Cortisol gets a lot of attention, and is often associated with increased difficulty to lose body fat. So, a good place to start is to break down the primary roles that cortisol plays in our bodies. Cortisol has numerous functions but the primary roles we'll focus on in this article as they pertain to fat accumulation are:
1. Stress Response:
This is an evolutionary adaptation that developed to allow you to respond to potentially dangerous situations. For instance, when you encounter a lion your sympathetic nervous system kicks in which triggers a cascade of hormonal and physiological responses to allow you to respond accordingly. Cortisol, is one such hormone released during this SNS response which allows you to maintain a high level of alertness throughout this period of potential danger (1).
2. Muscle Catabolism
With regard to muscle and body composition cortisol is catabolic (it breaks down tissue, in this case muscle) and with chronic elevation you risk muscle loss (2). Cortisol is often produced as a response to a stressful state, so strenuous physical activity or a high level of psychological stress can signal the production and release of cortisol. Chronically elevated cortisol can also increase fat deposition.
3. Stress And Hunger Signalling
Stress can trigger hunger signalling. Specifically for highly palatable (often high sugar and high fat) foods which themselves have a hedonic element. So over time chronically elevated cortisol can increase hunger signalling through reduced reward sensitivity (3).
First lets make an important distinction between acute elevation and a chronic elevation of a hormone. Hormones are tightly regulated, and acute spikes are often not all that significant. The impact of hormones comes with time and consistent exposure. Contrary to what most people believe about cortisol, it's not a bad hormone and it actually plays a critical role in your health.
Hypothetically, if you have a man who decides to start taking steroids. He takes 500mg of testosterone per week for 3 months. Then take this same man and have him take the entire 3 month supply in a single week. Which protocol is going to yield better outcomes in terms of muscle growth and strength? Obviously taking a smaller dose consistently for a longer period produces better results because instead of an acute elevation you have a chronic elevation in testosterone that allows your body to pack on more muscle.
This is a bit of an oversimplification but it makes the point well enough. Professor Jamie Tartar studied neurobiological pathways that occur in stress responses. She has done a lot of research specifically on cortisol and on Episode 60 of the Iraki Nutrition Podcast she attests that chronic elevation of cortisol is really quite rare.
So for most people high cortisol is not to blame (or at least not the sole culprit) of their inability to decrease body fat. Chronic elevation of cortisol may occur if you have very high chronic anxiety, significant chronic sleep deprivation, maintain a caloric deficit for too long, if you get too lean (although the last one is likely not an issue outside of bodybuilding contest prep) and more. But often it's the combined effect of these factors that add up to create a physiological state where the response is chronic cortisol elevation.
But most people do not experience the above list to the degree that would trigger chronic cortisol elevation. And coming back to the role of cortisol in fat accumulation, it's incredibly rare for chronic elevation to occur much less exist as the primary reason you can't lose fat (4). Fat loss is regulated by energy balance. How many calories you consume vs how many calories you expend throughout the day. And even if you have chronic elevation of cortisol, the principle of energy balance supersedes abnormal hormone regulation (5).
Although at the micro level of analysis it's easy to think that cortisol is both to blame and a common occurrence, on a macro level of analysis it just doesn't play out like this in the vast majority of cases.
That being said, it's never a bad idea to create a buffer. Try to get 8hr of restful sleep each night, eat a well balanced and healthy diet, do what you can to minimize life stress and you can be fairly confident that cortisol is not impacting your body composition results.
If you are still concerned about your cortisol you can get blood work done to have a more in depth look at your hormone profile.
1. Kajantie, E., and D. Phillips. "The Effects of Sex and Hormonal Status on the Physiological Response to Acute Psychosocial Stress." Psychoneuroendocrinology 31, no. 2 (2006): 151-78. doi:10.1016/j.psyneuen.2005.07.002.
2. Ferrando, Arny A., Charles A. Stuart, Melinda Sheffield-Moore, and Robert R. Wolfe. "Inactivity Amplifies the Catabolic Response of Skeletal Muscle to Cortisol1." The Journal of Clinical Endocrinology & Metabolism 84, no. 10 (1999): 3515-521. doi:10.1210/jcem.84.10.6046.
3. Born, J. M., S. G T Lemmens, F. Rutters, A. G. Nieuwenhuizen, E. Formisano, R. Goebel, and M. S. Westerterp-Plantenga. "Acute Stress and Food-related Reward Activation in the Brain during Food Choice during Eating in the Absence of Hunger." International Journal of Obesity 34, no. 1 (2009): 172-81. doi:10.1038/ijo.2009.221.
4. Abraham, S.b., D. Rubino, N. Sinaii, S. Ramsey, and L.k. Nieman. "Cortisol, Obesity, and the Metabolic Syndrome: A Cross-sectional Study of Obese Subjects and Review of the Literature." Obesity 21, no. 1 (2013). doi:10.1002/oby.20083.
5. Rui, Liangyou. "Brain Regulation of Energy Balance and Body Weight." Reviews in Endocrine and Metabolic Disorders 14, no. 4 (2013): 387-407. doi:10.1007/s11154-013-9261-9.