Brain calories

How many calories does thinking burn? Is there a correlation with the nature of mental activity (say, doing calculus vs. reading)? Does knowledge cut down on the mental work load? I’m trying to come up with the new fad diet…“Lose weight the smart way!”

I’ll buy the diet book, if history is any indication, but I still won’t lose any weight.

To check the calories consumed, divert your carotid artery and jugular vein, and track the difference in sugar levels.
Or, start with a guinea pig.

Good luck.

I believe the brain does consume a disproportionate amount of calories in the form of sugar.

A friend of mine has gone on a high protein very low carbohydrate diet and he has definitely become much dumber but this could be coincidence.

At least according to David Winsemius, as posted here on the Mad Scientist Network. He also says it doesn’t matter what you think about so I guess contemplating the origins of the universe uses the same number of calories as contemplating the lint in your bellybutton. How disappointing.

That is disproportionate to the rest of the body (and darn it, Sailor, that’s the second time you’ve made me laugh tonight).

WARNING! Annecdote ahead!

I know that when I spend a day doing difficult programming, or a similarly demanding mental task, I seem to be as hungry, come suppertime, as when I spend a day in some demanding physical task. On the other hand, when I spend a day without doing anything particularly difficult, mental or physical, I’m much less hungry. Make of that what you will, but it seems to support the premise of the OP.

The interesting thing about the brain is that unlike the muscles and other organs, it almost relies solely on glucose for energy. You will definitely feel it when you go on a fast and your body depletes its stores of glucose and glycogen (quick glucose). You will also feel it when excersing in such a manner that it rapidly depletes the glucose levels in your blood. For instance, doing hard squats in a weight room will burn tons of glucose. The muscles in your legs are huge and when that glucose-depleted blood from the legs hits your brain–wooooo–I have fainted before. When your body if forced to burn its stores of fat you will definitely feel extremely dumb. For a NOLS course, we had a 3 1/2 day fast with hiking up an over mountain ridges. The first day wasn’t bad. But the next few were murder when it came to going to the map and compass. Trying to coherently think was just as hard as the hiking I thought.

I had read somewhere that the brain uses up to 25% of the calories one burns when sedentary. I’m not sure where I read it, though. Another thing I read on this topic (it might have actually been in the Dr. Atkins diet book) was that ketones, a byproduct of burning fat, are actually the preferred fuel for one’s brain; that’s why going on a fast while searching for enlightenment seems to help. Don’t quote me on any of this; I’m just repeating what I read.

That is not what I learned in my biochemistry class. I think that ketone levels in the blood actually screw up the pH of the blood–that can lead to some light-headedness and, well, goofiness, and even hallucinations eventually. Keep in mind that most people seeking enlightenment usually do mind-disrupting things, like taking peyote. It doesn’t make you smarter–you are just screwing with the brain chemistry.

Ordinarily, glucose is the only fuel used by nerve cells. When there is a deficiency of carbohydrates in the diet, the body will break down muscle protein to form glucose (making glucose from pyruvate and pyruvate from amino acids). After a longer period of fasting, the body breaks down fat to form ketones, which can be used as fuel by nerve cells. But even when ketone production is at a peak, it provides only half the energy the brain needs.