i know your brain uses a significant amount of the carbs you eat, around 25% i think.
question is: if you think more (say a day full of studying and exams), do you burn more carbs? what exactly burns the carbs, simply the brain tissue existing, or the activity of the brain?
does brain use fat and protein for energy?
thanks people.
I love the stuff I learn in this board, looking up things like this.
The brain uses glucose for fuel. In the case of low-carbohydrate diets, where that source of glucose isn’t so readily available (2/3 of the brain’s fuel source comes from carbohydrates, it seems), then the liver starts manufacturing more ketones or “fat fragments” to feed the brain. Brain processes start to slow down in consequence.
Lots of sites in Google regarding the brain, carbohydrates and ketones. Here’s one.
Actually, according to the cite that Ice Wolf gave:
"Meanwhile, the group that ate the low-fat diet ended up with a protein deficiency. This deficiency made it difficult for their brains to use glucose. In short, the brains of the low-carb rats received adequate energy supplies, the brains of the low-fat dieters were damaged by energy shortages. "
I got that babble out of reading sites like this one on nutrition, Cuckoorex. Sorry if I’ve put anyone wrong – as I said, this is a new topic for me, but fascinating nonetheless.
Hmmm…so which is it? According to the rat study, the low-carb rat brains (great band name!) were fine while the low-fat rat brains experienced problems with energy levels, and according to the “Nutriquest” site all brain functions are slowed down…so much so and so completely that apparently the person suffering the slowdown cannot even perceive it…??
Well, looks like the OP was close with the figure of 25% of the body’s energy needs going to the brain. This thesis puts the figure at 30%. Glucose and oxygen are the brain’s main sources of energy.
It might be best if the resident doctors among the Dopers answer this further, I think, Cuckoorex, especially if there’s conflicting citations.
bump, think more, burn more?
Yes. PET scans are based upon this fact. They detect the areas in the brains that are using the most glucose, which means those areas are the most active.
cool. barbitu8, what actually burns the glucose or how does the glucose get used?
Through the chemical energy of ATP and the Krebs’ cycle in mitochondria, glucose is burned. A chemist can give you a more detailed descpn, or Google Krebs’ cycle, ATP, etc. This is the method for any energy you may expend: muscle contraction, neural activity, etc. In neural activity, there is also repolarization and depolarization of the chemical balance inside and outside the neuron.
Thinking more may increase your brain’s carbohydrate demand, but I think the amount you burn will be insignificant. You would probably burn more carbs typing the post than thinking about what to type.
And then if you tap your foot while you are waiting for your post to post, Whew! Stand back! (kind of joking, and kind of not, it has been found that nervous tapping and drumming of fingers burns calories compared to sitting stil)
Good Luck,
-Sandwriter
Hmm, in biochem, I was taught that the brain (along with tissues such as the testes, red blood cells, and the kidney medulla) could only use glucose as a fuel. Other tissues, such as muscles, switch to using ketone bodies as energy. Thus, if your body’s glucose levels dropped too low, a process called gluconeogenesis kicked in. Your body takes amino acids (found in proteins) and strips off the nitrogens, then uses the carbon skeletons to synthesize glucose. This requires energy, which is supplied by the beta-oxidation of fatty acids. When lots of beta-oxidation is occuring (during starvation, but also in untreated diabetes), acetyl-CoA builds up, and is converted to the ketone bodies that have previously been mentioned.
More info, with links to fatty acid and ketone metabolism, can be found at this site.
Which is the basis for the Atkins Diet. As the body goes into Benign Dietary Ketosis, the brain’s demand for glucose gives the dieter a weight loss advantage.
In the first two weeks, of 20 grams or less of carbohydrates per day, the liver is drained of all it’s stored energy.
After the first two weeks, when carbohydrate levels are determined by the amount of weight lost - the amount stored in the liver (buy the book), the above process kicks in and the dieter converts fat to carbs.
But it doesn’t really matter. The OP is, will I burn more carbs if I think harder.
I say yes, but it’s too small to measure, like turning up your stereo while driving the car. Sure it requires more energy, more of a drain on the alternator, more work from the motor, more fuel for the extra work, but you can’t measure the effect on mpg due to the noise in the system.
And not that I’m promoting the Atkins diet. It has the same problems with all other diets, i.e. the weight comes back after you go off the diet. You need to change your lifestyle man.
I was told in Freshman Bio that heavy thinking (taking a stack of SAT tests, or coming up with the theory of General Relativity, or whatever) causes you to burn as many calories as you would burn while running a Marathon, i.e. that the increase in the brain’s calorie demand is very significant. Unfortunately I don’t have any cites for this, and it has also been eight years since I took Freshman Bio. Oh well…
loinburger, come on man. re-think that one!
I just thought about that myself, and lost 10 pounds!!
Careful, if he thinks too much it’ll be like he ran TWO marathons. As for the rest of you, don’t try that at home … or anywhere.