The purpose of this study is to determine the effect of a slowly digesting starch on gut bacteria, sugar and fat metabolism, hunger hormones, and body fat in people with pre-diabetes.

In a double blind randomized controlled clinical trial, the investigators will test the effect of slowly digesting starch (amylose) versus a placebo starch (amylopectin) on risk factors for type 2 diabetes. For the study, about 95 obese participants (ages 35-65) with pre-diabetes (impaired fasting glucose) will consume a yogurt containing about 45 g of either the experimental or placebo starch daily for 3 months. The investigators will test the hypothesis that, compared to controls, a daily intake of 45 g of amylose for 3 months will improve risk factors for the development of type 2 diabetes (insulin sensitivity and secretion) by decreasing ectopic fat depots and decreasing inflammation in parallel with a change in colonic microbial populations.

Inclusion Criteria

• Have a body mass index between 30 and 44.9 kg/m2
• Are 35-65 years of age
• Have pre-diabetes, which means impaired fasting glucose (IFG)
• Are willing to complete nutritional and activity questionnaires and 2-3 weeks of baseline testing
• Are willing to enroll in the 3-month intervention and maintain the same level of exercise during the study
• Are willing to maintain weight throughout the study

Exclusion Criteria

• Have evidence of cardiovascular disease, diabetes, symptomatic cholelithiasis (gallstones), or cancer
• Have a fasting blood glucose less than 100 mg/dL or greater than 125 mg/dL
• Have an average screening blood pressure > 150/100 mm Hg
• Are a pre-menopausal woman but do not have a regular menstrual cycle
• Are pregnant or breastfeeding
• Chronically use medications including diuretics, steroids, and adrenergic-stimulating agents
• Have emotional problems such as clinical depression or other diagnosed psychological conditions
• Use hormonal contraceptives, oral or parenteral glucocorticoids, or any other medication known to influence glucose or insulin homeostasis (balance), within 1 month of study
• Have a clinically significant gastrointestinal malabsorption syndrome, chronic diarrhea, or use antibiotics within one month of study
• Have abnormal laboratory markers (e.g., elevated potassium levels, hemoglobin or hematocrit below the lower limit of normal)
• Chronically consume alcohol (> 4 servings per day) or actively smoke cigarettes (> 1/4 pack per day)
• Are on any chronic medication that has not had a stable dose for 1 month or longer
• Are required to perform of any kind of heavy physical activity
• Have metal objects in the body, such as a pacemaker, metal pins, bullet, etc.