BMI Linked to Lung Function, Physical Activity Shows No Significant Effect in Indonesian Adult Study
A 2026 study by Hana Fajrin Kamilia and Eveline Margo from Universitas Trisakti, Indonesia, reveals that body mass index (BMI) has a significant relationship with lung function, while physical activity does not show a measurable impact. Published in the International Journal of Integrative Sciences (IJIS), the research highlights how body composition may play a more decisive role than daily activity levels in determining peak expiratory flow (PEF), a key indicator of respiratory health in adults.
The study focuses on adults working in an academic environment and provides important insights into how modern sedentary lifestyles and nutritional status influence lung performance. These findings are particularly relevant as office-based work and low physical activity become increasingly common in urban populations.
Why Lung Function Matters in Modern Lifestyles
Peak Expiratory Flow (PEF) measures how fast a person can exhale air after a deep breath. It is widely used as a simple and quick indicator of lung function, especially for detecting early signs of respiratory problems.
In today’s work environments—especially academic and office settings—many adults spend long hours sitting, often with limited physical activity. This sedentary pattern has been associated with declining physical fitness, including reduced respiratory capacity.
Previous studies have suggested that both physical activity and BMI influence lung function. Regular exercise is believed to strengthen respiratory muscles, while BMI reflects body composition, which can either support or restrict breathing depending on fat and muscle distribution. However, results from earlier research have been inconsistent, particularly among healthy adult populations.
How the Study Was Conducted
Kamilia and Margo conducted a cross-sectional study between September and October 2025 at the Faculty of Computer Science, Kuningan University. The study involved 57 healthy adult respondents, including lecturers and administrative staff aged 18 to 59 years.
The researchers used simple and widely accepted measurement tools:
- Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ-Short Form)
- BMI was calculated from height and weight measurements
- PEF was measured using a peak flow meter, with the highest value from three attempts recorded
The data were analyzed using statistical tests to determine whether there were meaningful relationships between variables.
Key Findings from the Study
The results reveal a clear pattern in lifestyle and health indicators among respondents:
- 73.7% of participants had low physical activity levels
- 59.6% showed low PEF values, indicating reduced lung function
- 63.1% were classified as overweight or obese
When examining relationships between variables, the study found:
No significant relationship between physical activity and PEF
- Significant relationship between BMI and PEF
More specifically:
- 55.6% of overweight-obese individuals had normal PEF
- Only 26.7% of underweight-normal individuals had normal PEF
Understanding the Surprising BMI Result
The finding that higher BMI is associated with better lung function may seem counterintuitive. However, the researchers provide a physiological explanation.
In younger and productive-age adults, higher BMI does not always indicate excess fat. It may also reflect greater muscle mass, including muscles involved in breathing such as the diaphragm and intercostal muscles. Stronger respiratory muscles can generate higher airflow during exhalation, resulting in better PEF values.
On the other hand, individuals with lower BMI may have less muscle mass, which can weaken respiratory performance. This highlights the limitation of BMI as a standalone measure, as it does not distinguish between fat and muscle composition.
Why Physical Activity Showed No Effect
Despite expectations, physical activity did not show a significant relationship with lung function in this study. Several factors may explain this:
- Most respondents engaged in low-intensity activity, which may not be sufficient to improve lung capacity
- Physical activity data were based on self-reported questionnaires, which can be inaccurate
- The sample size was relatively small, limiting statistical power
- PEF measurements depend on maximum effort, which can vary between individuals
The findings suggest that not all physical activity contributes equally to respiratory health. Structured and higher-intensity exercise may be required to produce measurable improvements in lung function.
Real-World Implications
This study provides important insights for multiple sectors:
- For individuals: Maintaining a healthy body composition, including muscle mass, may be more important for lung function than simply increasing activity levels
- For workplaces: Sedentary environments should incorporate health programs, including regular screening of lung function
- For healthcare providers: PEF can be used as a simple screening tool to detect early respiratory decline
- For policymakers: Public health strategies should promote not only physical activity but also balanced nutrition and body composition awareness
The high proportion of respondents with low PEF (59.6%) also signals the need for routine respiratory health monitoring, even among individuals without apparent symptoms.
Limitations and Future Research
The study acknowledges several limitations:
- BMI does not distinguish between fat and muscle mass
- External factors such as smoking and air pollution were not controlled
- Physical activity measurement relied on subjective reporting
Future research is expected to use more precise tools, such as accelerometers for activity tracking and body composition analysis methods like Bioelectrical Impedance Analysis (BIA) or DEXA scans.
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