When you’re pregnant, that bag of cookies or chips can look pretty irresistible. But resist anyway. A new study suggests that eating a junk food diet during pregnancy may alter not only your own brain chemistry, but also the developing brain of your baby. As a result, your child’s brain may be prewired for later junk food addiction.
It’s the latest—and some of the strongest—evidence that junk food addiction is all too real. Recently, I had a chance to chat with Beverly Muhlhausler, PhD, study coauthor and head of the Metabolic Health Unit at the University of Adelaide’s FOODplus Research Centre in Australia. Here’s what she told me about how a junk food junkie is born.
What do we already know about how junk food affects brain chemistry?
Beverly Muhlhausler, PhD: Junk food has the same effect on the brain as addictive drugs and alcohol. When you eat junk food, it switches on part of the brain known as the mesolimbic reward center. This causes opioids to be produced and released, and the opioids initiate a series of reactions that ultimately lead to the production of the feel-good chemical dopamine. And this, in turn, creates a pleasurable feeling that’s equivalent to the high experienced from a drug—although obviously in a milder form!
Consuming excessive amounts of junk food for long periods changes your brain in the same way as addictive drugs and alcohol do. As a result, you need to consume larger amounts of junk food to get the same high—and you experience withdrawal symptoms when you can’t get it.
Which components of junk food have this effect?
Dr. Muhlhausler: We still don’t know exactly what it is that switches on the reward center, because junk food is made up of a lot of different ingredients. Studies have shown that just feeding fat or sugar to animals is enough to activate the reward system. But it’s unlikely that fat or sugar can cross the blood-brain barrier and reach the reward center directly. We think that a hormone that increases in response to junk food, such as insulin or leptin, acts as a middleman. It’s actually the hormone that binds directly to brain cells in the reward center.
What did you do in this particular study, and what did you find?
Dr. Muhlhausler: In our study, we fed pregnant and lactating rats either normal rat food or a “cafeteria” diet, which consisted of a range of human junk foods, including potato chips and chocolate cookies. Then we studied the effect on their pups.
In a previous study, we had shown that pups born to junk food-fed mothers were fatter and ate more fat than their control counterparts. The part of the brain that controls reward and addiction had developed differently in those pups as well. In this experiment, we tested whether the response of pups to a drug that blocks opioid signaling in the reward center differed between the two groups.
We found that pups whose mothers had been fed a junk food diet were less responsive to the drug. This tells us that their reward system was less sensitive to the effects of opioids—and therefore to natural rewards, such as junk foods, which activate the same system. That means these pups probably would have to consume more junk food to get a feel-good effect. Consequently, they might be more prone to overindulge in this type of food.
What does your research show about the addictive power of junk food?
Dr. Muhlhausler: Our study supports the results of other research showing that junk foods do indeed have addictive properties. Eating too much junk food over a long period of time can literally cause us to become addicted. We probably all know people who have withdrawal symptoms when they can’t get access to chocolate or chips—and what our research shows is that this really is a biological response.
“A Maternal ‘Junk-Food’ Diet Reduces Sensitivity to the Opioid Antagonist Naloxone in Offspring Postweaning.” J.R. Guguseff et al. FASEB Journal, 2013, vol. 27, pp. 1275-84.