I recently wrote a forum posting on a bodybuilding forum I’m a part of. A user asked about difficulty thinking during the first few days on a Cyclical Ketogenic Diet.
The overzealous rationalist returns!
I recently went back on Atkins (very similar to the MANS/CKD diet, at least five days out of the week) after a four-year lapse, but I’d maintained it for two years before getting sick and falling off my eating plan.
What you’re referring to, if you’re new to low-carbohydrate eating, is “brain fog”. A lot of people experience it, particularly in the first three to five days on the diet. It’s usually a symptom of insufficient glucose to the brain. When you are low-carbing, your body relies on ketogenesis (fat to acetoacetate metabolism) and gluconeogensis (protein to glycerol metabolism) to power your body, rather than carbohydrates.
The issue is that the brain takes some time to get used to the idea of using acetoacetate for function. It takes long-term low-carbing (or starvation) of at least several days for it to reach its maximum use of acetoacetate rather than its preferred food, glucose. That said, the maximum amount of acetoacetate the brain can use is about 70% of its total energy consumption. The remainder MUST come from glucose, which if you are on a very low-carb diet will mainly come from gluconeogenesis of proteins. If you aren’t eating enough protein to support this metabolically “expensive” process, then your body will pillage other protein sources in the body (read: muscles and vital organs) to keep the brain supplied with glucose.
All that said, there are a few things you can do to improve the first-few-days brain-fog: * Take ginko biloba * Take B-complex vitamin supplements (and your multivitamin, of course!). In particular, large doses of thiamin up to 50mg enhance brain function by facilitating glucose uptake. Any thiamin above around 50mg per day passes in the urine, so once again, drink a lot of water! * Ensure you’re getting plenty of protein and healthy veggies. * If all else fails, just wait another day or two. The brain fog should pass shortly.
Now, some people’s brains don’t switch into acetoacetate consumption in substantial quantities. The rest of the body switches faster, and will begin consuming ketones in preference to glucose to save glucose for the brain. If the brain fog doesn’t resolve itself within a couple of weeks of the start of regular low-carbohydrate eating, then you may need to modify your carbohydrate consumption expectations to the higher end of the range (~60g carbs/day) rather than the lower end of the range (less than 20g carbs/day), as well as increase your protein consumption compared to fats.
The brain and central nervous system together, in an average person, consume right around 100g of glucose per day (more or less; the actual average for American males is around 104g). Acetoacetate can substitute for the brain and central nervous system nutritional requirement up to around 50-70g. But the process of the brain “turning on” its metabolism of acetoacetate takes a few days.
That said, however, once it’s made that adjustment, the brain can “turn on” its ability to use acetoacetate rather than glucose much more quickly. This, combined with the fact that glucose stores in the muscles and liver are readily given up to the needs of the brain, is part of the reason CKD works at all.
Sorry, that was probably TMI, but I spent a lot of time researching the biological pathways used in low-carbohydrate metabolism prior to getting into the diet years ago, and the intervening six years has introduced an enormous amount of research into why our bodies can work this way. Some animals can’t!