Look AHEAD: Action for Health in Diabetes (LookAHEAD)

Inclusion Criteria: Type 2 diabetes Overweight BMI of 25 kg/m2 or greater If on insulin, BMI of 27 kg/m2 or greater Blood pressure less than 160/100 mmHg HbA1c less or equal to 11% Triglycerides less than 600 mg/dl Willingness to participate Exclusion Criteria: Unable or unwilling to give informed consent or communicate with local study staff. Current diagnosis of schizophrenia, other psychotic disorders, or bipolar disorder. Hospitalization for depression in past six months. Self-report of alcohol or substance abuse within the past twelve months. Current consumption of more than 14 alcoholic drinks per week. Current acute treatment or rehabilitation program for these problems. Plans to relocate to an area not served by Look AHEAD or travel plans that do not permit full participation in the study. Lack of support from primary care health provider or family members. Failure to complete the two-week run-in for dietary intake and exercise. Weight loss exceeding 10 lbs. in past three months. Current use of medications for weight loss. Self reported inability to walk two blocks. History of bariatric surgery, small bowel resection, or extensive bowel resection. Chronic treatment with systemic corticosteroids. Another member of the household is a participant or staff member in Look AHEAD. Currently pregnant or nursing. Cancer requiring treatment in the past five years, except for non-melanoma skin cancers or cancers that have clearly been cured. HIV positive (self-report), due to effects on weight and body composition of HIV and medications used to treat HIV. Active tuberculosis (self-report). Cardiovascular disease (heart attack or procedure within the past three months). Participation in a cardiac rehabilitation program within last three months. Stroke or history/treatment for transient ischemic attacks in the past three months. Pulmonary embolus in past six months. Unstable angina pectoris or angina pectoris at rest. A history of cardiac arrest. Complex ventricular arrhythmia at rest or with exercise (e.g., ventricular tachycardia). Uncontrolled atrial fibrillation (heart rate of 100 beats per minute or more). New York Heart Association (NYHA) Class III or IV congestive heart failure. Acute myocarditis, pericarditis or hypertrophic myocardiopathy. Clinically significant aortic stenosis. Left bundle branch block or cardiac pacemaker unless evaluated and cleared for participation by a cardiologist. Cardiac defibrillator. Heart transplant. History of aortic aneurysm of at least 7 cm in diameter or aortic aneurysm repair. Resting heart rate less than 45 beats per minute or greater than 100 beats per minute. Any abnormality during the maximum exercise stress test that indicates that it would be unsafe to participate in the Lifestyle Intervention. Angina pectoris. Significant ST segment depression at low levels of exercise. (ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave) Exercise induced ventricular arrhythmias. Abnormal hemodynamics, such as flat or decreasing systolic blood pressure with increasing workload. Those at moderate to high risk for cardiac complications during exercise. Those who are unable to self-regulate activity or understand the recommended activity level. Renal disease or dialysis. Chronic obstructive pulmonary disease that would limit ability to follow the protocol. Self-reported chronic hepatitis B or C or cirrhosis. Inflammatory bowel disease requiring treatment in past year. Cushing's syndrome. Acromegaly. Amputation of lower limbs as result of non-traumatic causes. Any major organ transplant.