Prolonged Sitting May Undo Exercise Benefits

Here’s some less-than-good news for weekend warriors. Findings from a small study suggest that sitting throughout the day may alter the typical metabolic benefits of a bout of exercise. Whether sitting for endless hours daily is hazardous to our health because we’re not exercising or whether the health risks of sitting may be counteracted by exercise are questions to which scientists continue to tease out answers. University of Texas at Austin researchers designed a study to shed some light.

Investigators recruited 10 healthy, recreationally active men and women ages 20–28. All subjects participated in 4 days of mostly sitting with no exercise, followed by a fifth morning with a high-fat, high-sugar breakfast shake. After a break, the same subjects then repeated 4 days of mostly sitting but with the addition of 1 hour of vigorous-intensity treadmill exercise on the night of the fourth day, again followed by the same breakfast shake. On each fifth morning, after the breakfast shake, investigators measured blood lipids, glucose and insulin.

Biomarker analysis showed that the 1-hour bout of vigorous exercise failed to improve the next morning’s metabolic responses after the heavy meal, not the expected result after acute exercise. The typical expectation is that exercise—particularly high-intensity exercise—mitigates the elevation of fats in the bloodstream after a meal, while also improving glucose tolerance and insulin sensitivity. The lack of this typical response is characterized by researchers as a type of “exercise resistance” induced by prolonged sitting or other sedentary behavior.

“People seem to become resistant to the normal metabolic benefits of acute aerobic exercise after prolonged inactivity. This may indicate that someone who sits throughout the week and chooses to exercise on the weekend may not derive the full health benefits of the exercise, particularly regarding improved fat metabolism,” the study authors noted.

The report appeared in the Journal of Applied Physiology (2019; oi:10.1152/japplphysiol.00968.2018).