The investigators have hypothesized that dietary flavonoids reduce insulin resistance and subclinical inflammation secondary to reductions in intestinal inflammation and permeability and that these events are mediated through alterations in gut microbiota composition. To test this hypothesis, 30 overweight/obese men and women will be provided two well-controlled diets that are identical in macronutrient content (Protein, 17% en; Fat, 30% en; Carbohydrate, 53% en), but differ markedly in flavonoid content (Low Flavonoid Diet, 10 mg/1000 Kcals; High Flavonoid Diet, 340 mg/1000 Kcals). All meals for both diets will be prepared and fed for 6 weeks each in a randomized cross-over design with endpoints determined in duplicate during the last week of each diet period.

Inclusion Criteria:

• BMI between 25 and 35 kg/m2

Exclusion Criteria:

• Documented presence of atherosclerotic disease;
• Diabetes mellitus
• Uncontrolled hypertension
• Renal, hepatic, endocrine, gastrointestinal or other systemic disease
• For women, pregnancy, breast feeding or postpartum < 6 months
• History of drug or alcohol abuse
• History of depression or mental illness requiring hospitalization within the last 12 months
• Use of antibiotics within the last 6 months
• Multiple food allergies or significant food preferences or restrictions that would interfere with diet adherence
• Chronic use of over-the-counter medication which would interfere with study endpoints including NSAIDS, laxatives and antacids
• Lifestyle or schedule incompatible with the study protocol
• Other medical, psychiatric, or behavioral conditions that in the view of the principal investigator may present a safety hazard to the participant or interfere with study participation or the ability to follow the intervention protocol.

De-identified individual data will be deposited into a public repository as the data are published.