There is a large body of observational data showing strong associations between time spent engaged in sedentary behaviour and a number of adverse health outcomes, including mortality, cardiovascular disease, type 2 diabetes and obesity. These often persist after adjustment for time spent in moderate-to-vigorous physical activity, although our recent data suggests that association between sedentary time and adverse health outcomes may be attenuated in those with high levels of physical activity and/or high functional capacity. There is also observational evidence to suggest that individuals who break up sedentary time more frequently have a more favourable cardio-metabolic risk profile – particularly with respect to adiposity variables – than those who habitually engage in prolonged periods of uninterrupted sedentary time, independent of total time spent sedentary. Recent data from lab-based studies have shown that breaking up periods of prolonged sitting with short walking breaks, elicits reductions in postprandial glucose, insulin and triglyceride responses. Studies evaluating the effects of breaking up sitting with static standing on these postprandial blood responses have had more mixed results, with reductions in postprandial glucose and insulin responses observed in older women with impaired glucose regulation, but no clear changes in younger normoglycaemic adults. Our recent data suggests that increasing the frequency of breaks in sedentary time, independent of total time spent sitting, increases energy expenditure and fat oxidation, which provides an explanation for the association between frequency of sedentary breaks and adiposity observed in the epidemiological data.