When you want to get as ripped and jacked as humanly possible, there’s not a lot of margin for error. What this really means is that you need to know your enemies. One prime example of this concept is the hormone cortisol.

Ask any bodybuilder—even the top guys in the world—and they’ll tell you cortisol is some kind of “death hormone” that they try to avoid like the plague. Why? Because cortisol breaks stuff down, and the last thing any bodybuilder wants is for a highly destructive hormone to be running through his body, creating a massively catabolic environment.

There’s more to the story, however. As it turns out, cortisol may not be as evil as we’ve been led to believe—and since pretty much everyone in the game is still on the anti-cortisol and anti-long-duration training session bandwagon, it’s time to revisit some of the reasons that our perspective on cortisol has been so far off for so long.


Cortisol belongs to a class of hormones called glucocorticoids (GCs), and it’s important to stipulate here that nearly all GCs share the properties I’ll be discussing. GCs are essential hormones in your body. When they’re released at the proper time, and in the proper amounts, they regulate your immune function, and they may help to repair tendons and ligaments. In fact, they may actually accelerate the fatburning process, too.

Still, we’ve been afraid of cortisol for decades because of its ability to waste away muscle tissue. Even short bursts of GCs will cause this to happen. When your GCs are elevated for extended periods of time, or at the wrong times, it’s even worse for you. At that point, they can suppress your immune system, prevent your body from burning fat, and increase hunger.

It gets worse. Once GCs have done what I’ve already listed, it’ll then target other hormones. They adversely affect the fat-mobilizing ability of leptin—as well as potentially eradicating the hunger control benefits of ghrelin. They’ll even decrease your testosterone levels. 

That’s a long list of negatives. When viewed together like this,

It’s no surprise that these adverse effects have scared the crap out of the bodybuilding community for so long. On the surface, it appears as though nothing good can come from any of it.


Here’s the thing, though. Aside from the negatives, most of us don’t have the faintest notion of what else cortisol does, so we simply fear it and avoid it. Most nutrition books offer no useful information other than using changes in cortisol levels as evidence that what they’re telling you is working—operating on the assumption, of course, that higher levels of cortisol are automatically a bad thing.

Under normal conditions, your cortisol will rise rhythmically throughout the night, peaking first thing in the morning. 

When you wake up in the morning, your body is primed to begin burning fat before you eat. Cortisol is a key part of this process. Your body will be operating in the absence of both carbs and insulin, and when there’s no insulin present, cortisol doesn’t attack your muscle. When acting without insulin, cortisol triggers the breakdown of triglycerides into free-fatty acids (FFAs) for metabolisation, a process known as lipolysis. Without insulin, cortisol is an incredibly effective fat burner. In other words, skip breakfast.

Elevated cortisol levels during training isn’t necessarily a bad thing, either. Research has shown that the higher the cortisol response you elicit, the greater the anabolic effect your session will give you. Additional research in the Journal of Applied Physiology and Chronobiolog  showed that having high cortisol during training lowers cortisol levels at “bad” times—in the presence of insulin—for up to 24 hours.


It’s a proven fact that your GC levels will become elevated in response to both mental and physical stress, and that chronic stress will keep your GC levels high for long periods of time. By chronic stress, I’m referring to both emotional stress and excessive physical activity. This is especially important when you’re dieting, because dieting can be both mentally and physically stressful, causing your GC levels to elevate as you change your nutritional regimen.

When you’re trying to lose body fat, your stress levels can make this whole process a lot more diffcult than it should be. Avoid this situation by avoiding extremes. For bodybuilders, my carb back-loading system is tailormade for stress-free fat loss and muscle gain, so I’d suggest taking a look if you’re cortisol-phobic.

By timing your workouts correctly—training in the evening causes a lower cortisol response than normal, leaving your other hormones alone (or elevating them)—and avoiding breakfast until your cortisol levels return to normal, you can use correct nutrition to essentially pick and choose which cells (muscle or fat) get bigger and smaller.

Finally, we need to address all the talk you’re hearing about limiting your workouts to an hour or less in order to mitigate your elevated cortisol levels. If you think this is a problem, check the research, but it runs contrary to common industry wisdom. A significant number of studies have shown that extending your sessions, and your elevated cortisolresponse, will actually boost the anabolic effects of your workouts. Again, know your enemy—and more important, know why. – FLEX