The good news? Thinking burns calories! The bad news....
Scientists from Laval University in Quebec City (NOT Montreal, as I mistakenly wrote earlier) determined that you burn more calories while sitting and thinking (such as, working at the computer) than you do if you are just sitting and relaxing. But not many. In 45 minutes, you might burn an extra 3 calories. However, that wasn't really the point of their research.
It's what happens next that is really interesting: They found that you are likely to eat more after doing some sort of intellectual work than after resting. A lot more!
The study divided a small group of students into three groups. One groups relaxed for 45 minutes. A second group had to read and summarize an article. A third group spent the 45 minutes completing some computerized tests involving memory and attention.
The students were then given a snack and allowed to eat as much as they wanted. All three groups were engaged in basically sedentary activities and burned virtually the same number of calories during the session. Yet the reading group ate 200 more calories than the resting group, and the group that worked on the computer ate almost 300 more calories!
Why would thinking make you hungry?
I've often noticed that a long day at my computer (which seems like most days, lately!) can lead me to eat more throughout the day. And now I have some insight into why.
The scientists noticed that even though the differences in calorie expenditure were minimal, those engaged in thinking work had much larger changes in blood glucose levels during and after the session. Glucose is the main fuel for the brain and thinking may increase the brain's requirements for fuel, leading to fluctuations in blood sugar levels.
The researchers guess that these fluctuations in blood sugar might trick the body into thinking it has burned more calories than it actually has, leading you to overeat. (Here's a link to the study in the Journal of Psychosomatic Medicine.)
As someone who spends much of every day at my computer, here are the take-home lesson for me:
First, I need to avoid eating reflexively, especially when I'm working hard. Instead of munching absent-mindedly at my desk, I should stop what I'm doing and pay attention to what I'm eating!
Second, I need to be extra diligent about my daily exercise! Burning some real calories (as opposed to the "phantom" calories we burn by thinking) should help normalize--or at least compensate for--the body's cues to consume.
Have you noticed this phenomenon yourself?
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Posted by: Ihan | Apr 17, 2009 10:20:20 AM
"The study divided a small group of students into three groups"
You need to have large enough random samples to support this claim, you can't just do it over "a small group of students". Also the changes in calories burned need to be calculated that they are significant enough with a stated degree of confidence (like, 95% for example). Therefore, based on how the study is described, we can't accept the hypotheses that studying makes you eat more/ feel more hungry.
Posted by: Kashif Ansari | Apr 13, 2009 4:12:01 AM
You are right on that one.
The brain runs on glucose. But thinking and reading also increase the metabolism (no matter how small in comparison to physical exercise).
And you can lose a few pounds by really concentrating hard on a problem (like a psychic does).
People who do a lot of intellectual work tend to drink coffee and smoke cigarettes as these are mind-stimulants. They also eat smoked and cured meats for some reason as yet undiscovered.
Posted by: Jeny | Oct 6, 2008 10:35:33 AM
yes, it's worst when i'm revising, I just feel ravenous all the time, and i usually have a small apetite.
Posted by: | Sep 23, 2008 10:24:07 AM
Laval University is in Quebec City...
Posted by Monica:
Thanks for the correction. I've updated the post!
Posted by: Yuri | EatingforEnergy.ca | Sep 23, 2008 9:59:45 AM
I've totally noticed this, as a student and now on a daily basis as I crank through my work.
Posted by: Robert Martin-Hill II | Sep 22, 2008 11:02:16 PM
Yes you want to eat and for good reason. When you eat you release vasopressin a hormone which reduces the production of urine, as you will need the water to process the food. The other effect of this hormone is to help in memory formation. This means that it is good to eat a bit after you study. But obviously one needs to watch that one does not eat to much.
