The main purpose of this research study is to determine if exercise improve or worsen cachexia.

In this study the investigator would like to better understand how cachexia may improve or worsen, and how exercise may impact this process. The investigator would like to see whether a progressive resistance exercise program (EXCAP©®, Exercise for Cancer Patients) can improve symptoms in patients with gastrointestinal cancers with weight loss and cachexia. The investigator would also like to find out if this exercise intervention improves physical performance, day-to-day function, quality of life, and how exercise may affect different markers in the blood over time.

Inclusion Criteria:

• Have a primary diagnosis of colorectal, esophageal, gastric, pancreatic or biliary tract cancer and plans to initiate systemic chemotherapy within the next 4 weeks after enrollment.
• Have been diagnosed as having an advanced unresectable cancer with no plans for surgical intervention during the active study period (12 weeks).
• Have an ECOG performance score of 0 or 1.
• Have a life expectancy of >3 months as determined by their primary oncologist.
• Have experienced at least 2% weight loss of the patient's reported previous body weight over the 6 months prior to enrollment. Patients who have 2 - 4.9% weight loss should also have one of the following metabolic changes: a hemoglobin level <13, an albumin level <3.5, and/or impaired glucose tolerance within the past year such as a new diagnosis of diabetes, an A1C level >5.7, a random glucose level >200 or a fasting glucose level >100.
• Have permission from primary oncologist to engage in low to moderate intensity exercise regimen.
• Be able to read English (since the assessment materials are in printed format).
• Be able to give written informed consent.

Exclusion Criteria:

• Have any of the following limitations: unable to walk the 4 meters of the SPPB test, wheel-chair bound, unable to perform low-to-moderate intensity exercise regimen (patients unable to perform 6 minute walk or stair climb test will be allowed to participate, but will be held out of these measurements).
• Have had major surgery (excluding diagnostic procedures like laparoscopy, EGD/EUS, esophageal stent placement) in the past 4 weeks.
• Be experiencing dysphagia that requires enteral or parenteral feeding for nutrition.
• Be enrolled on hospice at time of consent.
• Be engaged in an active exercise routine by being identified as in the Active or Maintenance Stage of exercise behavior as assessed by the 1-item Exercise Stages of Change Short Form (40).