The opposite of a low fat, snacking lifestyle would be the lifestyle our ancestors lived for tens of thousands of generations, the lifestyle for which our brains are primarily evolved. It seems reasonable that we would have had extended periods without food, either because there was none available, or we were busy doing something else. Then we would follow that period with a filling meal of gathered plant and animal products, preferentially selecting the fat. During the day we might have eaten a piece of fruit, or greens, or a grub we dug up, but anything filling or high in calories (such as a starchy tuber) would have to be killed, butchered, and/or carefully prepared before eating. Fortunately, we have a terrific system of fuel for periods of fasting or low carbohydrate eating - our body (and brain) can readily shift from burning glucose to burning what are called ketone bodies.

It is true that some parts of some brain cells can only burn glucose, but fortunately our bodies can turn protein into glucose through a process known as gluconeogenesis. This fact means that while there are essential requirements for both fat or protein (meaning we would die without eating at least some fat and at least some protein), we can live quite happily while consuming no carbohydrate at all. That's not saying there aren't some disadvantages or side effects to a so-called "zero carb" diet, but it won't cause the massive health problems and death that consuming zero fat or zero protein would.

All of us who are metabolically healthy will shift into some amount of ketosis, typically overnight while we are sleeping. If your breath is a little funky when you wake up, and your urine smells a bit strong, you may well be in ketosis, which, unless you are a poorly controlled diabetic (a different kind of pathologic ketosis occurs in uncontrolled diabetes), being in ketosis in the morning is a good sign of a healthy metabolism. What does ketosis mean to the brain, and why would it be more healthy, perhaps, than our regular old carbohydrate burning metabolism? And does the high carbohydrate, low fat diet of constant snacking have a cost to our brains by robbing us of more regular and deeper bouts of ketosis?

Ketogenic diets, which are very high in fat and low in carbohydrate and protein, have been prescribed for seizures for a long time. The actual research diets used in the past were pretty dismal and seemed to involve drinking a lot of cream and eating a lot of mayonnaise (premade ketogenic formulas are nightmarish combination of omega 6 seed oils and corn solids).  At Johns Hopkins, pediatric patients were admitted to the hospital for a 48 hour fast and then given eggnog (minus the rum and sugar, I'm guessing) until ketosis was achieved (usually took about 4 days). In addition, ketogenic diets were calorie restricted to just 75-90% of what would be considered a child's usual calorie intake, and often they were fluid-restricted too (1)! If we're talking soybean oil mayonnaise, you could see how someone could get into trouble with mineral deficiencies and liver problems pretty quickly.

To understand "dismal," some of the latest research showed that a "modified Atkins protocol" was just as good as the classic ketogenic diet, and so much more liberating, as the patients were allowed up to 10 grams of carbohydrates daily, and they didn't begin with the fast, and they weren't calorie restricted (2)(3). While the classic ketogenic diet was 4:1:1 fat to carbs to protein. If you use medium chain triglyceride (MCT) oil for 50% of your calories (have to add it in slowly though to prevent vomiting, diarrhea, and cramping!), you could increase the carbohydrates and proteins to a 1.2:1:1 fat:carb:protein and still get the same numbers of magical ketones circulating. And while "MCT oil" sounds nice and yummy when it is gorgeous coconut milk, this MCT Oil 100% Pure 32 fl.oz doesn't look quite as appetizing, especially when that is going the be half of what you eat for the foreseeable future (4). You can see why researchers consider ketogenic diets (especially the original versions) to be extremely difficult and unappetizing (they were), whereas seasoned low-carbers (who have a bit of a different idea what a ketogenic diet is) will find that attitude ridiculous, especially when you compare a ketogenic diet to the side effects of some anti-epileptic medications.

So it looks like modified Atkins (very very low carb, but not zero carb) and a preponderance of MCT is the same, ketone-wise, for the brain as the classic ketogenic diet. And what does it mean to have a ketogenic brain? Let's examine neurotransmitters and brain energy more closely. Specifically, glutamate and GABA (5).

GABA is the major inhibitory neurotransmitter in the mammalian nervous system. Turns out, GABA is made from glutamate, which just happens to be the major excitatory neurotransmitter. You need them both, but we seem to get into trouble when have too much glutamate. Too much excitement in the brain means neurotoxicity, the extreme manifestation of which is seizures. But neurological diseases as varied as depression, bipolar disorder, migraines, ALS, and dementia have all been linked in some way to neurotoxicity.

Glutamate has several fates, rather like our old buddy tryptophan. It can become GABA (inhibitory), or aspartate (excitatory and, in excess, neurotoxic). Ketogenic diets seem to favor glutamate becoming GABA rather than aspartate. No one knows exactly why, but part of the reason has to do with how ketones are metabolized, and how ketosis favors using acetate (acetoacetate is one of the ketone bodies, after all) for fuel. Acetate becomes glutamine, an essential precursor for GABA.