Predictors of the acute postprandial response to breaking up prolonged sitting

Purpose
To identify predictors of favourable changes to postprandial insulin and glucose levels in response to interrupting prolonged sitting time with standing or light intensity physical activity.
Methods
Data were combined from four similarly designed randomised acute cross-over trials (n=129; BMI range 19.6 to 44.6kg/m2; South Asian=31.0%; dysglycaemia=27.1%). Treatments included: prolonged sitting (6.5hours) or prolonged sitting broken-up with either standing or light-intensity physical activity (5 minutes every 30 minutes). Time-averaged postprandial responses for insulin and glucose were calculated for each treatment (mean±95% CI). Mutually adjusted interaction terms were used to examine whether anthropometric (BMI), demographic (age, sex, ethnicity (white European vs. South Asian)) and a cardiometabolic
variable (HOMA-IR) modified responses.
Results
Postprandial insulin and glucose were reduced when individuals interrupted prolonged sitting with bouts of light physical activity, but not with standing. Reductions in time-averaged postprandial insulin were more pronounced if individuals were South Asian compared with white European (-18.9mU/L (-23.5%) vs. -8.2mU/L (-9.3%)), female compared to male (-15.0mU/L (-21.2%) vs. -12.1mU/L (-17.6%)) or had a BMI ≥27.2kg/m2 (-20.9mU/L (-22.9%) vs. -8.7mU/L (-18.2%)). Similarly, being female (-0.4mmol/L (-0.6mmol/L, -0.2mmol/L) (-6.8%) vs. –0.1mmol/L (-0.3mmol/L, 1mmol/L) (-1.7%)) or having a BMI ≥27.2kg/m2 (-0.4mmol/L (-0.6mmol/L, -0.2mmol/L) (-6.7%) vs. –0.2mmol/L (-0.4mmol/L, 0.0mmol/L) (-3.4%)) modified the postprandial glucose response. No significant interactions were found for HOMA-IR or age.
Conclusion
Being female, South Asian or having a higher BMI, all predicted greater reductions in postprandial insulin, while being female and having a higher BMI predicted greater reductions in postprandial glucose when sitting was interrupted with light physical activity. These results could help to guide personalised interventions in high-risk participants for whom breaking prolonged sitting time with light activity may yield the greatest therapeutic potential.