About Authors:
Madhuri Sharma*1, KC Mathur1, Rajnee2, Raaz K Maheshwari3
1Department of Physiology, Sardar Patel Medical College, Bikaner, Rajasthan
2Department of Physiology, Sarojini Naidu Medical College, Jodhpur, Rajasthan
3Department of Chemistry, SBRM Govt PG College, Nagaur, Rajasthan

Pulmonary function test are affected by the obesity. Various studies demonstrate important modifications in the pulmonary function tests of obese adults and adolescents, there is scarce information on obese children, and the findings remain inconclusive. Although there are some studies which demonstrate important modifications in the respiratory pattern of obese children, but there are some contradictory findings. So such type of study should be done which give us different and separate findings for overweight, mild obese, moderately obese, and morbidly obese criteria in obese school children in comparison with age, sex and ethnically matched control group.


Obesity is emerging as a global epidemic in both children and adults. This has been called “New world syndrome” and is a reflection of massive social, economic and cultural problems currently facing developing and developed countries. Obesity is regarded as a complex disease because it arises from multifaceted interactions of genetic and environmental factors[1]. As the prevalence of this disorder grows worldwide, obesity is increasingly considered a major public health problem[2],[3],[4]. McClean KM, Cardwell CR, Kee F, et al. in their  10-year longitudinal study of middle-aged men in Northern Ireland showed that the decline in lung function was greater in those who had the largest increases in BMI over the study period.[5]Naimark and Cherniack have demonstrated that total respiratory compliance is reduced by as much as two-thirds of the normal value in obese individuals. This is due, in part, to a decrease in lung compliance that may relate to the increased pulmonary blood volume seen in obese individuals.[6]

In a study by Sahebjami and Gartside,[7] reductions in FEV1, FVC and maximal inspiratory flow rate in obese subjects were associated with a low MVV. Both FEV1 and FVC were similarly reduced (in terms of percentage predicted), the FEV1 to FVC ratio was normal and static lung volumes were reduced, suggesting the reduction may be due to restriction as opposed to air flow obstruction. Lazarus et al[8] found that the FEV1 to FVC ratio decreases with increasing BMI in overweight and obese individuals. In morbidly obese subjects (defined as individuals with a body weight (in kilograms) to height (in centimetres) ratio greater than 0.9 kg/cm.Parameswaran K, Todd DC, Soth M has illustrated that obesity has a modest effect on conventional respiratory function tests until the BMI is >40 kg/m2.[9]

Collins et al demonstrated that multiple measures of adiposity showed a significant inverse relationship with both spirometry and static lung volumes.[10]Lazarus R, Sparrow D, et al17 showed that the ratio of abdominal circumference to hip breadth and subscapular skinfold thickness were negatively associated with FEV1 and FVC. This suggests that central abdominal obesity has a greater impact on spirometric measures compared with back or lower body obesity.Ulger et al conducted an investigation based on previous studies to explain the effects of obesity on respiratory function tests in childhood and to define the association between the degree of obesity and respira­tory function.[11]

He et al examined the association between obesity and asthma and the characteristic symptoms of asthma with pulmonary function. Their main result in the analysis of obesity and pulmonary function was the positive correlation between FVC and BMI increases.[12]Boran P, Tokuc G,  Pisgin B, et al demonstrated that pulmonary function test parameters of the mildly obese children were similar to those of the normal weight children. Anthropometric measurements had no significant effect on spirometric measurements in children as they did on adults.[13]Tang RB et al found that physiologic responses of pulmonary function tests were not statistically different in obese and non-obese.[14]Inselman et al confirmed that, in relation with theoretical values for sex, age, and Height, the expiratory reserve volume, FEV1, FEF25-75, MVV (maximal voluntary ventilation), and absolute and corrected DLCO (alveolar diffusion capacity) were reduced. That was explained with abnormality in alveolar diffusion with possible structural alterations of the lung interstice by lipid deposition and/or a reduction in alveolar surface area.[15]Rubenstein I, Zamei N, Dubarry L, et al stated that classically obesity does not affect spirometric values other than maximum voluntary ventilation (MVV) until vital capacity becomes reduced in extreme cases.[16]

Consequences of obesity
Arterial hypertension, atherosclerosis, dyslipidemia, diabetes, obstructive sleep apnoea and altered pulmonary function test, alterations in the musculoskeletal system, depression and a reduction in quality of life[17],[18]. Obesity is characterised by an excessive deposition and storage of fat in the body[19]. Body mass index is the marker for body fat content.

Etiology of obesity
Obesity occurs when caloric intake exceeds energy expenditure and the excess calories are stored in an adipose tissue. Therefore, the ultimate cause of obesity is suggested to be an imbalance between energy intake and expenditure resulting from complex interaction of genetic, physiological, behavioural and environmental factors.[20]

Effect of obesity on respiration
Excess weight on the anterior chest wall due to obesity lowers chest wall compliance and respiratory muscle endurance with increase in work of breathing and airway resistance.[21],[22],[23] Furthermore, the build up of adipose tissue in the anterior abdominal wall and in the intra-abdominal visceral tissue hinders diaphragmatic movement, diminishes basal lung expansion during inspiration, and with the closure of peripheral lung units, causes ventilation–perfusion abnormalities and arterial hypoxemia.[24],[25] These changes contribute to an increase in prevalence of respiratory problems in obese individuals.

Number of studies are done to evaluate the effect of obesity on pulmonary function test, but the results are controversial. So longitudinal studies should be done to see the effect in pulmonary functions on overweight, mild obese, moderately obese, and severely obese children.


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