When it comes to the rules of a healthy diet, the only constant is change. Conventional wisdom changes all the time; if it didn’t, Dr. Atkins would never have sold more than 15 million copies of his book and Whole30 would not have swooped in to reprogram early-2000s Atkins practitioners, followed by Keto. But “saturated fat” has pretty much always been a dietary bogeyman, and a new study published in The American Journal of Clinical Nutrition this month has found yet another detrimental effect of saturated fat on the human body—and the human mind.
The study, “Afternoon distraction: a high-saturated-fat meal and endotoxemia impact postmeal attention in a randomized crossover trial,” looked at how consuming meals high in saturated fat disrupted one’s ability to concentrate. Fifty-one test subjects all started by taking a CPT, or continuous performance test, to establish their baseline attention span. Next, they were split into two groups: both were fed a meal of turkey sausage, eggs, biscuits, and gravy, a meal containing 60 grams of fat. However, half of the participants ate a version cooked with sunflower oil, lowering its level of saturated fat. After eating, everyone had to tackle another continuous performance test, and the results were compared to their baseline. In short, the saturated fat group totally blew it.
Why would saturated fat impair our ability to concentrate? There’s no definitive conclusion, but one possibility is that these fats increase inflammation, which could cause a sort of cognitive ripple effect—all that gut disruption creates a lot of extra “noise” in our brains. Also notable is just how immediate the negative cognitive impact was. According to lead study author Annelise Madison, “Most prior work looking at the causative effect of the diet has looked over a period of time. And this was just one meal—it’s pretty remarkable that we saw a difference.”
All this might just reinforce what we already knew: that a double bacon smokehouse burger with a milkshake on the side is a mighty fine meal, but maybe not right before you take the SAT.