What Everyone Got Wrong About Brain Health (Until Recently)

What Everyone Got Wrong About Brain Health (Until Recently)

New research reveals that working out contributes to improvements in memory, focus, sleep and overall cognitive function. Here’s how.

By Richard Isaacson, MDUpdated July 5, 2022


As a preventive neurologist, I see patients every day who are concerned about their memory or Alzheimer’s disease (AD) and want to do whatever they can to reduce their risk of cognitive decline. And every day, I say the same thing: “Regular exercise is one of the smartest things you can do if you want to keep your brain healthy and strong as long as possible.” I even go so far as to write workout “prescriptions” to encourage patients to exercise three to four days a week for 45 to 60 minutes per session. It’s that powerful.

Recent and emerging research has helped pinpoint some of the extraordinary outcomes seen in the brain as a result of exercise—even after a single bike ride, running or weight-lifting session. In fact, a new study published in the Journal of the International Neuropsychological Society found that 30 minutes of indoor cycling was enough to improve a subject’s ability to remember names compared with those who didn’t complete a ride.

The really exciting changes happen with consistent physical activity. Take my patient Steve, a physical therapist and former college athlete who came to me in his 40s. A strong family history of AD inspired him to be proactive in lowering his own risk, so he enrolled in one of my studies and received a customized program with frequent exercise as its cornerstone. After 18 months, his cognitive functioning soared from the 50th percentile for his age group and education to over the 90th percentile.

How Does Exercise Power Your Brain?

There are several science-backed ways a dedicated workout routine can support optimal brain function. Here are four to name a few:

1. Exercise helps you grow new brain cells.

For many years, the common understanding about brain health was that we are born with a certain number of brain cells, and that’s all you get for the rest of your life. We now know that’s not correct. Not only is it possible to generate new brain cells, but exercise is a key contributor to this phenomenon.

It has to do with something called BDNF, or brain-derived neurotrophic factor. When we work out, the production of this protein spikes, leading to an increase in the number of brain cells, also called neurons, in the hippocampus, which is the memory and learning center of the brain. Elevated BDNF levels have been linked with enhanced cognitive performance, as well as focus and spatial memory (the type that helps you remember where things, like your keys, house and parked car are). Alternatively, reduced levels of BDNF have been seen in patients with dementia and its precursor, mild cognitive impairment. BDNF also helps support the survival of existing brain cells.

Generally speaking, the more intense the workout, the more BDNF is produced. In a 2021 Journal of Sport and Health Science meta-analysis (a review of several studies on the same topic, 22 in this case), high-intensity interval training, or HIIT, resulted in an immediate increase in BDNF among young adults ages 20 to 31. The effect was especially noticeable when compared with non-exercisers or those engaging in light workouts. Findings like these are one reason BDNF has been called “Miracle-Gro for the brain.”

2. Exercise strengthens your heart, which in turn helps your brain.

Whether you’re doing a 60-minute Peloton Bootcamp class or a quick Flash 15 (a 15-minute burner with instructor Jess Sims), your heart has to pump harder and faster to get energizing, oxygen-rich blood to your muscles. But that blood doesn’t just go to your shoulders and quads; it also floods into the brain. So not only are you spurring the growth of new neurons via BDNF, but you’re also bathing your brain in nutrient-saturated, memory-enhancing blood.

Regular exercise can also strengthen your heart and lead to lower blood pressure, which, when elevated, is a strong risk factor for future dementia. Elevated blood pressure can also damage tiny blood vessels in the brain, slowing your processing speed over time and increasing the risk of a stroke, a potentially fatal event that occurs when a blood vessel that carries oxygen and nutrients to the brain becomes blocked by a clot or bursts. A single exercise session has the power to reduce blood pressure for up to 24 hours, and regular workouts can lower blood pressure over the long term—enough to decrease your chances of dying from a stroke or heart disease by 14 percent and 9 percent, respectively.

3. Exercise promotes restful sleep, which helps sweep toxic proteins out of the brain.

Exercise tires you out. That’s a good thing, considering the enormous impact sleep has on cognitive health. Moderate-to-vigorous workouts make it easier to fall asleep, reduce tossing and turning and relieve anxiety and insomnia, two factors that frequently sabotage sleep.

Sleep also helps your brain recover in a major way. During the day, sticky toxic proteins called amyloid build up in the brain. Excess amounts of accumulated amyloid are often found in the brains of individuals with AD. At night, when we sleep, those toxins and other waste products are shuttled out of the brain by something called the glymphatic system. The act of exercise itself can be thought of as “loosening” the sticky amyloid, making it easier for the glymphatic system (or “garbage removal” network) to sweep it away. Think of it as your brain taking the trash out while you snooze.

4. Exercise regulates blood sugar, keeping insulin levels low, which protects your brain.

When it comes to brain health (or cardiac or metabolic health, for that matter), high blood sugar levels are nobody’s friend. Consistently high blood sugar, whether due to a high-sugar diet, too little physical activity, excess weight or some combination of the three, spurs the body to produce high amounts of the hormone insulin. Insulin increases inflammation throughout the body and also signals the body to store fat. Both of those consequences spell trouble for brain health.

Fortunately, exercise works to keep insulin levels low. That’s because when you work out, your muscles use the sugar that’s hanging out in your bloodstream or cells for energy. Even a 15-minute brisk walk after lunch or dinner can make a dent.

The Ideal Type and Amount of Exercise For Better Brain Health

I usually recommend that my patients exercise four, five, even six days a week to truly reap the brain-friendly benefits. And it doesn’t need to all be super high-intensity to get the job done. Plenty of research indicates moderate-intensity exercise (such as indoor cycling with a pedal cadence between 60 and 80) is effective in boosting cognition. How do you know if you’re pushing hard enough? It should be difficult, but not impossible, to have a conversation. Staying balanced with a mix of more intense cardio and less intense cardio (such as fast walking for 45-60 minutes) along with strength training can be thought of as a trifecta for both brain and body health.

For some people, smaller amounts of activity will work, too. A 2018 scientific review determined that a minimum of 52 hours was an optimal amount of exercise in terms of improving cognitive performance over a six-month period. That comes out to about two hours of exercise per week. Take the stairs as much as you can instead of elevators, use a standing desk for part of your workday or try a balance ball when you do sit at your desk to keep your core engaged. A sedentary lifestyle is associated with a higher overall risk of cognitive decline.

Just don’t overdo it and if you have any questions, ask your doctor. Exercising so much that you begin to feel rundown and depleted can lead to muscle loss, even if you’re lifting weights or doing strength training. Muscle loss is associated with cognitive decline, particularly among older adults. Instead of doing back-to-back hour-long cycling sessions, you’d be better off exercising for one hour and then going to bed an hour early that evening and letting your sleeping brain take out the trash.

Richard S. Isaacson, MD is a neurologist and clinician-researcher who specializes in Alzheimer’s disease (AD) prevention and treatment; he is also a paid consultant member of the Peloton Health & Wellness Advisory Council. Dr. Isaacson is currently the director of the newly launched Florida Atlantic University Center for Brain Health and Alzheimer’s Prevention Clinic within the Schmidt College of Medicine. He is committed to using technology and lifestyle interventions, such as physical exercise and nutrition, to optimize patient care, AD risk assessment and early intervention. For more on what you can do to support brain health, check out Dr. Isaacson’s free online video course.

This content is for informational and educational purposes only and does not constitute individualized advice. It is not intended to replace professional medical evaluation, diagnosis, or treatment. Seek the advice of your physician for questions you may have regarding your health or a medical condition. If you are having a medical emergency, call your physician or 911 immediately.