Researchers at the VU University Medical Centre in Amsterdam found 62 per cent of severely obese children under 12 years of age already had one or more cardiovascular risk factors, the BBC news reported.
Heart disease is normally associated with middle age, but in the study, two-thirds of the 307 children had at least one early symptom such as high blood pressure.
The findings were presented in Archives of Disease in Childhood journal.
Two-year-olds with a Body Mass Index, a measure of obesity, greater than 20.5 were classed as severely obese. By the age of 18, a BMI of 35 was a sign of severe obesity.
The data was collected from the Dutch Paediatric Surveillance Unit between 2005 and 2007.
More than half had high blood pressure, and there were also cases of low "good cholesterol" and high blood sugar, which can result in Type 2 diabetes.
The researchers said this "may lead to cardiovascular disease in young adulthood".
"It's a huge concern so many obese children were identified as already having at least one risk factor for heart disease, including high blood pressure, high blood glucose and problems with cholesterol levels," Doireann Maddock, a senior cardiac nurse with the British Heart Foundation, said.
"However, this is a problem that can be addressed by stopping young people becoming overweight and obese in the first place," Maddock added.
