The paper describes the application of user-centred design (UCD) methods to a case study of the development of visual decision support tools to support epidemiological research. Understanding the causes of obesity requires analysis of complex medical surveys and geographic information. Translating research on obesity into effective public health measures requires collaboration between medical researchers and public health analysts. The objective of this research is to develop software tools to support medical researchers and public health analysts in collaborative investigation of obesity in children. The UCD approach consisted of scenario-based design, storyboarding and prototyping to explore design options to meet the needs of public health analysts and academic researchers. An evaluation of the prototype was carried out to assess the extent to which the medical researcher model would support public health professionals in their analysis activities. The design and evaluation of the prototype are discussed. A visualization-based research and decision-support system was implemented leading to positive evaluation results from users.