The study is to examine the effect of four diets differing in glycemic index and amount of carbohydrate on blood sugar and insulin and in hunger, satiety, and vigor.

The extent to which a food raises blood sugar after its consumption is ranked using the Glycemic Index (GI). Foods with a high GI are those taht cause a large and rapid rise in blood sugar while those with a low GI produce small fluctuations in blood sugar. It is believed that low GI foods are advantageous for health since the swings in blood sugar and insulin resistant or diabetic. Interestingly, some studies suggest that low GI food make you less hungry and that this may play an important role in body weight regulation.

Inclusion Criteria:

• Body Mass index between 25-35 kg/m2
• Fasting serum glucose
• Fasting serum glucose < 125 mg/dl
• Free of chronic disease
• Willing to eat only the foods that are provided by the Center during the diet periods
• Willing to abstain from the consumption of alcohol during the diet periods
• Regularly cycling and willing not to become pregnant using birth control (abstinence, barrier methods, partner surgically sterile
• Monophasic birth control (same dose each day)
• Hormone replacement therapy
• Post-menopausal (over 1 year without bleeding)
• Have had partial hysterectomy over the age of 55
• complete hysterectomy at any age

Exclusion Criteria:

• Documented presence of atherosclerotic disease
• Diabetes mellitus
• Renal, hepatic, endocrine, gastrointestinal, hematological or other systemic disease
• Body Mass Index <25 or > 35
• History of drug or alcohol abuse in the last year
• For women, pregnancy, breast feeding or postpartum < 6 months
• History of depression or mental illness requiring treatment or medication within that last 6 months
• Multiple food allergies or significant food preferences or restrictions that would interfere with diet adherence
• Lifestyle or schedule incompatible with the study protocol
• Planned continued use of dietary supplements through the study trial
• Smoking or tobacco use