Overweight children may be at higher risk of oesophageal (gullet) cancer when they grow up than their slimmer friends, according to research published in the British Journal of Cancer.
Researchers* studied the health records of more than 255,000 Danish school children, born between 1930 and 1971, whose height and weight was measured every year between the ages of 7 and 13**. The researchers used this to go back and calculate their Body Mass Index (BMI).
BMI looks at weight compared to height and is a simple way of assessing whether people are a healthy weight.
More than 250 of the children went on to develop oesophageal cancer over the age of 40. By matching these middle-aged patients with their school records, researchers found that children aged 9-13 with a higher BMI, who were more likely to be overweight or obese, appeared to be at greater risk of developing this type of cancer in later life.
Using their results from the 1930s to the 1970s, they calculated that 2.1 per cent of all oesophageal cases in adult men in Denmark could be attributed to boys being overweight or obese at the age of 13.
But they estimate that this figure could go up to around 17.5 per cent of all these male oesophageal cancer cases in the future due to the rise in childhood obesity levels.
Dr Jennifer Baker, associate professor at The Institute of Preventive Medicine in Denmark and the University of Copenhagen, said: "Our results suggest that the increase in the number of overweight and obese children might lead to a significant rise in future cases of oesophageal cancer.
"It may be that being overweight as a child is directly linked to a higher risk of developing this cancer in later life. Or it might be that overweight children are more likely to become overweight adults, and we know that being above a healthy weight as an adult is a risk factor for many cancers, including oesophageal. More research is needed, but however the link works, our results underline how important it is for children to be a healthy weight - particularly as there is some evidence that overweight children could be at higher risk of other cancers later in life."
Oesophageal cancer - sometimes called cancer of the food pipe or gullet - is the 13th most common cancer in adults, with around 8,300 cases diagnosed each year in the UK. It is about twice as common in men as in women.
A previous Cancer Research UK study estimated that being overweight or obese causes more than one in four oesophageal cancers in men and around one in 10 in women. This may be because people who are obese are more likely to suffer from acid reflux - when acid coming back up from the stomach can irritate the lining of the oesophagus - which is a risk factor for oesophageal cancer. A higher BMI is also associated with gastroesophageal reflux disease in children.
The Danish research did not take into account any social or lifestyle factors that might contribute to a person's risk of developing cancer, but researchers say there was little evidence that these might have affected their results.
Dr Julie Sharp, head of health information at Cancer Research UK, said: "This research suggests that being overweight as a child could have effects on your health even decades later. It highlights how important it is to ensure that children eat healthily and are active, as this gives them the best possible start in life and could help to prevent them from developing diseases such as cancer in the future."