From the NYTimes an article on how exercise improves brain functioning. This could be part of the anti-aging aspect to exercise. (More info on my practice here.)

How Exercise Fuels the Brain
By GRETCHEN REYNOLDS
Moving the body demands a lot from the brain…
This increase in brain activity naturally increases the brain’s need for nutrients, but until recently, scientists hadn’t fully understood how neurons fuel themselves during exercise. Now a series of animal studies from Japan suggest that the exercising brain has unique methods of keeping itself fueled. What’s more, the finely honed energy balance that occurs in the brain appears to have implications not only for how well the brain functions during exercise, but also for how well our thinking and memory work the rest of the time...
But about 10 years ago, some neuroscientists found that specialized cells in the brain, known as astrocytes, that act as support cells for neurons actually contained small stores of glycogen, or stored carbohydrates. And glycogen, as it turns out, is critical for the health of cells throughout the brain.

While a brain with more fuel reserves is potentially a brain that can sustain and direct movement longer, it also “may be a key mechanism underlying exercise-enhanced cognitive function,” says Hideaki Soya, a professor of exercise biochemistry at the University of Tsukuba and senior author of the studies, since supercompensation occurs most strikingly in the parts of the brain that allow us better to think and to remember. As a result, Dr. Soya says, “it is tempting to suggest that increased storage and utility of brain glycogen in the cortex and hippocampus might be involved in the development” of a better, sharper brain...
He and his colleagues have found that “glycogen supercompensation in some brain loci” is “enhanced in rats receiving carbohydrates immediately after exhaustive exercise.” So for people, that might mean that after a run or other exercise that is prolonged or strenuous enough to leave you tired, a bottle of chocolate milk or a banana might be just the thing your brain is needing.