As a cognitive scientist, I’ve been fascinated by the concept of mental clarity ever since I started experiencing it as a major benefit of living in a state of ketosis. Since no scientific definition of mental clarity exists and I don’t intend to invent one, here’s a bad analogy: Ketosis is to consciousness what glasses are to myopia, bringing blurry images into focus.
Thus my first hypothesis: Mental clarity augments the vividness by which you see cognitive structures in your mind, enhancing your conceptual lucidity, your focus on the elements of thinking, your ability to discern mental representations.
When I have a meal that contains over 250 grams of carbohydrates, the effects on my mind are striking. Thoughts start buzzing, making me feel dizzy, and I find myself becoming too tired to think straight. With my brain running on carbs, thinking becomes more effortful, and it’s more difficult to imagine ideas and concepts distinctly; like reading in dim light, it’s strenuous and exhausting.
This was less of an issue back when I was used to carbs. I was following a high-carb meal plan with 600-700 grams of mainly complex carbs a day for half a decade and, despite the typical tiredness after a large meal, I did quite well, both physically and mentally. So my mental performance depends mostly on what I’m used to eating, as long as I get enough calories from high-quality foods. However, my experience of mental performance—let’s call it “mental life”—seems to have been positively affected by my brain running on ketones.
From my personal experience, I’d say that more mental clarity doesn’t necessarily mean that I can use my brain better, but it’ll feel better when I’m using it, as my mind is in a perfect balance between sleepy and hyperalert, between sluggish and lightheaded, between lethargic and manic. This makes mental clarity a harmony in the brain that can be consciously experienced; as if ketones were greasing the cogs in my head.
Thus my second hypothesis: Mental clarity is a state of stress-free focus, calm alertness, and healthy arousal.
Still, my experiences may be nothing but the result of random imagination based on biased assumptions and theoretical expectations. If you want to read a more intersubjective perspective on the ketogenic diet, check out the book Keto Clarity by Jimmy Moore (and no, the book doesn’t define the concept of mental clarity either).
But there’s something more important than clinical knowledge and scientific fact, and that’s you. So important. Have you ever been on a ketogenic diet and experienced some form of mental clarity? How would you describe it? And how do you know that it’s not just your mind making up an effect or your perception being biased by overcompensation after the mind fog you’ve probably experienced during the adaptation phase? Tell me in the comments below!
To be frank, this blog post was mainly an impromptu exercise in phenomenological charlatanry. It’s just funny to me how keto gurus and supplement companies throw around buzzwords while nobody even knows what they mean. What we need is clear concepts, well-formulated hypotheses (unlike the ones above), and interdisciplinary studies that test the psychological changes in human subjects over a controlled process of keto-adaptation for several months. We don’t have any such studies, so don’t believe anyone who talks to you “scientifically” about how a ketogenic diet improves “mental clarity.”
Edit. If we simply define mental clarity as “not being/feeling confused,” the question becomes: How can we best measure an absence of confusion? By testing—relative to an individual baseline—the ability to put thoughts into sentences, the speed by which one solves mathematical equations, or the accuracy on certain memory or attention tests? Yet all such tests would measure objective cognitive performance, not the subjective experience of cognitive function, both of which are not necessarily correlated (Walitt et al., 2016).
Edit 2. In a self-report study (n = 138, Ross et al., 2013), the most common descriptors of brain fog were “forgetful,” “difficulty thinking,” “difficulty focusing,” “cloudy,” and “difficulty finding the right words or communicating.” If we assume that mental clarity is the inverse concept of brain fog, we can describe mental clarity as a state of well-functioning memory, thinking, attention, speaking, and communicating. Of course, this is still far from a useful definition and does not tell us anything about its relation to ketosis; although, considering the anti-inflammatory effects of a ketogenic diet, it probably leads to mental clarity by decreasing focal brain inflammation, which might be the physiological correlate of brain fog (Theoharides et al., 2015).
Edit 3. In a study by Ota et al. (2016), elevation of ketone levels through MCT oil improved cognition (working memory, visual attention, and executive functioning) in adults over 60 years old. Still, it is not clear to what extent this matches “mental clarity” as a subjective experience.
Edit 4. Proposal for an experiment: Put two groups on the same ketogenic diet protocol, with calories systematically adjusted to individual requirements. Give group A a bogus scientific report on how the diet should positively affect mental focus, motivation, and conceptual clarity; group B reads about the same effects, but reversed to be negative. Then survey their subjective cognitive states with phenomenologically verified questionnaires throughout and beyond the process of keto adaptation. T-test whether their experiences reflect what they have read in the bogus reports. Write and publish a paper on the results.
Ota, M., Matsuo, J., Ishida, I., Hattori, K., Teraishi, T., Tonouchi, H., Ashida, K., Takahashi, T., Kunugi, H. (2016). Effect of a ketogenic meal on cognitive function in elderly adults: potential for cognitive enhancement. Psychopharmacology, Vol. 233 (21-22), pp. 3797-3802, doi: 10.1007/s00213-016-4414-7.
Ross, A. J., Medow, M. S., Rowe, P. C., Steward, J. M. (2013). What is brain fog? An evaluation of the symptom in postural tachycardia syndrome. Clinical Autonomic Research, Vol. 23(6), pp. 305-311, doi: 10.1007/s10286-013-0212-z.
Theoharides, T. C., Stewart, J. M., Hatziagelaki, E., Kolaitis, G. (2015). Brain “fog,” inflammation and obesity: key aspects of neuropsychiatric disorders improved by luteolin. Frontiers in Neuroscience, Vol. 9, Art. 225, doi: 10.3389/fnins.2015.00225.
Walitt, B., Ceko, M., Khatiwada, M., Gracely, J. L., Rayhan, R., VanMeter, J. W., Gracely, R. H. (2016). Characterizing “fibrofog”: Subjective appraisal, objective performance, and task-related brain activity during a working memory task. NeuroImage: Clinical, Vol. 11, pp. 173-180, doi: 10.1016/j.nicl.2016.01.021.
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