Associations of Sedentary Time with Fat Distribution in a High-Risk Population.

Purpose. The effect of sedentary behaviour on regional fat deposition, independent of physical activity remains equivocal. We examined the cross-sectional associations between objectively measured sedentary time and markers of regional fat distribution (heart, liver, visceral, subcutaneous and total body fat) in a population at a high risk of type 2 diabetes mellitus (T2DM). Methods. Participants were recruited from primary care to two diabetes prevention programmes. Sedentary time (<25 counts per 15 seconds) was measured using Actigraph GT3X accelerometers. Heart, liver, visceral, subcutaneous and total body fat were quantified using magnetic resonance images (MRI). Fat volumes were calculated by multiplying the crosssectional areas of the fat-containing pixels by the slice thickness. The liver fat percentage was measured using a representative region of interest created in the right lobe of the liver avoiding the main portal veins. Linear regression models examined the association of sedentary time with markers of regional fat deposition. Results. Sixty-six participants (age = 47.9±16.2 years; male = 50.0%) were included. Following adjustment for several covariates, including glycaemia, whole body fat and moderate-to-vigorous physical activity (MVPA), each 30 minutes of sedentary time was associated with 15.7cm3 higher heart fat (p=0.008), 1.2% higher liver fat (p=0.026) and 183.7cm3 higher visceral fat (p=0.039). Conclusion. This study provides new evidence suggesting that objectively measured sedentary behaviour may have an independent association upon heart, liver and visceral fat in individuals at a high risk of T2DM.