Young adults are up to six times more likely to be obese by the time they celebrate their 21st birthday if their parents were overweight or obese before they conceived their child, research shows.
A study of 2200 Brisbane parents and their children found that the pre-pregnancy body sizes of mums-and-dads-to-be had a big impact on the waistlines of their offspring as young adults.
Previous research has consistently found that having overweight or obese parents increases the risk of a child following the same path.
However, few studies have been done on links between the Body Mass Index (BMI) - a common measure of body size - of men and women before they conceive and the chances of their child being overweight or obese in adulthood.
Researchers from the University of Queensland's School of Public Health based their findings on data collected for a long-running study of thousands of mums who received ante-natal care at a major Brisbane public hospital between 1981 and 1983.
They had their pre-pregnancy and current weights recorded, along with their height, so their BMIs could be calculated.
They also provided details about the weight and height of their partners.
About 16 per cent of the mums and 28 per cent of dads were overweight or obese before pregnancy.
When their children turned 21, one third were overweight or obese based on their BMI.
The researchers found that the 21-year-olds were more than twice as likely to be overweight or obese if their mum or dad were too before they conceived, compared to children of parents who had been at a healthy weight.
After adjusting for a range of factors including whether they were breastfed as babies, and the amount of TV they watched, fast food they ate and sport they played at 14, the chances were even greater.
"The odds increased up to six times of becoming overweight/obese during young adulthood in the fully adjusted model when both father and mother were overweight/obese compared to both healthy weight parents," the researchers wrote in a paper published in the Australian and New Zealand Journal of Public Health on Wednesday.
"The risk was stronger when both parents were overweight/obese compared to one parent."
Obesity rates have increased from about three per cent to 10.8 per cent in adult men, and from about six per cent to 15 per cent in women in the past four decades, making obesity a major public health problem in Australia.
The researchers said the study highlights the importance of men and women maintaining a healthy weight before having a baby.
© AAP 2018