Overweight or obese children use up antioxidants from fruit and vegetables much faster than other children, according to the University of Newcastle.
Dietician Dr Tracy Burrows and colleagues investigated blood levels of carotenoids in nearly 100 children.
Carotenoids are nutrients found in fruit and vegetables that act as antioxidants that repair damaged cells.
Studies in adults have linked high levels of carotenoids in the blood to lower levels of disease.
"Fruit and vegetables are the only major source of carotenoids in the human diet, so if we measure that in the bloodstream then we're basically measuring their fruit and vegetable intake," said Burrows.
The researchers also divided the data on the children's diet into three different groups, according to the child's weight.
Unexpectedly they found that, on average, overweight children had lower levels of carotenoids than children with a healthy weight who consumed the same amount of vegetables. Obese children had even lower levels of carotenoids.
The report also found that the more fruit and vegetables children were reported as eating, the higher their blood levels of carotenoids.
"There was a significant decrease in carotenoids the more overweight [the children] became," she said.
Burrows said overweight and obese children could be chewing through their antioxidant carotenoids faster to counteract a higher rate of inflammation in their tissues.
"We've come to the conclusion that overweight and obese children have higher requirements for carotenoids because they're using them up more," she said.
