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Uh, Do High-Impact Workouts Mess With Your Hormones?

Emily Kelleher
August 30, 2023
Emily Kelleher
Editorial Operations Manager
By Emily Kelleher
Editorial Operations Manager
Emily Kelleher is the editorial operations manager at mindbodygreen. Her work has appeared in Shape, Well + Good, Greatist, Romper, Fatherly, and more.
Image by VegterFoto / Stocksy
August 30, 2023
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At its best, exercise bolsters heart health, fights depression, and supports longevity. But too much of a good thing can swing in the opposite direction. As any athlete knows, overdoing it in the gym can lead to injury and even hormonal disruptions.

Recently, social media has zeroed in on the effects of overexercise on cortisol, a hormone best known for its role in the stress response. Some say that overdoing it with high-impact workouts could jack up your cortisol so much that it results in weight gain. But is that true? And if so, where is the line between a healthy dose of movement and one that wreaks havoc? Fear not, we've tapped the experts to get to the bottom of it. 

How exercise benefits hormones

Exercise, when done right, "gives your hormones a workout," says Nicky Keay, M.B., a sports endocrinology researcher and author of Hormones, Health, and Human Potential. 

Working out increases growth hormone, which is key to healthy body composition and increases insulin sensitivity, which helps regulate blood sugar, Keay says. It triggers the release of dopamine and serotonin, well known for their mood-boosting effects. Exercise also boosts estrogen1, a reproductive hormone whose decline is to blame for many menopause symptoms, and testosterone, which supports everything from bone health to libido. Several studies have demonstrated that regular exercise can relieve menstrual pain2, which can at least in part be explained by increased progesterone, which has anti-inflammatory effects.

Exercise generally lowers cortisol levels, though exact effects depend on the type, intensity, duration, and timing of exercise. One meta-analysis found that HIIT workouts increased cortisol in the short term (30 to 60 minutes after) but decreased cortisol levels below baseline within two hours of the workout, with levels returning to normal after 24 hours. Researchers noted that the time it takes for cortisol levels to come back down to earth is longer with HIIT workouts than other less intense workouts. Another study found that cortisol decreased over time with endurance exercise, (cycling for 40 minutes at 75% of maximum heart rate) but decreased more slowly with resistance exercise (30 to 40 minutes of repeating sets of 10 of a series of exercises). 

It's important to note that cortisol isn't all bad. Besides regulating the stress response, cortisol helps us wake up in the morning and respond quickly to danger, Keay says. "Cortisol is an important hormone, so I'm not saying we should try and keep it low," Keay says. "But equally, we don't want to encourage it to be overactive when it's not needed." 

Can too much exercise create excess cortisol? 

According to Keay, if high-intensity workouts are done too often, with too little rest or proper nutrition, they can spur an overproduction of cortisol. 

She says this is particularly likely when one does high-intensity workouts early in the morning before eating anything. Cortisol is already highest in the morning3, and working out on an empty stomach puts the body in a state of stress, further increasing cortisol, Keay says. 

While this stress state might be useful short term, it becomes problematic when it becomes chronic. 

Can excess cortisol cause weight gain? 

The question that's left, then, is whether this increase in cortisol has negative effects, like the weight gain that people warn about on social media. 

Keay is decisive. She says that while overexercise may not cause weight gain, "it certainly won't help you lose weight." She sees it often in her work with people with relative energy deficiency in sports, or RED-S, a condition that occurs when athletes exercise too much without adequate nutrition. 

"The person often comes and says they can't understand why they're doing all this intense exercise, and they're not eating much and they're not losing weight," Keay says. This happens because excess cortisol puts the body into a state of emergency and encourages fat storage in preparation.

Other side effects of overexercising

Disruptions extend to other hormones whose imbalances are further reinforced by an excess of cortisol. "Cortisol tends to be the dominant hormone for evolution reasons, running away to quickly escape danger…cortisol reinforces the downregulation of the other ones," Keay says. 

Levels of human growth hormone will dip, which will do no favors for body composition. Estrogen is also at risk. Overexercising famously causes amenorrhea, or the loss of a menstrual period. It requires a lot of energy for the body to produce reproductive hormones, so if you're pushing yourself to your limits and not properly fueling, these hormones are some of the first to go, Keay explains. 

To conserve energy, the body will suppress the pituitary gland. In turn, the ovaries don't receive the signal to produce the estrogen needed for a normal cycle. This can also lead to disrupted ovulation and can have long-term effects, from fertility challenges4 to an increased risk of heart disease, osteoporosis, and dementia. 

What to do 

None of this is to say that exercise is bad or you should never do a HIIT workout again. It's just that high-intensity workouts necessitate proper fuel and adequate rest. Here are three essential components of a balanced workout routine:

  • Fuel properly: Carbohydrates are the body's main source of fuel during high-intensity workouts, so it's important to eat enough of them. If you're doing a high-intensity workout in the morning, Keay says it's essential to eat beforehand. With cortisol already at its peak, your body doesn't need the additional stress of a fasted workout. 
  • Take rest days: Keay recommends at least one per week. 
  • Switch up your workouts: HIIT is great, but when you only do HIIT, you miss out on the benefits of other kinds of movement. Work on your flexibility with yoga or Pilates, build endurance with strength training, or seek out connection on a walk with a friend. 

The takeaway

HIIT workouts are lauded for their ability to deliver quick results in a short amount of time. They certainly have their benefits, but because they can raise cortisol levels in a way that other workouts don't, you need to be extra careful to refuel to avoid negative effects. By mixing in low-impact workouts and rest days and eating balanced meals with enough carbs, you can avoid messing with your all-important hormones.

Emily Kelleher author page.
Emily Kelleher
Editorial Operations Manager

Emily Kelleher is mindbodygreen's editorial operations manager. Her work has appeared in Shape, Well Good, Greatist, Romper, Fatherly, and more. She holds a bachelor's degree in journalism and political science from Syracuse University.