Does Saturated Fat Impair Ability to Focus?

Does Saturated Fat Impair Ability to Focus?

Headlines warn, “Our ability to focus may falter after eating one meal high in saturated fat” [1, 2, 3].

Another tells us, “Fried Mind: Just One Meal High In Saturated Fat Impedes One’s Ability To Focus” [4].

Intrigued, I looked up the study: Afternoon distraction: a high-saturated-fat meal and endotoxemia impact postmeal attention in a randomized crossover trial [5].

After reading the article, I paused — there’s more to the story.

The study was published in the American Journal of Clinical Nutrition by Annelise Madison, et al.  The subjects, 58 women, ate a high fat meal with 60 grams of either monosaturated or saturated fat.

Before the meal, they completed the Continuous Performance Test (CPT)* and repeated it five hours later. The CPT measures attention, concentration, and reaction times.

Good news for saturated fat

Out of the five CPT measurements (detectability, errors of omission, errors of commission, reaction times, and reaction time consistency), the only statistically significant postmeal difference was the detectability score.

The monosaturated fat group scored better (lower scores are better) in that one area, but the difference was less than five points on a 100-point scale.

In fact, the postmeal detectability scores were better than the premeal baseline numbers. Perhaps the headlines should have exclaimed: “Read all about it! Eating a high-saturated-fat meal increases ability to focus!”

More good news about ability to focus

Subjects in both groups ate a high fat meal and both groups scored less than 50, which is better than the CPT average.  Even better: both groups were far below a clinically significant score of 60.

While a study can show statistically significant results (results that are unlikely to be the result of chance), those results may not be clinically significant.

Since four out of five CPT measures didn’t show a difference between meal types, the clinical impact appears to be low.

Leaky Gut and Endotoxemia

In addition to studying the effects of mono- and saturated fat, I applaud the researchers for measuring the impact of endotoxemia on the ability to focus.

Most of the endotoxins in our bodies are in the intestinal tract. When a certain type of bacteria in the gut dies, the endotoxin in its cell wall is released. This causes inflammation. If the intestinal wall is “leaky,” endotoxin enters the bloodstream and causes endotoxemia.

The study participants with higher endotoxemia markers at baseline had more erratic response times and were less able to sustain attention through the entire CPT.  Participants with the highest endotoxemia markers had higher (worse) CPT scores. In fact, scores approached the clinically significant level of 60 which may impair cognition.

Endotoxemia should get more attention.

The researchers conclude endotoxemia impacts ability to focus. That motivated me to dig a little deeper. I looked at other articles that discussed endotoxin and brain function.

Endotoxemia should get more attention. A recent review article identified several studies that found an association between high levels of endotoxin and several neuro-degenerative diseases: Alzheimer’s disease, Parkinson’s disease, ALS, MS, autism, and schizophrenia. While association isn’t causation, there’s also evidence that increased endotoxin causes neuro-degeneration [6].

Another disease that’s associated with endotoxemia is diabetes. A 10-year study found that patients with more endotoxin activity at baseline had a higher likelihood of developing diabetes [7].

Why do I mention diabetes? Diabetes also affects cognition [8, 9].  If the goal is improved brain function, it seems prudent to lower levels of glucose, insulin, and endotoxin.

What about the low-carb, keto community?

Keto meals pack a lot of fat, including saturated fat. Does this put our brain function at risk? Do headlines overplay the impact of mono- versus saturated fat meals? [1, 2, 3] Frying our mind? [4]

The headlines are masters of illusion. They focus (pun intended) on saturated fat, while ignoring the culprits: carbohydrates and insulin resistance.


Carbohydrate isn’t necessarily a bad actor, but its good-for-nothing companion, insulin resistance, gets it into trouble. Unlike fat and protein, there is no dietary requirement for carbohydrate. And high amounts increase the risk of insulin resistance [10].

In the mono- and saturated-fat study, subjects in both groups ate 60 grams of carbohydrate in one meal. That may be typical of a fast food meal, but it is double the amount many low-carb, keto people eat in a day!

Insulin Resistance

The waistlines and blood sugars of the participants suggest that some may have been insulin resistant or diabetic. The average waist circumference of study participants in the two groups was 91.2 cm and 96.6 cm [11].

That’s higher than the American Heart Association’s abdominal obesity cut-off of 88 cm [12]. Excess abdominal obesity is a sign of insulin resistance.

The brain prefers ketones over glucose.

Fasting glucose levels were 95.1 mg/dL and 96.8 mg/dL, near the cut-off between normal glucose and the pre-diabetic level of 100 mg/dL [11, 13].

Unfortunately, insulin levels were measured but not reported [11]. If high, the pancreas could be working overtime, pumping out more insulin to keep blood sugars deceptively low. This could hide insulin resistance [14].

Insulin resistance, even in the absence of elevated fasting glucose, has demonstrated impaired cognitive performance [15].

As the T-shirt says, “Don’t blame the butter for what the bread did.”

Don’t let the culprits get away. Put insulin and carbohydrates under surveillance!

Keto-adaption and the brain

In 1980, Steve Phinney, MD, PhD coined the term keto-adaptation [16]. By eating a low carbohydrate, high-fat diet, the body uses fat from diet and from body stores as fuel. The liver converts fatty acids into ketones — primarily beta-hydroxybutyrate and acetoacetate.

As the body transitions to primarily using fat (as fatty acids or indirectly as ketones), it becomes more efficient .The long-term result is keto-adaptation. And good news for the low-carb, keto community: the brain prefers ketones over glucose as fuel [17].

Jeff Volek, PhD, RD at Ohio State University has identified the many benefits of keto-adaptation [18]. Keto-adaptation has positive effects on the brain and cognition [19, 20, 21].

Does that mean saturated fat is good for us?  With more research, we will learn (and unlearn) more about poly-, mono-, and saturated fats. Perhaps, as Volek states in the following video, “Embrace saturated fat” [22].

*The CPT is a computerized test. Participants press the space bar when target stimuli appear. “Detectability” measures ability to distinguish targets from nontargets. “Omissions” measures errors of not reacting to a target. “Commissions” measures errors of pressing the bar when no target appears. “Reaction time” is the time it takes to respond and “Reaction time SE” measures response time consistency.


1 Caldwell, E, Ohio State News, May 12, 2020. Our ability to focus may falter after eating one meal high in saturated fat 

2 Science Daily, May 12, 2020 Our ability to focus may falter after eating one meal high in saturated fat

3 Development Channel, May 13, 2020 Our ability to focus may falter after eating one meal high in saturated fat

4 Anderer, J, StudyFinds. Fried Mind: Just One Meal High In Saturated Fat Impedes One’s Ability To Focus

5 Madison AA, Belury MA, Andridge R, Shrout MR, Renna, ME, Malarkey, WB, Bailey MT, Kiecolt-Glaser JK Afternoon distraction: a high-saturated-fat meal and endotoxemia impact postmeal attention in a randomized crossover trial Am J Clin Nutr 2020;00:1-9.

6. Brown G The endotoxin hypothesis of neurodegeneration Journal of Neuroinflammation 2019 16:180

7 Pussinen P, Havulinna A, Lehto M, Sundvall J, Salomaa, V Endotoxemia Is Associated With an Increased Risk of Incident Diabetes Diabetes Care 2011;34:392-397

8 Logroscino G, Kang JH, Grodstein F Prospective study of type 2 diabetes and cognitive decline in women aged 70-81 years BMJ 2004;10.1136/bmj.37977.495729.EE

9 Zilliox LA, Chadrasekaran K, Kwan JY, Russell JW Diabetes and Cognitive Impairment Curr Diab Reports 2016 Sep:16(9);87

10 Volek JS, Feinman RD Carbohydrate restriction improves the features of Metabolic Syndrome. Metabolic Syndrome may be defined by the response to carbohydrate restriction Nutr Metab (Lond) 2005;2,31

11 Kiecolt-Glaser JK, Habash DL, Fagundes CP, Andridge R, Peng J, Malarkey, WB, Belury MA Daily Stressors, Past Depression, and Metabolic Responses to High-Fat Meals: A Novel Path to Obesity Biological Psychiatry 2015;77:653-660

12 American Heart Association About Metabolic Syndrome 2020

13 American Diabetes Association Diagnosis 2020

14 Kraft JR (2011) Diabetes Epidemic and You Trafford Publishing

15 Sorice GP, Improta I, Mezza T, Grioni S, Iacobucce GM, Moffa S, Mari A, Marra C, Giaccari A Insulin Resistance Impairs Cognitive Performance Even in Healthy Subjects at Risk for Diabetes Mellitus Diabetes 2018 Jul;67(Supplement 1) General Poster Session American Diabetes Association

16 Volek J, Phinney S (2012) The Art and Science of Low Carbohydrate Performance Beyond Obesity, LLC

17 Courchesne-Loyer A, Croteau E, Castellano CA, St-Pierre V, Hennebelle M, Cunnane S Inverse relationship between brain glucose and ketone metabolism in adults during short-term moderate dietary ketosis: A dual tracer quantitative positron emission tomography study J of Cerebral Blood Flow and Metabolism 2017;37:2485-2493

18 Volek JS, Phinney SD Translating Basic Science to a Well-Formulated Ketogenic Diet Emerging Science of Carbohydrate Restriction and Nutritional Ketsosis conference at Ohio State University (2018) Aug 16 (Video)

19 Newport MT, VanItallie TB, King MT, Veech RL A new way to produce hyperketonemia: Use of ketone ester in a case of Alzheimer’s disease AlzheimersDementia (2015)Jan:11(1)99-103

20 Krikorian R, Shidler M, Dangelo K, Couch SC, Benoit SC, Clegg DJ Dietary ketosis enhances memory in mild cognitive impairment Neurobiol Aging (2012) Feb;33(2):425.e19-425.e27

22 Henderson ST, Vogel JL, Barr LJ, Garvin F, Jones JJ, Costantini LC Study of the ketogenic agent AC-1202 in mild to moderate Alzheimer’s disease: a randomized, double-blind, placebo-controlled, multicenter trial Nutrition & Metabolism (2009) Aug 10;6:31

23 Volek JS Keto-Adaptation: Implications for Human Performance JumpstartMD Weight of the Nation Conference (2018) Nov 2 (Video)

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