2011 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.
Two studies were conducted during FY2011 in cooperation with colleagues at George Washington University and the U.S. Army Institute of Environmental Medicine. These studies examined the impact of a diet and exercise intervention on glucose regulation and whole body carbohydrate, fat, and protein oxidation in both young and elderly men and women. A third study entitled “Metabolic Flexibility as a Biomarker of Adaptation to Diet and Exercise Challenges” has been planned and submitted to the IRB at MedStar Research Institute. These studies examine 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 interventions. They also provide continuous real time data on glucose and substrate oxidation levels needed in the development of mathematical models to predict substrate utilization.
Included in this project is the participation of the Beltsville Human Nutrition Research Center in the HEALTH (Healthy Eating and Lifestyle for Total Health) Study. During FY2011, new personnel were hired to assist in the study, a new IRB protocol was submitted to and approved by the Johns Hopkins University Institutional Review Board, volunteers recruited, and procedures developed for completing the second Phase I of the protocol, the pilot study. BHNRC is responsible for completing pilot studies on 67 African American and 67 Caucasian-American dyads (fifth-graders and their caregivers). As of the end of FY2011, testing of over 60 child-caregiver dyads has been completed for the pilot study. This is part of an ARS multi-site study conducted among 5th grade children and their caregivers to develop a survey instrument to be used for the Phase II of the final study.
Diabetes has become a significant health problem in the United States. This disease is a consequence of dysregulation of glucose metabolism. This work has demonstrated the clear influence of exercise on the ability of an individual to maintain a stable glucose level over an entire day. This is significant because it is widely recognized that many of the adverse consequences of diabetes are due to high levels of circulating glucose for significant periods during the day.