We might not realize the influence they have on us, but junk food advertisements are capable of changing our beliefs. Remarkably, ads for healthy food don’t do the same thing, a new study showed. Researchers wanted to see just how much junk food ads can influence our emotions. They found that these ads can have a pretty big impact on our expectations.

Food and beverage companies spend billions of dollars promoting unhealthy foods, especially for kids. Studies have found strong links between more ads for junk foods and rates of childhood obesity. In fact, junk food marketing can increase the amount of unhealthy food choices kids make within as little as 30 minutes of exposure.

Now, researchers have found that adults aren’t immune either. In adults who didn’t have strong beliefs about how food affects their emotions, ads for junk food makes people think they’ll feel better while eating that type of food. However, the same didn’t happen for adults exposed to ads about eating healthier products.

“Many people think that eating highly processed foods like cheeseburgers and French fries will make them happier, and these beliefs are especially strong in people struggling to control their intake of highly processed foods,” Jenna Cummings, lead author and former research fellow at the University of Michigan, said in a statement.

Influential junk food ads

The study involved 718 participants, who were tested on how food ads affected their food-related emotional expectations. The researchers also assessed how the effects changed with individual levels of food addiction symptoms. Food addiction is marked by cravings for junk food, reduced control over their intake and overconsumption.

Participants were randomly split into four groups. The groups had to watch a 15-second video ad for either:

• highly processed foods;
• minimally processed foods;
• both food groups;
• or ads for cell phones (this was the control group).

The food products were picked from the menus of fast food chains. Participants also had to complete questionnaires about beliefs, feelings, and behaviors.

In individuals with fewer symptoms of food addiction, viewing highly processed food video ads increased expectations that one would feel positive emotions while eating those foods, the researchers found. This fits with previous research.

Cummings said the findings show that regulating junk food ads as well as changing beliefs about how highly processed foods affect emotions could help people eat more nutritious foods. She suggested further studies to look at how longer exposures to food ads changes beliefs about the emotional effects of food and how long changes endure.

Around the world, governments are cracking down against fast food ads, especially concerned about their impact on children. Canada has recently laid out plans to restrict TV and digital media that promote unhealthy food, while Germany’s agriculture minister has called for a ban on all ads accessible by children on unhealthy food.

The study was published in the Journal of Health Psychology.