It may not just be a 3 p.m. slump if you find yourself foggy after lunch, particularly when you eat a take-out meal at your office, or if you’ve reheated yesterday’s pizza dinner. The fat content in your meals could be affecting more than just your waistline.
Fat is a necessary macronutrient; and whether you love it or avoid it, your cognitive processing and attention could be better or worse off for it.
A study conducted at Ohio State University investigated how dietary fat can impact attention. Yet not all fat is created equal—sources of dietary fat that are high in saturated fat may not have the same effects that dietary fat on the lower end of saturated fat may have. To test this, researchers divided adult women into two groups. One group ate a high-fat meal based in a high-saturated fat meal example that was heavy in palmitic oil, while the other group ate a high-fat meal with the same fat composition derived from sunflower oil (which is lower in saturated fat).
The meals each contained 60 grams of fat and 930 calories, amounts which are commonly found in fast food “burgers and fries” meals. To see how these meals affected their cognitive processing and attention, the participants took a continuous performance test designed to measure their attention span and reaction times before and after the meals.
As well as the concentration tests they took, blood samples were collected to check for signs of an inflammatory molecule that is a marker of leaky gut syndrome. In leaky gut syndrome, endotoxemia is present when intestinal toxins leak into the bloodstream due to a compromised barrier in the intestinal tract. Leaky gut syndrome causes inflammation.
After the meals, the participants waited five hours to take the same attention test again, and then they followed the same testing and meal regimen as the other group anywhere from one week to four weeks later (swapping the types of saturated fat).
All of the participants who ate the high-fat meal saw their reaction times drop by 11%! Those people that did test positive for endotoxemia markers suffered impaired reaction times and attention deficits whether they ate the high-saturated fat oil or the lower-saturated fat oil. This finding is important because there are healthy oils and unhealthy oils (such as olive oil versus a partially hydrogenated oil, a.k.a. trans fat oil). Healthy oils are an important part of balanced diets, but if your gut is leaking like some of the participants in the study, it won’t matter if the fat you’re consuming is healthy or not—you might also be experiencing attention and concentration shortages.
This study didn’t go into detail about why attention may be affected by dietary fat, but it’s true that saturated fatty acids increase inflammation in the body and the brain. Saturated fatty acids have been linked to neurological inflammation and increased risk of cognitive function, dementia, and Alzheimer’s disease. High-fat diets, in general, have been associated with causing a state of chronic low- grade inflammation; but it’s really important to stress here that not all fats are created equal.
Healthy fats, such as the polyunsaturated fats (like safflower oil, corn oil, nuts, seeds, and the fish salmon, trout, albacore tuna, herring, and mackerel) or monounsaturated fats (like olive oil), actually reduce your risk of cognitive impairment and cardiovascular disease. It’s all due to the ratio of the omega-3 versus the omega-6 fatty acids found within them. Usually, when people talk about a standard, high-fat diet, they are referring to a diet high in animal fat (which is saturated fat), rather than the healthy, unsaturated fats.
So don’t pass up on fat altogether, but choose a healthy fat if you’ve got a big afternoon ahead of you.
Madison, Annelise A., et al. “Afternoon Distraction: a High-Saturated-Fat Meal and Endotoxemia Impact Postmeal Attention in a Randomized Crossover Trial.” The American Journal of Clinical Nutrition, 12 May 2020, https://academic.oup.com/ajcn/advance-article-abstract/doi/10.1093/ajcn/nqaa085/5835679?redirectedFrom=fulltext.