To determine the impact of nutritional supplementation with whey protein on postoperative functional capacity in patients undergoing colorectal surgery for cancer.It is hypothesized that, compared with a control group receiving nutrition counselling only, patients receiving nutritional counselling along with preoperative and postoperative nutritional supplements will have a significantly improved change in functional walking capacity from baseline to 8 weeks after surgery.

The aims of this research project are the following:

1. Determine to what extent a nutritional prehabilitation regimen, which includes whey protein, initiated before surgery and continued after surgery, optimizes the recovery of functional walking capacity following colorectal resection for cancer.
2. To understand further which measures of immediate surgical recovery are sensitive to prehabilitation interventions, and predict change in later outcome measures.

Inclusion Criteria:

• +18 years of age
• referred electively for resection of malignant, non metastasized, colorectal lesions
• French or English speaking

Exclusion Criteria:

• ASA class 4-5
• co-morbid medical, physical and mental conditions (e.g.dementia, disabling orthopedic and neuromuscular disease, psychosis)
• cardiac abnormalities
• severe end-organ disease such as cardiac failure (New York Heart Association classes I-IV), COPD, renal failure (creatinine > 1.5 mg/dl, and hepatic failure ALT and AST >50% over the normal range)
• sepsis
• morbid obesity (BMI >40)
• anemia (hematocrit < 30 %, haemoglobin <10g/dl, albumin < 25mg/dl).