Not only does this offer an insight into the ever-increasing rate of human obesity, it may also explain why some people easily resist fatty and sugary foods, while others seem hopelessly addicted, the FASEB Journal reports.

"These results will help us to better help women about diet during pregnancy and breastfeeding for giving their infants the best start in life," said Beverly Muhlhausler, study co-author from the University of Adelaide, Australia.

Muhlhausler and colleagues studied two groups of rats, which during pregnancy and lactation were either fed standard "rat chow" or a junk food diet made up of a selection of common human foods high in fat and high in sugar.

After the baby mice were weaned, the pups from both groups were allowed to select their own diets from either the same range of junk food or the standard rat chow, according to a University of Adelaide statement.

Brains from some of the pups also were collected at different times after birth and measured for the levels of the "feel good" chemicals (dopamine and opioids) and receptors that these chemicals act upon.

The scientists found that the group of rats whose mothers had eaten the junk food diet had higher levels of the receptor for opioids after they were weaned.

This group also chose to eat more of the fatty foods as compared to the pups whose mothers ate the standard rat chow.

This suggests that infants whose mothers eat excessive amounts of high fat, high sugar junk foods when pregnant or breastfeeding are likely to have a greater preference for these foods later in life.

"How ironic that your mother nags you to eat your fruits and vegetables, but it could have been her actions that helped you to prefer junk food!" said Gerald Weissmann, editor-in-chief of The FASEB Journal.