The Effect of Blueberries on Enhancing Insulin Sensitivity in Humans: A Pilot Study

Inclusion Criteria: * Subjects ≥ 20 years of age. * Subjects not currently treated with diabetes medication. * Subjects with fasting blood glucose at time of screening is ≤ 110 mg/dL. * Subjects with a Body Mass Index (BMI) ≥ 32 and ≤ 45. * Written Informed Consent obtained PRIOR to performing any screening tests or study procedures. * Subjects who have glucose disposal rate ≤ 650 mg/min assessed clinically at visit 4 Exclusion Criteria: * Subjects with a prior history of Type 2 diabetes. * Women who are pregnant or who are lactating. * Women of childbearing potential who are not using an effective method of birth control, condoms with spermicidal gel or foam, contraceptive patch, are not surgically sterilized, or not at least 2 years postmenopausal. * Subjects who have type 1 diabetes. * Subjects who are currently on thiazolidinediones (rosiglitazone or pioglitazone) or who have taken these agents in the previous 12 weeks. * Subjects who are on concomitant therapy with glucocorticoids (except topical or inhalant glucocorticoids). Other medications that have an effect on glucose homeostasis (i.e. ACE inhibitors) are acceptable if they have been administered in a stable dosage during the preceding 6 months and dosage will continue unchanged during the study. * Subjects with a history or evidence of significant gastrointestinal dysfunction. * Subjects who have chronic use of laxatives or cathartics. The use of stool softeners is acceptable. Use of bulking agents, if required, should remain constant. * Subjects who are taking concomitant therapy with medications known to be nephrotoxic, such as aminoglycosides, methicillin, and cyclosporin. * Subjects who have evidence of clinically significant renal dysfunction or disease, e.g. serum creatinine \>1.5 mg/dL in males and \>1.4 mg/dL in females and/or BUN \>50 mg/dL, proteinuria of \>1 gram/day or 4+ proteinuria on dipstick urinalysis. * Subjects with clinically significant cardiovascular dysfunction and/or history (within the preceding 6 months) of significant cardiovascular dysfunction, e.g., congestive heart failure or serious arrhythmia, myocardial infarction, cardiac surgery; transient ischemic attacks or cerebrovascular accident during the preceding six months; diagnosis of symptomatic autonomic neuropathy with a history of orthostatic hypertension, syncope, or hypertension with a systolic blood pressure of ≥180 mm Hg and diastolic blood pressure ≥110 mm Hg at the time of screening visit. * Subjects who have evidence within the preceding 6 months of hepatic disease or dysfunction, e.g. AST, ALT, alkaline phosphatase or total bilirubin twice the upper limit of normal; hepatitis; jaundice; cirrhosis. * Subjects with clinically significant pulmonary, neurologic, hematologic, immunologic, neoplastic or metabolic disease. * Subjects with evidence or recurrence of malignancy within the past five years, other than excised basal cell carcinoma. * Subjects for whom surgery is anticipated during the study period. * Subjects with an history of substance abuse or alcoholism within the past 5 years, or significant psychiatric disorder that would interfere with the subject's ability to complete the study. * Subjects who have donated blood during the month prior to study entry or planned during the study. * Subjects who have participated in other studies using an investigational drug during the preceding 3 months. * Subjects who are current smokers or have smoked within the previous 6 months. No smoking will be allowed during the study. * Subjects who are allergic to blueberries. * Subjects who are lactose intolerant. * Subjects who consume and drink daily servings of berries (i.e., blueberries, strawberries, bilberries, cranberries, elderberries, and raspberries), grapes, fruit juices that contain berries and grapes, and wine more than 3 times per week. * Subjects that have had a fluctuation in body weight \>5% in the preceding 2 months. * Subjects who are taking prescription or over the counter medication or supplements for desired weight loss.