The euphoria that marathon runners experience is actually a food-seeking behavioral response produced by low levels of the satiety hormone leptin. Stephanie Fulton of the University of Montreal is the first to decipher the chemistry that produces runner’s high.
Leptin levels decrease in the body as a person runs long distances. Distance runners have developed a body chemistry that has adjusted their bodies to lower levels of leptin. The decrease in leptin initiates a brain response that is a reward that is actually tied to food-seeking. Similar responses in mice and marathon runners have were observed by the researchers.
A leptin-sensitive protein called STAT3 (signal transducer and activator of transcription 3) becomes active when blood levels of leptin are low. The activity of STAT3 produces a large release of dopamine that is responsible for the euphoric feeling of runner’s high. The researchers verified the function of STAT3 in producing runner’s high by producing mice that did not have the protein or the ability to make the protein. The STAT3-deficient mice ran almost twice as far as normal mice without producing the high levels of dopamine that are associated with a reward for food-seeking behaviors in mice and men as well as increased stamina needed to find food.
Practical applications of the discovery include a reduction in the hyperactivity that is associated with anorexia. Naturally, now that the chemistry of runner’s high is known some people will attempt to produce the effect artificially. The potential for a new drug market that mimics runner’s high has slim chance of success because the only means of producing low levels of leptin artificially is a congenital genetic defect that causes obesity.