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Most of us are probably familiar with “the shakes.” They happen when we go without food for longer than we’re used to. When the shakes set in, we get irritable, lose patience, and even make careless decisions.
We’ve seen those funny Snickers commercials in which someone inadvertently says or does something utterly stupid because of hunger. Maybe we’ve done the same in our own state of hunger.
The shakes, the mindless dribble, the impatient trembling. They’re the result of low fuel in the brain. “I’ve got to get some food…”
This physical response to diminishing fuel for the nervous system and the brain — blood glucose — is real. Although the body has mechanisms to prevent blood glucose from dropping below the physiologic safe point, glucose does fluctuate and this drop can affect the brain. (And the words that come out of the mouth.)
In the absence of food, glucagon, epinephrine and other catecholamines trigger the release of fatty acids from fat cells. While peripheral tissues like those of the muscles and the heart can use fatty acids, the brain cannot.
But there’s another source of fuel for the brain — ketone bodies. Ketone bodies are the byproduct of fatty acid metabolism.
But even with the small amount of ketone bodies produced naturally from fatty acid metabolism (e.g. from a missed meal, or during sleep), the typical brain remains inefficient at using ketone bodies for fuel. The frequent-meal pattern typical in North America acclimates the brain to using the available glucose as the primary source of fuel, instead of ketones.
So thus the shakes, the stupid slip of the tongue, the left turn instead of the right, when blood glucose begins to diminish.
However, given the chance, the brain undergoes metabolic changes to adapt to this decreased availability of glucose. A major change in the brain is the upregulation of enzymes that help to metabolize ketones. The brain can learn to use ketone bodies for fuel.
Many of you are probably thinking that a very-low-carb diet can produce this adaptation to a fat-based fuel source. It takes a couple of weeks, yadda yadda. You’re right. But a very-low-carb diet sucks, and my wife and I love our sweet potato fries.
The other option may be the regular use of intermittent fasting (IF). A period of fasting decreases blood glucose and causes the body to mobilize and metabolize fatty acids to meet energy demands, thus producing ketone bodies.
Given a regular exposure to intermittent fasting, the brain may adapt to metabolizing ketone bodies for fuel. So even if you eat carbohydrates during your feeding windows, the upregulation of ketone-metabolizing enzymes may help to continue fueling the brain even when food is not available — such as when you miss a meal or during intermittent fasting.
As discussed frequently here and on other blogs, intermittent fasting has its many benefits. Now you can add sustained brain function even in the prolonged absence of food intake.
With regular use of intermittent fasting, there may no longer be a need to eat a Snickers bar, or to inadvertently say something utterly stupid.
What has been your own experience, before the regular practice of IF and after?