Background: Overweight and obesity can have psychological causes. but the main question is: What are the psychological causes of obesity? Aims: The purpose of the present study was to investigate the lived experiences of obese people in overeating: Psychological causes of obesity in Isfahan. Method: This was a qualitative study. The statistical population of the study consisted of all adults with weight gain in Isfahan in 2018. Fourteen overweight adults were selected through purposive sampling. Tools include: In-depth semi-structured interviews. data were analyzed using Colaizzi's seven-step method. Results: The results of the study consisted of 115 concepts, 25 categories and 5 themes. The themes extracted are: 1) stress 2) emotional maladjustment 3) expectations and values 4) personality traits and 5) negative mood. The results of this study clearly indicate the role of negative mood and especially emotional dysregulation in overweight in obese individuals. Conclusions: Lack of necessary skills in stress management, emotions and relationships with specific personality traits can lead to overweight in obese individuals.