It's pretty clear that exercise is a Paleo issue just as much as food: in that classic stereotype of the couch potato lying in front of the TV eating Cheetos, the Cheetos are only half the problem. Our bodies are about as well-adapted to the sedentary lifestyle as they are to the modern food environment: they aren't!
The physical benefits of exercise are enormous, but don’t just hit the gym for your body. Do it for your brain, too. In the same way that honoring your evolutionary heritage can improve physical health, it can also give your brainpower a serious leg up. If you’ve ever felt more clear-headed or energetic after a hard workout, it’s not just your imagination. Exercise really does “clear out the cobwebs” and improve your mental clarity and brain function – especially if you pair it with a healthy diet.
Exercise and Brainpower
“Cognitive function” is the technical term, but most of us think of it more simply as brainpower: the ability to learn new things, remember them, solve puzzles, connect the dots, or just feel clear-headed, without that muggy, exhausting “brain fog” feeling.
If that all sounds pretty good, then you’ll definitely want to be getting sweaty on a regular basis.
For one thing, exercise increases levels of brain-derived neurotrophic factor (BDNF), a type of protein called a neurotrophin. Neurotrophins support neuroplasticity, the brain’s ability to adapt to its environment. When you learn something new, that’s neuroplasticity in action. In other words, exercise helps you learn things more easily.
Exercise can even change the physical structure of your brain. In this study, children with greater physical fitness had greater volume in their hippocampus (part of the brain associated with memory and spatial awareness). Of course, associations always have to be taken with a grain of salt: for example, children who are more physically fit are probably also wealthier, on average, and they probably also eat better, which could have a huge effect on brain function.
But in this case, there’s evidence that the exercise itself is at least partly responsible: for example, this study found in a randomized intervention trial that aerobic exercise did increase hippocampal volume in older adults. This study (another randomized intervention trial) found the same thing in women specifically, especially for aerobic training (yet another reason why cardio isn’t that bad).
This study also found that children with a higher level of physical fitness had larger dorsal striata. The dorsal striatum is an area of the brain important for making decisions and balancing rewards (like, say, the reward you’d get immediately from a cupcake vs. the reward you’d get down the line from making a healthier choice).
Finally, exercise can actually provide your brain with more of the fuel it needs to do its job, by increasing the number of mitochondria. Mitochondria supply fuel to your cells, so more mitochondria means more “gas in the tank” and a greater ability to work harder and faster.
Exercise is most famous for creating new mitochondria in muscle cells, but your brain has mitochondria, too, and exercise increases the number. This has exactly the effect you’d expect: greater power production in the brain increases cognitive function, or in other words, you think better.
Considering all of that, is it any surprise that exercise has a track record of boosting grades? This study found that aerobic exercise was associated with a higher GPA among college students. This one found that increased physical activity was associated with higher academic performance in school children (grades 5 and 9).
It’s not just for the students, though. This study found that even one bout of aerobic exercise improved scores on a test of memory, reasoning, and planning. And even though everyone tells you not to skimp on sleep for the sake of the gym, if you have to short your rest for some other reason, a workout might help make up for it: in this study, exercise helped reduce the effects of sleep deprivation on cognitive function.
Most of these trials used aerobic training, although high-intensity interval training works too: this study found that a single bout of high-intensity exercise improved attention and memory.
Exercise and Stress Reduction
Stress is dangerous, to your body and your brain. But exercise is the original chill pill. It increases levels of opioids (think morphine), endocannabinoids (yes, the same chemicals found in marijuana), and dopamine (the same “feel-good” hormone that rewards us for things like eating tasty food or having sex). That’s a powerful triple whammy of relaxation and pain reduction, and it has some very desirable cumulative effects. For example, this study found that adults who exercised even a little bit (at least once a week) were more resilient to stress than adults who didn’t.
In fact, this effect can actually make exercise physically addicting. This isn’t necessarily a problem – it’s fine to seek out pleasure from exercise, and obviously huge numbers of people can enjoy the “buzz” without ever going too far. And the line between “healthy” and “dangerous” will be different for everyone. But the dangers of exercise addiction are something to bear in mind. If working out is starting to feel like a compulsion rather than a joy, or if your exercise habit it starting to have negative consequences for the rest of your life, it might be time to talk to someone about it.
Exercise and Psychiatric Disorders
Reducing garden-variety stress is one thing, but exercise actually has some efficacy for even serious mood disorders, most notably depression. It’s not just a cute saying that “exercise is the most underused anti-depressant.” There’s actually a substantial amount of research backing it up.
This article gives a great overview of the benefits of exercise for mood disorders like depression and bipolar disorder. Although some evidence is conflicting (when is the evidence not conflicting?), the reviewers concluded that both aerobic exercise and resistance training are likely to help. And if you’re wondering how on earth a depressed person is supposed to find the energy to get up and go for a run, the authors note that even walking has a noticeable effect: activity doesn’t have to be extreme to be effective.
Other psychiatric disorders aren’t as well studied, but this review suggests that exercise might also be helpful for schizophrenia, and this review also suggests that it may benefit children with ADHD.
This isn't meant to set up exercise as some kind of "miracle cure" for depression or anything else: it isn't. If you have a serious mental health condition, talk to a licensed therapist or psychiatrist! But a regular exercise routine might be useful in addition to professional help.
Exercise and the Aging Brain
Exercise is important for everyone, but it gets a special mention for preserving brain function in the elderly. Many neurodegenerative diseases (think Alzheimer’s Disease or Parkinson’s Disease) are marked by brain changes like loss of mitochondrial function – changes that are significantly slowed by exercise. Since exercise stimulates the production of new mitochondria, it's a promising way to improve mental health even in the face of serious age-related diseases.
This review goes over the topic of exercise, aging, and cognitive function. The authors stress that a lot of the trials weren’t very well-designed, but they’re still optimistic on the whole, and they conclude that physical exercise is useful.
Summing it Up
Exercise doesn’t have to be ridiculously intense to have mental health benefits, but if you can get out even for a brisk walk, your brain will thank you! Our brains weren’t designed for the modern sedentary lifestyle any more than our bodies were, and the health benefits of a good workout extend well beyond the physical.
What's more, exercise can actually help you stick to healthy eating: it's a natural mood-booster (so no need to turn to food for comfort), and it benefits the part of your brain that helps you make decisions. Eating better makes you feel good, which makes it easier to get to the gym for a workout, and then you feel even better - it's a great way to get on a roll with heath and lifestyle goals.
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