(CBS/VALLEYNEWS) -- Slacking off on exercise for just a few weeks can have an impact on your body that last much longer, new research suggests.
Two recent studies from the University of Liverpool and McMaster University, among others, monitored active people who abruptly started sitting more and found their blood sugar levels rose, their insulin sensitivity decreased and they gained weight. The studies' volunteers returned to an active lifestyle after two weeks, but the undesirable metabolic changes did not fully reverse.
Dr. David Agus told "CBS This Morning" that a two-week break can have "real ramifications" that linger for many weeks afterward – especially for older people.
Previous studies of college students who suddenly became more sedentary demonstrated many of the same effects as the new research. The difference is that their bodies were able to bounce back within two to three days after they started exercising again.
"But in this study over the age of 65, they didn't. After two weeks most of them hadn't changed at all. They were still back to that change that happens with being sedentary. So age does matter," Agus said.
Agus stressed that most people are not active enough to begin with and for older people it's important to get moving every day.
"Five to 10 minutes every hour and try to do 10 to 15 minutes a day where your heart rate gets 50 percent higher from where it starts. And that's kind of the minimum. But really do it every day. Movement over time is critical," he said. "Walking makes you live longer, as simple as that. … So those couple of weeks of being sedentary when the [blood] sugar goes up, that changes your blood vessels, raises your risk of heart disease, stroke, blood pressure, all those other things. So the key is life is a marathon. Every day you need to build something into it. So really the take-home is movement over time."
Also key: intensity. Agus said that even people in their 60s and 70s should strive to get in a brief, intense work out.
"There are clear benefits to it. So our bodies were kind of designed to move during the day, but that intensity helps both cardiovascular and brain-wise. You know, sitting helps thin the part of the brain involved in memory. So you want to remember names of people and all? Exercise and get out there."