How workouts give your brain a boost

Squats for the booty — and the brain? Inside your head, there are about 86 billion neurons designed to bark orders to the rest of your body — all with the help of chemical messengers called neurotransmitters. These neurotransmitters regulate everything from your mood and sleep cycle, to memory and appetite.

What's it to you? Studies show that low levels of two of these neurotransmitters in particular, glutamate and gamma-aminobutyric acid (GABA), can lead to mood disorders such as depression. The good news: moderate exercise can increase these levels, according to a recent study in The Journal of Neuroscience. The result, whether you suffer from depression or not, is an increased resilience and capacity to respond to mental challenges, a concept known as "mental fitness," explains study author Richard Maddock, MD, a research professor at UC Davis Medical Center.

This study measured neurotransmitter levels in participants before and after 20 minutes of moderate-intensity exercise, so Maddock says it's not clear if lower intensity exercise would have the same effect on glutamate and GABA. But one small study suggests that GABA increases after 12 weeks of practicing yoga.

If you're constantly feeling overwhelmed by the stressors in your life, you might want to step up your fitness routine. Why? When you're stressed out your brain secretes the "fight or flight" stress hormone cortisol. This is good if you're about to get mugged on the street, but if your cortisol levels are chronically elevated, it can cause problems, says Jaffin. (Studies have linked high cortisol levels to heart disease, diabetes, high blood pressure, memory loss and more.)

Hit the track, weights or heavy bag, though, and you expose your body to something called "controlled stress," which helps sharpen your brain's stress response, Jaffin says. "You turn it on when you need it and turn it off when you don't." Done and done.

It's never too early to think about having a healthy brain as you age, and exercise can help by increasing your cognitive reserve. Translation: Your brain will be able to handle the deterioration that comes with age without taking its toll on your memory, says Jaffin.

"If you have more to begin with, you have more margin to suffer any aging decline without actually exhibiting cognitive impairment," she says. "Exercise seems to be preventive in aging and cognitive decline and potentially Alzheimer's disease as well."

Another A+ fact about exercise and the aging brain? Believe it or not, older adults who exercise actually have larger brain volumes than those who don't, according to a 2006 University of Illinois study. After six months of aerobic training, study participants had significant increases in both gray and white matter regions of the brain compared to those who participated in non-aerobic stretching and toning activities. Gray matter includes neurons, which are the basic cells of the central nervous system, Jaffin says, and preservation of white matter is associated with improved processing speed.

Plus, the hippocampus, the brain system associated with memory and learning (and often shrinks with age), is larger in people who are active, says Jaffin. This won't make you smarter, per se, but it will help you remember the important things the older you get. And that's as good a reason as any to fit in a workout today!