The single most proven way to get smarter and happier

As an illustration of just how new this territory is, I'll go back to the story of neurogenesis, the once-heretical theory that the brain grows new nerve cells throughout life. "Ten years ago people weren't even convinced that it happened," says neurologist Scott Small. It was at his Columbia University lab, in 2007, where they witnessed telltale signs of neurogenesis for the first time in live humans. "Five years ago people said, OK, it might happen, but is it really meaningful? Now there isn't a week that goes by where there's not another study that shows neurogenesis has some kind of effect on the brain." [Spark: The Revolutionary New Science of Exercise and the Brain]

In his study, Small put a group of volunteers on a three-month exercise regimen and then took pictures of their brains. By manipulating a standard MRI machine's processing — essentially zooming in and cocking the shutter open — he captured images of the newly formed capillaries required for nascent neurons to survive. What he saw was that the capillary volume in the memory area of the hippocampus increased by 30 percent, a truly remarkable change. [Spark: The Revolutionary New Science of Exercise and the Brain]

"One of the prominent features of exercise, which is sometimes not appreciated in studies, is an improvement in the rate of learning, and I think that's a really cool take-home message," Cotman says. "Because it suggests that if you're in good shape, you may be able to learn and function more efficiently." [Spark: The Revolutionary New Science of Exercise and the Brain]

A notable experiment in 2007 showed that cognitive flexibility improves after just one thirty-five-minute treadmill session at either 60 percent or 70 percent of maximum heart rate… Cognitive flexibility is an important executive function that reflects our ability to shift thinking and to produce a steady flow of creative thoughts and answers as opposed to a regurgitation of the usual responses. [Spark: The Revolutionary New Science of Exercise and the Brain]

In 2004 researchers at Leeds Metropolitan University in England found that workers who used their company's gym were more productive and felt better able to handle their workloads. Most of the 210 participants in the study took an aerobics class at lunchtime, for 45 minutes to an hour, but others lifted weights or practiced yoga for 30 minutes to an hour. They filled out questionnaires at the end of every workday about how well they interacted with colleagues, managed their time, and met deadlines. Some 65 percent fared better in all three categories on days they exercised. Overall, they felt better about their work and less stressed when they exercised. And they felt less fatigued in the afternoon, despite expending energy at lunchtime. [Spark: The Revolutionary New Science of Exercise and the Brain]

In a landmark study affectionately called SMILE (Standard Medical Intervention and Long-term Exercise), James Blumenthal and his colleagues pitted exercise against the SSRI sertraline (Zoloft) in a sixteen-week trial… Blumenthal concluded that exercise was as effective as medication. [Spark: The Revolutionary New Science of Exercise and the Brain]

One interesting study in 2005 measured the physical and mental effects of exercise in a group of Chilean high school students for nine months… The experimental group's anxiety scores dropped 14 percent versus a statistically insignificant 3 percent for the control group (an improvement that could be explained by the placebo effect). [Spark: The Revolutionary New Science of Exercise and the Brain]

Researchers tracked 8,023 people for twenty-six years, surveying them about a number of factors related to lifestyle habits and healthiness starting in 1965. They checked back in with the participants in 1974 and in 1983. Of all the people with no signs of depression at the beginning, those who became inactive over the next nine years were 1.5 times more likely to have depression by 1983 than their active counterparts. [Spark: The Revolutionary New Science of Exercise and the Brain]

A massive Dutch study of 19,288 twins and their families published in 2006 showed that exercisers are less anxious, less depressed, less neurotic, and also more socially outgoing. A Finnish study of 3,403 people in 1999 showed that those who exercise at least two to three times a week experience significantly less depression, anger, stress, and "cynical distrust" than those who exercise less or not at all. [Spark: The Revolutionary New Science of Exercise and the Brain]

The best, however, based on everything I've read and seen, would be to do some form of aerobic activity six days a week, for forty-five minutes to an hour… In total, I'm talking about committing six hours a week to your brain. That works out to 5 percent of your waking hours.[Spark: The Revolutionary New Science of Exercise and the Brain]