The mid-term analysis of the study showed no significant difference between the two groups.

Postoperative insulin resistance refers to the phenomenon that the body's glucose uptake stimulated by insulin is reduced due to stress effects such as trauma or the inhibitory effect of insulin on liver glucose output is weakened after surgery.

There is a clear link between postoperative insulin resistance and poor perioperative prognosis. Therefore, exploring interventions to reduce postoperative stress insulin resistance, stabilize postoperative blood glucose, and reduce postoperative complications are clinical problems that need to be solved urgently. In recent years, research on branched-chain amino acids and metabolic diseases has become a hot spot. Studies have found that in the rat model, preoperatively given a high branched-chain amino acid diet can inhibit postoperative insulin resistance and stabilize blood glucose levels. This research plan is to try to add branched-chain amino acids before surgery to observe the occurrence of postoperative insulin resistance in patients.

Inclusion Criteria:

1. Age 50-80 years old ;
2. Clinical diagnosis of colorectal cancer;
3. Planned elective laparoscopic radical resection of colorectal cancer;
4. Preoperative American Society of Anesthesiologists（ASA）score grade I-III ;
5. Informed consent was obtained from patients.

Exclusion Criteria:

1. Clinical diagnosis of Diabetes mellitus;
2. Preoperative insulin resistance ;
3. Renal insufficiency requires dialysis, hepatic insufficiency (Child - Pugh grade B and above);
4. Eating disorders caused by gastrointestinal obstruction;
5. Pregnant or lactating women;
6. Patients with severe mental illness.