Inclusion Criteria:

- Male or female

- Completed a colonoscopy within the past 36 months

- Ages 40-75 years at time of identification

- Sedentary activity pattern

- Gives informed consent, agrees to be randomly assigned

- Able to perform all study requirements, able to follow directions and complete forms

Exclusion Criteria:

- Colorectal cancer at any time; any other invasive cancer within the past 10 years
(simple basal or squamous cell carcinoma okay)

- Plans to leave Western Washington during the follow-up period

- Morbidly obese (BMI > 41), weight loss of > 10 pounds in the previous 3 months

- Familial polyposis, Gardner's syndrome, or other known familial colorectal cancer
syndrome

- Ulcerative colitis or short bowel

- "Excessive"(> 3 x week) laxative or enema use that might interfere with rectal crypt
studies

- Current use of certain medications likely to interfere with success of the
intervention, or with outcomes measures (for example, anticoagulants because of risk
from colorectal biopsy, diet medications within past 6 months)

- Diabetes mellitus or fasting glucose > 140

- Hemochromatosis- if diagnosed by physician

- Abnormal screening labs (hematocrit < 32 or > 48, white blood cells < 3.0 or > 15.0,
potassium < 3.5 or > 5.3, fasting glucose > 140, creatinine > 2.0), or abnormalities
on screening physical exam judged by study physicians to contraindicate participation
in an exercise program

- Contraindications for entry into a training program 131 including: unstable angina,
uncontrolled hypertension (systolic > 200, diastolic > 100), orthostatic hypotension
(>20 mm fall in systolic), moderate/severe aortic stenosis, uncontrolled arrhythmia,
uncontrolled congestive heart failure, third degree heart block, pericarditis,
myocarditis, pulmonary/systemic embolism within the past 6 months, thrombophlebitis,
ST displacement > 3 mm at rest, history of cardiac arrest)

- Contraindications for exercise testing 131 including: recent (within 6 months)
cardiac event (MI, pulmonary edema, myocarditis, pericarditis), unstable angina,
uncontrolled arrhythmia, third degree heart block, left bundle branch block, acute
congestive failure, recent (within 6 months) pulmonary/systemic embolus, severe
electrolyte abnormality

- Meets criteria to stop screening exercise test 131 as decided by overseeing physician

- Volunteering in order to lose weight; alcohol or drug abuse, significant mental or
emotional problems such as would interfere with compliance (as assessed by study
staff impression)