LONDON, April 27 -- It's well established that exercise is good for our bodies, but what about our brains? A new American study, published in the Journal of Physiology, suggests that physical activity could play a key role in preserving our mental capacities, even when one of the brain's key energy sources isn't available.

This study focuses on a little-known mechanism: the production of ketones. These organic compounds are produced by the liver when the body is subjected to fasting, a low-carb diet or poorly controlled diabetes. Ketones then serve as an alternative energy source, particularly for the brain, when glucose is in short supply. Under normal circumstances, when glucose reserves are depleted, the liver takes over, generating t...