Saturday science subject: Brain hunger

Do you ever feel hungry after solving a difficult mental problem, writing a long paper, or perfecting a piece of code? Evidence shows our brains don't consume much energy regardless of how hard we think, so that doesn't make a whole lot of sense. However, Steve Mirsky over at Scientific American has come upon a study that confirms the phenomenon—and suggests an explanation.

The study, which was published in the Psychosomatic Medicine journal, involved getting 14 Canadian students together and asking them to do three different things at different times: relax, work on memory and attention tests, and summarize a text. Here's what happened:

Each session of intellectual work required the burning of only three more calories than relaxing did. But when the students hit the buffet table after the text summation, they took in an additional 203 calories. And after the memory and attention tests, the subjects consumed another 253 calories. Blood samples taken before, during and after the activities found that all that thinking causes big fluctuations in glucose and insulin levels. And because glucose fuels the neurons, a transitory low level in the brain may signal the stomach to get the hands to fill up the mouth, even though the energy actually spent has gone up just a hair.

Mirsky says the researchers who wrote the study claim such "caloric overcompensation" could be playing a part in the obesity problem. Of course, sitting in front of a computer all day probably doesn't help either way.

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