Eating greasy foods may feel like a friend during these trying times, but new research suggests eating just one meal high in saturated fat can hinder our ability to concentrate. The study compared how 51 women performed on a test of their attention after eating either a meal high in saturated fat or the same meal with sunflower oil, which is high in unsaturated fat. Their performance on the test was worse after eating the meal with high saturated fat than after they ate the meal with healthier fat, indicating a link between that fatty food and the brain.
Researchers also looked at whether a condition called leaky gut, which allows gut bacteria to enter the bloodstream, had any effect on concentration. Participants with leaky gut performed worse on the attention rating regardless of which meal they ate.
The loss of focus after a single meal was an eye opening for the researchers.
“Most of the previous work looking at the causative effect of the diet has been over a longer period of time. And this was just one meal — it's remarkable that we saw a difference," said Annelise Madison, lead author of the study and graduate student of clinical psychology at Ohio State University.
Madison also noted that the meal made with sunflower oil, while low in saturated fat, was still high in dietary fat.
“Since both meals were high-fat and potentially problematic, the cognitive effect of the high-saturated-fat meal could be even greater when compared to a low-fat meal,” she said.
For this work, Madison performed a secondary analysis of data from another study, which assessed whether high-fat meals increased fatigue and inflammation in cancer survivors.
Women in the study completed a baseline measurement of their attention during a morning visit to the lab. The tool, called a continuous performance test, is a measure of sustained attention, concentration and reaction time based on 10 minutes of computer-based activities.
The high-fat meal followed:eggs, biscuits, turkey sausage, and gravy with 60 grams of fat, either a palmitic acid-based oil high in saturated fat or the low-saturated-fat sunflower oil. Both meals have a total of 930 calories and are designed to mimic the contents of various fast food meals, such as a Burger King Double Whopper with cheese or a McDonald's Big Mac and medium fries.
Five hours later, the women took the continuous performance test again. One to four weeks later, they repeated these steps and ate the opposite meal to what they had eaten on the first visit.
Researchers also analyzed participants' fasting blood samples at baseline to determine whether they contained an inflammatory molecule that indicates the presence of endotoxemia — the toxin that escapes from the gut and enters the bloodstream when the gut barrier is compromised.
After eating the meal high in saturated fat, all participating women were on average 11 percent less able to detect target stimuli in the attentional assessment. Loss of concentration was also evident in the women with signs of leaky gut:their response times were more erratic and they were less able to sustain their attention during the 10-minute test.
“If the women had a high level of endotoxemia, the differences between meals were also wiped out. They performed poorly regardless of the type of fat they ate,” said Madison.
While the study didn't pinpoint what was going on in the brain, Madison said previous research has suggested that foods high in saturated fat can trigger inflammation throughout the body and possibly the brain. Fatty acids can also cross the blood-brain barrier.
"It may be that fatty acids interact directly with the brain. What it does show is the power of gut-related dysregulation," she said.
The statistical analysis took into account other potential influences on cognition, including depressive symptoms and the participants' average consumption of saturated fat. The women in the study ate three standardized meals and fasted 12 hours before each lab visit to reduce dietary variations that could affect their physiological response to the high-fat meals.
The findings suggest that concentration could be reduced even more in people stressed by the pandemic who turn to fatty foods for convenience.
“What we know is that when people are more anxious, many of us will find foods high in saturated fat more appealing than broccoli,” she said. “We know from other research that depression and anxiety can also disrupt concentration and attention. If we add that on top of the high-fat meal, we could expect the real effects to be even greater.”
