PROJECT SUMMARY/ABSTRACT Nearly one in five 2-5 year old U.S. children has obesity, and over half of today’s children are expected to have obesity by adulthood. Failure to prevent childhood obesity thus puts a majority of our children at increased risk of diet-related chronic diseases including type II diabetes mellitus. Early childhood is critical for the formation of habits for eating, physical activity, and other behaviors that contribute to a healthy weight, yet diet in early childhood is currently poor. A promising public health approach to establishing healthy eating habits in early childhood is through strengthening the nutrition standards of the Child and Adult Care Food Program (CACFP), a federal food assistance program that reaches millions of young children attending child care settings in the US. CACFP standards for meals served were recently updated, but incomplete implementation has weakened the impact of this policy change. Identification of a strategy to improve implementation could help to ensure that the intended policy improvements to CACFP translate into improved child health. This study proposes to first collect novel data the implementation challenges that child care providers face in adopting healthier eating standards. Then, using this formative research, we will develop an implementation intervention to help child care centers adopt stronger CACFP nutrition standards. The efficacy of the intervention will be pilot-tested by conducting a cluster-randomized, controlled trial at the child care center level. Lastly, the study will collect qualitative data on the process of the implementation intervention and quantitative data on costs. The NIDDK K01 Mentored Research Scientist Development Award will help fill critical training gaps in 1) dissemination and implementation science and 2) cost analysis, and will build on my advanced training in intervention evaluation and social epidemiology. My long-term career goal is to develop a robust research program that uses strategic science to inform effective policy development and policy implementation, to prevent nutrition-related chronic diseases at a population level. The training plan involves coursework in implementation science and cost analysis, combined with structured mentoring, meetings, workshops, and seminars, to establish new skills in these areas. The research plan proposed will allow me to apply these new skills and build on my existing skill set. The combined training and research plan, with the strong institutional support and excellent intellectual environment of the Harvard T.H. Chan School of Public Health, will ensure my transition into an independent researcher able to compete successfully for R01 funding and help me develop into a leader in the field of public health approaches to improving child nutrition and preventing later diet-related chronic diseases.