Introduction There has recently been increased interest in the assessment of body composition in patients with gastric cancer for the purpose of prognostication. This systematic review and meta-analysis aim to evaluate the current literature on body composition assessment in patients with gastric cancer and its impact on peri-operative outcomes. Methods A systematic literature search was conducted for studies reporting assessment of body composition in patients with gastric cancers. Meta-analysis of postoperative outcomes (overall and major complications, anastomotic leaks, pulmonary complications) and survival was performed using random effects models. Results Thirty-nine studies reported the assessment of body composition in 8402 patients. Methods used to assess body composition in patients with gastric cancers were computerized tomography (n = 26), bioelectrical impedance analysis (n = 9), and dual-energy-X-ray-absorptiometry (n = 3). Only 21 studies reported the impact of pre-operative sarcopenia on post-operative outcomes. Sarcopenic patients have significantly higher rates of postoperative major complications (n = 12, OR 1.67, CI 95% 1.14-2.46, p = 0.009), and pulmonary (n = 8, OR 4.01, CI 95% 2.23-7.21, p < 0.001) complications after gastrectomy. Meta-analysis of nine studies reporting overall survival after gastrectomy identified significantly worse survival in patients with pre-operative sarcopenia (HR 2.12, CI 95% 1.89-2.38, p < 0.001). Conclusions Assessment of body composition has the potential to become a clinically useful tool that could support decisionmaking in patients with gastric cancer. However, variation in methods of assessing and reporting body composition in this patient group limits assessment of current post-operative outcomes