New research from the University of Sydney has found that diets high in sugar and fat could harm how the brain works, especially when it comes to memory and navigation. While we’ve long known that unhealthy diets increase the risk of obesity, heart disease, and diabetes, this study shows they may also weaken how well the brain functions—even in young adults.
The study was published in the International Journal of Obesity and is the first of its kind to explore how fatty, sugary diets affect a specific type of brain task in humans: spatial navigation.
Spatial navigation is your brain’s ability to remember directions and paths—like finding your way through a city or remembering how to get home. This ability is closely linked to a part of the brain called the hippocampus, which is also responsible for forming memories.
Dr. Dominic Tran, from the School of Psychology at the University of Sydney, led the study. He explained that while the whole brain isn’t affected equally, the hippocampus seems to be particularly sensitive to poor diet.
“The good news,” Dr. Tran said, “is that this kind of brain effect appears to be reversible. Making healthier food choices could improve how well the hippocampus works—and with it, your ability to navigate your environment.”
To carry out the study, the research team recruited 55 university students between the ages of 18 and 38. Each participant filled out a questionnaire about how often they ate foods high in sugar and saturated fat. The researchers also measured each person’s body mass index (BMI) and tested their working memory.
Then came the main test. Participants put on a virtual reality headset and were asked to find a treasure chest hidden inside a maze. The maze was filled with familiar landmarks to help them learn and remember the route. They had to find the chest six times.
If they couldn’t find it within four minutes, they were teleported to its location and given a few seconds to study where it was.
In the final part of the test—the seventh round—the treasure chest was removed. Participants had to remember where the chest had been and mark its former location.
The results showed that people who ate high amounts of sugar and fat several times a week were less accurate in locating the chest’s former position. In contrast, participants who ate healthier diets were much better at remembering the right location.
Even after accounting for BMI and working memory scores, the connection between diet and navigation performance remained strong. This means the effect wasn’t just because some participants were overweight or had poor memory skills—it had more to do with what they were eating.
Dr. Tran emphasized that the study’s sample was small and made up of relatively healthy students, so the negative effects of a poor diet might be even stronger in the general population. “If our group reflected the broader public, who may have less healthy lifestyles, we expect the results would show an even bigger impact of diet on brain function,” he said.
The research offers a strong reminder that what we eat affects more than just our bodies. Even in young adults—when thinking and memory are typically at their best—a diet filled with processed foods and added sugar can dull brain performance. And while fast food and sugary snacks are easy to reach for, small changes in diet could bring big improvements in brain health.
In short, this study suggests that eating better may not only help prevent chronic diseases but also keep your brain sharp—and help you find your way home.
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The research findings can be found in International Journal of Obesity.
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