"Makes you smarter - - - - - Researchers have long believed that exercise boosts smarts but there was not any hard scientific evidence until a few years ago. Now, says Fernando Gomez-Pinilla, a neurosurgery professor at the University of California, Los Angeles, it's known that exercise increases levels of some molecules in the brain that are very important for cognition. One such chemical is brain-derived neurotrophic factor (BDNF), a molecule that promotes the growth and survival of brain cells as well as communication between them. Studies in rats show that physical exercise boosts BDNF levels in the hippocampus, a brain structure critical for learning and memory formation, which in turn helps them remember how to navigate their way through underwater mazes. "The more exercise, the more changes in the brain; we found almost a linear relationship," Gomez-Pinilla says. "If we block the BDNF gene, we block this capacity of exercise to help learning and memory." - Michael Muller