"There are many important factors we don't understand about sedentary time yet," Young said. She stressed that, "the types of studies available identify trends but don't prove cause and effect."
"We don't have information about how much sedentary behavior is bad for health -- the best advice at this time is to 'sit less and move more,'" she added.
How much more? According to the AHA, people should try to get at least 30 minutes of moderate to vigorous exercise a day to reach the recommended 150 minutes of moderate exercise or 75 minutes of vigorous exercise a week.
Dr. Suzanne Steinbaum is a preventive cardiologist at Lenox Hill Hospital in New York City. She agreed that, based on the evidence, sitting is more than just a "lack of moving."
"The real risk simply comes down to the amount we sit, without there being a true antidote [such as exercise]," Steinbaum said.
Still, society has evolved to encourage sitting, she added.
"Our lives have become focused around activities requiring us to be still -- whether it be commuting or transportation, our computers, or the television or computer in our leisure time," Steinbaum said. "Sociologically, instead of being active to be productive or to have enjoyment, our productivity and fun often requires minimal exertion.'
For her part, George offered up some tips to help minimize sitting and the health dangers it may cause:
Take a one- to three-minute break every half-hour during the day to stand (which burns twice as many calories as sitting) or walk around.The new statement was published Aug. 15 in the AHA journal Circulation.
Stand or exercise while watching TV or working on the computer.
Give up your seat on public transportation and enjoy the people watching from above rather than below.
"Walk and Talk" rather than "Sit and Speak" while talking on cell phones or land lines.
Introduce walking meetings to the work calendar (you're more productive and less distracted).
If you sit at your job all day long, set an alarm on your cell phone (on low) to remind yourself to stand up at least every 2 hours for more than a minute at a time. Stretch, bend or take a short walk.
Gradually reduce daily sitting time by 15 to 20 minutes per day, aiming for two to three fewer sedentary hours over a 12-hour day.