This is a feasibility study to test the potential efficacy of diets of different amounts of protein and calories for patients with cancer. We hypothesize that nutritional deficits play a significant role in muscle loss and that nutritional therapy is an important first step in reversing or preventing muscle loss and maintaining/improving physical function.

Severe muscle depletion (sarcopenia) is a common issue among cancer patients and adequate nutrient intake is pivotal to maintain muscle mass. Yet, optimal amounts of protein are undefined for preventing or treating sarcopenia in people with cancer as most methodological approaches to assess protein requirements are expensive, burdensome and unfeasible for this population. This study's overarching goal is to investigate the potential efficacy of diets of different protein content on: 1) muscle mass maintenance (primary endpoint); and 2) improvements on physical function in cancer patients capable of oral nutrition support. Additional study measurements include: energy metabolism (including total body), body composition using multi-compartment models, blood biomarkers, and quality of life.

In a randomized controlled trial approach, we will employ high protein feeding (2 g/kg/d, n=16) versus a standard recommendation (1 g/kg/d, n=16) in patients with newly diagnosed colorectal cancer for 12 weeks. Prescribed energy intakes will be framed by the amount of calories to meet energy needs and to support protein synthesis, but prevent fat mass gain. Carbohydrate, fat and protein intake will be adjusted throughout the intervention to achieve the desired rate and amount of energy and protein intake. An oral protein powder supplement made from high-quality whey protein will be provided to the participants to help increase their protein intake as needed. A multivitamin will be given to all participants throughout the study. Participants will receive weekly calls from the study coordinator to ensure adherence to the dietary intervention.

Inclusion Criteria:

• Ambulatory adults 18 - 85 years of age;
• Able to communicate in English;
• Recent diagnosis of colorectal cancer (stage II, III or IV);
• Able to complete all baseline assessments within 2 weeks of commencement of chemotherapy or chemoradiotherapy (when applicable);
• ≥1 year life expectancy and believed to be able to complete 12 weeks of intervention (based on clinical judgment);
• Able to provide a blood sample;
• Adequate hepatic function, as confirmed by medical records and to be checked with patient's oncologist;
• Adequate renal function, as confirmed by medical records and to be checked with patient's oncologist;
• If a woman of childbearing potential, she must agree to use an effective form of contraception during the study (are considered effective forms of contraception: abstinence, a hormonal contraceptive, or a double-barrier method).

Exclusion Criteria:

• Acute inflammation assessed by neutrophil/leukocyte ratio or in consultation with oncologist;
• Ongoing (non-treatment related) nutritional impact symptoms that would impact ability to follow dietary recommendations (ie. anorexia);
• Severe food restrictions (severe food allergy or dietary pattern - e.g. vegetarian);
• Current medical condition that impacts the patients ability to take part in study or impacts the ability to increase muscle (e.g. cachexia, post-surgical wound infection, muscular dystrophy or any degenerative muscle disease or condition);
• Individuals with pacemakers;
• Comorbidities: active treatment for another cancer site, major chronic conditions that would interfere with dietary restriction such as recent myocardial infarction, unstable angina, stroke, or unstable disease such as congestive heart failure;
• Women who are pregnant or breast-feeding;
• Body weight > 450 lb due to limit of body composition measurement instrumentation;
• Presenting with any health condition that would severely affect nutrient absorption (e.g.: enteric fistula);
• Patients diagnosed with metabolic disorders in consultation with the oncologist (e.g. uncontrolled diabetes, recent diagnosis (< 3 months) thyroid disease);
• Cognitive impairment or dementia.