Location: Children's Nutrition Research Center
2013 Annual Report
1)confirmed genes found in other studies;.
2)localized novel genes in plausible biological pathways; and.
3)revealed novel genes of unknown function in the development of obesity. Our extensive characterization of the children and dense genotyping allowed us to find novel genetic variants associated with childhood obesity in Hispanic children. For Sub-objective 1C we plan to evaluate model energy balance in growing children to predict the obligatory changes in energy intake and/or energy expenditure and PAL required for obesity prevention. Energy balance underlying changes in body weight in growing children is poorly described. Laws of thermodynamics dictate that energy consumed in food must equal losses of energy in excreta, heat produced by metabolism, and changes in energy stores within the body. Factors that influence energy balance as a result of changes in energy intake and/or physical activity in children remain uncertain. In addition to determining the energy density of the tissue gained/lost, the means by which the energy balance is achieved must be considered. Energetic adaptations with regards to basal metabolic rate and energetic efficiency of muscular work may occur. We developed a mathematical model based on empirical data from our studies in growing children and fundamental principles of thermodynamics to predict changes in energy intake and/or energy expenditure and physical activity required for changes in body weight and composition. We introduced the first quantitative model of energy balance dynamics that accounts for normal growth and development of obesity in children. The model can be used to assess the effect of diet and physical activity interventions on the body weight and composition of children. Sub-objective 2.C was modified during FY13. While we had achieved the milestones for sub-objectives 2.A and 2.B, the pilot data gathered to support improvement in children's weight status in order to initiate sub-objective 2.B was not robust enough to warrant evaluating the intervention in a larger trial. For this reason, sub-objective 2.C will not be carried out. Our new objectives are focused on children's physical activity (PA), a key behavioral target for obesity interventions. Although our pilot intervention failed to confirm improvements, we believe that inaccurate assessments of children's PA through self-report can lead to imprecise estimates of PA and thereby underestimate its contribution in obesity interventions. The new sub-objective aims to correct inaccurate self-report assessment, using new technology now available to address this problem. PA has many determinants including the physical and social environment in which children are raised. Advances in technology, such as the Personal Activity Location Measurement System (PALMS) developed by scientists at the University of California, San Diego (https://palms.ucsd.edu:8443/PALMS/) now allows processing of time stamped location (GPS) and accelerometer data that can determine the location of PA and sedentary time. The current algorithms have been established for other geographic locations (San Diego, CA) in adults. Different angles of the satellites, fewer tall buildings, and no mountains could require different algorithms for processing this data in Houston; therefore they need to be validated for use with children in Houston. Utilizing these tools to investigate young children's PA will allow more precise understanding of their normal PA and identify social (such as parenting) and environmental influences on children’s PA that can be targeted to increase young children's PA and thereby improve their weight status. To this end, the following new sub-objectives were proposed for the last 24 months to address NP Action Plan Problem Statement: 3B, Develop and Evaluate Strategies to Prevent Obesity and Related Diseases: 2.C Assess the accuracy, sensitivity, and specificity of established algorithms in PALMS to identify a trip, mode of trip (pedestrian or vehicle), and indoor versus outdoor location in Houston, TX, using established validation studies. 2.D Pilot test protocols for simultaneously collecting location (GPS) and physical activity (accelerometer) data on preschool-aged children, and verify their trip and location data with parent-reported diaries of child activity and location. Objective 2.C: We have completed 30 trips by three staff members using established protocols by the University of San Diego group, collecting GPS data with QStarz GPS Dataloggers at 5-, 15-, and 30-second intervals, physical activity data using accelerometers, and staff-recorded activities and trips via established self-report diaries. The data have been processed using the PALMS system to identify indoor/outdoor time, trips, and mode of transportation. Analysis for sensitivity, specificity, and other accuracy are currently under way. Objective 2.D: We recruited and successfully collected GPS and accelerometer data on 15 Hispanic preschool children for a 24-hour period. Simultaneously, the parents complete a location and travel diary for the children. Data were processed using the Personal Activity Location Measurement System (PALMS) and location, trips and mode of transportation compared between the PALMS output and diaries. Children successfully wore the GPS data loggers and accelerometers simultaneously, 12 of which yielded data that met quality standards. The average percent correspondence between GPS- and diary-based estimates of types of location was high and statistics were moderate to excellent, ranging from 0.49 to 0.99. The simultaneous use of GPS and accelerometers to assess Hispanic preschool children's location and physical activity was deemed feasible. This methodology has the potential to provide more precise findings to inform environmental interventions and policy changes to promote physical activity among Hispanic preschool children. These results have been published and summarized.