This study tests whether chronic caloric restriction improves risk factors of longevity in humans as it is known to do in animals, by measuring a variety of factors dealing with metabolism and oxidative stress, through physical evaluations and laboratory tests.

Participants will receive dietary counseling and free medical evaluations. In addition, each volunteer will be asked to do one of the following:

1. Follow a reduced calorie diet
2. Follow a reduced calorie diet using a liquid diet
3. Increase physical activity while on a reduced calorie diet
4. Follow a standard diet.

Three separate five-day inpatient stays are required.

Inclusion Criteria:

• Resident of greater Baton Rouge area for 1 year or longer
• Men between ages 25-50
• Women between ages 25-45
• Body Mass Index (BMI) between 25-30 (never having had BMI greater than 32)
• Healthy, non-smokers with no history of cardiovascular disease, high blood pressure, diabetes, eating disorder, or major psychiatric disorder

Exclusion Criteria:

• Pregnant or breastfeeding
• Personal history of cardiovascular disease or elevated high blood pressure (higher than 160/90 mmHg)
• Abnormal electrocardiogram (EKG)
• Personal history of diabetes
• Personal history of major psychiatric disorders
• Personal history of eating disorder
• Smoking
• Exercising regularly (more than twice a week)
• Individuals with alcoholism or other substance abuse
• Post obese (never have had a BMI greater than 32)
• Regular use of medications, except oral contraceptives
• Individuals who were ever injured by a metallic foreign body which was not removed
• Individuals who wear braces on their teeth, have non-removable false teeth, or non-removable bridgework
• Individuals in occupations requiring full alertness and motor skills (airline pilots, etc.) where even a small chance of postural dizziness would be unacceptable.