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How Stress and Cortisol Affect Weight Loss

Updated: Sep 21, 2020

This blog post will cover how stress and cortisol (hormone produced by stress) affect our bodies and how it stops weight loss. In order to lose weight, we ultimately need to be aware of not just our exercise and nutrition, but our lifestyle also. This blog will tell us why that is.

First, let's understand what cortisol is and how it is produced. Cortisol is known as the 'stress hormone' which puts us in a flight or fight response. In paleolithic times, the stress that led to the release of cortisol was often for physical threats, such as running from a predator or hunting a prey. Cortisol helps us prepare for fight or flight. When cortisol is released, our body enhances glucose absorption to our muscles for us to use as quick energy so we can effectively fight or run away. All energy is directed to us fighting or fleeing, other systems in our bodies such as immune system, digestive system is temporarily put on hold as our focus is on surviving first. Once this danger or threat is passed, our cortisol goes back down and everything goes back to normal. Once the stress has passed, no more cortisol will be produced. That is the point of stress and cortisol, our bodies are well adapt to short term increase in cortisol. It is with long term stress that it becomes a problem.

In our modern society, we face non-physical stressors that are prolonged and chronic. These can be anything from family issues, work issues, relationship issues to sleep deprivation. The fact is that long term stress and continually high levels or cortisol will not help with weight loss.

In the short term, cortisol may be good for us as it does the opposite of insulin. Insulin is a storage hormone that stores energy in muscles and as fat. However, cortisol helps us use energy in our muscles, a seemingly opposite effect. This is true for the short term. Long term, however is a different story.


Under conditions of chronic stress, glucose levels remain high in our blood as the stressor never leaves us. Maybe it is our work that is stressing us, unless we leave our job, the stress will always be there. This means that our blood sugar can be elevated for months. Since we are not actually under any physical threat, meaning that we don't actually have to physically run or fight, our muscles don't use the glucose that is in our blood. And what does this do? It triggers insulin production to get the glucose out of the blood and lower our blood glucose levels back to normal. As we know now, insulin is a storage hormone that doesn't help with weight loss. So the more insulin produced by our bodies, the worse or the harder it is to lose weight. (Read Understanding how Weight Loss Works blog)

The more our bodies continually produce insulin, the more chance we have to becoming insulin resistant as our bodies become accustomed to insulin. Insulin resistance is a big factor for diabetes and obesity. So to put it very generally, cortisol increases blood glucose levels while insulin lowers it. This means the higher levels of cortisol, the higher level of insulin.


Sleep deprivation is a huge cause of the rise in cortisol. For the past couple of decades, sleep has been slowly reducing as we are all focusing more on the hustle of life chasing success. Sleep deprivation is a psychological stressor that increases cortisol. One night of sleep deprivation increases levels of cortisol by more than 100%! By the next evening, cortisol levels are still 30%-45% higher. Without sleep, cell function is compromised which means that insulin sensitivity will be reduced, this will lead to more insulin production to get the job done. It is a lose lose situation. Can we see the impact of sleep deprivation now?

A side note I want to add is that high stress levels also cause our immune system to weaken. This doesn't have any direct effect on weight loss but I wanted to add it in here because it is important to know. As stated above, cortisol puts survival fist which means all functions such as immune system is put on hold temporarily, the key word is temporarily. Once stress becomes chronic, our bodies will always think we need to fight or take flight. This means our immune system is constantly put on hold not so temporarily. As our immune system weakens, we will find ourselves more susceptible to sickness and diseases in the long run. Something that needs to be known and taken seriously for long term health. That is why we always see highly stressed people sick, or getting sick easily and finding it hard to fully recover.

Back to the issue of weight loss, so if higher cortisol levels mean higher insulin, which leads to obesity, that means that lowering cortisol will be a benefit. Reducing stress is difficult but vitally important. What we need to know is that sitting down in front of the TV or computer is a poor way of reducing stress. What we see and watch on TV are usually stimulants for us to keep us interested, this type of distraction does not have great stress reducing effects. There have been tried and tested methods of reducing stress such as mindfulness meditation, yoga, massage therapy and exercise to name a few.*

We really need to make a conscious effort to reduce our stress levels on a daily level if we want to improve our health and weight loss results. The biggest one that we can change as soon as we want to is our sleeping patterns. If we slowly put in stress reduction practices, even if it is just a small amount of time everyday, we will slowly start to feel and see the results.

There will be a separate blog post on practices that can reduce stress, this blog post was written to let us know the implications of high and chronic stress. I hope we all understand the effects that stress and cortisol has on our bodies.

*Check out the post on Methods of Stress Reduction here.