Background: Glucose concentrations in a fasted and during a glucose challenged state rely on different mechanisms for regulation. In a fasted state, hepatic regulation of glucose is important; while in a glucose challenged state, muscle glucose disposal becomes more important. Evidence suggests that physical activity of moderate or higher intensities can increase muscle glucose disposal during an insulin-stimulated state, but has less effect on hepatic insulin sensitivity. The purpose of this study was to examine the associations between glucose concentrations (fasting and after an oral glucose ingestion) and minutes of physical activity at moderate- and vigorous-intensity in a large population.
Methods: The sample included 2,807 adults (47.4% male and 52.6% female) aged 18-80 years who participated in the National Health and Nutritional Examination Surveys (NHANES) from 2013-2014 and who did not take any diabetic medications. Minutes being physically active at moderate- and vigorous-intensities during work, and recreationally, were collected using the Physical Activity Questionnaire, which was based on the Global Physical Activity Questionnaire. Moderate-intensity physical activity was defined as any activity that caused a small increase in breathing or heart rate, while vigorous-intensity physical activity was defined as large increases in breathing or heart rate. Both intensities had to be performed for a minimum of 10 continuous minutes. Plasma glucose concentrations at fasting and 2 hours after consumption of a drink containing 75g glucose (2-hour glucose) were determined. Pearson product correlations were performed for analysis.
Results: The population had 141±133 (mean±SD) minutes of moderate-intensity physical activity during work and 63±56 minutes recreationally, as well as 174±156 minutes of vigorous-intensity physical activity during work and 77±56 minutes recreationally. Minutes of vigorous-intensity physical activity performed during work was associated with 2-hour plasma glucose concentrations (r=0.15; p=0.045); this association was not affected after adjusting for age, race, and sex (p=0.049), but was no longer significant after BMI was also adjusted (p=0.059). Recreational or total minutes of vigorous-intensity physical activity, and moderate-intensity physical activity was not associated with 2-hour glucose (p>0.20). Additionally, none of the physical activity minutes was associated with fasting glucose (p>0.27).
Conclusion: Self-reported vigorous-intensity physical activity during work was positively associated with 2-hour glucose, but not fasting glucose. The results are surprising. Further studies with objective physical activity measures are needed to examine the associations with fasting and 2-hour glucose.