Impact of Exercise on Appetite Regulation

Understanding the Role of Body Temperature

It is widely recognized that physical exercise can lead to a reduction in appetite. Researchers have investigated whether even slight increases in body temperature might also play a role in appetite suppression. The hypothalamus, a small yet crucial area in the brain, is primarily responsible for regulating key functions, including circadian rhythm, body temperature, and emotional responses. Within the hypothalamus, nerve cells that produce proopiomelanocortin (POMC) are significant in appetite control.

Exercise and Appetite Suppression

While it is established that vigorous exercise can diminish appetite, the relationship between body temperature increases from exercise and appetite regulation remains unclear. Specifically, whether these temperature changes affect appetite directly or through the hypothalamus is still under investigation.

Research Findings on Thermoreceptors and Appetite

Connection Between Body Temperature and Appetite

A recent study published in PLoS Biology by a team of American researchers explored the link between body temperature and appetite through experiments conducted on mice. The researchers found that up to two-thirds of POMC-expressing nerve cells in the hypothalamus also express TRPV1 thermoreceptors, which help the body adapt to temperature variations. Previous research indicated that these paired TRPV1 thermoreceptors activate only at dangerously high temperatures, above 42°C.

Activation of TRPV1-like Thermoreceptors

The study revealed that lower temperature ranges (34°C-38°C), typical of exercise-induced increases, could activate TRPV1 thermoreceptors when paired with TRPV3 or TRPV4 thermoreceptors, referred to as TRPV1-like thermoreceptors.

Effects of Exercise on Thermoreceptor Activation

Physical Activity and Hypothalamic Temperature Increase

The researchers demonstrated that physical activity activates TRPV1-like thermoreceptors by raising both overall body temperature and hypothalamic temperature. After just five minutes of running on a treadmill, the body and hypothalamus temperatures in the mice rose by approximately 1°C to 37°C. After 40 minutes of exercise, these temperatures approached nearly 39°C.

Appetite Reduction Post-Exercise

Mice that engaged in physical activity consumed significantly less food within ten minutes following a 40-minute treadmill session compared to their sedentary counterparts. The increase in hypothalamic temperature due to exercise activated TRPV1-like thermoreceptors, which subsequently released a hormone responsible for appetite reduction.

Conclusion and Future Research Directions

Implications of Increased Body Temperature on Appetite

Overall, the findings confirm that minor increases in body temperature, similar to those experienced during physical exercise, can influence the brain and activate thermoreceptors that suppress appetite. However, as this study was conducted with mice, the extent of appetite suppression observed may not directly translate to humans. Additional research involving human subjects is necessary to further explore these findings.

References

(1) Jeong JH, et al. Activation of temperature-sensitive TRPV1-like receptors in ARC POMC neurons reduces food intake. PLoS Biol. 2018. 16(4): e2004399. Available at doi: 10.1371/journal.pbio.2004399.
(2) Mandal, A. What is the hypothalamus? https://www.news-medical.net/health/What-is-the-Hypothalamus.aspx. Accessed 7 May 2018.