January 19, 2010
Couch Potatoes At Risk Of Disease
Scientists reported on Tuesday that sitting all day might significantly boost the risk of lifestyle-related disease, even if one adds a regular dose of moderate or vigorous exercise.
The health benefits of pulse-quickening physical activities help ward off cardiovascular disease, diabetes and obesity, among other problems.
However, recent scientific research has uncovered that long times of sitting down may be independently linked to these same conditions.
"Sedentary time should be defined as muscular inactivity rather than the absence of exercise," concluded a team of Swedish researchers.
"We need to consider that we are dealing with two distinct behaviors and their effects," they reported in the British Journal of Sports Medicine.
Elin Ekblom-Bak of the Karolinska Institute in Stockholm, who led the research, said she and her colleagues proposed a new "paradigm of inactivity physiology," and urged fellow researchers to rethink the definition of a secondary lifestyle.
The team pointed to a recent study in Australia that found adults showing each daily one-hour increase in sitting time while watching television upped the rate of metabolic syndrome in women by 26 percent, regardless of the amount of moderate-to-intensive exercise performed.
Thirty minutes of physical exercise decreased the risk by about the same percentage, suggesting that a couch potato can cancel out the benefits of hitting a treadmill or biking.
Metabolic syndrome is when three or more factors like high blood pressure, abdominal obesity, high cholesterol or insulin resistance are present.
The scientists said new research is required to see if there is a causal link between being sedentary and these conditions.
One candidate is lipoprotein lipase (LPL), which is an enzyme that helps break down fat within the body into useable forms.
Recent studies have found that LPL activity was significantly lower in rats with restrained muscle activity, some as low as one tenth of the levels of rats allowed to walk around.
The LPL level during such activity "was not significantly different from that of rats exposed to higher levels of exercise," the scientists reported.
"This stresses the importance of local muscle contraction per se, rather than the intensity of the contraction."
They said these studies suggest that people not only need to exercise frequently, but avoid sitting in one place for too long.
The researchers recommended climbing stairs instead of using an elevator, taking five-minute breaks from a desk job, and walking when possible to do errands rather than driving.
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