Many of us feel ravenous after doing a challenging brain activity.
Does this mean we’re burning up so many kilojoules that we can ditch the afternoon run?
Your brain gobbles up more energy than any other organ, accounting for up to 20 per cent of your total energy intake. Its preferred source of energy is glucose, the sugar your body makes after eating carbohydrates.
Without sufficient glucose your brain’s chemical messengers, called neurotransmitters, will not be produced. This means that communication between your brain’s nerve cells would break down.
If the brain uses all this energy, could this explain why many of us feel hungry after doing any serious ‘brain work’?
Fourteen university volunteers took part in a study to measure the difference between hunger after rest, and after taxing brain activities. Despite the small number of students, the results were clear. Those students who did challenging brain activities consumed nearly 30 per cent more kilojoules than those who just rested.
The intellectual work, it turned out, caused much bigger fluctuations in glucose levels than during rest periods, perhaps owing to the stress of thinking. In response to these fluctuations, the body demanded food to restore glucose, leading to increased hunger.
So a brain workout will burn up excess kilojoules?
Yes, but not so that you’d notice, says David Levitsky, professor of nutrition and psychology at Cornell University. “It is true that the metabolic rate increases when you’re engaged in mental activity,” he says, “but it would take years for the difference to show up on the scales.”
“There are good, sophisticated studies that show that concentrated mental activity, like doing a difficult multiplication problem in our head, increases the glucose uptake to the brain,” says Levitsky. But he estimates that the difference would equate to about 40kJ a day.
The best thing to do after challenging brain activity? Go to the gym or head out for a brisk walk.
This article was previously published in the Well at Work Newsletter
