Stress and six-pack abs just don't go together. After all, when every shirt you own has been soaked in stress-induced sweat, why would you want to get your heart pumping at the gym?

But it turns out, perpetually too-high levels of stress—and, more specifically, the stress hormone cortisol—can do a number on way more than your mental approach to gym time. It can actually make your muscles waste away and fat pack onto your gut like you're preparing for hibernation.

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Take a deep breath and check out these six workout-wrecking effects of chronic stress.

Say 'Bye' to Muscles

When you're in the Serengeti attempting to outrun lions, cortisol acts to quickly increase your blood sugar and give you the energy to hopefully win the foot race, explains Jamie Zimmerman, M.D., a physician and Sonima.com meditation expert. However, when you're stressed over your boss chewing you out or being stuck in traffic, cortisol still works to give you fight-or-flight energy. The serious downside is that cortisol will do this by any means necessary, breaking down muscle tissue and converting into glucose, she says. With chronic stress, you can actually see your muscles shrink. It's called "muscle wasting."

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Testing Your Testosterone

Testosterone is one of the key hormones behind muscle hypertrophy (aka growth). As luck would have it, though, cortisol acts in the brain to inhibit testosterone production, according to research from the University of California, Berkeley. Without that testosterone, you will build less muscle during each of your workouts, says sports medicine specialist Jason J. Brucker, M.D., assistant professor of orthopedic surgery in at the NYU Langone Medical Center. Add that to the fact that cortisol is simultaneously breaking down your muscles for energy, and you might end up reaping zero muscle gains from your workouts.

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Recovery Status: Stalled

At too-high levels, cortisol also suppresses your immune system, so it doesn't clear inflammation from your muscles and jumpstart the post-workout repair process like it should. "Your body isn't able to build itself back up," Brucker explains. Plus, slower recovery times not only stall your results, but could end up contributing to overtraining and injury.

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Gut Instincts

By constantly increasing your blood sugar levels for energy, chronic stress throws your insulin response into overdrive, Brucker says. Each time your blood sugar spikes, your pancreas churns out insulin, which responds by shuttling the extra sugar straight into your fat cells. Even worse, this fat tends to hang out on your belly, in between your vital organs, which increases your risk of chronic diseases such as heart disease and diabetes, Zimmerman adds.

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Constant Cravings

Breaking down muscle isn't the only way cortisol ensures you're energized. The stress hormone also triggers cravings for high-sugar, high-fat foods, Zimmerman says. What's more, these "comfort foods" temporarily inhibit stress-related activity in the brain, according to Harvard Medical School. However, since the stress-curbing effects don't last long, it could take as little as a half an hour for you to be ready for your second donut.

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Counting Sheep

Not only can stress keep your mind busy at bedtime, but since cortisol helps regulate your circadian rhythms, chronic stress can make good sleep just about a biological impossibility, Brucker says. Without proper sleep, your body will crave even more sugar, fat, and calories for energy and according to research in the Journal of the American Medical Association, your muscle-building testosterone levels will dip even further. Plus, when you slack on sleep, cortisol levels rise. And so the cycle continues.

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