Duke Medicine HealthLine
Published: Nov. 26, 2007
Updated: May 7, 2010
Fighting the Sedentary Sickness
Just when you think your life can’t become any more automated, Starbucks installs a drive-through window. We can collect our venti lattes from our cars and then cruise across the street to idle at another drive-through -- this one’s the drugstore. All this and we haven’t even gotten to our McBreakfast sandwich yet. The result? On some days, the most exercise many people get is rummaging through the sofa cushions in search of the remote control.
If exercise is good for you, then no exercise is likely bad for you. But until recently it wasn’t clear just how bad for you it is. Now the evidence is in, and it turns out that sitting still is a downright dangerous thing to do. According to results from a Duke-led study, sedentary living is so dangerous that it is simply not an option for long-term health.
The STRRIDE study measured important health markers in the blood of people who were inactive, moderately active, and vigorously active. “What really surprised us,” says Duke exercise physiologist Cris Slentz, PhD, “is just how much worse the health measures got in the inactive group. Anything bad that could happen to a cholesterol molecule happened.” The inactive group showed an array of worsening risk factors for heart disease, from weight gain to rising bad cholesterol and blood sugar levels.
The good news is that it really doesn’t take much to undo this sedentary sickness. The American Heart Association currently recommends a half-hour of moderately intense exercise (such as brisk walking) on most days, or 20 minutes of vigorous exercise three times a week. And according to the STRRIDE study, even less than that is still a good start. “Just walking four to seven miles a week can stabilize many of these risk factors,” says Duke cardiologist William Kraus, MD. “It takes remarkably little.”
In some measures of health, those in the moderate intensity exercise group actually did better than the vigorous intensity group. “On the surface, it seems to make sense that the harder we exercise, the better off we’ll be,” says Slentz. “But our studies show that a modest amount of moderately intense exercise is the best way to significantly lower the level of triglycerides, which are a key blood marker linked to higher risk of heart disease and diabetes. More intense exercise doesn’t seem to do that.”
Slentz says a possible explanation for this surprising finding comes from how our bodies burn fuel during different types of exercise. “If you walk three miles versus jog three miles, the person jogging will use a lot of carbohydrates (in the form of glucose) for energy. The person walking will get more of their energy from fat.” Triglycerides are particles of fat that the body uses for energy, so during low-intensity exercise, more triglycerides are used for energy than are during high-intensity exercises.
“These triglyceride levels stayed low even two weeks after the study’s workouts ended,” says Kraus, whereas longer, more intense workouts didn’t have nearly the same impact. “And a proper exercise program can lower a person’s insulin resistance in a matter of days.”
“There are some experts who think vigorous exercise is necessary -- and it may be,” says Slentz. “But the point is not to get too caught up in worrying about what to do or when to do it. The important thing is to get out there and move.”