Sedentary time not linked to lower liver fat content, reduced insulin resistance
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Study results published in Diabetologia found no association between the number of daily sedentary time breaks and lower liver fat content or reduced insulin resistance.
“Previous studies have shown that exercise is associated with reduced liver fat content and consequent improvement in insulin sensitivity,” Jeroen H. P. M. van der Velde, MD, from the department of clinical epidemiology at Leiden University Medical Center in the Netherlands, and colleagues wrote. “Therefore, we hypothesized that breaks in sedentary time may reduce liver fat and insulin resistance, ultimately preventing type 2 diabetes.”
Using data from 775 participants (mean age, 56 years; 42% men) from the Netherlands Epidemiology of Obesity study, researchers evaluated sedentary time, breaks in sedentary time and different physical activity intensities. All participants wore activity sensors, and researchers assessed liver fat content through magnetic resonance spectroscopy for 256 participants. All participants were categorized according to timing of most of their physical activity: morning between 6 a.m. and noon (16%), afternoon between noon and 6 p.m. (63%), evening between 6 p.m. and midnight (8%) or as engaging in moderate to vigorous physical activity evenly throughout the day (13%).
Researchers also analyzed associations between sedentary time, breaks and timing of moderate to vigorous physical activity with liver fat content and homeostatic model assessment for insulin resistance (HOMA-IR).
In the cohort, mean BMI was 26.2 kg/m2, median liver fat content was 2.6% and median HOMA-IR was 1. Overall, total sedentary time was not associated with liver fat content or insulin resistance. However, 10 daily sedentary time breaks vs. no breaks was associated with 22% higher liver fat content; the researchers attributed this finding to small sample size.
Total moderate to vigorous physical activity and timing of moderate to vigorous physical activity were both associated with reduced insulin resistance, but not liver fat content. Compared with those with an even moderate to vigorous physical activity distribution throughout the day, researchers observed similar insulin resistance of –3% among participants who were most active in the morning. In addition, insulin resistance reduced by –18% and –25% among participants who were most active in the afternoon or evening, respectively.
“In contrast to our hypothesis, a lower amount of sedentary time or more breaks in sedentary time were not associated with reduced liver fat content or insulin resistance,” the researchers wrote. However, the other findings from the study “suggest that timing of physical activity throughout the day is relevant for the beneficial effects of physical activity on inulin sensitivity.”
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