Sitting for prolonged periods can increase the risk of diabetes and other health problems. While physical activity recommendations suggest breaking up sitting time, it is not known if all individuals respond the same way. Therefore, investigators examined whether an individual’s age, ethnicity, sex or body mass index (BMI – a weight to height ratio) influenced the response to breaking up prolonged sitting. Participants from the United Kingdom (129 men and women, average age of 64) took part in a 6.5-hour protocol where they either sat continuously, broke up sitting every 30 minutes with five minutes of standing, or broke up sitting every 30 minutes with five minutes of slow walking. Only the slow walking group had lower sugar and insulin levels following a meal than the continuous sitting group. Reductions were larger if individuals were South Asian (compared with white European), female or had a higher BMI. These results may be used to help tailor interventions for breaking up sedentary time in individuals that may benefit the most. Future studies should address whether these effects persist over longer time periods.