Preoperative oral carbohydrates are strongly recommended for routine use before various elective procedures. The regimen mainly includes preoperative oral single-dose carbohydrate (2-3h before surgery) and preoperative oral double-dose carbohydrates (10h before surgery and 2-3h before surgery). The choice between the two options is still controversial. A total of 139 patients with gastric cancer who underwent radical gastrectomy were recruited from a hospital in Sichuan Province, China. The patients were randomly assigned to a single-dose group (n=70) or a double-dose group (n=69). Insulin resistance indicators, subjective comfort indicators, inflammatory mediators, immunological indicators, postoperative recovery indexes, and complications were compared between the two groups. There were no differences in insulin resistance indicators (fasting plasma glucose, fasting insulin, and homeostasis model assessment indexes), inflammatory mediators (C-reactive protein, interleukin-6, and tumor necrosis factor-α), immunological indicators (CD3+, CD4+, CD8+, and CD4+/CD8+) between the single-dose group and double-dose group (all P>0.05) at preoperative day 1, preoperative 3h, and postoperative day 1. There were no differences in subjective comfort indicators (thirst, hunger, anxiety, nausea, fatigue, and weakness) between the two groups (all P>0.05) at preoperative day 1, preoperative 3h, preoperative 1h, and postoperative day 1. The postoperative recovery indexes and complications (exhaust time, liquid intake time, postoperative hospital stay, complication incidence, unplanned readmission rate, and unplanned reoperation rate 30 days after operation) did not significantly differ between the two groups (all P>0.05). The number of preoperative nighttime urinations in the double-dose group was higher than that in the single-dose group (88.3% VS 48.5%, P<0.001), and the number of hours of preoperative sleep in the double-dose group was lower than that in the single-dose group (4.56±0.68 VS 5.71±0.57, P<0.001). Oral carbohydrates administered the night before surgery did not enhance the effects of oral carbohydrates administered 2-3h before surgery on insulin resistance, subjective comfort, inflammation, and immunity and might affect the patients' night rest. In making a decision between oral carbohydrate regimes, evening carbohydrates could be omitted. ChiCTR, ChiCTR1900020608. Registered January 10, 2019, http://www.chictr.org.cn: ChiCTR1900020608.