Regular exercise, much like calorie restriction, has a beneficial effect on near all measures of aging in humans - though unlike calorie restriction it doesn't increase maximum life span in laboratory animals. Here is a reminder that decline in brain function is slowed by exercise:
The new research included about 700 people living in the United Kingdom who all had brain scans when they reached the age of 73. Three years earlier, at age 70, the study participants were questioned about the leisure and physical activities they engaged in. People in the study who reported being the most physically active tended to have larger brain volumes of gray and normal white matter, and physical activity was linked to less brain atrophy. Regular exercise also appeared to protect against the formation of white matter lesions, which are linked to thinking and memory decline.
[In another study, researchers] recruited 120 older inactive adults with no evidence of dementia. ... Half began a modest exercise routine that included walking at a moderate pace for 30 to 45 minutes, three times a week. The other half did stretching and toning exercises. A year later, MRI brain scans showed that a key region of the brain involved with memory, known as the hippocampus, was slightly larger in the walking group, while it has shrunk slightly in the non-aerobic stretching group.
"The old view is that as we get older our brains become less malleable and less able to change. The new view is that it remains plastic even very late in life. We were able to show positive change after just one year of moderate-intensity physical activity."