How exercise changes your brain before it changes your body

You wake up, the alarm goes off and the bed’s gravity feels ten times stronger. The idea of putting on sneakers and working up a sweat sounds almost like a punishment.

Exercise changes your brain well before it changes your body. Within the first few weeks, movement releases substances that lift your mood, energy and focus, which is why people who work out usually end the day with more energy, not less.

It’s a frustrating cycle: you feel drained and low on energy, so you don’t exercise. But by not exercising, the tiredness only grows. We’re led to believe that we need energy to work out. What nobody tells us is that movement is exactly the gear that produces that energy.

The obstacle isn’t lack of time. It’s the heavy inertia that builds up when the mind is foggy and the body is still.

What does exercise do to the brain? The pharmacy inside your body

The magic starts the moment you make an effort. When you lift a weight, run or simply make your muscles really work, they’re not just burning calories. They start acting like a kind of natural pharmacy.

These muscle contractions release powerful chemicals into your bloodstream that travel straight to your brain. It’s like opening the windows of a stuffy room to let fresh air in. That mental fog that keeps you from focusing starts to clear quickly.

Does exercise really give you more energy? What science has already measured

That feeling of “more energy after a workout” isn’t just in your head. A review that brought together 70 studies, with more than six thousand people, found that regular physical activity increases feelings of energy and reduces fatigue, even in people who were always tired or had a chronic illness.¹ Exercise uses energy in the moment, but gives back more for the rest of the week.

The brain also changes shape, literally. In a study published in the journal of the U.S. National Academy of Sciences, older adults who walked three times a week for a year had about a 2% increase in the hippocampus, the region linked to memory, while the group that only did stretching lost volume in that area, as is common with age.² Those who gained the most volume also showed higher levels of BDNF, a protein that helps neurons grow and connect.

Then there’s mood. A large review published in 2023, with data from more than a hundred thousand people, concluded that exercise has an important effect on reducing symptoms of depression and anxiety, comparable to other first-line treatments.³ That doesn’t mean swapping medical care for running shoes, but it shows how much movement talks to the mind.

Sleep is on the list too. A review of dozens of studies found that exercise helps you sleep better and longer, both right after a session and, above all, when it becomes a routine.⁴ The result? At night, instead of tossing and turning with your head spinning, you tend to fall asleep more easily and wake up truly rested.

The invisible win at 7:30 a.m.

Picture the scene: you beat the inertia and head to the gym early, around 7:30. Your body complains for the first few minutes. But by 9 a.m., when you sit down to start working, everything feels different. The energy is there, and you can feel it.

Your self-esteem doesn’t go up just because you looked in the mirror. It grows from the concrete proof that you were able to keep a promise you made to yourself at the start of the day. You’ve already started the day by beating resistance, and any other problem after that seems smaller.

And it doesn’t have to be the gym or 7:30. A brisk walk in the late afternoon, taking the stairs instead of the elevator, dancing in the living room or biking to the grocery store all count. Your brain doesn’t care about the name of the exercise, it cares about a body that moves often enough.

Voluntary discomfort

Our bodies were designed to move. Keeping them still is what creates real exhaustion in the long run.

As the philosopher Seneca pointed out: “It is part of the cure to wish to be cured.” Exercise is the daily, physical expression of that wish. It’s the decision to embrace a little voluntary discomfort now, during the workout, so you don’t have to deal with the involuntary discomfort of poor health, bad mood and chronic tiredness for the rest of your day.

The change is in your hands. You sharpen your body so your mind can cut through obstacles more easily.

To keep your body and mind moving, here are three more reads:

• Tomorrow morning’s workout doesn’t depend on willpower, and here’s why it’s worth grabbing the oars even without it.
• Exercise and sleep go hand in hand. See what you lose when you cut your hours of rest.
• If you rely on coffee to get going, find out why it sometimes doesn’t work.

Editor’s note: We all have that friend who complains about being tired all day, but whose biggest marathon is scrolling through Instagram on the couch. Do their energy levels a favor and text them this article. Maybe they’ll realize the energy missing from their life is hiding in those running shoes they haven’t worn in months.

Footnotes

1. Puetz, T. W., O’Connor, P. J. & Dishman, R. K. (2006). Effects of chronic exercise on feelings of energy and fatigue: A quantitative synthesis. Psychological Bulletin, 132(6), 866-876. ↩ source

2. Erickson, K. I. et al. (2011). Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences, 108(7), 3017-3022. ↩ source

3. Singh, B. et al. (2023). Effectiveness of physical activity interventions for improving depression, anxiety and distress: an overview of systematic reviews. British Journal of Sports Medicine, 57(18), 1203-1209. ↩ source

4. Kredlow, M. A., Capozzoli, M. C., Hearon, B. A., Calkins, A. W. & Otto, M. W. (2015). The effects of physical activity on sleep: a meta-analytic review. Journal of Behavioral Medicine, 38(3), 427-449. ↩ source