Could Over-Snacking While Pregnant Predispose Children to Be Obese?

Women who constantly binge on junk food while pregnant might pass their penchant for sweet and fatty food on to their children, a new study suggests

New research suggests that an apple might be the safer choice for pregnant eating.
New research suggests that an apple might be the safer choice for pregnant eating. Photo by Jamie Grill/Tetra Images/Corbis

Pickles and potato chips, ice cream and burgers: the cravings that hit women during their pregnancies might be more than strange–they may be permanently changing the brains of their unborn children. New research, to be presented by scientists from the University of Adelaide on August 1 at the annual meeting of the Society for the Study of Ingestive Behavior (SSIB) in New Orleans, suggests that women who eat a junk-food heavy diet during their pregnancies alter the opioid signalling pathways in their unborn child’s brain, transforming the way these pathways operate when the child is born.

The word “opioid” may conjure images of semi-synthetic drugs like oxycodone, a strong painkiller. But not all opioids are synthetic, or even semi-synthetic–in fact our body creates natural opioids known as endogenous opioids. Endogenous opioids are chemicals that are released in the brain and in turn signal the release of dopamine, the “feel good chemical” that is responsible for the euphoric feelings.

When we eat food high in sugar or fat, our brains release large amounts of opioid, which accounts for the “high” we experience after raiding the kitchen for a midnight bowl of ice cream or tucking back a bag full of Cheetos. As psychologist Leigh Gibson explains in an interview with the Daily Mail, our brains are rewarding us for ingesting foods loaded with calories. “From an evolutionary point of view, junk food cravings are linked to prehistoric times when the brain’s opioids and dopamine reacted to the benefit of high-calorie food as a survival mechanism,” Gibson said. Although foods rich in calories are available with much greater ease–and in greater abundance–than they were for our evolutionary predecessors, our brain chemistry remains the same, rewarding our intake of fatty, sugary foods with euphoria.

In the study to be presented at the SSIB meeting, researchers found that the chemical response to junk food was higher in rats whose mothers consumed a junk-food laden diet while pregnant. In comparing the rats who ate junk food with rats who ate standard rat feed, scientists found that in the offspring of the junk-food fed rats, the gene encoding one of the key endogenous opioids, enkephalin, was expressed at a higher level. This means that means that the baby rats of junk-food fed moms have more pathways to receive opiods than those whose moms were fed regular food. These findings add to previous research conducted by the group that shows that injecting the rats with a chemical that blocks opioid reception was less effective at stemming the fat and sugar intake in the offspring of the mothers who were fed junk food.

Combining these results, the group concludes that opioid signalling pathways are less sensitive in the offspring of the rats who ate only junk food. The findings reenforce prior research conducted by members of the group, which initially suggested a distinct preference for junk foods in the offspring of junk-food fed mothers. The new study adds to previous knowledge by pinpointing the specific brain chemistry at work, singling out the genetic encoding of enkephalin. More pathways and decreased sensitivity to opioids means that offspring of junk-food fed mothers would need to eat larger amounts of fatty and sugary foods to attain the same kind of high–leading scientists to speculate that they would consistently overeat junk food as they grow older.

If the implications of these findings hold true for humans, those who sport a baby bump are sure to pay attention. Expectant mothers are already told not to consume alcohol, sushi, cold cuts, soft cheeses, and daring to consume anything on the laundry list of off-limits items is a quick way to earn public censure. Could junk food become the next no-no for pregnant women? Could what you eat while you’re expecting inadvertently contribute to a more obese next generation? Or will the finding mirror the recent revelation that “crack babies,” children whose mothers used crack cocaine while pregnant, were no more worse off than other children of similar socioeconomic backgrounds?

For now, it is likely too soon to make sweeping generalizations about “junk food babies,” though the University of Adelaide researchers hope to continue building on their findings with continued research. Says Jessica Gugusheff, the graduate student leading the team’s recent research, “the results of this study will eventually permit us to better inform pregnant women about the enduring effect their diet has on the development of their child’s lifelong food preferences and risk of negative metabolic outcomes.”

Get the latest Science stories in your inbox.