Scientists from Albert Einstein College of Medicine in New York found why one's appetite was reduced after exercise, using a mouse model.
A study published on Tuesday in the open-access journal PLOS Biology said exercise could heat up the hypothalamus to drive down food intake.
Short-term appetite suppression is a well-known consequence of vigorous exercise, but the physiological mechanism behind it has been unclear, according to Jae Hoon Jeong, the paper's first author.
Scientists suggested that one likely mediator of the effect was the hypothalamus, a region of the forebrain that integrates many different kinds of signals from the body, including hormones, nutrients, and temperature, to produce homeostatic responses such as feeding or food avoidance.
Many of those responses are driven by cells of the hypothalamic arcuate nucleus, but these cells have not previously been shown to possess a key temperature sensor found elsewhere in the hypothalamus, called the TRPV1-like receptor or transient receptor potential vanilloid 1 receptor-like receptor).
The authors first showed that food-suppressing proopiomelanocortin (POMC) neurons in the arcuate nucleus express these receptors.
Next, they showed that POMC neuron activity increased in response to a rise in temperature. This response could be prevented either by blocking the receptor with a chemical antagonist or preventing its expression through genetic means.
When capsaicin, a hot pepper extract that also activates the TRPV1-like receptor was administered into the arcuate nucleus, the mice reduced the amount of food they ate for up to 12 hours.
This effect could be mitigated by blocking the receptor or preventing its expression before capsaicin administration.
Finally, the authors showed that exercise increased the temperature in the arcuate nucleus within 20 minutes of the onset of exercise, and that temperature remained elevated for more than one hour.
At the end of 40 minutes of exercise, mice spontaneously reduced their food intake by about 50 percent compared to non-exercised mice. Blocking the receptor or preventing its expression abolished this difference.
"Our results support the interpretation that arcuate nucleus cells of the hypothalamus have the ability to respond not only to hormones and nutrients, but also to temperature," Young-Hwan Jo, the paper's senior author, said. "We believe these cells are likely to play a role in suppressing food intake in response to exercise."