Why sport drives hunger away

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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Those who do sport burn a lot of energy - but usually have little appetite afterwards. The explanation for this contradiction lies in the hypothalamus, a brain region that plays a central role in the regulation of metabolism and weight.

Neuroscientist Young-Hwan Jo from the Albert Einstein College of Medicine in New York was able to observe in himself what many athletes are familiar with: After an intensive training session, his body temperature rose slightly for several hours. At the same time, his appetite was significantly reduced.

Gap in the blood-brain barrier

When looking for the cause, he mainly focused on special nerve cells that reduce appetite, the so-called POMC neurons. They sit on the Arcuate Nucleus, a specific section of the hypothalamus. The special thing about it: unlike most brain structures, these cells are not shielded by the blood-brain barrier, which protects the sensitive organ from harmful substances and pathogens. Therefore, the neurons can sense hormones and nutrients in the bloodstream.

Temperature meter in the brain

In studies with mice, Jo was able to show that the appetite suppressing neurons were equipped with temperature receptors. If the body temperature rises due to physical activity in the animals, the nerve cells reduce their appetite. After 40 minutes in the running bike, the sports mice ate 50 percent less than their fellow species who had not been physically active.

Twelve hours less hunger

The researcher achieved the same effect when he introduced capsaicin into the arcuate nucleus. This substance is found in chili peppers, among other things, and is responsible for the burning heat that characterizes it. The appetite suppressing effect lasted up to twelve hours.

In animals that did not have the appropriate temperature receptor, the appetite was not reduced by either capsaicin or exercise.

"Body temperature acts like a biological signal that regulates eating behavior," says Jo. Possibly one could use this connection to make it easier for people to lose weight.

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