Whole grain intake beneficially affects body weight, body fat and glucose metabolism, and the investigators' previous work has shown that a high whole grain intake significantly reduced body fat in the abdominal region as measured by dual energy X-ray absorptiometry (DEXA) compared to a refined grain intake. Additional research is needed with regard to the mechanisms by which whole grains may affect visceral adiposity and the adipokines, which have been associated with risk for insulin resistance and type 2 diabetes. Therefore the proposed study aims to address these issues and in addition, includes exploratory work with adipocytes in cell culture to evaluate the effects of whole grains on adipocyte function.

Hypothesis:

There will be a greater reduction in visceral adiposity, indicators of insulin resistance (HOMA score), improvement in inflammatory status and improvement in adipokine levels after six weeks of a weight stable period and after six weeks of weight loss in subjects consuming 6-9 servings compared to 0 servings of whole grains per day.

Including whole grains as part of a heart-healthy diet has been shown to be beneficial in decreasing body weight and body fat. The beneficial effects of whole grains on body weight may be explained by the larger volume and relatively low energy density of whole grain food thus leading to increased satiation. Reducing visceral fat is of particular importance as visceral adiposity has been associated with increased risk for metabolic diseases and cardiovascular disease.

The proposed study is a randomized, 2-parallel arm controlled feeding study. Subjects will be fed one of two weight maintenance diets (refined grain and whole grain) for 6 weeks, followed by a 6 week controlled weight loss period where subjects are fed the same diets, but at a reduced calorie level, designed to elicit weight loss (~2 lbs per week). Diets for both groups will have the same nutrient profile (percent of calories from fat, protein, carbohydrates, etc.); however, the whole grain (WG) group will substitute whole grains for refined grains in their grain intake (breads, tortillas, cereals, etc.). The WG group will be expected to take in 6-9 servings of whole grains per day on both diets. Plasma endpoints will be measured at baseline and at the end of the 6-week diet periods. Blood samples also will be taken at the mid-point of each period and held for analysis if deemed appropriate after initial data is reviewed. Endo-PAT will be conducted at baseline and at the end of each diet period as well as DEXA and MRI testing.

Inclusion Criteria:

• BMI > 25 to < 42

• Waist circumference of > 40 inches for males and > 35 inches for females and having one other of the criteria for metabolic syndrome will be recruited

• In this population, we will also accept the following:

  • LDL-C < 175 mg/dL
  • HDL-C > 25 mg/dL
  • Triglycerides < 400 mg/dL

• All subjects will be required to meet one specific criteria for metabolic syndrome beyond increased waist circumference

Exclusion Criteria:

• Smokers
• Have insulin-dependent diabetes
• Are pregnant or expecting to be pregnant, lactating in the last 6 months
• Are taking NSAIDS or other medications known to affect inflammatory markers or drugs affecting glucose metabolism

Blood pressure lowering medications are acceptable if the person has controlled BP at screening, <140/90 mmHg.