The prevalence of obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) continues to rise. Physical activity (PA) guidelines for health are often prescribed in an effort to reduce physical inactivity and improve health in overweight adults at risk of T2DM and CVD. However, freeliving individuals struggle to regulate PA intensity. Primarily this research aims to examine the effects of walking on T2DM and CVD risk in overweight adults with intermediate hyperglycaemia (IHG). A pilot study (Appendix 1) was undertaken to investigate the usefulness of 13C stable isotope as a method of assessing glucose disposal in this population; as results did not support this methodology it was not explored further within the thesis. The systematic review (Study 1; Chapter Four) highlights that aerobic exercise, particularly walking, is an effective method of reducing T2DM and CVD risk in overweight adults. Study 2 (Chapter Five) uses objective accelerometer data to identify ambulatory activity habits of a cohort of overweight IHG adults from Northern Ireland. Study 2 highlights this population spend the majority of time in sedentary-to-light-intensity activity, do not meet current PA guidelines and concluded that time spent in sedentary activity is significantly correlated with two-hour glucose concentration. Study 3 (Chapter Six) assessed the ability of overweight IHG adults to regulate their walking intensity to self-selected music with a predetermined tempo. Results proved this is a useful method to help this population regulate their walking intensity. This study also found that using music with a predetermined beat helps adults to attain at least moderate intensity walking. Study 4 (Chapter Seven) concluded that a novel walking intervention (music with a predetermined beat using a mobile application) with behaviour change support was not more effective than usual care for improving glycaemic control in overweight IHG adults. This nine month study found significant improvements in perceived quality of life and flow mediated dilation (FMD), however this latter result should be cautiously accepted. Future research incorporating greater sample sizes should investigate if this novel intervention achieves statistical significance in various parameters as primary outcome measures.