Why Fast-Food Gives You Brain Fog, According to Science

Jodi Helmer
by Jodi Helmer
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Why Fast-Food Gives You Brain Fog, According to Science

The next time you have a deadline or need to focus, skip the drive-thru. The high saturated fat foods associated with fast-food joints — like hamburgers and fries — are not only linked to health problems like heart disease and high cholesterol, but they could also tank your attention span and concentration.

Researchers at Ohio State University compared test results for 51 women who ate high saturated fat meals with 930 calories and 60 grams of fat (designed to mimic the contents of various fast-food meals such as a double Whopper with cheese or a Big Mac and medium fries). They discovered participants’ performance was worse after eating a meal high in saturated fat (turkey sausage, biscuits, eggs and gravy with a palmitic acid-based oil high in saturated fat) compared with the same meal made with lower-saturated fat sunflower oil. The results illustrate a connection between diet and cognitive health, according to study co-author Annelise Madison, a PhD candidate at The Ohio State University.


The data studied the impact on concentration within five hours of eating a meal high in saturated fat, but Madison suggests the effects may take hold sooner and have longer lasting effects — and may be even more pronounced when comparing a high-fat meal to a low-fat meal.

“There have been some longer term dietary studies that have found associations between diet and outcomes related to dementia and cognitive decline over time and we were interested in finding out whether we’d see the effect after one meal,” says Madison.

Among high-fat meals, it appears the type of fat you consume matters, she adds. While heart-healthy fats like omega-3’s have been linked to brain health, your body may have a different metabolic and inflammatory response to meals that are high in saturated fat.


The study is part of a growing body of research linking high-fat meals to impaired concentration and poor decision making and an increased risk of cognitive decline. Similarly, research shows those with high levels of trans fats in their blood might be up to 75% more likely to develop Alzheimer’s disease.

Dr. Nicolas Cherbuin, a professor at Australian National University believes eating high-fat meals is hastening declines in brain health. His research found a diet high in saturated fats was linked to neurodegeneration, or the loss and function of neurons, leading to a higher risk of declining brain health and cognition and a higher risk for developing dementia later in life.
“Our research showed that, within the normal range, those who had higher blood glucose had more neurodegeneration, their brains shrunk more than those who had lower levels [of blood glucose],” Cherbuin explains. “When we are young, we don’t see these differences … but as the damage piles up, the repair mechanisms stop working quite as well and lead to brain aging.”

Eating meals high in saturated fat appears to exacerbate inflammation, triggering oxidative stress, a process that leads cell molecules to damage cell walls and DNA, impairing concentration and focus and creating progressive issues in the brain.

“If one eats highly processed junk food, there are some effects on the brain that occur remarkably rapidly,” Cherbuin says. “If people decrease their risk exposure, they have better cognitive outcomes.”


Meals high in saturated fat should be avoided before activities requiring focus and concentration but the long-term impacts matter, too. “You might think, ‘Tomorrow I’ll deal with my diet,’ especially during COVID-19 when you might be turning to some [unhealthy] foods to deal with everything,” Madison says. “If you really want to have your full cognitive capacity and be firing on all cylinders, it’s important to consider even the short-term impact of what you’re consuming.” Aim for a well-balanced diet that incorporates complex carbs, healthy fats and quality proteins.

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About the Author

Jodi Helmer
Jodi Helmer

Jodi Helmer writes about health and wellness for publications like WebMD, AARP, Shape, Woman’s Day, Arthritis Today and Costco Connection among others. She often comes up with the best story ideas while hiking with her rescue dogs. You can read Jodi’s work or follow her on Twitter @helmerjodi.


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