Most of us know that junk food can expand our waistlines, but a new study suggests that chips, pop and candy may have the opposite effect on our brains: It shrinks them! In particular, eating junk may diminish the area of the brain that is important to memory and learning. That means those chips could be related to problems such as depression, anxiety memory loss and dementia.

Junk food has long been linked to childhood obesity, heart disease and other health problems, but now risks to your brain health offer another good reason to limit your intake of sweet and salty treats.

The Australian researchers behind the study used magnetic resonance imaging to measure the size of the left hippocampus regions in 250 adults aged 60 to 64. They found that study participants who ate more unhealthy foods, such as sweet drinks, salty snacks and processed meats, had smaller left hippocampi, while those who ate more nutrient-rich foods, such as vegetables, fruits and fish, had larger hippocampi.

Diet's impact on your brain

Lead researcher Felice Jacka, an associate professor at Deakin University School of Medicine in Geelong, Australia, told ABC News that, while your hippocampus gets smaller as you age, diet can have a major influence—being responsible for up to 60 percent of the decline.

This study builds on other research linking depression, diet and small hippocampi and offers a new way to understand the role food plays in brain health.

"The food that we put in our mouths needs to be of the best quality," Jacka told ABC, and that isn't just true for people later in life. The hippocampus is critical to learning, memory and mental health throughout life, she said, adding that the work underscores the need for good nutrition for children, teens and adults.

Learn more about protecting your brain health and how to deal with junk food cravings.