Objective To analyze the impact of body mass index (BMI) on tumor characteristics of colorectal patients served by West China Hospital as a regional center in the current version of Database from Colorectal Cancer (DACCA). MethodsThe data of DACCA was updated on October 16, 2021. All data items included BMI, precancerous lesions, cancer family, tumor site, tumor morphology, location, differentiation, pathological properties of tumor, obstruction, overlap, perforation, pain, edema, and bleeding. The patients were divided into lean (BMI<18.5 kg/m2), normal (BMI 18.5–23.9 kg/m2), overweight (BMI 24.0–27.9 kg/m2) and obesity (BMI≥28.0 kg/m2) by Chinese classification methods. ResultsAfter scanning, 5 761 data rows were analyzed. Chi-square test showed that there was significant difference in the type composition ratio of tumor location in colorectal cancer patients under different BMI groups (χ2=31.477, P<0.001). Rank sum test showed that there was significant difference in the degree of obstruction (H=42.490, P<0.001), intussusception (H=8.179, P=0.042), edema (H=14.795, P=0.002), and bleeding (H=9.884, P=0.020) among different BMI groups. ConclusionsThe BMI classification of colorectal cancer patients is related to the location of tumor and the occurrence of some tumor complications. Patients with tumor involving intestinal lumens for one week are more likely to have low BMI. The patients with low BMI are more likely to have severe bleeding, obstruction, intestinal intussusception, and severe intestinal wall edema.