## 2 Materials and Methods
### Clinical Information  
From the surgery registries in both hospitals and computer tomography (CT) body morphometry analysis, clinical information and body morphometry information with 59 variables were collected (Supplementary Table S1). With respect to demographic information, patients' age, sex, body weight, and height were collected. Clinical information about the type of surgery (open vs. laparoscopic approach), type of operation (distal vs. total gastrectomy), type of anastomosis, and pathologic data, including [PERSON]'s classification [17] and pathologic tumor stage, were also included in the analysis.  
Laboratory test results, such as serum albumin and cholesterol at pre- and postoperative periods, were also collected. The nutritional risk index (NRI) was calculated based on the formula (1.519 \(\times\) serum albumin g/L) + 0.417 \(\times\) (present weight/usual weight) \(\times\) 100 [18].  
Body morphometry information was obtained from CT images. CT scans obtained at pre- and postoperative periods (i.e., one year after surgery) were selected for body morphometric analysis. Preoperative CT was evaluated on average within one month prior to the surgery. Body composition was assessed with abdominopelvic CT using automated artificial intelligence software (AID-UTM, iAID Inc., Seoul, Korea), which was developed using a fully convolutional network segmentation technique [19] (Figure 1). Skeletal muscle area (SMA), including all muscles (i.e., psoas, paraspinal, transversus abdominis, rectus abdominis, quadratus lumborum, and internal and external obliques) on the selected axial images at the inferior endplate level of the third lumbar vertebra (L3) were demarcated using predetermined thresholds (\(-\)29 to +150 Hounsfield units (HU)). The subcutaneous fat area (SFA) and visceral fat area (VFA) were also assessed using fat tissue thresholds  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Characteristics**} & **AMC** & **AUH** & **Total** \\  & **(n = 621)** & **(n = 33)** & **(n = 654)** \\ \hline TNM stage 1 & & & \\
1A & 78 (12.6\%) & 18 (54.5\%) & 96 (14.7\%) \\
1B & 21 (3.4\%) & 3 (9.1\%) & 24 (3.7\%) \\
2A & 138 (22.2\%) & 2 (6.1\%) & 140 (21.4\%) \\
2B & 135 (21.7\%) & 1 (3.0\%) & 136 (20.8\%) \\
3A & 110 (17.7\%) & 3 (9.1\%) & 113 (17.3\%) \\
3B & 93 (15.0\%) & 3 (9.1\%) & 96 (14.7\%) \\
3C & 42 (6.8\%) & 3 (9.1\%) & 45 (6.9\%) \\
4 & 4 (0.6\%) & 0 (0\%) & 4 (0.6\%) \\ Preoperative & & & \\ Body/Nutrition & & & \\ SMA (cm2) & 124.2 \(\pm\) 30.0 & 125.8 \(\pm\) 31.7 & 124.3 \(\pm\) 30.0 \\ SFA (cm2) & 118.0 \(\pm\) 55.2 & 118.0 \(\pm\) 55.2 & 118.1 \(\pm\) 55.5 \\ VFA (cm2) & 97.7 \(\pm\) 56.6 & 100.3 \(\pm\) 72.1 & 97.9 \(\pm\) 57.4 \\ NRI & 101.1 \(\pm\) 6.4 & 103.9 \(\pm\) 7.6 & 101.3 \(\pm\) 6.5 \\ \hline \hline \end{tabular} Data are numbers (and percentages) or mean \(\pm\) standard deviation. BMI = body mass index, NRI = nutritional risk index, SFA = subcutaneous fat area, SMA = skeletal muscle area, VFA = visceral fat area. 1 TNM stage was based on the American Joint Committee on Cancer 7 th edition.  
\end{table}
Table 1: \(Cont.\)(\(-190\) to \(-30\) HU). The SMA was adjusted using the square of the height (SMA/height2) and BMI (SMA/BMI).