This document summarizes an interdisciplinary research project on obesity in Ireland. The project uses a lifecourse approach, drawing on data from multiple Irish cohort and cross-sectional studies spanning different age groups. The aims are to describe risk factors for obesity, cardiovascular disease, and diabetes over the lifecourse and relate these to health outcomes. The research team includes investigators from the various studies as well as experts in biostatistics, epidemiology, health services, nutrition, and clinical areas. Work packages will investigate health service utilization across the lifecourse, statistical methods for accelerometer data, and relationships between diet, physical activity, and non-communicable disease risk.