Hungry? Or Just Stressed…

Published by on November 18, 2023

You’ve been working on a physics problem for what feels like hours. Suddenly, it hits you. “What’s in the pantry? If I had a sweet treat right now, surely, I’d figure this out.” For the most part, stress-eating seems harmless, and for many, it’s an involuntary response. The feelings of stress evoke a different response from each individual; however, is there a relationship between stress and hunger? If so, why are they related?

Although short-term stress is usually correlated with the suppression of hunger cues, long-term chronic stress is linked with weight gain (Chao, et al., 2017). This type of stress is closely related to the disturbance of the hypothalamic-pituitary-adrenal axis (HPA), which is the chain of command between the hypothalamus, pituitary gland, and adrenal cortex. The HPA axis is significant because it maintains a kind of homeostasis when it comes to our bodies dealing with long-term stress. The brain releases stress hormones called glucocorticoids, which are steroid hormones that come from the adrenal cortex (Chourpiliadis and Aeddula, 2023). These hormones are regulated by the HPA axis, which regulates glucocorticoids through a negative feedback loop (Figure 1).

Figure 1: The negative feedback loop in the HPA axis regulating glucocorticoids. A stressor posed to the brain then triggers the hypothalamus to release corticotrophin-releasing hormone to trigger the pituitary gland; subsequently, the pituitary gland produces adrenocorticotrophin hormone, which finally causes the adrenal gland to produce cortisol. Once cortisol levels are high, they induce the negative feedback by inhibiting the process (Mikulska, et al., 2021)

The glucocorticoid released by our brains under stress is cortisol; once there is too much cortisol in the blood, that is an indication to the hypothalamus and anterior pituitary to stop releasing tropic hormones. Cortisol stimulates the increase of glucose in the blood (Marik and Bellomo, 2013). It is also an antagonist to insulin, and insulin lowers your blood sugar. Cortisol binds to pancreatic β-cells that inhibit the intake of glucose, further inhibiting metabolism. This pattern signals to the body that it needs more food, thus causing us to crave sugary foods that are full of glucose (Janssen, 2022). Not only does this long-term stress cause an increase in weight but it also perpetuates the breakdown of amino acids present in muscle to turn them into glucose. This process is called glyconeogenesis, which is how we convert glucogenic amino acids into glucose through a series of oxidation reactions and phosphorylation. This process begins when the body needs to resort to fat stored as a source of glucose to further create ATP (Thau, Gandhi, and Sharma, 2023). The process of glyconeogenesis begins with pyruvate present in the amino acids (Figure 2).

Figure 2: The phosphorylation and series of oxidation reactions that pyruvate and its intermediates undergo during glyconeogenesis in order to create glucose (Sanders, 2016).

When the body has finished processing energy from fat stores, it will move on to processing muscle as a source of fuel. This is because our muscle tissue is primarily made of amino acids, which can undergo glyconeogenesis. Although stress accumulates in many aspects of students’ lives, there are real physiological effects that can be dangerous if such a pressure-ridden lifestyle is sustained. However, understanding these involuntary responses can indicate to us exactly what our bodies need. 

References

Chao, A.M., Jastreboff, A.M., White, M.A., Grilo, C.M. and Sinha, R., 2017. Stress, cortisol, and other appetite-related hormones: Prospective prediction of 6-month changes in food cravings and weight. Obesity (Silver Spring, Md.), 25(4), pp.713–720. https://doi.org/10.1002/oby.21790.

Chourpiliadis, C. and Aeddula, N.R., 2023. Physiology, Glucocorticoids. In: StatPearls. [online] Treasure Island (FL): StatPearls Publishing. Available at: <http://www.ncbi.nlm.nih.gov/books/NBK560897/> [Accessed 18 November 2023].

Janssen, J.A.M.J.L., 2022. New insights into the role of insulin and hypothalamic-pituitary-adrenal (HPA) axis in the metabolic syndrome. International Journal of Molecular Sciences, 23(15), p.8178. https://doi.org/10.3390/ijms23158178.

Marik, P.E. and Bellomo, R., 2013. Stress hyperglycemia: an essential survival response! Critical Care, 17(2), p.305. https://doi.org/10.1186/cc12514.

Mikulska, J., Juszczyk, G., Gawrońska-Grzywacz, M. and Herbet, M., 2021. HPA axis in the pathomechanism of depression and schizophrenia: New therapeutic strategies based on its participation. Brain Sciences, 11(10), p.1298. https://doi.org/10.3390/brainsci11101298.

Sanders, L.M., 2016. Carbohydrate: Digestion, Absorption and Metabolism. In: B. Caballero, P.M. Finglas and F. Toldrá, eds. Encyclopedia of Food and Health. [online] Oxford: Academic Press. pp.643–650. https://doi.org/10.1016/B978-0-12-384947-2.00114-8.

Thau, L., Gandhi, J. and Sharma, S., 2023. Physiology, Cortisol. In: StatPearls. [online] Treasure Island (FL): StatPearls Publishing. Available at: <http://www.ncbi.nlm.nih.gov/books/NBK538239/> [Accessed 18 November 2023].