A total of 120 participants were included in the study, with a male-to-female ratio of 60% (n=72) to 40% (n=48), respectively (Table 1). Participants were categorized based on BMI into normal weight (18.5–24.99 kg/m²), overweight (≥25–29.9 kg/m²), and obese (≥30 kg/m²). The distribution was equal across these groups, with 33.33% (n=40) in each category (Table 2).

• The distribution of BMI and PEFR among normal weight (BMI 18.5–24.99 kg/m²) participants is presented in Table 3. The Mean± SD of BMI was 21.24 ± 2.34 kg/m², while the Mean± SD of PEFR before exercise was 415.45 ±7.97 l/minutes, which significantly increased to 443.13 ± 8.82 l/minutes after exercise (p < 0.0001). The Mean ± SD of PEFR increased significantly from 415.45 ± 7.97 l/minutes to 443.13 ± 8.82 l/minutes, with a mean increase of 27.68 l/minutes (p < 0.0001).

Table 1 . Gender-wise distribution of all the study participants, of which 60% were males and 40% were females.

Table 2. Distribution of all the study participant’s BMI and PEFR. The entire group had an equal number of participants.

• Among overweight (BMI ≥ 25 kg/m²), individuals, there was a statistically significant change in PEFR before and after exercise. The Mean ± SD PEFR increased from 400.55 ± 11.45 l/minutes to 409.60 ± 12.04 l/minutes, with a mean improvement of 9.05 l/minutes (p < 0.0001), as shown in Table 4.

• In the obese (BMI ≥ 30 kg/m²) group, the Mean ± SD BMI was 34.52 ± 3.26 kg/m², and PEFR before exercise was recorded as 349.38 ± 11.72 l/minutes. Following exercise, the PEFR increased to 354 ± 11.82 l/minutes, showing a mean improvement of 5.32 l/minutes, which was statistically significant (p < 0.0001)(Table 5).

Table 3. Correlation/association between and PEFR. There was a significant negative association between BMI and PEFR, including before and after exercise. PEFR increased substantially from 415±7.97 to 443.13±8.82 L/min, with a mean increase of 27.68 L/min.

Table 4. Association between BMI and PEFR in overweight group before and after exercise. There was statistically significant PEFR from 400.55±11.45 to 409.60±12.04 L/min with a mean increase of 9.05L/min.

Table 5. Association between BMI and PEFR in obese group before and after exercise. There was statistically significant PEFR from 349.38±11.72 to 354.70±11.82 L/min, with a mean increase of 5.32 L/min.

• Result shows that PEFR increased significantly after exercise across all BMI categories. Individuals with normal BMI had the highest baseline PEFR and the greatest post-exercise improvement. Overweight and obese individuals exhibited lower PEFR before and after exercise, with a more limited increase compared with those with normal BMI. The results suggest that higher BMI is associated with reduced pulmonary function and diminished respiratory response to exercise, highlighting the impact of excess weight on lung mechanics. Chinnaiyan and Ramayyan reported that PEFR was lower in obese females than in non-obese females. They suggested that this reduction may be due to excess fat exerting mechanical pressure on the chest, abdomen, or diaphragm, restricting its movement and limiting its descent into the abdominal cavity (Chinnaiyan and Ramayyan, 2021). King GG et al found a strong relationship between BMI, lung volume, and airway size in obese individuals. As BMI increases, the airways become narrower than expected, suggesting structural or functional changes in the airways (King et al., 2012). Sharma R, Ranade V, Nagulkar J. Demonstrated that exercise in the form of swimming significantly improves PEFR (Sharma et al., 2020).

• As BMI increases, PEFR decreases among young students. The same is shown in the scatter diagram. The scatter plot illustrates an inverse relationship between BMI and PEFR, showing that PEFR decreases as BMI increases. The image appears to depict the relationship between BMI categories (normal, overweight, and obese) and PEFR (peak expiratory flow rate).

• X-axis: Represents BMI values (in kg/m²).

• Y-axis: PEFR values (in L/minutes).

• Data Series: Series 1 (Normal BMI): Data points seem to be scattered toward higher PEFR values.

• Series 2 (Overweight BMI): The data points are in the middle range.

• Series 3 (Obese BMI): The data points were more clustered toward lower PEFR values.

• From the pattern, it appears that as BMI increases, PEFR tends to decrease. These negative correlations indicate that higher BMI is associated with reduced pulmonary functions (Fig. 3).

---

Discussion

Obesity is a prevalent health issue, and despite available treatments, they often prove ineffective (Richardson, 2016). This study provides objective evidence of the effect of BMI on respiratory response to exercise, a relatively underexplored area in young and healthy populations. Lung function was notably affected by BMI (Haslam, 2007). Given this context, the study assessed the role of BMI in the immediate impact of exercise on PEFR among 120 undergraduate students at one of the medical colleges of Ahmadabad. In this study, the baseline PEFR was highest in the normal BMI group (415.45 ± 7.97 l/minutes), followed by the overweight group (400.55 ± 11.45 l/minutes), and lowest in the obese group (349.38 ± 11.72 l/minutes).

After exercise, all groups exhibited a statistically significant increase in PEFR ( p < 0.0001) although the degree of improvement varied:

•Normal BMI group: PEFR increased from 415.45 ± 7.97 l/minutes to 443.13 ± 8.82 l/minutes (mean increase: 27.68 l/minutes).

• Overweight group: PEFR increased from 400.55 ± 11.45 l/minutes to 409.60 ± 11.53 l/minutes (mean increase: 9.05 l/minutes).

•Obese group: PEFR increased from 349.38 ± 11.72 l/minutes to 354.70 ± 11.82 l/minutes (mean increase: 5.32 l/minutes).

In this study, we found a significant negative correlation between BMI and PEFR. As BMI increased from the normal weight group to the obese group, PEFR depressed among these young individuals, comparable results were also observed in a study conducted by Mov and Tartari, who suggested that Obese individuals tend to have reduced PEFR and a diminished ability to perform physical activities, as evidenced by shorter distances covered in the 6-minute walk test (Tartari, 2021). A similar finding was observed in the present study, which confirmed that obesity is associated with reduced PEFR, indicating impaired pulmonary function in overweight and obese individuals. The findings also suggested that lower PEFR contributes to exercise intolerance, reinforcing the notion that obesity limits both respiratory efficiency and physical performance.

Participants in the normal BMI (18.5–24.9 kg/m2) group showed a notable increase in PEFR after exercise. This suggests that individuals with a normal BMI likely have optimal lung compliance and respiratory muscle strength, which facilitate better airflow during and after physical exertion. In contrast, the overweight group with BMI (25–29.99 kg/m²) and the obese group with BMI (≥30 kg/m²) groups showed a smaller increase in PEFR after exercise. This finding could be attributed to reduced lung compliance and higher airway resistance due to fat deposition around the thorax and abdomen. Obesity is associated with lower strength and endurance of the diaphragm and intercostal muscles, which ultimately impairs the function of the respiratory muscle. Regular exercise strengthens the diaphragm and intercostal muscles, thereby improving respiratory muscle endurance and lung function. In individuals with obesity, rapid fatigue of the respiratory muscle limits the expected increase in PEFR after physical exertion (Rubinstein et al., 1990).

A higher BMI is associated with reduced diaphragmatic mobility and weakened respiratory muscles, resulting in inefficient ventilation. Jena et al. (2017) suggested that obesity decreases the strength and endurance of the diaphragm and intercostal muscles, which could explain the smaller increase in PEFR observed in overweight and obese individuals. Increased airway inflammation and hyperresponsiveness in obese individuals can lead to greater airway resistance. This made it harder to achieve high expiratory flow rates. This finding could explain why obese participants exhibited only a minimal increase in PEFR value after exercise compared with those with a normal BMI. In individuals with normal weight, exercise-induced bronchodilation, increased airway diameter, and enhanced PEFR. However, in individuals with obesity, higher airway resistance limits the effectiveness of bronchodilation, and consequently, a smaller PEFR increase after exercise (Luzak et al., 2018).

Obesity reduces lung and thoracic compliance, making it more difficult for the lungs to expand and contract efficiently. Chen Y, Horne s, et al found that lung compliance is reduced to one-third of normal in obese individuals due to increased pulmonary blood volume and closure of dependent airways (Chen et al., 1993). As a result, higher BMI leads to greater airway resistance, which restricts airflow and limits PEFR. In normal-weight individuals, exercise leads to increased lung expansion, improved airway dilation, and enhanced PEFR. In overweight and obese individuals, restricted lung expansion and increased airway resistance limit the improvement in PEFR after exercise. Moreover, pulmonary function decreased proportionally with an increase in body fat percentage (Anuradha et al., 2008). A comparable result was also observed in a study conducted in a Nepalese population where a decline in post-exercise PEFR was associated with a higher BMI in the younger age group population (Aryal et al., 2020).

These findings highlight the negative impact of obesity on lung function and show that higher BMI is linked to lower PEFR and a weaker response to exercise. Our results supported previous studies and confirmed that excess weight limit lung expansion increases airway resistance and weakens respiratory muscles. PEFR improvement was lower in overweight and obese individuals. Interventions such as weight management, pulmonary rehabilitation exercises such as inspiratory muscle training (IMT), diaphragmatic breathing exercises, pursed-lip breathing, and structured aerobic exercise programs (e.g., treadmill walking and cycling), and regular exercise may help to improve lung function. Further research with a larger sample size is needed to explore the long-term effects and potential treatments for obesity-related respiratory issues.

Although this study provides valuable insights into the relationship between BMI and PEFR, certain limitations should be acknowledged. First, baseline fitness levels were not formally assessed using parameters such as resting heart rate, VO2 max, or physical activity levels. Cardiopulmonary fitness influences PEFR; therefore, future studies should incorporate these measures to distinguish the effects of BMI from overall fitness levels. Second, the study was conducted in a single-center setting with a limited sample size, which may have affected the generalizability of the findings. Third, although PEFR measurements were standardized, factors such as diurnal variations, participant effort, and lung volume adjustments could introduce variability. Finally, although the current study focused on immediate changes in PEFR after exercise, long-term adaptations to structured exercise interventions should be explored in future research.

---

Conclusion

This study demonstrated that BMI significantly affects PEFR before and after exercise, with a statistically significant correlation (p < 0.0001). Obese individuals showed minimal improvement in post-exercise PEFR compared with those with normal BMI, likely due to reduced lung compliance, increased airway resistance, and weakened respiratory muscles. The students included in the normal BMI group showed the most substantial improvement in PEFR after exercise, followed by the overweight group. The obese group exhibited the least improvement in PEFR. This study demonstrated a significant relationship between BMI and lung function, as measured by the PEFR before and after exercise. Individuals with higher BMI (overweight and obese categories) exhibited reduced PEFR values compared with those with a normal BMI, suggesting an inverse association between excess body weight and pulmonary function. Obese students showed minimal changes in post-exercise PEFR. These findings suggest that BMI significantly influences the pulmonary response to exercise, with excess body weight potentially limiting respiratory adaptation. The observed decline in lung performance among overweight and obese individuals may be attributed to increased airway resistance, reduced lung compliance, and greater respiratory muscle workload, which collectively impair pulmonary efficiency. Despite these differences, exercise was found to enhance PEFR across all BMI categories, indicating that physical activity with a low duration plays a crucial role in improving respiratory function. These findings also highlight the potential benefits of maintaining a healthy lifestyle and optimal body weight for improving pulmonary function.

Notably, individuals with normal BMI showed the greatest improvement in PEFR after exercise, whereas the increase was relatively modest in overweight and obese participants. This suggests that excess body weight limits the extent of pulmonary adaptation to exercise, likely due to mechanical restrictions imposed by adipose tissue and increased metabolic demands. This study helps to understand the importance of weight management for improving respiratory health and improving fitness among young medical students.

These findings highlight the importance of early weight management strategies for young adults that support long-term pulmonary health and enhance exercise capacity. Interventions such as structured aerobic exercise programs and respiratory muscle training may help improve pulmonary function in overweight and obese individuals. Future research should explore the longitudinal effects of weight loss and targeted respiratory interventions to improve lung function across BMI categories.

Future directions of this study

• Larger, multicenter studies with diverse populations are needed to validate these findings and explore supplementary factors contributing to changes in PEFR. Longitudinal studies could assess the long-term effects of structured exercise programs on PEFR and overall pulmonary function across BMI categories. Exploring interventions, such as pulmonary rehabilitation, tailored to overweight and obese individuals may yield practical solutions for improving their respiratory health.

Acknowledgments

I gratefully acknowledge the support and guidance received from my mentor, and institutional staff during the preparation of this manuscript. Their insights and encouragement were invaluable throughout the research and writing process.

Authors’ contributions

Dr. Jahnavi Sudhirkumar Upadhyay was responsible for the conception and design of the study, data collection and analysis, and drafting of the manuscript.

Funding

This research did not receive any specific grant from funding agencies.

Data availability

The datasets generated and analyzed during the current study are available from the corresponding author.

Conflict of interest

There is no conflict of interest.

---

References

Aryal, V., Mahotra, N.B., Shrestha, L., et al. 2020. Post-exercise change in peak expiratory flow rate and its relation with body adiposity in Nepalese settings. Europasian J. Med. Sci. 2(1), 36. https://doi.org/10.46405/ejms.v2i1.36.

Bora, G., Sudhir, G.K. and Swamy, K.N.N. 2017. Impact of exercise training on peak expiratory flow rate in relation to body mass index-an Indian perspective. Indian J. Clin. Anat. Physiol. 4(1), 34–39.

Chen, Y., Horne, S. and Dosman, J. 1993. Body weight and weight gain related to pulmonary function decline in adults: a six year follow up study. Thorax 48, 375–380.

Coelho, C.M., Reboredo, M.M., Valle, F.M., et al. 2018. Effects of an unsupervised pedometer-based physical activity program on daily steps of adults with moderate to severe asthma: a randomized controlled trial. J. Sports Sci. 36(10), 1186–1193.

Das, D., Mondal, H. and Patnaik, M. 2017. Study of dynamic lung function parameters in normal, overweight, and thin school boys. J. Sci. Soc. 44(1), 36–39.

Freedman, S. 1992. Exercise as a bronchodilator. Clin. Sci. 83(4), 383–389.

Gibson, G.J. 2000. Obesity, respiratory function and breathlessness. Thorax 55(Suppl 1), S41–44.

Haslam, D. 2007. Obesity: a medical history. Obes. Rev. 8(Suppl. 1), 31–36.

Ismail, W.S. 2011. Evaluating the validity and reliability of Harvard step test to predict VO2 max in terms of the step height according to the knee joint angle. J. Appl. Sports Sci. 1(2), 126–132.

Jaakkola, J.J.K., Aalto, S.A.M, Hernberg, S., et al. 2019. Regular exercise improves asthma control in adults: a randomized controlled trial. Sci. Res. 9(1), 20188.

Jain, A.K. 2023. Text book of physiology. 10th edition. Delhi: Arya Publishing Company. Vol. 2 chapter: 67, pp: 687–689.

Jena, S.K., Mirdha, M., Meher, P. and Misra, A.K. 2017. Relation of peak expiratory flow rate to body mass index in young adults. Muller J. Med. Sci. Res. 8, 19–23.

Jones, R.L. and Nzekwu, M.M. 2006. The effects of body mass index on lung volumes and Chest. Am. J. Med. 130(8), 27–33.

Joshi, A.R., Singh, R. and Joshi, A.R. 2008. Correlation of pulmonary function tests with body fat percentage in young individuals. Indian J. Physiol. Pharmacol. 52(4), 383–388.

King, G.G., Brown, N.J., Diba, C., Thorpe, C.W., Muñoz, P., Marks, G.B., et al. 2012. The effects of body weight on airway calibre. Eur. Respir. J. 25, 896–901

Luzak, A., Karrasch, S., Thorand, B., Nowak, D., Holle, R., Peters, A., et al. 2018. Association of physical activity with lung function in lung-healthy German adults: results from the KORA FF4 Study. BMC Pulm Med. 2018, 17.

Mansfield, L., McDonnell, J., Morgan, W. and Souhrada, J.F. 1979. Airway response in asthmatic children during and after exercise. Respiration. 38(3), 135–143.

Melo, L.C., Silva, M.A. and Calles, A.C. 2014. Obesity and lung function: a systematic review. Einstein 12, 120–125.

Pal, G.K. and Pal, P. 2003. Textbook of practical physiology. 5th edition, pp. 149–156.

Parmar, D. and Modh, N. 2013. Study of physical fitness index using modified harvard step test in relation with gender in physiotherapy students. IJSR 6, 14.

Patil, S.R. and Mehta, A. 2019. Comparison of peak expiratory flow rate in obese and non-obese women. Int. J. Health Sci. Res. 9(9), 39–45.

Richardson, L.A. 2016. Obesity: evaluation and treatment essentials, 2nd edition, chapter: 2, etiology of obesity, Milton Park, UK: Taylor and Francis. pp: 25, 26, 30.

Rochester, D.F. and Enson, Y. 1974. Current concepts in the pathogenesis of the obesity-hypoventilation syndrome: mechanical and circulatory factors. Am. J. Med. 57, 402–420.

Rubinstein, I., Zamel, N., DuBarry, L. and Hoffstein, V. 1990. Airflow limitation in morbidly obese, nonsmoking men. Ann Intern Med. 112, 828–832.

Saikia, K. and Barman, S. 2017. Study of the effect of body mass index (BMI) on peak expiratory flow rate (PEFR) in Young Healthy Individuals. GJRA 5(9), 816.

Sandhu, P.K., Bajaj, D. and Mehta, K. 2017. Correlation of peak expiratory flow rate with age and anthropometric parameters in elderly (>65 years). Natl. J. Physiol. Pharm. Pharmacol. 6, 89–92.

Shanmugapriya Chinnaiyan A. and Ramayyan, V. 2021. Comparison of peak expiratory flow rates (PEFR) between obese and non-obese females. J. Pre-Clin. Clin. Res. 15(3), 111–115.

Sharma, R., Ranade, V. and Nagulkar, J. 2020. Effect of swimming as an exercise on peak expiratory flow rate in healthy adult females. Int. J. Allied. Med. Sci. Clin. Res. 8(3), 698–701.

Shenoy, J.P., Kalpana, B. and Bhat, S.K. 2014. Impact of adiposity markers on peak expiratory flow rate in young adult South Indian Females. Muller J. Med. Sci. Res. 5(2);121–124.

Tartari, J.L.L. 2021. Relationship between peak expiratory flow and impaired functional capacity in obese individuals. Fisioter. Mov. 34, 34105. https://doi.org/10.1590/fm.2021.34105.

Varshney, V.P. and Bedi, M. 2023. Ghai’s Text book of practical physiology 10th edition, Human experiments, unit 1: Respiratory system, chapter 2.2: Pulmonary function test, New Delhi, India: Jaypee Publisher. pp: 112–116.

World Health Organization 2023. Obesity: preventing and managing the global epidemic. World Health Organization Obesity Technical Report Series. Geneva, Switzerland: WHO.