Purpose: We evaluated the changes in body composition (BC) and quality of life (QoL) in patients who underwent gastrectomy for advanced gastric cancer. Methods: BC data using segmental multifrequency bioelectrical impedance analysis and QoL data from the EORTC (European Organisation for the Research and Treatment of Cancer) gathered via QLQ-C30 and QLQ-ST022 questionnaires were obtained from 300 patients preoperatively and at 1, 2, and 3 years after surgery. In total, 114 patients underwent total gastrectomy (TO group) and 186 underwent distal gastrectomy (DO group). Results: According to BC analysis, at 3 years postoperatively, the average body weight (P = 0.0021, protein mass (P = 0.0281, body fat mass (P = 0.009), skeletal muscle mass (P = 0.037), and visceral fat area (P = 0.012) was significantly decreased in the TG group than in the DG group compared to the preoperative. In the QLQ-C30, physical functioning (P = 0.001), role functioning (P = 0.0131, and fatigue (P = 0.0051 showed significantly worse QoL in the TG group than in the DO group at 2 and 3 years postoperatively. In the QLQ-ST022, pain (P = 0.0011, reflux symptoms (P = 0.0091, eating restrictions (P = 0.0011, anxiety (P = 0.008), taste (P = 0.011), and body image (P = 0,014) showed greater continuous deterioration postoperatively in the TG group than in the DG group. Conclusion: Persistent deterioration of BC and QoL is a serious concern following total gastrectomy. Long-term management of BC is required after gastrectomy and efforts should be made to improve the QoL in patients as soon as possible, postoperatively.