The Elixir of Youth That Once Gave Meaning to Our Lives
We have all grown up believing that our age is something we cannot control. As youths we wished to be older, seeking out fake IDs and chasing the luxuries of an adult lifestyle. Now, progressing through adulthood, our enthusiasm wanes just a little each year, as we unceremoniously mock the idea of adding another stroke to our birthday tally. While we certainly cannot control the rate at which time passes us by, a multidisciplinary research team from Portugal has given new life to the notion that age is not a number, but rather, a biologically measurable process that is subject to influence by our lifestyle.
Modern society is defined by an aging population, which can be largely attributed to advances in medical science that keep our organs in working order. As such, there is a growing obsession with the concept of “anti-aging,” giving rise to a booming industry filled with skin creams, hair growth ointments, miracle remedies and plastic surgery. And while looking younger is a highly sought after trait, very little effort goes into informing us about how we can actually be younger.
Exercise & Functional Independence
There are comprehensive explanations behind why physical activity keeps us younger at the molecular and physiological levels. In fact, we have reached the point at which we no longer need to question whether or not exercise benefits our health; we can presume that it does and move on to investigating how and why. Yet, the importance of exercise in the maintenance of our functional independence, the physical and mental capacity to carry out everyday activities that make our lives enjoyable, is incredibly undervalued. Moreover, the loss of our functional independence is perhaps the greatest indicator we have of the aging process.
The systemic benefits of exercise across the human lifespan are well documented, including, but not limited to, the following areas:
(1) Cognitive Capacity & Brain Function
(2) Cardiovascular Function
(3) Respiratory Function
(4) Muscular & Skeletal Function
(5) Metabolism & the Regulation of Body Composition
(6) The Immune System
While many of us are already familiar with the far-reaching benefits of exercise, we often think about them in terms of our immediate health. However, it’s not much of a stretch to see, for example, how stimulating cognitive processes and revitalising brain function can preserve our ability to think clearly as we get older. In an analogous manner, improving our cardiovascular, respiratory and skeletomuscular health clears the way for maintaining physical functions throughout the aging process.
Evolved to Exercise?
The question we cannot answer with a great deal of certainty is why we need to exercise in the first place in order to attain health benefits across our lifespan. However, one of the leading theories can be inferred from our evolutionary past. As long-distance hunter-gatherers, evolutionary processes likely favoured individuals that were better adapted to survive in such a manner. As a result, our physical and mental capacities evolved to be optimised when we were “thinking on the move” (for more on this, see Evolutionary Insights into the Prevention of Cognitive Decline).
We often consider exercise a lifestyle choice, but scientific evidence is now pointing more toward the idea that physical activity is our default setting. And, although technological advancements have made our lives infinitely simpler, we have failed to combat the health issues that arise from a sedentary lifestyle.
Our body adopts a “use it or lose it” approach to physiological functions. While I personally wouldn’t trade the luxuries of modern life to return to a hunter-gatherer lifestyle, I think we could all be more aware that our evolutionary past calls us to prioritise exercise in our daily lives.
In terms of survival, physical activity may have given purpose to our brain and body throughout the aging process. So long as we continued to perform physical activity, the molecular processes that preserved physical and mental functions would work in our favour.
Scientific theories and philosophy aside, the case for more exercise is only strengthened by its anti-aging effects at the molecular level.
The Molecular Hallmarks of Aging & the Benefits of Exercise
In recent decades, our understanding of the molecular basis of aging has greatly expanded. Thanks largely to technological advances that allow us to see what is happening inside our cells, researchers have uncovered nine molecular hallmarks of aging. What’s really interesting, however, is that exercise appears to have an anti-aging effect on each of them.
(1) Loss of Genomic Stability
Throughout the course of your life, DNA is damaged by both exposure to external agents (e.g. ionising radiation, genotoxic chemicals, viruses etc.) and through internal cellular processes (e.g. the production of reactive oxygen species, DNA replication ‘errors’ when your cells divide etc.). The body, however, can defend against DNA damage using specialised “DNA repair mechanisms,” which are greatly boosted by exercise.
(2) Reduced Telomere Length
Telomeres can be considered the “protective cap” at the end of your chromosomes. As you get older (as the cell cycle repeats itself), telomeres gradually wear away due to incomplete replication. Eventually, this exposes your DNA, limiting your capacity to produce new cells that are essential for growth and repair. Although the exact mechanism is still a matter of debate, exercise, most likely through the action of telomerase (a telomere-producing enzyme), increases telomere length, keeping your chromosomes “protected” for longer.
(3) Epigenetic Modifications
Epigenetics, in a general sense, refers to the way your DNA is packaged, making certain genes more accessible (or less accessible) than others. This packaging is achieved through chemical modifications (methylation, acetylation etc.) to DNA and histones (the proteins that structurally package DNA). Interestingly, there are some well-established epigenetic patterns that are characteristic of aging. This phenomenon has sparked the idea that we have a true “biological age.” Regular physical activity has been linked to favourable patterns of DNA packaging, reflective of a younger epigenetic profile in the brain, cardiovascular system and muscles.
(4) Loss of Proteostasis
In order for your cells to function efficiently, damaged proteins must be constantly replaced by newer parts. These damaged proteins, however, do not go to waste and are normally recycled by the cell. As you age, your cells become less efficient at constructing new proteins (protein folding), breaking down old proteins (protein degradation) and recycling used parts (autophagy). Various types of exercise have been associated with immediate improvements in these processes as well as a generally positive long-term effect on proteostasis.
(5) Deregulated Nutrient Sensing
The somatotrophic axis in mammals is comprised of growth hormone, produced by the pituitary gland, and insulin-like growth factor, produced by various cells throughout the body in response to growth hormone. However, the same pathway that is used by insulin-like growth factor is also used by insulin. This means that the somatotrophic axis is responsive to both insulin and glucose (blood sugar).
This system plays a seemingly paradoxical role in aging.
Firstly, the availability of energy in the form of glucose favours an “anabolic” state that leads to cell growth. However, activation of this system is associated with accelerated aging.
On the other hand, both growth hormone and insulin-like growth factor levels naturally begin to decrease when you reach your thirties. This means that you have a reduced capacity to enter the favourable anabolic state for cell growth. Exercise, however, induces the production of these hormones, thus stimulating cell growth throughout the aging process.
(6) Mitochondrial Dysfunction
Mitochondrial dysfunction is at the heart of many age-related lifestyle diseases, including obesity, type-2 diabetes and dementia. In the same way that your cells must constantly recycle proteins, mitochondrial function must be sustained through the production of new mitochondria. With increasing age, however, your body tends to display a lower rate of mitochondrial biogenesis and a reduced clearance of damaged mitochondria. For a long time, exercise has been known to stimulate the production of mitochondria across the human lifespan.
(7) Cellular Senescence
Almost every cell in your body is required to divide. This is how your organs carry out growth and repair. However, most cells can only divide a limited number of times before the cell cycle reaches its endpoint. Eventually, cells reach a state of senescence, whereby cell division is arrested.
While cellular senescence is still under investigation, one of its primary purposes is thought to be the prevention cell division by damaged cells. Many organs exhibit a regenerative capacity, clearing out dysfunctional cells and replacing them with younger cells. Exercise appears to both protect against the progression of cells into a senescent state and promote the clearance of senescent cells. Ultimately, this helps maintain the function of your organs.
(8) Stem Cell Exhaustion
The regenerative capacity of your organs is provided by stem cells, specialised cells with the ability to differentiate into new cells that your body requires. As you get older, your body’s pool of stem cells gets smaller, reducing your ability to repair dysfunctional organs. Exercise has been shown to stimulate stem cell production and promote their distribution around the body.
(9) Breakdown in Intercellular Communication
We often think of the brain as our body’s control centre, orchestrating our bodily functions and all of our behaviours. However, many of our other organs are also capable of sending out signals to one another. As we get older, our cells experience higher levels of “inflammation” and “stress,” which interfere with the regular communication between our organs. Exercise has an established role in reducing “inflammation” and “stress” signals and can therefore protect against the breakdown of intercellular communication.
Reversing the Aging Process
Although aging is inevitable, there is no single comprehensive scientific theory to explain it. There are, however, two lines of philosophy that have historically guided the field. The first is that aging is genetically programmed, a biologically “designed” deterioration of our cells. The second, on the other hand, upholds that aging is the result of cumulative damage to our cells over time. As is often the case, a combination of these two theories is preferred, favouring the idea that biological aging is influenced by both “nature” and “nurture.”
On the whole, increased human longevity can be interpreted as a strong indicator of how far we’ve come as a species. But living longer does not necessarily mean that we are sustaining our quality of life throughout the aging process. While we will continue to stand to face-to-face with the challenges of an aging population in the years to come, we can take refuge in the idea that we have more control over our age than was once believed.