London - Primary school pupils who are overweight may have poorer thinking skills, a study has suggested.
Children aged nine to 11 were found to do worse in problem-solving and memory tests if they were obese or overweight.
The study of 2 700 children also found that those who were overweight had a thinner cortex – the part of the brain which is important for reasoning.
However, the reasons for the study’s findings are unclear. A fatty diet may cause damaging inflammation at a time when a child’s brain is still developing.
Another theory is that children have different brains which make fatty and sugary foods more rewarding and reduced their willpower, while also affecting youngsters’ thinking abilities.
The study, which was led by Cambridge University, involved US children asked to do tests, including remembering a list of animals in size order and spotting matching patterns.
On average, lean children scored almost six points higher than obese children and nearly four points higher than those who were overweight.
The tests were designed to measure "executive function", which includes short-term memory and decision-making.
Study author Dr Lisa Ronan, from the department of psychiatry, said: "The study shows reduced executive function in obese and overweight children, which might suggest they would struggle with planning, problem-solving and regulating emotions. That could affect their performance at school."
According to the latest stats, almost one in five children are overweight or obese when they start primary school. The study was published in the journal Cerebral Cortex.