Background & Objective: Obesity is one of the most important global health priorities as far as it increases illnesses and disorders the life quality. Alpha-1-Antitrypsin (AAT) is the most abundant serum protease inhibitor and prevents tissue degradation through proteases. Hence, its defect or deficiency significantly increases the risk of various diseases. AAT may be involved in the development and complications of obesity. The present study then was performed to determine the activity of AAT in the obese people compared to those with normal weight. Materials & Methods: In this cross- sectional study, determining the AAT’s activity was performed through Trypsin-Inhibitor-Capacity (TIC) in healthy individual who were referred to the laboratory of Dr.Shariati in Fasa Hospital in April 2013. Serum of 150 people with normal weight (Body Mass Index, BMI, ranges between 18.5 and 24.9) and the serum of 140 obese people (BMI more than 30) were surveyed. The data were analyzed by SPSS software using t-test and Pearson correlation coefficient. Results: The serum amount of TIC in obese people (1.774±0.618 µmol/min/ml) was significantly lower than its amount in people with normal weight (3.047±0.498 µmol/min/ml) (P-value< 0.001). There was a significant negative correlation between TIC and weight (P< 0.001, R=-0.686). In addition, no significant correlation was observed between TIC and age sex and height. Conclusion: The results showed that AAT in obese people was less in healthy individuals compared with the ones with normal weight. Therefore, it can be stated that AAT can be introduced as a clinical biomarker and be a potential target for treating obesity
