During the past few decades, more jobs require people to sit at their desks for long stretches. Adults are prone to sedentary behavior at home, too, whether it be reading, watching TV or working on the computer.

All of that time sitting may lead to health risks, according to a science advisory from the American Heart Association (AHA). The statement, which was released on Aug. 15 and published online in Circulation, notes that evidence suggests sedentary behavior increases risk for cardiovascular disease and diabetes and may contribute to excess morbidity and mortality. The Obesity Society also endorsed the advisory.

Still, the researchers said there was insufficient evidence to recommend the appropriate amount of sedentary behavior to maximize cardiovascular disease health benefits.

“Given the current state of the science on sedentary behavior and in the absence of sufficient data to recommend quantitative guidelines, it is appropriate to promote the advisory, ‘Sit less, move more,’” they wrote.

The advisory pertains to U.S. adults, who sit an average of six to eight hours per day, according to the researchers. Adults older than 60 years old average 8.5 to 9.6 hours of sedentary time per day.

The researchers cited data that showed sedentary occupations constituted more than 20 percent of total U.S. jobs in 2008, up from approximately 15 percent in 1960. In addition, the average sedentary time in the U.S. increased from 26 hours per week in 1965 to 38 hours in 2009.

The committee defined sedentary behavior as “any waking behavior characterized by an energy expenditure ≤1.5 metabolic equivalents while in a sitting or reclining posture.” They defined one metabolic equivalent as “the energy expended while sitting at rest, or the standard of 3.5 mL of oxygen per kilogram of body weight per minute.”

Examples of sedentary behavior include watching TV, driving, reading or staring at a computer, cell phone or tablet screen. For this advisory, the AHA relied on self-reports from people, including questionnaires and diaries.

Deborah Rohm Young, PhD, the chair of the committee, and her colleagues recommended adults do at least 30 minutes of moderate to vigorous physical activity per day. However, even physically active adults who have too much sedentary time might be at an increased cardiovascular disease risk.

The committee suggested that observational prospective and randomized trials are necessary to identify risk factors for sedentary behaviors. They recommended the studies examine modifiable risk factors such as personal psychological characteristics to microenvironmental and macroenvironmental factors.

“There’s a lot of research that we need to do,” Young said in a news release. “This statement is important because it starts the ball rolling and suggests sedentary behavior may play an important role in heart health and more. But, it’s too early to make conclusive recommendations other than to encourage Americans to ‘sit less, move more.’”