Purpose The prevalence of obesity is increasing along with the number of sleeve gastrectomies. Patients' mental health and social life, along with their physical health, should be considered. Their cultural and religious values are an important part of treatment. Fasting is an important act of worship in all religions. Ramadan fasting is one of the five pillars of Islam. In this study, we aimed to investigate the effect of Ramadan fasting on quality of life in patients who underwent sleeve gastrectomy. Materials and Methods Data regarding the demographic characteristics, weight, the time elapsed after surgery, and the amount of liquid and solid food consumed during fasting were collected with two surveys, one of which was carried out at the beginning and the other at the end of Ramadan. In addition, the SF-36 health survey questionnaire was administered to evaluate the impact of Ramadan fasting on patients' quality of life. Results Fifty-one people participated in the first survey, but the second survey included 19 of them. While the median weight of the patients was 86.52 +/- 17.78 kg before fasting, the median weight after 25 days of fasting was 83.31 +/- 17.06 kg. A significant decrease was observed in weight after 25 days of fasting (p < 0.001). A comparison of the SF-36 scores for quality of life revealed a significant increase in the social functioning (p = 0.032). Conclusion Ramadan fasting caused significant weight loss in patients who underwent sleeve gastrectomy. Besides, it did not adversely affect the quality of life, but rather increased social functioning.