OBJECTIVE: The objective of this study was to examine the effects of orlistat use on metabolic control and weight loss in diabetic and nondiabetic patients. METHODS: A total of 119 patients with body mass index≥40 kg/m2 and receiving orlistat therapy, who applied to the Endocrinology polyclinic between January 2016 and October 2019, were included. The patients' weight changes and biochemical values (i.e., fasting glucose, HbA1c, ALT, creatinine, and lipid parameters) were evaluated at the drug beginning and the last polyclinic control. The patients were divided into groups, whether they had diabetes or used metformin, and compared. RESULTS: The mean age of the 119 patients in the study was 45.3±11.5 years. A total of 94.1% of the patients were females and 5.9% were males. A total of 38.7% of the patients had diabetes and 29.4% had prediabetes. When the patients were compared to whether they had diabetes or used metformin, there was a statistically significant difference between the groups according to weight loss. The mean weight change of patients without diabetes and receiving metformin and orlistat was statistically significantly higher than that of patients with diabetes and receiving metformin and orlistat. DISCUSSION: It was determined that the weight loss effect of orlistat in obesity was seen in all groups, but this effect decreased in the diabetic group.