It’s no longer a secret that a sedentary life can’t do you any better. New research comes to underline the idea, this time in children’s case, saying those having a sedentary lifestyle are up to six times likelier to be at serious risk of heart disease later in life, debuting in their adolescence than active peers.

Researchers at the University of North Carolina, led by Robert McMurray, measured key health indicators in 389 kids between 7 and 10, including height, body mass, percentage of body fat, blood pressure and cholesterol levels. Researchers also monitored frequency and duration of physical exercise.

The children were examined again seven years later as teenagers in order to see how many of them developed signs of metabolic syndrome.

The results showed that almost half of the teenagers had developed at least one characteristic of “metabolic syndrome” (a group of symptoms including obesity, abnormal fat levels in the blood, high blood pressure, high cholesterol and insulin problems). Metabolic syndrome can further lead to heart disease, diabetes and increased risk of stroke.

Also, 4.6 percent or 18 teenagers had developed three or more characteristics of metabolic syndrome. These teenagers did low levels of exercise as kids meaning less than 20 minutes a day of moderate activities such as walking or riding a bike. The U.S. Centers for Disease and Prevention recommends this kind of activities for at least one hour per day.

“Children today live a very sedentary life and are prone to obesity. This is the first study to examine the importance of childhood fitness levels on your metabolism as a teenager. Previously we didn’t know low fitness levels were an influence. It’s obvious now that there is a link and this is something which we need to pay attention to by encouraging our kids to keep fit, or suffer the consequences later in life,” Prof. McMurray said.

The findings were welcomed by Paul Gately, the professor of exercise and obesity at Leeds Metropolitan University, and a director of Carnegie Weight Management who said, “The findings show that inactive children at a relatively young age are already storing up health risks for the future.”

The results of the study, supported by the National Institutes of Health, were published Friday in the journal Dynamic Medicine.