Hormone Series Part 6: Cortisol, the 'Stress' Hormone

Cortisol is a hormone with a bad reputation, and when you look at some of the effects it has on the body it is easy to see why. But in this blog I am going to stand up for cortisol a little bit. If we take our understanding of physiology back to our body’s primary goal, survival, you will start to understand the roles that cortisol plays within our ongoing existence; this means that far from being ‘bad’, cortisol is essential.

The problems associated with cortisol are to a large extent determined by our own actions, or inactions. So instead of blaming this steroid hormone for its negative effects, maybe we need to take a little time to look in the mirror and figure out how, why and under what conditions cortisol is elevated and the relationship this has with health, muscle growth and metabolism.


Firstly, I’d like to separate elevations in cortisol into two different ‘camps’. The first camp is short term, acute elevations in cortisol and this response is actually beneficial in number of ways; on waking up after our overnight fast, our cortisol levels are typically at their highest. The reason for this is because cortisol is a key hormone in the breakdown of fatty acids from stored body fat, so to provide energy when we are sleeping to support recovery, repair and growth, cortisol allows us to maintain the fuel to drive these processes. This includes the breakdown of glycogen stored in the liver which is essential to maintain blood glucose levels and without it you could be in serious bother. See… It’s not always a bad thing! We also get an acute increase in cortisol after strenuous exercise and this is associated with a couple of things that happen to us physiologically that are related to cortisol’s catabolic actions. The second camp is when we get long term chornic elevations in cortisol and this, as we will see, has very different effects.


Firstly, it is important to understand that catabolism is a process that involves the breakdown of tissue or energy in the body; for many of us we associate the word catabolism with a loss of muscle tissue but in reality this is only one small piece of the puzzle. The catabolic response of cortisol to exercise includes the breakdown of glycogen and the release of fatty acids for energy; these are a positive catabolic response that enables us to maintain exercise performance. Secondly, although it is true that cortisol breaks down muscle tissue, but it is important to note that cortisol response is actually positively associated with muscle growth! This may seem surprising, but when we consider that muscle tissue needs to be broken down, proteins need to be removed and rebuilt bigger, stronger and more numerous, you can start to see that without some form of catabolism that anabolism would not effectively take place. The real issue becomes when we start to get elevations of cortisol for sustained periods, when the acute responses become chronic and when catabolism starts to overpower anabolism.


Chronically elevated cortisol levels can be caused by a number of different stressors. Environmental stress, work stress, emotional stress, dietary stress and over training can all elevate cortisol levels and keep them there for longer that we desire. It is during these periods that elevated cortisol can interfere with many of the body’s fundamental functions, such as response to insulin, interfering with the actions of our sex hormones in both men and women, fluid balance regulation, our immune response and bone turnover to name but a few systems that can be disrupted when cortisol levels get out of control. Although this is not ideal for health, many of these functions such as increased fat storage or impaired fat release and certain positive effects on the immune system, as well as keeping us alert and at the ready to drive the search for food or to flee from prey, would be helpful for our survival in harsher times.


Interestingly, when it comes to certain types of long term stress, such as stress associated with work or certain types of emotional stress or pressure, it appears that our perception of stress determines the health outcomes from it! When we are busy, under pressure at work and feel stressed, we can choose to view that as negative ‘I can’t cope, I can’t switch off, this will never get done, I’ll fail and lose my job’ or we can choose to accept that we feel stress and that stress is associated with positive outcomes, because we feel a sense of responsibility ‘yes there’s stress, but that’s because people are reliant on me, this means people trust me and know I am capable of coping when others might not, I’m feeling stress because I am trying to be successful and that doesn’t come easy’. The perception of stress and attitudes towards it are likely to determine if and how stress affects your health.


Fortunately for us, many of the other kinds of stress that lead to unwanted chronic cortisol levels can be reduced and often avoided. Dietary stress can be avoided by ensuring we eat enough calories, including enough dietary fat to support hormone production. Carbohydrates will raise insulin levels, which will reduce cortisol levels effectively and enough protein in the diet can preserve muscle tissue, even on calorie restriction. The important thing for any fat loss diet is to get the balance between creating enough of a deficit between energy intake and expenditure to cause a loss in body fat, but not so much that it causes rapid increases in cortisol, especially when combined with larger increases in exercise output.


For a bodybuilding type diet, these elevations in cortisol during the last few weeks of a contest prep are often unavoidable and is often indicated by a lack of quality sleep, feelings of extreme fatigue but an inability to switch off mentally even when feeling exhausted. This can lead to impairment in insulin sensitivity, effecting how the body deals with carbohydrates and puts the body at risk of muscle loss. It is important from this perspective that periodical days of higher calorie intake that are combined with adequate rest are used, especially if calorie deficits become severe in order to help reduce cortisol and allow refuelling of the muscles glycogen stores.


In summary, cortisol is not inherently ‘bad’ and has some important physiological roles to play, even for muscle growth. The real issue is exposing the body to too much stress for too long a period, but with sensible nutrition strategies, appropriate rest and the correct emotional support, many of these problems can easily be avoided.