Going for a run every once in a while perks us up and makes us feel happy, and it all happens because this pastime activity transforms our body's chemistry, researchers at the University of Montreal write in a study in the science journal Cell Metabolism.
The scientists explain that, having experimented on lab mice, they learned that the so-called runner's high that avid joggers experience comes down to more than just a release of endorphins, which are chemicals known to act on the brain to reduce perception of pain and trigger a positive feeling similar to that produced by morphine.
Thus, it appears that yet another compound known as leptin comes into play when we take up jogging and pushes us to keep moving by dictating specific responses in the brain.
Our body is a complex machinery
Leptin is a key metabolism hormone that is produced by adipose tissue and that keeps our appetite in check. The more adipose tissue we have in our body, the more leptin is produced and so our appetite is suppressed, seeing how we have plenty of energy reserves.
When we lose adipose tissue and leptin levels drop, the brain knows that it is time to get physical and go in search of food. This is when the neurotransmitter dopamine, known to be involved in motivation, kicks in and encourages us to stay active so that we might find food.
More precisely, dopamine acts on our behavior in that it makes running feel as a pleasant, rewarding experience. When our ancestors had to chase game to feed themselves, this was most certainly the case. Although food is no longer an issue, we still get the same runner's high.
“Mammals in general are thought to have evolved to increase the return on effective food acquisition behaviors. Ultimately, hormones are sending the brain a clear message: when food is scarce, it's fun to run to chase some down,” the University of Montreal researcher say.
Testing the theory on laboratory mice
As part of their investigation into how and why running makes us feel good, the scientists genetically engineered mice lacking a molecule that is activated by leptin and that is involved in the production and the release of the reward chemical dopamine.
When left alone in their cages, these rodents ran on their wheels more than normal mice used as a control did. The research team think this happened because, what with the link between leptin levels and dopamine production disrupted, their brain assumed that they needed food and so got them all worked up.
“Previous studies have clearly shown a correlation between leptin and marathon run times. The lower leptin levels are, the better the performance. We speculate that for humans, low leptin levels increase motivation to exercise and make it easier to get a runner's high,” explains researcher Stephanie Fulton
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