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Dr. Thomas Johnson discusses Harvard Medical School's A Guide to Cognitive Fitness, focusing on the importance of regular exercise to cognitive health and drawing from his personal experiences to illustrate this connection.

A Guide to Cognitive Fitness Part Three
From Dr. Thomas Johnson, NCSP, CPQ
April 2025

Image from Canva

The Harvard Medical School’s A Guide to Cognitive Fitness: Part Three - Exercise Regularly
Edited by Dr. Alvaro Pascual-Leone

In a previous article written for All-Creatures.Org, I reviewed Chapter 1 (Step 1) of the Harvard Medical School’s publication A Guide to Cognitive Fitness which focused on the importance of eating a plant-based diet in developing cognitive fitness. See the March 2025 issue. A second article focusing on cultivating positivity and identifying your purpose was published in the April 2025 issue of All-Creatures.Org. The following is Part three of the Harvard publication and focuses on the benefits of regular exercise which have been well documented. Among its many positive effects on the body include the following:

• “lowers blood pressure and reduces your risk for heart disease, heart attacks, and strokes


• decreases your odds of getting diabetes and certain cancers—including breast and colon cancer


• strengthens your muscles and bones and helps prevent debilitating falls


• helps prevent weight gain and obesity and is especially useful for keeping weight off (provided that you don’t offset your exercise sessions with more sedentary time and increased calories in your diet).

Exercise is also a powerful tool to protect the brain against the detrimental effects of aging. Among other things, it

• rushes oxygenated blood to nourish brain cells and fosters the growth of new blood vessels in the hippocampus, cerebellum, and other brain regions


• increases levels of brain-derived neurotrophic factor, a molecule that encourages the growth of new neurons and maintains the health of existing ones


• preserves and even increases volume in regions of the brain that tend to shrink with age, such as the prefrontal areas and hippocampus


• maintains the integrity of white matter, which is fundamental for the transmission of information within the brain


• enhances cognitive control and reduces impulsivity, promoting better decision making


• improves function of the brain networks that promote sleep


• improves brain activity related to sustaining mood and relieving stress


• boosts production of a hormone-like substance called irisin, which appears to have a protective effect against dementia—at least in mice (researchers are working to translate these results to humans)


• may help clear the plaques that contribute to Alzheimer’s disease (this possible effect of exercise is still under investigation).

Given all these benefits exercise has been found to improve a variety of cognitive functions that tend to decrease with age and the onset of dementia.” (p. 26)

The authors stress the fact that “Exercise is especially potent when partnered with a brain healthy diet” (p. 27) which is a plant-based diet! Additionally, this combination can be enhanced with good sleep hygiene and stress management.

In this next section I will try to explain how I came to use my knowledge of exercise and nutrition to enhance the cognitive fitness and overall wellbeing of my clients and consultees.

My training in cognitive assessment started at Harvard in their graduate programs in counseling psychology and school psychology. I had practicum placements in The Arc of Greater Boston (Previously the Boston Association for Retarded Children), Cambridge Settlement House, and the Suffolk University Counseling Center.

Following my graduation from the Harvard master’s degree program I went on to complete my doctor’s degree in the Division of Counseling Psychology at the University of California at Berkeley. Practicums at Berkeley including time in the university’s Counseling Center with undergraduates and work in the Tenderloin section of San Francisco. After finishing my course work, I completed my doctoral internship at Duke University, again providing counseling and testing undergraduate students. I also provided psychological services to Peace Corps trainees in Durham, NC.

My last training placement was at a community mental health center in Maine. During this entire period there was very little attention on the part of my supervisors paid to exercise or nutrition either in the assessment process or the follow up consultations. This was somewhat perplexing to me as I thought of exercise and nutrition as being vital to physical and cognitive health.

Since completing my psychology licensure requirements, I have reviewed hundreds of neurological, psychological and psychiatric cognitive assessments. Again, I rarely saw significant attention paid to the patients’ exercise and/or nutritional practices. On the other hand, I recognized early in life the importance of exercise and nutrition. As I reflected on this I came up with the following insight.

In my youth I experienced 2 life threatening experiences. First as a preschooler I was in a car accident resulting in a fractured skull and was placed on the “danger list” of the hospital. Fortunately, I survived without any identifiable brain damage. Later in my early teens I developed infectious hepatitis resulting in a hospitalization. I lost so much weight and strength I could barely walk to the bathroom hospital room unaided. My weight dropped to 89 pounds. Fotunately, I survived again.

Left: The author as a child a few years before developing infectious hepatitis. He thought of himself as a normal healthy young boy. Right: The author (in the back) a few months after his recovery from the hospitalization for liver disease.
Photos courtesy of Dr. Thomas Johnson

As part of my recovery, I paid much more attention to my physical fitness and nutrition. I later discovered forms of exercise that could help me develop my muscularity. The exercises that helped me develop my strength and muscularity included dynamic tension and weightlifting. I became strong enough to become a highly successful high school wrestler (during my senior year I was undefeated when I wrestled in my weight class). I also continued my weightlifting as well as wrestling into college. Both athletic sports require great attention to strength and therefor exercise and nutrition. Both sports require competing in certain weight classes.

Clockwise from top left: (1) The author in his teens, a few years after his illness. (2) The author (left) with friends, approximately age 20. (3 & 4) The author, approximately age 20.
Photos courtesy of Dr. Thomas Johnson

At the time healthy nutrition included dairy, fish, whole grains, fruits and vegetables, nuts and seeds as well as animal protein. I was unaware of vegan diets and certainly did not know any vegetarians. I assumed that the mainstream view of a balanced diet included all these foods and beverages was valid. I can remember eating a lot of tuna fish sandwiches, cottage cheese, milk and other dairy foods, peanut butter, fruits and vegetables thinking that I was on a muscle building diet.

My life-threatening experiences and subsequent discovery of the benefits of exercise and healthy nutrition sensitized me to looking for ways I could better assess and provide consultations to my clients/patients and the master’s and doctoral students I supervised and trained to become psychological examiners and counselors. My best professional source of guidance became the Harvard Medical School’s Stress Control model which emphasizes the importance of plant-based nutrition as well as different kinds of exercise. A copy of one of my publications reviewing this reference is on my thomasjohnson.academia.edu website.

Hopefully the readers of this article will appreciate the impressive scientific findings summarized on page 1 of this article. Also, my personal life-threatening experiences and subsequent recovery through exercise and nutrition may be inspirational for some of the readers. I suspect that some of my readers can think of challenging injuries and/or illnesses that have had “silver linings” as part of the recovery process.

While I had great university training to become a psychologist, I have had these difficult life-threatening experiences which have enhanced my ability to empathize with others who may have had similar stress life experiences or are during crises when they come in for assistance.

In conclusion and in summary, in this article I have attempted to enhance the readers awareness of some of the most important knowledge from Harvard neurologists regarding exercise in combination with plant-based nutrition and encouraging positivity and developing a clear sense of purpose. Additionally, using myself as an example I disclosed how a life-threatening injury and a life-threatening illness (infectious hepatitis) motivated me to become more knowledgeable in how exercise and healthy nutrition could help me rebuild my strength and health. I have found that my personal experiences with the accident and illness increases my ability to provide more empathy, positive regard and genuineness in the helping process with patients and credibility with my students and supervisees.

Biographical Notes

Dr. Thomas B. Johnson completed his graduate studies at Brown University (US Public Health Fellowship in social psychiatry and medical sociology), Harvard University (master’s degree in counseling psychology), UC-Berkeley (doctor’s degree in counseling psychology) and Duke University (doctoral internship in psychological services). He is a licensed psychologist, nationally certified school psychologist and a health psychologist and certified by the National Register of Health Services Psychologists. He has served as a faculty member at Bates College, Rutgers University and the University of Southern Maine. He was a contributing editor of the NASP Communique for 10 years as their editor for alternative and complimentary approaches to health and learning. He has been providing a full range of psychological services over many years including assessments, consultations, education, psychotherapy, supervision and research. He now serves as a consulting psychologist and research scientist.

Learn more about Dr. Thomas Johnson and see his other contributions to All-Creatures here!

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Posted on All-Creatures: May 1, 2025
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