Signs of significant heart disease and heart muscle abnormalities can be seen in obese children as young as 8 years old, according to a recent study.

Researchers found that obesity in children was linked to 27 percent more muscle mass in the left ventricle of their hearts and 12 percent thicker heart muscles -- both signs of heart disease, The Washington Post reported.

"Parents should be highly motivated to help their children maintain a healthy weight," Linyuan Jing, lead study author and a researcher at Geisinger Health System, said in a statement. "Ultimately we hope that the effects we see in the hearts of these children are reversible; however, it is possible that there could be permanent damage. This should be further motivation for parents to help children lead a healthy lifestyle."

The typical American diet for children has been cited as a contributor to the problem with French fries accounting for 25 percent of a child's vegetable intake and fruit juice, which is often high in sugar but low in fiber, accounting for 40 percent of a child's fruit intake. Lack of regular physical activity and high amounts of screen time in front of televisions and computers has also been cited as an issue for children's health.

For the study, researchers collected and analyzed data from 20 obese kids and 20 normal-weight kids, Health Day reported. Jing and colleagues measured a child's obesity based on U.S. Centers for Disease Control and Prevention standard growth charts. Pediatric obesity is determined by whether a child's body mass Index -- a calculation derived from a child's height and weight -- exceeds the 95th percentile.

Of the 20 obese children, seven were teenagers. Among those seven teens, five had a body mass index over 35 (the healthy range varies for children but is 18.5-25 for adults). Some of the obese kids had conditions associated with excess weight, including asthma, high blood pressure and depression. All 40 children -- obese and normal-weight -- underwent magnetic resonance imaging tests so that researchers could measure the function and dimensions of their hearts.

Despite childhood obesity being a common problem, researchers were surprised to see evidence of heart disease among those as young as 8 years old.

"This implies that obese children even younger than 8 years old likely have signs of heart disease too," Jing said. "This was alarming to us. Understanding the long-term ramifications of this will be critical as we deal with the impact of the pediatric obesity epidemic."

The findings were presented at the American Heart Association's Scientific Sessions 2015.