Cortisol and Fitness: The Truth About the Stress Hormone and Your Workouts

Michael Ulloa
Sep 9
6 min read

If you spend any time on social media, you’ve probably seen cortisol, often called the “stress hormone”, being blamed for everything from stubborn belly fat to burnout. Wellness influencers love to use it as a villain, but the truth is far more interesting (and far less scary).

Cortisol isn’t your enemy. It’s a hormone essential for survival, recovery, and even peak performance. The problem isn’t cortisol itself, it’s when our modern lifestyles push it out of balance.

In this post, we’ll break down what cortisol actually does, when it becomes a problem, how it relates to exercise and fitness, and why most of the supplements promising to “fix” your cortisol are a waste of money.

What Is Cortisol?

Cortisol is a hormone produced by your adrenal glands (the small, triangular glands sitting above your kidneys). Its main role is to help your body respond to stress, whether that stress is physical (like running a 10K), mental (like a looming deadline), or even danger (picture being chased by a predator).

When your brain detects a threat, it activates the hypothalamic–pituitary–adrenal (HPA) axis, which signals your adrenal glands to release cortisol. This hormone acts like your body’s built-in alarm system. It:

increases blood sugar for quick energy
sharpens focus and alertness
temporarily suppresses non-essential functions like digestion and reproduction so you can deal with the threat.

Think of it as your body’s power surge, helping you perform when it matters most.

But here’s what often gets overlooked: cortisol isn’t only a “stress hormone.” It plays critical roles in everyday functions, including:

Regulating your circadian rhythm (highest in the morning to wake you up, lowest at night to support sleep)
Supporting metabolism and energy balance
Managing immune response and inflammation
Assisting with tissue repair.

So if someone tells you that high morning cortisol is bad, know that it’s exactly what your body is supposed to do.

Why Does Cortisol Get a Bad Reputation?

Short-term cortisol spikes are normal, healthy, and necessary. They help you wake up, get through a workout, or rise to a challenge.

The problems arise when cortisol stays elevated for too long. Chronic stress, whether from lack of sleep, overtraining, financial pressure, or under-eating, keeps your cortisol system switched “on.” That can lead to:

Poor sleep quality
Increased cravings and appetite
Mood swings and anxiety
Sluggish recovery from exercise
Lowered immunity

This is where the wellness industry steps in, using half-truths to push fear-based narratives and expensive “hormone balancing” supplements.

Common Causes of Chronically High Cortisol

Chronic psychological stress

Ongoing work, money, or relationship stress keeps your system on high alert. Your body doesn’t distinguish between being chased by a lion or buried under emails.

Poor sleep

Even small amounts of sleep loss disrupt the natural cortisol rhythm, delaying recovery and reducing resilience to stress.

Overtraining without recovery

Exercise raises cortisol in the short term — that’s healthy. But constant high-intensity training without proper rest or fuel pushes cortisol into unhealthy territory.

Undereating or restrictive dieting

Studies show that tracking every calorie and eating very low-calorie diets (e.g. ~1200 kcal/day) can increase cortisol levels.

Medical conditions

Conditions like Cushing’s syndrome, long-term corticosteroid use, or chronic illness can also elevate cortisol. These are rare but worth noting if symptoms are severe.

Does exercise spike cortisol?

This is one of the biggest areas of confusion online. Posts claiming HIIT, running, or weightlifting “ruin your hormones” by raising cortisol are misleading.

Here’s the truth: exercise raises cortisol temporarily, and that’s a good thing. It mobilises energy, sharpens focus, and primes your body for performance. Once the workout ends, cortisol levels fall, and recovery begins.

This is the stress–recovery cycle in action. It’s how you adapt and grow stronger.

Problems only arise when:

You’re training hard but not sleeping or fuelling properly
Life stress is already sky-high, and workouts just add to the load
You ignore signals like fatigue, poor recovery, or mood swings
Red flags that your training might be tipping into “too much stress”:
Feeling exhausted after workouts instead of energised
Declining performance
Poor sleep quality
Constant soreness
Anxiety worsening with exercise

The solution isn’t to avoid training altogether, it’s to train smart, recover hard, and adjust intensity based on your overall stress load.

Do cortisol supplements work?

Type “cortisol” into any search bar and you’ll be bombarded with products: blockers, adrenal tonics, mushroom powders, hormone-balancing teas.

But here is the reality:

Cortisol blockers are not only ineffective but potentially dangerous. You need cortisol to survive.
“Adrenal fatigue” supplements target a condition that isn’t recognised medically. Real adrenal disorders (like Cushing’s or Addison’s disease) require proper diagnosis and treatment,not powders sold on Instagram.
Adaptogens like ashwagandha, rhodiola, or reishi mushroom have some evidence of mild stress-reducing effects, but results are mixed, and they only work when paired with solid lifestyle habits.
Supplements with some supportive evidence for stress management include magnesium, omega-3s, L-theanine, and ashwagandha, but none of these are miracle fixes. Lifestyle always comes first.

Should You Test Your Cortisol?

Cortisol can be tested via blood, urine, or saliva, usually in medical contexts where conditions like Cushing’s or Addison’s are suspected. For the average healthy person, at-home cortisol tests are unnecessary and often misleading.

Unless you’re experiencing serious, unexplained symptoms, your energy is better spent improving sleep, nutrition, recovery, and stress management.

The Takeaway

Cortisol isn’t the villain it’s made out to be. It’s a vital hormone that supports energy, resilience, and performance. The real problem is chronic stress without recovery, not your morning coffee, your HIIT class, or your strength training.

So instead of fearing cortisol, focus on:

Prioritising quality sleep
Fuelling with balanced meals (including enough carbs)
Building recovery into your training
Managing stress in sustainable ways
No supplement or quick fix will replace the basics. But when you get them right, your cortisol rhythm supports you, not sabotages you.

To listen to our latest podcast episode about cortisol, click the link here to check it out!

Frequently Asked Questions About Cortisol and Fitness

1. What is cortisol and why is it called the “stress hormone”?

Cortisol is a hormone produced by your adrenal glands that helps your body respond to stress. It increases blood sugar for quick energy, sharpens focus, and suppresses non-essential functions like digestion when you need to react quickly. While often called the “stress hormone,” cortisol also regulates your sleep–wake cycle, metabolism, and immune system.

2. Does exercise increase cortisol levels?

Yes, but that’s not a bad thing. Exercise temporarily raises cortisol to give you energy and improve performance. Once the workout ends, levels return to normal, which helps your body adapt and get stronger. Problems only occur when exercise is combined with chronic stress, poor sleep, and under-recovery.

3. Can high cortisol cause weight gain?

Chronically elevated cortisol can increase cravings for sugary and salty foods, disrupt sleep, and affect energy balance, all of which may contribute indirectly to weight gain. But cortisol itself isn’t the direct cause of fat storage. Lifestyle factors like diet, sleep, and recovery play a bigger role.

4. How can I naturally lower cortisol levels?

You don’t need supplements to manage cortisol. Evidence-based strategies include:

Getting 7–9 hours of quality sleep
Eating balanced meals regularly (including carbohydrates)
Managing stress with activities like walking, yoga, or meditation
Taking recovery days from training
Limiting excessive caffeine and alcohol

5. Should I test my cortisol levels?

For most people, testing cortisol isn’t necessary. Cortisol naturally fluctuates throughout the day, and online testing kits aren’t very reliable. If you’re experiencing serious symptoms, like unexplained weight changes, extreme fatigue, or very irregular blood pressure, please speak to your doctor, who can order clinical tests if needed.

6. Do supplements really help with cortisol?

Most cortisol supplements are overhyped and not supported by strong evidence. Adaptogens like ashwagandha may have mild effects, but lifestyle factors (sleep, nutrition, recovery, stress management) are far more effective. Beware of products marketed with fear-based claims about “adrenal fatigue” or “cortisol blockers.