2013 Annual Report
1a.Objectives (from AD-416):
This study will test in overweight humans if the effect of regularly incorporating monosodium glutamate (MSG) into the diet prevents body weight and body fat regain following a period of moderate energy restriction and weight loss (Aim.
1)and, over this same period of post-weight loss, if the MSG intervention alters sensory response, food choice and intake. Intake will be studied under free living conditions, as well as in the lab from a self selected snack food buffet in response to stimuli known to evoke emotional eating and dietary relapse (Aim 2). To begin to understand the possible mechanisms through which MSG imparts its effects on food intake and energy balance, Aim 3 of this work is to identify changes in neural, physiological (e.g., cortisol, gut peptides), and metabolite correlates of eating behavior in response to the intervention.
1b.Approach (from AD-416):
A completely randomized design will be used to examine effects of consuming MSG in overweight (BMI 27 – 32) women (N = 48), ages 19 – 45. Refer to the study schematic below for study design. For all subjects during the first 10 weeks of the study, the goal of the weight reduction phase is to have each participant achieve a weight loss that is equivalent to 5-6% of their initial body weight. During the first week, a customized diet plan will be developed and outlined for each participant so that this degree of weight loss can be achieved within the following 9-week period. In most cases energy intake will be reduced by 500-750 kcal/day to reach this goal, depending on participant’s height and weight. We have used this approach successfully in previous studies and expect about a 5 - 6% loss of weight. After the 9 week weight loss period, two weeks will be devoted to obtaining baseline measurements before the 12-weeks of intervention. During these weeks subjects will receive a metabolic (maintenance) diet with energy intake set to maintain current body weight. All foods will be prepared, pre-portioned, and dispensed by the dietary staff of the WHNRC metabolic kitchen. Vehicle foods (no MSG) will be provided to all subjects during baseline testing. Following the baseline testing period, subjects will be randomized to a 12 week trial where subjects will supplement daily their breakfast, lunch, and dinner with provided and commonly used food and beverage items treated with MSG (N = 24) or without MSG (N = 24). Subjects will be blinded to the intervention. Two weeks will be devoted to obtaining baseline and then post-treatment measurements at the end of the 12 weeks of intervention. During these weeks subjects will receive a metabolic diet with energy intake set to maintain current body weight.
This research relates to objective 1 of the inhouse project, “Evaluate mediators of behavior change critical for adopting a healthy diet by investigating interrelationships between psychosocial stress, nutritional behavior and metabolism in humans and animal models". Salary support for a postdoctoral position was provided by a Trust Fund Cooperative Agreement between ARS and Ajinomoto USA, Inc. The postdoctoral researcher hired with this funding assisted ARS researchers to coordinate and conduct subject recruitment, enrollment, screening, and testing procedures, including brain imaging, appetite assessment, and cognitive testing.