Natural High Linked to Leptin
Turns out the natural endorphins released during exercising often coined the "runner's high" comes from leptin (a key hormone in metabolism).
Researchers have found that leptin levels send signals to the brain's pleasure centre to generate rewarding effects after exercise
It was discovered that the rewarding effects of endurance activity come from leptin. Leptin inhibits physical activity through the release of dopamine (an important neurotransmitter for motivation).
Low leptin levels have previously been linked to exercise addiction and greater running speed. But this is the first time it’s been linked with the feeling of euphoria many runners get :)
Check out more about the research here