Background: Obesity is a complex, multi-factorial, chronic condition that is associated with mortality and significant morbidity and is prevalent worldwide. The aim of the study is to determine the effect of obesity on pulmonary function abnormality in young adults in our population. Method: A cross sectional study on 140 individuals, selected randomly from general population of Rajkot city was performed. A thorough history analysis (Height, Weight, BMI), Physical examinations Spirometry were done on all individuals after explaining the procedure and taking their consent. Parameters measured by the spirometer were FEV1, FVC, FEV1/FVC, PEFR, ERV, IC, EC, VC. Result & conclusion: It was observed that lung volumes decreased with statistically significant decreased ERV (0.66±0.09 L) & FVC (3.10±0.91) as the BMI increases (30-35Kg/m2). Negative correlation was found between BMI and ERV (-0.307) at higher BMI Values.