Spark

by John J. Ratey

stress seems to have an effect on the brain similar to that of vaccines on the immune system. In limited doses, it causes brain cells to overcompensate and thus gird themselves against future demands. Neuroscientists call this phenomenon stress inoculation.

The kicker is that even if we followed the most demanding governmental recommendations for exercise and logged thirty minutes of physical activity a day, we’d still be at less than half the energy expenditure for which our genes are encoded.

And in modern life, people tend to have fewer friends and less support, because there’s no tribe. Being alone is not good for the brain.

Studies show that by adding physical activity to our lives, we become more socially active—it boosts our confidence and provides an opportunity to meet people.