Predictors of the acute postprandial response to breaking up prolonged sitting

Purpose
To identify predictors of favorable 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 randomized acute cross-over trials (n = 129; body mass index [BMI] range, 19.6–44.6 kg·m−2; South Asian = 31.0%; dysglycemia = 27.1%). Treatments included: prolonged sitting (6.5 h) or prolonged sitting broken-up with either standing or light-intensity physical activity (5 min every 30 min). Time-averaged postprandial responses for insulin and glucose were calculated for each treatment (mean ± 95% confidence interval). Mutually adjusted interaction terms were used to examine whether anthropometric (BMI), demographic (age, sex, ethnicity [white European vs South Asian]) and a cardiometabolic variable (Homeostatic Model Assessment of Insulin Resistance)-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 (−18.9 mU·L−1 [−23.5%] vs −8.2 mU·L−1 [−9.3%]), female compared with male (−15.0 mU·L−1 [−21.2%] vs −12.1 mU·L−1 [−17.6%]) or had a BMI ≥27.2 kg·m−2 (−20.9 mU·L−1 [−22.9%] vs −8.7 mU·L−1 [−18.2%]). Similarly, being female (−0.4 mmol·L−1 [−0.6 mmol·L−1, −0.2 mmol·L−1], −6.8% vs –0.1 mmol·L−1 [−0.3 mmol·L−1, 1 mmol·L−1], −1.7%) or having a BMI ≥27.2 kg·m−2 (−0.4 mmol·L−1 [−0.6 mmol·L−1, −0.2 mmol·L−1], −6.7% vs –0.2 mmol·L−1 [−0.4 mmol·L−1, 0.0 mmol·L−1], −3.4%) modified the postprandial glucose response. No significant interactions were found for Homeostatic Model Assessment of Insulin Resistance or age.

Conclusions
Being female, South Asian, or having a higher BMI, all predicted greater reductions in postprandial insulin, whereas 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 personalized interventions in high-risk participants for whom breaking prolonged sitting time with light activity may yield the greatest therapeutic potential.