The Best Damn Cortisol Article Ever

by Christian Thibaudeau

What It Really Does and How to Control It

It's been called the stress hormone, the belly fat hormone, and the thief of gains. But it doesn't have to be any of those. Here's how to control it.

Cortisol is like the boogeyman. To scare lifters away from doing extreme things, we tell them that cortisol will eat their gains. While there's some truth to that, it's not the whole picture.

Believe it or not, there's no hormone in the body whose purpose is to destroy the body. Cortisol has many key functions, but sometimes the hormone causes a little collateral damage when it comes to looking good naked. Let's take a closer look.

The Functions of Cortisol

I call cortisol the "readiness hormone" rather than the stress hormone. Its main purpose is to make sure you'll be capable of facing any potentially threatening situation.

  1. It increases wakefulness, focus, energy, and drive. It does so by raising adrenaline. Cortisol increases the level and activity of an enzyme called Phenylethanolamine-N-methyltransferase (PNMT). This enzyme converts noradrenaline into adrenaline. It's through this action that cortisol increases adrenaline, which has a direct impact on your state of mind.
  2. It increases heart contraction strength and rate. This helps with oxygen transport to muscle and the clearance of metabolites. This is also done via the increase in adrenaline.
  3. It increases muscle contraction strength. This is the third impact of increased adrenaline.
  4. It mobilizes stored energy. It does so to keep you from running out of fuel when you're fighting a sabre-toothed tiger or fleeing from it. This is a non-selective process, meaning that all potential energy sources can be broken down and mobilized by cortisol: muscle and liver glycogen, fatty acids from body fat, and amino acids from muscle tissue.
  5. It helps you maintain stable blood sugar levels. It increases blood sugar when it's too low (along with glucagon and growth hormone).
  6. It inhibits the immune system. This happens so you'll have more resources to fight the enemy. Just like in Star Trek when the captain would say, "Divert all available energy to the deflector shields" in the midst of a battle, the body does the same when cortisol tells the body it's facing danger. For example, during times of fight the immune system will be inhibited. As soon as cortisol goes down, it'll be brought back to full force to repair the damage from the battle.

Note: You can't dissociate cortisol from one of its functions. When it's elevated, all of the six things above will happen.

So, cortisol is actually quite necessary. It's essential to have a boost in cortisol when you're fighting a tiger, deadlifting a PR, or trying to tackle a running back. But if it stays elevated for too long it can have negative effects. Let's take a look at how that affects our muscle growth, fat loss, recovery, and well-being.

Cortisol and Muscle Growth

When cortisol becomes chronically elevated it can severely hurt muscle growth via several mechanisms:

  1. It directly increases muscle breakdown. The amount of muscle you build depends on the difference between protein breakdown (catabolism) and protein synthesis (anabolism). If you increase protein breakdown (which cortisol does) it becomes a lot harder to be in a significantly positive balance.
  2. It decreases nutrient uptake by the muscles. This makes it harder to shuttle amino acids to the muscle to build new tissue and restore muscle glycogen stores.
  3. It increases myostatin. Myostatin is a myokine (protein) released by the muscles which limits muscle growth. The more myostatin you produce, the less muscle you can build. By increasing myostatin, chronic cortisol elevation will limit your potential for growth.
  4. Over time it can decrease testosterone levels. Testosterone and cortisol are both made from pregnenolone. If you overproduce cortisol, you can decrease the amount of available pregnenolone that would otherwise make testosterone.
  5. It slows muscle tissue repair. Repairing damaged muscle tissue after a training session is heavily dependent on the immune system. Chronic cortisol elevation weakens the immune system making muscle damage repair less efficient.

Note that after a workout, protein synthesis is elevated above baseline for 24-36 hours (although significantly only for 24-30 hours). This is the timeframe you have to repair the damage and add new tissue. If your immune system is weak, it might take you the full duration just to repair the damage you caused. This means you don't have time in that enhanced state to add muscle. It's a predicament that can make muscle growth a very slow process.

Cortisol and Fat Loss

If you're familiar with coach Poliquin's body composition analysis approach (biosignature, bioprint, metabolic analytics) you know the system claims that excess cortisol leads to abdominal fat storage.

But if you remember what the functions of cortisol are, you might see a contradiction here. After all, one of the functions of cortisol is to mobilize stored energy (including fat), not store it.

Cortisol is, in fact, a fat loss hormone, at least when produced in a pulsatile manner. But that doesn't mean chronic cortisol can't make it harder to lose fat. While a short-term elevation of cortisol is involved in fat loss, if it becomes chronically elevated it can make the fat loss process harder. How? Two ways...

1. Cortisol Can Decrease the Conversion of T4 Into T3.

Remember, T3 is the thyroid hormone that has the greatest impact on your metabolic rate. When it's higher, your metabolic rate increases so you burn more calories on a daily basis.

If T3 goes down, so does your metabolic rate. So T4 doesn't have as much of a direct impact. The body produces mostly T4 and converts it into T3 at the level deemed safe for survival by the body.

If you're chronically deprived of energy though, the body will reduce the T4 to T3 conversion, decreasing your metabolic rate. During our evolution, when cortisol was elevated chronically, it meant that we weren't able to find food and that, as a result, cortisol always had to be high to keep blood sugar stable and mobilize stored energy.

It adjusted by reducing T3 levels to lower energy needs. Back then, we needed that adjustment. Sadly, nowadays chronic cortisol elevation can come from many stressors, and even if we aren't in a deprived state, the chronic cortisol issue will still lead to a decreased T4 to T3 conversion.

2. It Can Lead to Insulin Resistance.

Cortisol increases blood sugar levels. When we were cavemen and women, that wasn't a big problem because cortisol normally spiked when we had to be physically active (fighting or running away) or were lacking food. So, we'd use the released glucose for energy.

But if blood sugar increases while we're sedentary, it just stays there, leading to hyperglycemia. The body doesn't want that, and it will release insulin to bring blood sugar back down to normal levels. All is fine and good, right? Not really.

If cortisol is chronically elevated it means it'll constantly increase blood sugar levels, which in turn will lead to frequent releases of insulin. That can lead to insulin resistance.

Both a decrease in metabolic rate and insulin resistance can make it harder to lose fat. No, they don't override the laws of thermodynamics. Establishing a caloric deficit is still the most important thing to lose fat. But if cortisol decreases metabolic rate, it means that it'll be harder to create a deficit (and easier to create a surplus).

Keep in mind, insulin alone won't make you fat. It can only store the nutrients you ingest; it doesn't create new nutrients. If you eat in a caloric deficit and have high insulin you won't gain fat.

However, insulin can make it harder to mobilize stored fat. As long as insulin is elevated above baseline, it'll be harder for you to mobilize fat efficiently. When you're insulin resistant, it means that your cells don't respond well to insulin. As a result, you need to produce more to do the same job. If you produce more, it takes longer to bring it back down. If it stays elevated for longer, you spend more time in a state where fat mobilization is less efficient.

Cortisol isn't a fat gain hormone, but its chronic elevation can make it harder to lose fat over time.

Cortisol and Recovery

It'll have a negative impact on your recovery when chronically elevated:

  1. Cortisol leads to elevated adrenaline levels. Great before a workout, but not so much when you want to go to bed.
  2. It inhibits growth hormone production. Oddly enough, in vitro (test tube) studies show that cortisol can increase GH, but in vivo (inside real human bodies) studies show it decreases it. If cortisol is high at night – when you're supposed get your natural GH spike – you'll severely hurt your recovery and progression.
  3. It can decrease muscle glycogen storage. This can be an important part of recovery from training.
  4. It can slow muscle repair. This element of recovery ties back to how it affects muscle growth... see above.

Cortisol and Well-Being

Chronically elevated cortisol affects well-being, especially mental well-being. But it's a bit more complex because it impacts neurotransmitters. The key thing to remember is that cortisol leads to an elevation of adrenaline (epinephrine). So when cortisol is chronically elevated...

  1. It can lead to noradrenaline depletion. Adrenaline is made from noradrenaline. If you convert too much noradrenaline into adrenaline you can deplete the former. Noradrenaline depletion leads to a decrease in focus, low blood pressure, and potentially depression and anxiety.
  2. It can lead to dopamine depletion. Noradrenaline itself is made from dopamine. When you over-produce adrenaline you also risk depleting dopamine. Symptoms of low dopamine include lack of motivation, anhedonia (lack of pleasure), depression, and laziness.
  3. It can desensitize beta-adrenergic receptors. If you overproduce adrenaline, especially if you keep producing it around the clock (which happens when cortisol is chronically elevated) you risk desensitizing the beta-adrenergic receptors. The body doesn't want to run on adrenaline all the time; it's not safe. It leads to high blood pressure and can have serious cardiovascular repercussions.
    Desensitization of the receptors is a protection against that, so you stop responding to your own adrenaline (or the response is much smaller). This leads to low energy, no motivation, self-esteem issues, lower performance, less competitiveness, laziness, and depression.
  4. It can cause increased production and transmission of glutamate (1). While this makes your working memory more effective in a stressful situation, if it leads to excessive glutamate it can cause mood swings, depression, being extremely hard on yourself, being overly emotional, and taking everything personally. Not to mention that excess glutamate is neurotoxic.

The effects of cortisol are even more far-reaching than that, but that's the gist of it. The bottom line? Short spurts of cortisol at the right time (in the morning and when you're lifting) is very useful, but chronic elevation can quickly become problematic if you want to look good and feel good.

How to Control Your Cortisol

I'll skip the woo-woo recommendations like, "Become at peace with the universe." Instead, let's get at the training, nutrition, and supplement strategies.


There are three main components of training that can affect cortisol output. To control it, avoid combining a high level of any two (or all three) of these cortisol-releasing factors.

  1. Training Volume: The more work you do, the more energy you need. The more energy you need, the greater the cortisol release will be to help you mobilize the required resources.
  2. Effort Required: The higher you go on the rate of perceived effort (RPE) scale, the more likely it is a set will release a lot of cortisol. If you go to failure, you're more likely to produce a lot of cortisol than if you stop 3-4 reps short.
  3. Psychological Stress: When a set or an exercise is perceived as stressful you'll release more cortisol. For example, if you're attempting a personal best on the squat, you'll get a big spurt of cortisol.

Also, complex exercises like a squat, deadlift, or even the Olympic lifts will release more cortisol than curls or machine work. Less complexity means less psychological stress. And when you learn a new exercise, you can also have a significant boost in cortisol production, especially if that movement is complex.

I've seen people drenched in sweat when first practicing snatch-grip high pulls with the empty bar. The sweating comes from the release in adrenaline stimulated by cortisol.

When you understand this, you can easily build a strategy to minimize cortisol. Here are some precautionary steps you could take:

  • If you do a high volume of work, decrease how hard you push each set.
  • If you do a lot of complex movements, decrease the overall volume.
  • Avoid pushing big compound lifts close to failure.
  • If you include very heavy work (92.5%+ range), keep the volume low.
  • If you introduce a new exercise, decrease overall volume until the exercise is mastered.
  • If you push yourself hard or do a good amount of volume, don't change your exercises too often or use too many exercises in a workout.
  • If you combine two of the cortisol-releasing factors (or all three), reduce the number of training sessions you do per week. Aim low (three per week) or you'll need frequent deload weeks.


One of the functions of cortisol is to maintain a stable blood sugar level; cortisol increases it when it's too low. One way of minimizing cortisol is... eating carbs! Or more specifically, maintaining a normal blood sugar level.

That's why I don't like very low-carb diets for people who are chronically stressed. It can easily lead to chronic cortisol production. Sure, you can create glucose from amino acids to maintain a stable blood sugar level. Just because you go keto doesn't mean you'll be flooded with excess cortisol. But eating next to no carbs, especially if you're very active, is likely to lead to higher cortisol levels.

A super high-carb diet isn't better though. It can lead to greater blood sugar swings. But certainly, consuming around 30% of your caloric intake from carbs, ideally low glycemic ones, will help keep cortisol under control.

I especially like having carbs around workouts and in the evening to decrease cortisol (and adrenaline). Remember, you want to lower cortisol in the evening to facilitate sleep and recovery.


There are many strategies you can use to keep cortisol at bay. You don't want to completely kill it; you need it to train hard. But you must be able to bring it back down when needed.

  1. Use Workout Nutrition. Easily-absorbed carbs during workouts can reduce cortisol by providing fuel. If you have carbs already available, you won't need to mobilize as much, which will mean there's less of a need to produce cortisol. This is especially effective when you're doing a higher volume training plan. Surge Workout Fuel (Buy at Amazon) is your best option by far.

  3. Use Vitamin D. This is especially important during periods of high stress. Vitamin D (Buy at Amazon) reduces the impact cortisol has on the conversion of noradrenaline to adrenaline. While it might not directly decrease cortisol, it prevents excessive adrenaline production, which can help prevent CNS fatigue (dopamine or noradrenaline depletion or adrenergic desensitization).
  4. Take Magnesium Post-workout and in the Evening. Magnesium (Buy at Amazon) decreases the binding of adrenaline to the adrenergic receptors and can help you calm down while protecting your beta-adrenergic receptors (keeping them sensitive).
  5. ElitePro Minerals

  6. Use Rhodiola in the Morning. Rhodiola helps keep the stimulatory and inhibitory neurotransmitters in balance and can lower cortisol.
  7. I Like Glycine Post-workout and in the Evening. Glycine is a neurological inhibitor. It slows the nervous system down when it's too amped up, which by extension decreases cortisol and adrenaline. Furthermore, glycine increases circulating serotonin (the feel-good neurotransmitter and the mood balancer) and activates mTOR, which will increase the protein synthesis from the workout.

The Cortisol Conclusion

Cortisol is not evil. It's required for survival and also to be able to function in the face of a stressor. But if it becomes chronically elevated it can be an enemy to optimal body composition and health. While you don't want to eradicate it, you do want to keep it under control to reach your goals, especially if you have stressful life.



  1. Popoli M et al. The Stressed Synapse: The Impact of Stress and Glucocorticoids on Glutamate Transmission. Nat Rev Neurosci. 2011;13(1):22-37. PMC.

Great article. Thanks.

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