Pregnant women, cut down your junk food intake or your children will grow up addicted.

New research shows that mothers-to-be who gorge on junk food while pregnant can cause changes in their unborn children's brain chemistry, causing the babies to be born with a higher tolerance to salt, fats and sugars.

This means that their children are more likely to become addicted "junk food junkies" who crave more and more junk food as they grow up in order to be satisfied, which puts them at risk for obesity and heart disease.

"The results of this research will ultimately allow us to better inform pregnant women about the lasting effect their diet has on the development of their child's lifelong good preferences and risk of metabolic disease," said Dr. Beverly Muhlhausler, a researcher from the University of Adelaide in Australia who led the study.

Eating junk food with high fat and sugar content activates the opioid signaling pathway in the brain, releasing brain chemicals that make the eater feel good.

Opioids are naturally released in the brain, but eating junk food, much like using the addictive drugs opium, heroin, and morphine, causes opioid surges that lead to such high feelings of pleasure that the user can easily become addicted.

With regular usage, the body becomes so sensitized to the opioid-inducing stimulus that it needs more of it in order to feel anything close to that initial burst of pleasure.

That's why junk food junkies have such a hard time cutting down, even when they know they should be eating more healthfully.

The new study, published in the March 2013 issue of the Federation of American Societies for Experimental Biology (FASEB) Journal, shows that high levels of junk food consumption in pregnant females causes the opioid signaling pathway in their unborn children to become sensitized to opioids.

The Australian researchers made this finding by studying pregnant rats before and after they gave birth.

One group of the mother rats was fed normal rat food, and another was fed "junk food" that was high in fats and sugars throughout pregnancy and lactation.

The rat pups absorbed the contents of whatever their mothers ate while gestating before they were born, and while weaning from their mother's milk for weeks after birth.

After the weaning period ended, the rat pups received daily injections of an opioid receptor blocker, which cuts off the effects of the opioid pleasure pathway.

Since the opioid pathway leads to the release of dopamine, the pleasure-causing brain chemical, opioid blockers lower fat and sugar intake by removing the rewarding feelings that come from eating junk food.

The results of the study revealed that in pups of the junk food-eating mother rats, the opioid receptor blocker was less effective. This implies that the opioid pathway in those rat pups was less sensitive than for pups whose pregnant mothers ate a normal healthy diet, making the junk-food-weaned rats more likely to be addicted.

"This study shows that addiction to junk food is true addiction." said Dr. Gerald Weissmann, Editor-in-Chief of The FASEB Journal in a statement. "Junk food engages the same body chemistry as opium, morphine or heroin. Sad to say, junk food during pregnancy turns the kids into junk food junkies.

This research comes after a great deal of recent coverage of the addictive qualities of junk food.

The New York Times published an extensive feature in February on the fast food industry's meticulous efforts to turn consumers into junk food junkies.

While the researchers behind Australian study put the onus on pregnant mothers to prevent their children's junk food addiction, the NY Times piece highlights just how difficult it is to control one's diet when the American food landscape is so dominated by unhealthful junk foods.

One in three American adults is clinically obese today, along with one in five kids. 24 million Americans suffer from type 2 diabetes, which is often caused by poor diet, and another 79 million people have pre-diabetes.

The new research suggests that American children's susceptibility to diabetes, obesity, and eventual heart disease is strongly affected by the junk food diets their mothers had while pregnant.

"Hopefully, this will encourage mothers to make healthier diet choices which will lead to healthier children," said Dr. Muhlhausler.