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What explains the lack of appetite after a workout?
Last reviewed: 02.07.2025
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People who actively engage in sports know: after an exhausting workout on the exercise machines, you don’t really want to eat. What is the reason? Is there really a special mechanism in the body responsible for suppressing appetite after physical exercise?
Scientists from the Albert Einstein College of Medicine wondered if this could be due to elevated body temperature, as physical activity contributes to this.
Internal temperature regulation, as well as the feeling of hunger, is controlled by the hypothalamus, a small section of the brain that controls many physiological processes in the body. A specific group of neurons is responsible for each of these processes. The experts decided to find out if the same group of neurons could be responsible for both thermoregulation and food requirements.
The appetite-suppressing structures are located in the arcuate hypothalamic nucleus. Their functional focus is the analysis of hormonal balance and blood composition (the brain does not have direct contact with blood due to the presence of the blood-brain barrier).
In order to identify the ability of neurons to respond to temperature changes, the scientists treated their surface with capsaicin, a pepper alkaloid that affects heat receptors. Most of the neurons felt the effect of the alkaloid, indicating that they had active heat receptors.
The next stage of the study was laboratory experiments. The rodents were injected with pepper alkaloid directly into the hypothalamus, the area where the necessary nerve cells are located. As a result, the mice lost their appetite for 12 hours: some rodents ate, but much less than usual. After blocking the thermal neuronal receptors, appetite suppression with capsaicin did not occur.
At the final stage, the rodents spent about 40 minutes on a kind of treadmill: their temperature readings rose and remained at high levels for an hour. During this time, the mice also did not show a pronounced appetite, unlike those animals that did not take part in the "training". It is noteworthy that those mice whose neural thermal receptors were blocked ate with appetite even after the training.
Thus, the hypothesis was confirmed: neurons that suppress appetite also respond to thermal changes.
It will be interesting to see if the researchers can somehow apply the results they have obtained in practice: for example, in the matter of reducing excess weight and treating obesity. Although, the answer is obvious to many: if you want to curb your appetite, go to the gym, sign up for fitness or just ride a bike.
Information about the experiment is presented on the pages of PLOS biology (http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2004399).