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Is all exercise good for my mental health?

Episode Summary

It’s widely known that exercise is good for us, not just for its physical effects, but for the positive effects on our mood and state of mind.

Episode Notes

Been told that exercise is good for anxiety and depression? It is, but you might want to stay away from one type of exercise...

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Episode Transcription

Hi, I'm Kevin Don, the Get-Fit Guy, and I’m here to help you develop a keen eye for the facts and body swerve the fallacies when it come to fitness! Welcome to episode 600—I may still be the new Get-Fit Guy on the block, but I wanted to take a second to thank you for listening to this podcast. Whether you’ve been here for all 600 episodes or you’re just joining us for the first time today, I’m so glad you’re here. Now let’s jump into the episode.

It’s widely known that exercise is good for us, not just for its physical effects, but for the positive effects on our mood and state of mind. Many care providers and fitness influencers shout loud about the positive effects of exercise on depression and anxiety. But are there any caveats to this? If we are feeling low and want to improve our mood, is it just a case of “hitting the gym”? Or are there specific types of exercise we should aim for or avoid?

Let’s dig into this and see if we can define further what “exercise is good for mental health” really means. 

According to the British NHS (National Health Service):

“Being depressed can leave you feeling low in energy, which might put you off being more active. Regular exercise can boost your mood if you have depression, and it's especially useful for people with mild to moderate depression. Any type of exercise is useful, as long as it suits you and you do enough of it…”

This is a pretty authoritative statement but at the same time pretty general. For the purpose of staying in my lane and this being a fitness show, let’s just focus on that last sentence, where they state that any type of exercise is useful, and have a look at if this really is the case as well as looking at why they say exercise is a great intervention.

The most common reason is that exercise boosts serotonin levels, and low levels of serotonin are associated with depression. There have been many studies conducted over the years which have positively demonstrated the role of serotonin in depression and anxiety. So much so that it’s quite common to find that most of the general population have, in fact, heard of this neurotransmitter. 

A neurotransmitter is a signaling molecule in the body. Although we typically associate it with our brains, more than 90% of the serotonin the body produces is actually in the gut. Serotonin is synthesized from tryptophan (an essential amino acid), which you’ve heard me mention on the show before when discussing protein intake levels.

Here is where we run into the first potential problem with the idea that “any exercise” can help with symptoms of depression. In a study (link in show notes), exhaustive aerobic exercise resulted in a 12% decrease in available tryptophan levels. This is because muscles uptake or use Branch Chain Amino Acids (of which tryptophan is one). Since tryptophan is a necessary ingredient in serotonin production, this reduction in available tryptophan can lead to lower serotonin levels and therefore lower mood. 

Over 90% of our serotonin is in the gut. As we know, our gut is home to many microbes and bacteria. In fact, over 100,000 trillion microorganisms call the gastrointestinal tract home and help with processes from digestion to immunity to mental health! This gut microbiome is affected by inflammatory diseases like IBS, diet and nutrition, pharmaceuticals (like antibiotics—which kill both the bad AND good bacteria), and also by exercise. 

Our digestion is controlled by what is known as the parasympathetic nervous system. These are bodily functions that take place at rest. The opposite is called sympathetic nervous system stimulation. When we are in a “sympathetic” nervous system state, such as during exercise, blood vessels contract and gastrointestinal secretion is inhibited. Our body prioritizes the exercise or task at hand and views digestion as an extra task not currently required. This is also why if we push too hard, we may vomit or feel sick. The body is emptying the stomach to spare energy for the task and not expend it on digestion. 

It is well-researched that long-distance athletes, such as ultra-marathon runners, triathletes, and so on, suffer from gastrointestinal problems. In fact, studies show that 60 minutes of exercise at 70% or above of maximal effort results in symptoms of “leaky gut.” These include digestive issues, brain fog (difficulty concentrating), and mood imbalances such as depression and anxiety. 

As I have discussed on the show many times, literally everything is nuanced and we have to be able to step back and use higher-order thinking skills to allow us to critically evaluate any recommendations. It is true that exercise will aid depression and anxiety by increasing serotonin production. But as we’ve seen, studies have shown that exhaustive long-duration aerobic exercise appears to reduce serotonin levels by depleting the essential precursor (the amino acid tryptophan) and also by negatively impacting the gut microbiome. 

So, if you’re looking at exercise as a way to help boost serotonin production, especially as winter and seasonal depression sneaks up on us, make sure to focus on your dose response. Stay away from exhaustive work—something above your maximum recoverable dose—as it’s likely it will have a negative effect on your gut. Our training has to be hard enough to result in stress to drive adaptation, but if it's exhaustive, you may find recovery difficult and in fact, create physiological problems.

If you want to check out the studies I mentioned today, head to the show notes and click on the link for the transcript to see my citations.

Get-Fit Guy is a Quick and Dirty Tips podcast. Thanks to the team at Quick and Dirty Tips, Adam Cecil, Morgan Christianson, Holly Hutchings, Davina Tomlin, and our intern Kamryn Lacy. I’m your host, Kevin Don. If you have a question for me, leave me a voicemail at 510-353-3104 or send me an email at For more information about the show, visit, or check out the shownotes in your podcast app.