Spanish researchers warn that overweight and obese kids as young as 12 are showing early signs of heart disease.
During a study, scientists in Barcelona analyzed 80 obese and overweight kids with an average age of 12 and compared them with 60 lean youngsters.
They found that larger kids had higher cholesterol and blood pressure, as well as more signs of pre-diabetes.
The researchers are now looking into "endothelial dysfunction" - a thickening of the arteries associated with heart problems.
By studying how easily the forearm relaxes, scientists are able to monitor the degree of the dysfunction.
They discovered the overweight and obese children had a similar level of the condition to adults with chronic heart disease.
"Endothelium-dependent relaxation of forearm arteries is already impaired by the same as in adults with chronic heart failure, and this in our 12-year old obese children," the Scotsman quoted the researchers as saying.
"Primary or secondary prevention strategies starting early in childhood should aim at reversing current increase in childhood obesity.
"These strategies can be initiated at home and in preschool institutions, schools or after-school care services to influence diet and physical activity in the entire children population. However, further research needs to explore the most effective strategies to prevent and treat obesity.
"Already in early childhood, overweight and obesity are associated with the risk factors for the development of cardiovascular diseases like diabetes, high blood pressure or high cholesterol levels," they added.
The findings were presented at European Society of Cardiology.