Scientists find a fat hormone toggles a runner’s high

A long run feels the worst until it feels the best. That’s primarily thanks to the runner’s high — those euphoric feelings that strike halfway through an endurance workout.

Now, researchers have charted what happens to the brain to produce a runner’s high. The sensation is tied to low levels of leptin — a brain hormone that tempers food consumption when you’ve had enough to eat, according to a study published today in the journal Cell Metabolism. The scientists sketch out a switch in a precise set of brain cells that drives the urge to run in mice. Leptin regulates this switch, causing the animals to seek opportunities to run as well as allowing them to run for twice as long as usual.

Leptin is a “fat hormone” that tells your mind that you’re full of food. When you eat, leptin levels rise and you become lethargic. In contrast, when animals lose leptin in their brains, they become hyperactive gluttons, uncontrollably seeking and consuming food. They can’t be sated.

However, this low-leptin turbo boost is seen in another scenario: endurance runners. Marathon runners tend to eat less, which reduces the amount of leptin in their bodies. An earlier study found that marathon runners with the lowest leptin run faster and take the least time to complete their races, regardless of their body mass index. Rodents run faster and longer with less leptin, too. These trends suggest that leptin may govern the will to run, but how?

Read the article at PBS: https://www.pbs.org/newshour/science/fat-hormone-leptin-behind-runners-high