How Does Cortisol Affect Weight Loss?


          Have you ever been so stressed out that you can’t focus on anything? Have you experienced high levels of fatigue and trouble losing weight despite your best efforts? Stress affects everyone, but do you know how it affects you? If the answer is no, then you are going to want to learn more about the hormone cortisol.


           Cortisol is a glucocorticoid, more commonly known as a stress hormone. It is one of the most important hormones in regards to maintaining a healthy functioning mind and body. It is essential in regulating blood sugar, proper immune functioning, blood pressure, and metabolizing fat, protein, and carbohydrate for use as fuel. When cortisol levels are too low, it loses its effectiveness to fight inflammation within the body. This can lead to the breakdown of healthy tissues such as the intestinal lining in your gut, which can cause digestive problems. Cortisol levels that are too high can decrease white blood cell and antibody formation, thus suppressing the immune system, and can lead to chronic diseases such as cardiovascular disease. The issue isn’t cortisol itself; it is the imbalance over a long period of time that does the damage.


           There are different times throughout the day where cortisol levels are naturally elevated, like in the early mornings between 7 and 9 am. This is the time period between light and dark where your body is signaled that it is time to wake up, kick start your appetite, and get moving so you can go about your day. After a hard workout when your muscles have been mutilated, inflammation is your body's’ first responder in repairing the damage. Once this process is complete cortisol comes in to reduce the inflammation and return your body to homeostasis or baseline. When you’re doing homework in your apartment and a spider decides to dangle itself in front of your face and you feel like this might be the end, your body immediately prepares for the “fight or flight” response. Different people have different responses to spiders but you get my point. These are all good and natural responses and that is why it is important to keep cortisol levels normal and functioning properly so when we need it, it’s there.


           That “fight or flight” response comes from the autonomic nervous system. This system contains two subdivisions: the sympathetic (SNS) releases epinephrine and norepinephrine in response to cortisol and is more commonly known as the “fight or flight” response, and the parasympathetic nervous systems (PSNS) which is activated during times of rest and relaxation. One cannot be activated at the same time as the other, but the two work together to maintain homeostasis within the body. Think of this as the SNS is the gas pedal, and the PSNS is the break in a vehicle. When you’re out for a drive (your daily activities) you’re using both your break and gas pedal, but not at the same time, to maintain a steady speed (homeostasis). When you get to your final destination, you apply the brake, put your car in park, and shut it down for the day. But what happens if you never apply the break… When your body doesn’t get to apply the brakes, stress is not resolved and your hormone levels are unable to return to normal. Having chronically elevated levels of cortisol in your body for an extended amount of time is when you run into trouble.


         It takes about eight days for your body to “reset” its baseline of cortisol levels. So if you are overly stressed for 8 days your body feels as if this is the new normal, and it responds by creating and releasing even more cortisol. To stick with the same car analogy, this is like adding a turbo to your car, and cutting the brake line. The following paragraphs will explain why this will have a negative effect on you physically and psychologically.


           There are two types of belly fat: visceral, and subcutaneous. Visceral fat is the stuff you can’t see when you look directly at someone. It is underneath the abdominal muscles and in close proximity to the organs, and because of this, it is hazardous to our health. Subcutaneous belly fat is above the abdominal muscles and isn’t necessarily a health risk.  When you are starting an exercise/clean-eating regimen, your visceral fat is the first to go because it has a greater blood supply and is more sensitive to fat burning hormones such as catecholamines. That is why you often hear about “stubborn fat” that won’t seem to come off. While you will burn some subcutaneous fat, if your regimen is solely focused on negative energy balance, you may be missing the hormonal role that cortisol plays.


           There are two main players; insulin, and of course, cortisol. The biggest influence on insulin comes from the range of starchy to sweet foods that you eat. Cortisol has the ability to increase fat storage because of the effects it has on fat storing enzymes. Your body can’t differentiate between stressors. An acute release of cortisol from exercise is the same as the stress caused from cramming for a final exam the night before. Both increase appetite, typically for “comfort foods”, and cause metabolic responses in the body. This is why insulin and cortisol working in accordance with each other is the biggest contributor to fat storage.


           Think of it this way… you had a hard workout in the gym, and you know that your body requires a certain amount of calories to fuel your workout, repair your muscles, and help you perform other bodily activities like proper organ functioning and breathing. Now add outside stressors to your day on top of that. The energy requirements are increased, and the increased amount of cortisol from the stress in the blood starts pulling amino acids from our muscles and breaking them down into glucose through gluconeogenesis to provide fuel for the body to combat the stress.


           This decreases the muscle mass within the body, and increases the amount of blood glucose, meaning that fat is no longer the primary source for fuel at rest. Over time, your body learns to produce more glucose than it needs by taking from your muscles, regardless of if your body is in a negative caloric balance or not. For those people who follow strict diets and exercise protocols, this is where you run into trouble with losing fat around the middle. You could be hitting your macronutrients day in and day out, eating the right amount and types of carbohydrate to spike your insulin at the right time, but you may also be chronically stressed from jobs, relationships, school, money, etc. That doesn’t sound ideal for someone who wants to build muscle and lose stubborn fat.


           Highly elevated glucose levels leads to a number of other issues as well, not just aesthetics. Not only does cortisol have an effect on your metabolism, but it affects your heart and your brain, as well. Chronic cortisol levels are activated by the sympathetic nervous system and cause blood vessels to dilate to allow greater oxygen exchange, and increase your heart rate in response to a stressor. This paired with elevated blood glucose levels is a recipe for disaster as it can easily lead to cardiovascular disease if not addressed. It is the number one killer in the United States and is highly preventable.


           The two areas of the brain that have the most glucocorticoid (stress hormone) receptors are the frontal cortex and the hippocampus. The frontal cortex is the area of the brain where impulse, judgment, and reasoning happens, and the hippocampus is the part of the brain that controls learning and memory. When we experience high levels of stress over a long period of time, the brain, and many other parts of the body experience atrophy, or the deterioration of cells. This causes a change in emotional and behavioral responses by the impairment of the frontal cortex. This impairment of the frontal cortex can lead to a lack of response to serotonin, which makes you feel gloomy and perceive more stressors. The more stressors you perceive, the more damage is done to this part of the brain, and the cycle just continues. The hippocampus “learns” depressive behaviors as the control you have over coping mechanisms to stress seems more and more out of your hands, and you begin to have feelings of self-doubt and helplessness. This is why stress is such a serious contributor to diseases like depression. Furthermore, when students are crunching for finals week, they don’t effectively absorb information because high levels of cortisol from the stressful environment impair learning. Has anyone ever told you it’s better to study a little bit every day leading up to an exam? There is a reason why.


           So if you feel like you have been constantly stressed, you may not be allowing your body to return to its natural state. You owe it to yourself to begin practicing some form of stress relief for your mental and physical health. Try any of the following activities to activate the parasympathetic nervous system, and decrease your stress levels. The possibilities do not end with the suggestions on this list. The key is to find something that you enjoy doing and can do consistently for relaxation.

  • Take a hot shower

  • Go for a walk

  • Perform deep diaphragmatic breathing

  • Practice light yoga

  • Meditate

  • Exercise

  • Get a massage

  • Spend time with a pet



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Donoho, C. J., Weigensberg, M. J., Emken, B. A., Hsu, J.-W. and Spruijt-Metz, D. (2011), Stress and Abdominal Fat: Preliminary Evidence of Moderation by the Cortisol Awakening Response in Hispanic Peripubertal Girls. Obesity, 19: 946–952. doi: 10.1038/oby.2010.287