Who doesn’t love junk food? Perhaps it’s the funnel cakes at a summer fair you can’t resist or digging through your child’s candy at Halloween to look for your favorite snack-size chocolate bar. Or maybe it’s a hamburger and fries that you’re craving even though a grilled chicken salad would be better for your waistline, heart, liver, kidneys, and teeth.

Besides the obvious deliciousness of junk food, there may be another reason we choose foods high in fat and sugar over healthier options: our brains have adapted to crave them.

The Research

A new study from the Max-Planck-Institute for Metabolism Research found that eating high-fat and high-sugar foods alters the brain’s reward centers to increase the desire for junk food and decrease the desire for healthier foods.

“Work in rodents has shown that diet alone can change preference and rewire brain circuits,” explained study author Dr. Marc Tittgemeyer. “We wanted to understand if diet alone (in the absence of weight gain) might cause changes in preference and rewire brain circuits in humans.”

The 8-week randomized, controlled study involved 57 participants who were not overweight. Approximately half the group consumed high-fat, high-sugar yogurt twice a day, while the other half received a low-fat, low-sugar yogurt twice day. Nothing else was changed in the participants’ regular diet.

The Results

Although neither weight nor metabolic parameters changed much in either group after the 8 weeks, the group that had eaten the high-fat, high-sugar snacks experienced rewiring in their brain circuits. But the rewiring didn’t just enhance their response to tastier foods; it also rewired the brain circuits for learning in general. In fact, the junk-food consuming group showed increased brain responses when anticipating and drinking milkshakes.

“The most important take-home message is that diet alone can rewire brain circuits in such a way that could promote overeating,” says Dr. Tittgemeyer. “You can be born with no genetic risk for obesity but then acquire risk by eating foods high in fat and sugar—like processed foods.”

Study Limitations

There were some limitations surrounding the study, including:

• The study was relatively small in terms of the number of participants.

• Participants accepted for inclusion had to have a baseline of at least “moderately” wanting to consume yogurt and milkshakes.

• The study did not include obese or overweight participants.

• The participants’ other food intake wasn’t examined.

• Researchers did not look at the effects of fat or sugar intake separately.

The results were published in the April 4, 2023 edition of the journal Cell Metabolism.

MBJ

Wendy Burt-Thomas writes about the brain, mental health and parenting.

Check out the original research:

https://www.cell.com/cell-metabolism/pdfExtended/S1550-4131(23)00051-7