Background

Little is known about the association of objectively measured temporal patterns of sitting (i.e., how sitting is distributed across time) with obesity indicators. We aimed to investigate the extent to which temporal patterns of sitting (time spent in long, moderate and brief uninterrupted sitting periods) are associated with obesity indicators (body mass index (BMI), waist circumference and fat percentage), independently from moderate-vigorous physical activity (MVPA) and total sitting time among blue-collar workers.

Methods

Workers (n=205) wore Actigraph GT3X+ accelerometers on the thigh and trunk for 1-4 working days. The time-line of sitting on working days was computed using the validated Acti4 software. Total sitting time and time spent sitting in brief (≤5 mins), moderate (>5 and ≤30 mins), and long (>30mins) periods were determined for the whole day, and for leisure and work separately. Obesity indicators, i.e. BMI (kg/m2), waist circumference (cm) and fat percentage were objectively measured. Associations between duration of sitting periods and each obesity indicator were determined using linear regression analysis adjusted for several potential confounders including objectively measured MVPA and total sitting time.

Results

Sitting time in brief periods was negatively associated with obesity indicators for the whole day (BMI, P<0.01; fat percentage, P<0.01; waist circumference, P<0.01) and work (BMI, P<0.01; fat percentage, P<0.01; waist circumference, P<0.01), but not for leisure time. Sitting time in long periods was positively associated with obesity indicators for the whole day (waist circumference, P=0.05) and work (waist circumference, P=0.01; BMI, P=0.04), but not for leisure time. Sitting in moderate periods was not associated with obesity indicators for any domain.

Conclusion

Time spent in brief and long periods of sitting during the whole day and at work were inversely associated with obesity indicators when adjusting for MVPA and total sitting time, while sitting during leisure time did not show these associations. Thus, the temporal distribution of sitting seems to influence the relationship between sitting and obesity.