Australian researchers have found the biggest risk factors making children obese - and some are pretty controversial.
The team at the Queensland Institute of Medical research say girls are more likely to be overweight if they are raised in a single parent household.
For boys, the biggest factor was too much junk food between the ages of 5 to 11, and refusing to play organised sport.
Boys whose parents didn't go to university were twice as likely to be obese.
12% of boys were classed as medically obese, while for girls that figure was 11%.