Researchers looked at the genetic make-up of 2,480 children with severe obesity and compared them with 7,370 healthy children. The study found nine genes which were strongly linked to early weight gain. Five of these genes had been previously linked to obesity whilst four were new.
Although the importance of genetics in obesity is debated, lead author Dr Eleanor Wheeler, of the Wellcome Trust Sanger Institute, says that scientists have 'known for a long time that changes to our genes can increase our risk of obesity. For example, the gene FTO has been unequivocally associated with BMI [Body Mass Index], obesity and other obesity-related traits'.
Two of the four new genes - PRKCH and RMST - appear to have a similar or stronger effect on obesity than the FTO gene.
Another of the new genes, LEPR, has several variants associated with an increased risk of obesity, with a common form found in six percent of the population. Rarer variations are thought to contribute strongly to a severe form of early-onset obesity.
A total of 29 genetic changes were more frequent in obese children than healthy children. Rare structural variations were identified which effectively delete sections of DNA important in maintaining proteins involved in weight control.
The study has brought the total number of genetic variants linked to obesity to 50 and suggests that there are different genetic influences on adult and child obesity.
Study co-author Professor Sadaf Farooqi, from the University of Cambridge, said that research indicates that 'some children will be obese because they have severe mutations'. Other children, she says, 'may have a combination of severe mutations and milder acting variants that in combination contribute to their obesity'.
Speaking to The Independent, Professor Farooqi added that a person's environment would also influence a child's risk of becoming obese. 'There have always been' heavily overweight children, she said, but now, 'because of the environment they are growing up in, we are seeing many more children in this category'.
The study was published in Nature Genetics and was funded by the Wellcome Trust. It is part of a wider project investigating genetics in obesity called UK10K.