Exercise, Oxidative Stress and the Brain with Dr. Gary Wenk

Dr. Gary L. Wenk is a Professor of Psychology & Neuroscience & Molecular Virology, Immunology and Medical Genetics at the Ohio State University and Medical Center. He is also a member of the OSU Center for Brain and Spinal Cord Repair. He received a B.A. in psychology and biology from Albion College and a Ph.D. in Neurotoxicology from the University of Cincinnati. Dr. Wenk’s research is focused upon the investigation of drugs that can slow the progression of Alzheimer’s disease and rescue the brain from the consequences of normal and pathological aging. He is the author of The Brain: What Everyone Needs To Know, Your Brain on Food: How Chemicals Control Your Thoughts and Feelings and Your Brain on Exercise. In this interview, we discuss Your Brain on Exercise and how exercise and oxidative stress affect the brain.

Dr. Gary Wenk, author of Your Brain on Exercise

Greg: What led you to write a book about how exercise affects the brain?

Gary: First, I’m not an athlete. The idea evolved from my TED talk. I shared a slide that showed that the older a person is, the more likely they are to die. Why? What do we do every day of our lives that makes us age? Answer: We eat and we breathe. We eat because we need energy. We get energy from the carbon bonds within the food we eat. We inhale oxygen to remove the carbon debris. That oxygen produces oxidative stress that causes cellular aging. The more we move, the more we need to eat, the more oxygen we need to breathe in, the faster we age. Exercise simply ages us faster.

Greg: So if someone wanted to minimize the aging process, would they be best off not moving at all?

Gary: Yes, in principle, but that would be a terrible idea overall. Without movement, our muscles would atrophy, bones would weaken, and the cardiovascular system would begin to collapse. We must move to survive and procreate. We did not evolve to live a long time; only long enough to procreate the next generation.

Greg: From what I’ve read, exercise has many positive effects on the brain. But it sounds like you’re saying that’s not the case.

Gary: Exercise has benefits for our cardiovascular health. Indirectly, this benefits the brain. Otherwise, exercise has minimal direct positive effects on the brain.

Greg: So what are some reasonable brain changes we can expect from regular exercise, and what is the limit of the effect of exercise on the brain?

Gary: Exercise (moderate, not extreme!) will induce blood vessel growth in some brain areas. This might improve function, but at a cost to the health of those areas. It’s a double-edged sword. Too much exercise will induce mitochondria-induced oxidative stress. Males have more mitochondria than females because they have more muscle mass. That’s why males of ALL species (flies, dogs, humans, etc.) die before females. Males produce more oxidative stress and thus age faster.

Greg: You said that males age faster than females because they have more muscle mass. But this 2014 study found that “muscle mass is associated inversely with mortality risk in older adults.” What am I missing?

Gary: Nothing. That statement is true for the conditions of the study. People who enter old age with better muscle strength and balance tend to live longer than people who do not have those characteristics. The reasons have little to do with the issue of oxidative stress.

Greg: Do different types of exercise have different effects on the brain?

Gary: Yes. In general, moderate daily aerobic exercise is better than extreme exercise or weight lifting. Our bodies evolved to tolerate moderate aerobic exercise and we have endogenous systems that defend our cells from modest amounts of oxidative stress.

Your Brain on Exercise by Dr. Gary Wenk, a book about how exercise and oxidative stress affect the brain

Greg: In general, what does your movement prescription look like? What are some examples of modest exercise? How much is best for longevity?

Gary: According to everything that I’ve read, walking every day for thirty minutes is adequate. It helps emotional health if you do it with someone else and in nature.

Greg: You’ve been very clear about the limited effects of exercise on the physical brain. Do you also believe exercise has limited cognitive and psychological effects?

Gary: The answer depends on which cognitive functions you’re referring to. It has a modest antidepressant effect but is not sufficient to treat depression without medication. It does temporarily increase mood. In animal studies, it does improve performance in memory tasks. I think that its benefits are mostly due to its positive impact on the cardiovascular system and changes in blood flow to the hippocampus, a region critical for memory and mood.

Greg: What most surprised you as you were researching and writing this book?

Gary: The biggest surprise was the myth about the role of the hormone brain-derived neurotrophic factor (BDNF). You can read many naïve, inaccurate claims about how exercise induces the entry of BDNF into the brain. Total nonsense. Muscles produce BDNF but don’t release it. Platelets release it, but no one knows why. Ironically, BDNF can’t cross the blood-brain barrier. Also, no has fully defined the actions of BDNF in the brain.

My biggest surprise was that there is so much myth filling the gaps in our current understanding of what exercise really does for the brain. All creatures obtain energy from breaking carbon bonds inside mitochondria. We must inhale oxygen to get rid of the carbon debris. This process is directly related to cellular aging. Thus, the more energy we consume, the faster we age. Exercise consumes energy, lots of it. So does brain function. I wrote the book to explore whether exercise harms or benefits the brain.

One interesting thing is that animals never exercise. It’s unlikely that our ancient ancestors ever did either. It’s a waste of energy. It’s unlikely that true exercise offers any evolutionary advantage. My conclusion was that it is best to do very modest levels of exercise every day, some occasional weight bearing exercise, be an omnivore and consume as few calories as possible. I’ve found that most athletes hate this information. They like exercising and want to believe the myths. All things being equal, someone who burns more calories per day will die sooner.

Check out Gary Wenk’s book Your Brain on Exercise to learn more about his research on exercise and the brain. And for more interviews like this one, visit The KineSophy Library.