Location: Food Components and Health Laboratory2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Determine the role of carbohydrates, including whole grain sources, protein, and fat and their interaction with physical activity on food intake and energy metabolism. Sub-Objective 1.A: Evaluate the influence of dietary macronutrient composition—specifically, on the role of complex carbohydrates (including whole grains) on metabolic flexibility, insulin sensitivity, and energy balance. Sub-Objective 1.B: Determine the extent to which the day-to-day variation in daily voluntary food intake is related to the variability in physical activity and changes in physiological and metabolic factors related to energy balance, satiety and hunger, and the extent to which these are modified by whole grain consumption. Sub-Objective 1.C: Identify behavioral and social influences on food intake and selection. Objective 2: Develop mathematical models relating blood glucose kinetics to whole body substrate oxidation. Sub-Objective 2.A: Determine the effect of physical activity, gender and age on postprandial and 24-h substrate oxidation and glycemic control. Sub-Objective 2.B: Develop predictive models and algorithms for existing ambulatory physiological monitoring systems to estimate real-time blood glucose and substrate oxidation based on continuous estimates of energy expenditure and duration and intensity of physical activity.
1b. Approach (from AD-416):
Acute and long-term controlled human studies will evaluate the effects of various macronutrients, including consumption of whole grains, on metabolic flexibility and risk factors observed with excess weight. Overweight/obese (body mass index [BMI] >27) and control (normal weight, BMI <25) adult individuals will be chosen from the diverse population with special interest in groups identified to be at high risk for obesity. Intervention studies in which intake is either controlled or ad libitum will be undertaken, with samples collected periodically. Measurements would be made during weight loss and weight maintenance periods in overweight subjects. Measurements will be made for markers of glycemic control, energy regulation, and lipid metabolism, blood pressure, body composition, measures of satiety, and energy expenditure, as well as the effect of physical activity on metabolic flexibility. In an effort to better understand macronutrient metabolism, mathematical modeling techniques will be used to estimate substrate oxidation from glucose monitoring techniques. In addition, a study evaluating factors perceived as influencing adherence to current Dietary Guidelines will be continued.
3. Progress Report:
Progress was made for both objectives of this National Program 107 plan, focusing on Component III on the Prevention of Obesity and Related Diseases. Progress has been made Problem Statement 3A: Understand the Causes and Consequences of Obesity and Related Disorders and Problem Statement 3B: Develop and Evaluate Strategies to Prevent Obesity and Related Diseases through studies on whole grains and exercise. To investigate the role of whole grains in modulating blood glucose, a clinical intervention study was conducted and data analysis was completed. Consumption of whole grains are purported to support a healthy body weight, reduced incidence of diabetes, promote GI health, and reduce cardiovascular (CVD) risk. However, clinical studies supporting these benefits have been inconclusive. To investigate the role of whole grains in modulating glucose response, we conducted a double blind, crossover, randomized controlled trial with 3 treatments: whole grain oats, whole grain barley, and refined wheat flour (as a control). Volunteers were enrolled, and all 18 volunteers completed the intervention. After 3 days of controlled feeding, volunteers consumed a treatment diet that contained whole oats, whole barley or a refined wheat control diet. Blood samples were collected immediately before and for 7 hours after consuming the treatments. Whole grain compared to refined grain consumption did not change blood glucose or insulin. To investigate the role of whole grains in reducing CVD risk, we conducted a double blind, parallel arm, randomized controlled trial for 6 weeks with 3 treatments: whole grain oats, whole grain barley, and refined wheat flour (as a control) providing 4, 4, and 0.7 servings/day of whole grain at 1800 kcal, respectively. Volunteers were enrolled, and 68 completed the intervention. Volunteers consumed a controlled diet at weight maintenance for 6 weeks, with the base diet being the same across treatments, and cereal and crackers incorporated as treatment foods. After 6 weeks, we found improvement in cholesterol markers for coronary heart disease (LDL cholesterol-to-HDL cholesterol ratio) as well as improvement in blood pressure. A study was completed with women and men examining the impact of intensity and duration of exercise on glucose regulation and substrate oxidation. Each participant completed 4-24h measures in a room calorimeter. Exercise treatments were either high intensity, short duration or low intensity and long duration. Data are currently being summarized and analyzed. A second study was initiated that examines the interaction of the consumption of meals containing predominantly fat, carbohydrate, or protein following either high intensity/short duration or low intensity/long duration exercise.