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The Role of Physical Activity in Successful Aging

May 1, 2023/in Blog, Exercise /by Maya Shetty

By: Helena Zhang and Marcia Stefanick, PhD

Physical activity is considered of utmost importance in the field of research on successful aging. However, the question of what physical activity should look like throughout one’s lifetime remains. While walking is an excellent way to begin exercising, it may not be sufficient for healthy aging in the long run. Instead, research suggests incorporating a variety of exercise modalities into your routine to improve overall health and well-being throughout life. Resistance training – which involves weights, resistance bands, and body weight exercise – plays an important role in muscle and bone density and cardiovascular health. The value of proprioception in physical activity is also emphasized. Proprioception is the body’s ability to orient and sense its own movement and is important for safe and efficient movement throughout life.

Balance exercises improve the mind-muscle connection and can help to prevent falls. These exercises include Tai Chi and Yoga, which are low-intensity physical activities that increase cerebral blood flow and involve sustained attention. Furthermore, endurance exercises, such as running or swimming, reduce inflammation, improve cardiovascular health, and can result in healthy gut microbiomes (Clauss et al. 2021 and Estaki et al. 2016). Members of the Stanford Lifestyle Team are currently researching the role of physical activity in successful aging. To learn more about an ongoing physical activity intervention trial for cardiovascular disease prevention keep on reading!

Key Guidelines for Older Adults

For substantial health benefits, adults should at least do either: 150 minutes to 300 minutes a week of moderate-intensity physical activity 75 minutes to 150 minutes a week of vigorous-intensity aerobic physical activity or an equivalent combination of moderate- and vigorous-intensity aerobic activity. With aerobic activity preferably spread throughout the week

Additional health benefits are gained by engaging in physical activity beyond these hours. Adults should also do muscle-strengthening and balance activities on 2 or more days a week.

Balance activities can improve the ability to resist forces within or outside of the body that causes falls.
Balance training examples include walking heel-to-toe, practicing standing from a sitting position, and using a wobble board. Strengthening muscles of the back, abdomen, and legs also improves balance.

Our Team’s Research

Women’s Health Initiative Strong and Healthy (WHISH): A pragmatic physical activity intervention trial for cardiovascular disease prevention

While national guidelines promote physical activity to prevent cardiovascular disease (CVD), the Women’s Health Initiative Strong and Healthy (WHISH) study is the first randomized control trial to test the effectiveness of increasing physical activity for cardiovascular prevention in older women. The WHISH trial is unique in its scale and study design. 49,333 women aged 68 to 99 were randomly assigned to two groups. While one group received a physical activity program, the other group continued with their usual activities. After 8 years of follow-up, the study aims to compare the heart health of these two groups. For the group that was assigned to the intervention, a multi-component physical activity intervention is being delivered.

Based on intervention goals from the U.S. Department of Health and Human Services, the physical activity program in WHISH aims to increase or maintain aerobic physical activity (primarily walking), decrease sedentary behavior (especially sitting), and increase multicomponent physical activity regarding muscle-strengthening, balance, and flexibility. The intervention is delivered through multiple channels including quarterly (seasonal) WHISHful Actions newsletters, with inserts targeted at 3 participant groups based on lower, middle and higher levels of self-reported physical functioning and physical activity levels, monthly telephone calls and emails with motivational messages, and access to exercise resources on the WHISH website. Crucial to our understanding of CVD prevention in older women, the comprehensive and pragmatic approach of the WHISH study make it a landmark study that will inform policy and future research.

Learn more about the WHISH study here: https://whish.stanford.edu/about/

WHISH PI: Dr. Marcia L. Stefanick

Dr. Stefanick is a Professor of Medicine, Professor of Obstetrics and Gynecology, and a member of the Lifestyle Medicine Program at Stanford University. Her research focuses on chronic disease prevention in men and women. She is the Principal Investigator of the Women’s Health Initiative Strong and Healthy (WHISH), a large-scale physical activity intervention trial investigating whether moving more and sitting less can reduce risk of heart disease in older women.

Can Lifestyle Reverse Your Biological Age?

April 26, 2023/in Blog, Cognitive Enhancement, Exercise, Nutrition, Sleep, Social Engagement, Stress /by Maya Shetty

By: Ben Maines, MD candidate

We all know that eating right, sleeping well, and minimizing stress are good for our health, but what if they could turn back the clock on biological aging? A small but groundbreaking 2020 study found that an 8-week prescription of a healthful diet, stress reduction breathing practices, and exercise decreased participants’ epigenetic age by a little over three years relative to a control group. Sounds too good to be true, doesn’t it? And what do we mean by epigenetic age? We’ll answer those questions and more, but first, a primer in epigenetics. Epigenetics describes reversible molecular modifications made to DNA. At the cutting edge of our modern understanding of medicine and cellular biology, epigenetics facilitates variation between genetically identical cells like your neurons and muscle cells. In the case of twins, for example, you can think of the DNA as the blueprint shared by twins, while epigenetics is the footnotes — instructions that dictate how the blueprint is interpreted and applied. Think of it as the mechanism that bridges nurture and nature, fine-tuning your genetics in response to your environment and lifestyle. At the molecular level, that tuning involves the addition or removal of small molecules like methyl groups to DNA and its packaging. Some molecules make the genes to which they are attached more accessible to the machinery that will translate them, essentially turning those genes on, while others do just the opposite. Evolutionarily, these changes facilitate rapid adaptation to an ever-changing environment. An individual’s experience of famine, for example, can epigenetically tune their metabolism and growth for energy conservation. These epigenetic changes may also be seen in their descendants for several generations to come. The exciting news is that tuning isn’t permanent, which is where lifestyle medicine comes in. Many of the epigenetic phenomena that we understand are related to metabolism and stress responses. Though evolutionarily conserved, these epigenetic changes can be maladaptive in the modern context. A traumatic childhood experience, for example, can trigger epigenetic modifications that not only alter an individual’s stress response to cause chronic stress, but are also heritable to their offspring. This enhanced stress response may have protected an early human in the savannah from repeating risky behaviors, but in our more predictable modern world, chronic stress more often contributes to poor mental health and diseases like cardiovascular disease and high blood pressure. Thinking back to epigenetic age, it seems rational then that if we know the patterns of epigenetic modifications associated with failing health and the diseases of aging, we can use them as a surrogate measure of healthfulness. Though we don’t yet fully understand its nuances, molecularly determined epigenetic age is a better predictor of an individual’s health and longevity than chronological age, presenting an exciting frontier for understanding and modifying health and longevity through lifestyle medicine and targeted therapeutics. For example, a team led by scientists here at Stanford and at the Buck Institute for Research on Aging used deep learning to identify key molecules of systemic inflammation such as CXCL9 that correlate closely with morbidity, cardiovascular degradation, frailty, and other signs of biological aging. As we age, this increasing chronic, systemic inflammation is likely driven by epigenetic changes, raising the tantalizing possibility that it could also be reversed.

How can we use lifestyle medicine to modify our epigenetic fate?

So far, the main clinical epigenetic therapies that have seen success are small molecules that reduce DNA methylation to treat cancer. These molecules function by pushing the reset button on many of the accumulated epigenetic changes that allow the cancer cells’ runaway growth. What if we could do the same to the changes that predict ageing, chronic inflammation, and disease? For now, it seems that our therapeutic tools are too blunt, lacking the precision to target the maladaptive and disease-associated epigenetic changes. So, for now, our best tool for harnessing our epigenetic destiny is our lifestyle. Let’s take a deeper dive into what that looks like at the cutting edge of each of our Stanford Lifestyle Medicine Pillars.

Epigenetics & Physical Activity

Daily exercise has long been associated with health benefits from reduced incidence of cardiovascular disease and improved cancer prognosis to slower cognitive decline. The CDC recommends getting at least 150 minutes of moderate-intensity aerobic activity and 2 strengthening workouts a week for optimal health benefits. There is now evidence that exercise also broadly improves the capacity of your cells to alter their methylation patterns. Exercise leads to higher levels of the protein superoxide dismutase, which works through a series of receptors and pathways in the liver to alter the methylation of key metabolism genes and enhance metabolic function. These pathways affect health in a myriad of ways including improving glucose tolerance to reduce the risk of diabetes. Though some of those epigenetic changes are maintained from parents to children, many are re-programmed during critical developmental periods in-utero, allowing maternal exercise during pregnancy to have profound impacts on offspring health later in life. Lifestyle, it seems, is preventive care that begins even before we’re born. The systemic epigenetic changes induced by physical activity were seen in a recent study by Washington State University that analyzed differences between physical activity and epigenetics in identical twins. Researchers found that twins who exercised for 150 minutes a week or more had more epigenetic markers related to lower risk of metabolic syndrome than twins who exercised less.

Epigenetics & Nutrition

According to recent research, what you eat, and perhaps more unexpectedly, what your parents ate, seems to affect our health through epigenetics in two interesting ways. First, by the availability of small molecules that participate in and modulate the biochemical reactions that add and remove epigenetic tags. For example, plant-forward diets tend to be high in epigenetic substrates like folate, a precursor of the methyl groups added to DNA; cofactors that facilitate that reaction like vitamins A and C; and polyphenolic compounds like curcumin (found in turmeric) that modulate DNA Methyltransferase, the protein that initiates the reaction. Leading theories suggest that by maintaining abundant nutrients involved in epigenetic processes, the body’s response to stress and ever-changing metabolic supply and demand can be efficiently fine-tuned. Diseases like diabetes arise in part because of maladaptive or improper metabolic tuning. A second way that nutrition impacts epigenetics seems to be mediated by metabolic stressors and nutrient sensing. Our cells work along the spectrum between two main modes; when nutrients are limited, pathways turn on that favor maintenance, and clearing and recycling debris, to enhance cellular function and efficiency. Abundant nutrients, on the other hand, downregulate the efficiency pathways and promote storage and more reckless use of resources. With time, famine or feast can become encoded as heritable epigenetic changes, contributing to the increased risk of obesity, diabetes, and several other health conditions in the offspring of parents with poor diet and nutritional profile.

Epigenetics & Sleep

Sleep, namely the lack thereof, has been associated with everything from heart disease and stroke to metabolic disruption. Its greatest impact, though, is on the brain. Interestingly, susceptibility to sleep deprivation is a highly genetic phenomenon. Some people can barely function without 8 hours of sleep, while for others, 6 is more than enough. This suggests a significant role for epigenetics. Cognitive functions like learning and memory rely on neural plasticity, which requires fine-tuned epigenetic adjustments to the gene expression patterns of individual neurons. This process requires sleep, and even single sleep disruption events can impair them, especially in the hippocampus, one of our primary memory and learning centers. More chronic sleep deprivation can alter mood, exacerbate psychiatric disorders, and increase the risk of neurodegeneration as in Alzheimer’s. Most of the epigenetic changes seen with sleep deprivation modify genes involved in metabolism, circadian rhythm, and synaptic plasticity and signaling. For example, night shift workers have altered expression of the genes CLOCK and Dlg4, a master regulator of our body’s internal clock, and a protein implicated in autism that scaffolds synaptic signaling respectively.

Epigenetics & Stress

Technically, stress is any stimulus that disrupts our body’s homeostasis, whether running from a predator in our evolutionary past, experiencing a traumatic life event, or persistent psychological distress. The hypothalamus-pituitary-adrenal (HPA) axis, then, is the stress response control center, a system that connects our brain to our hormone-secreting glands that release systemic stress signals like cortisol, adrenaline, and pro-inflammatory molecules. These signals go on to modulate all our body’s systems, from metabolism and neuronal activity to immune function, and are themselves epigenetically tuned. Typically, our bodies overcome the stressor and return to homeostasis, but traumatic and chronic stress can lead to compounding epigenetic changes that dysregulate our immune, metabolic, neuronal, cardiovascular, and other systems. For example, traumatic childhood experiences trigger epigenetic changes in immune cells like macrophage, increasing pro-inflammatory reactivity and hormonal dysregulation, which may underlie the plethora of adverse health outcomes associated with childhood trauma. Much like the epigenetics of nutrition and exercise, parental stress can be passed on to children both through inherited epigenetic patterns, and through stress hormones circulated from the mother to the developing fetus. On the bright side, positive life experiences, social relationships, and mindfulness practices like meditation and breathing exercises all work to short-circuit these maladaptive stress responses and associated epigenetic changes. For example, one mindfulness-based intervention in breast cancer patients resulted in a reduction of greater than 50% in the epigenetically controlled levels of 91 pro-inflammatory hormones and molecules compared to control patients, an effect that persisted 12 months later.

Epigenetics & Social Engagement

Our capacity to form complex social bonds is evolutionarily foundational to survival, so it’s no wonder that relationships, too, are intimately tied to epigenetics. On one hand, the epigenetic changes associated with chronic and traumatic stress are implicated in impaired capacity for developing and maintaining social bonds. On the other hand, Strong social relationships are important for mitigating stress and its deleterious epigenetic effects, and are one of the strongest predictors of health, happiness, and longevity. Though this is one of the more complex and least understood areas of epigenetics, it’s hard to overstate its role. For instance, mutations in MeCP2, a gene that helps interpret epigenetic methylation patterns, results in the profound cognitive and social dysfunction known as Rhett syndrome.

Epigenetics & Cognitive Enhancement

As it turns out, synaptic plasticity, the phenomenon underlying higher cognitive functions like memory and learning, is largely governed by epigenetic mechanisms. In a highly simplified sense, the strength of patterns and combinations of synaptic firing are enhanced by repeated stimulation, and conversely tuned down in the absence of activity. This is accomplished by epigenetic changes that modulate the sensitivity of neurons to subsequent stimulation. Carrying that principle one step farther, research indicates that enhanced synaptic activity is also essential in synaptic and axonal regeneration after damage such as in the brain of a stroke patient. In animal models, for example, exposure to stimulatory physical and social environments after a brain injury or in disease states such as Parkinson’s leads to increased synaptic activity, which triggers epigenetic changes that promote regenerative healing. Given this observation, it is speculated that similar mechanisms underlie the positive effects of exposure to nature and socially stimulating environments on cognitive and neurological recovery after a brain injury or in diseases like Alzheimer’s. Further, it is plausible that the epigenetic benefits of physical fitness, a varied, plant-based diet, sleep, and relationships translate to beneficial effects on cognitive performance in both health and recovery. For example, the Mediterranean Diet is associated with slowed brain aging and improved cognitive functioning, whereas the Western Diet has been implicated in accelerating natural brain aging processes.

Stop The Clock: The Shocking Truth About Age-Related Muscle Loss and Steps to Fight Back

April 11, 2023/in Blog, Exercise /by Maya Shetty

By: Sarita Khemani, MD

As a physician specializing in peri-operative medicine, I have witnessed firsthand the detrimental impact of muscle loss on patients. Whether it is individuals presenting with hip or spine fractures, or those who have suffered from bleeding in their brain following a fall, many of these acute conditions have a hidden underlying cause: the loss of muscle mass.

Although losing muscle may not seem like a significant concern, it can be a silent yet deadly issue that progressively drains our vitality and strength, leading us to become frail and dependent.

In this blog, we will explore the latest scientific research on the trajectory of muscle loss as we age and discuss practical steps that we can take to prevent or alleviate its effects.

Understanding Skeletal Muscle: Composition and Function

Skeletal muscle is the type of muscle tissue that we can control voluntarily, such as when we intentionally flex our biceps or perform other movements. It is composed of many smaller bundles of muscle fibers, each containing hundreds to thousands of individual fibers. These fibers are primarily made up of two proteins: myosin and actin, which work together to facilitate muscle contraction.

The muscle fibers themselves are arranged in a specific pattern, extending the muscle’s length between the tendinous ends, and are bundled together and wrapped in connective tissue. This arrangement allows the muscle to generate force and produce movement when it contracts.

In terms of composition, muscle tissue is approximately 70% water and 30% protein. The body synthesizes muscle protein from the amino acids that are present in the protein we consume through our diet.

Image credit: University of Miami: https://www.bio.miami.edu/dana/360/360F18_15.html

As we age, the gradual decline in muscle mass and strength worsens with each passing decade. This decline can be attributed to several factors, including reduced dietary protein intake, decreased physical activity, a decline in hormone levels, chronic inflammation, muscle denervation, mitochondrial dysfunction, infiltration of fat into muscle, and insulin resistance.

Research suggests that the rate of loss of muscle strength is greater than the loss of muscle mass and plays a crucial role in healthy aging. When low muscle mass and function, including strength and physical performance, occur with aging, it is known as sarcopenia. The term “sarcopenia” originates from the Greek words “sarx,” meaning flesh, and “penia,” meaning loss.

Sarcopenia can be classified into two categories: primary sarcopenia, which is the cumulative result of various factors leading to muscle loss with aging, and secondary sarcopenia, which is caused by a specific insult, such as surgery, hospitalization, or injury. By understanding these categories, we can better diagnose and manage sarcopenia in older adults.

The trajectory of age-related muscle loss

The loss of muscle strength with age can be surprising to many people, as it can start as early as age 30. As numerous research studies have shown, the rate of decline for muscle mass with age worsens with each decade.

Age	Percent loss of muscle mass/decade
50s	0.5-2%
60s	4-5%
70s	7-8%

The decline in muscle strength is more dramatic and can be 2-5 times greater than decline in muscle mass.

Age	Percent loss of muscle strength/decade
50s	3-4%
60s	9-10%
70s	11-12%

A study found that there was muscle loss of between 35% and 40% occurring between the ages of 20 and 80. Additionally, studies of nursing home residents have found that sarcopenia, affects 30-40% of individuals. Mobility aids, such as canes, walkers, or wheelchairs, are commonly used by older adults, with 24% of those aged 65 years and older relying on such aids. Alarmingly, the death rate from falls is projected to rise sharply in the coming years, as shown in the graph below.

Image Credit: CDC:

Skeletal muscle mass is shown to be an independent predictor of death, highlighting its crucial effect on longevity.

These statistics don’t consider the sudden health events that can accelerate muscle loss. A rapid decline in muscle mass and health occurs with hospitalizations and illnesses. In addition to the lack of activity during hospital stays, other factors like increased levels of pro-inflammatory agents and cortisol can have a compounding effect. For older adults, this loss of muscle mass and function can lead to permanent disability or even death.

Connection between muscle health and dementia

Dementia affects more than 55 million people worldwide, and physical inactivity is one of the modifiable risk factors for the condition. There is a well-established link between low muscle mass, low physical activity, and cognitive impairment in old age.

Exercise releases myokines from the muscle, which crosses the blood-brain barrier and helps regulate BDNF, a protein that supports the survival and growth of neurons in the brain. Furthermore, the lower an individual’s muscle mass, the more significant their cognitive decline, suggesting a dose-dependent effect.

Steps to preserving muscle health and function.

Protecting your muscle mass is like increasing your savings: the greater the savings, the more comfortable you will be as you age.. While we might develop pharmacological treatments for muscle loss in the future, currently, the best way to preserve muscle function is to put in work upfront.

1. Strength training, “the medicine”

Resistance training activates our DNA to respond to stress, leading cells to produce increased muscle protein.

Initially, we may see an improvement in strength but not much muscle hypertrophy because of an increase in muscle protein breakdown. However, this slows down after about six weeks, and we start seeing an increase in muscle size.

Strength training can counteract the accumulation of fat in the muscle, improve the health of neuromuscular junctions, improve muscle quality, and reduce inflammatory markers.

People who do regular resistance training have a 20-year advantage. For example, 85-year-old weightlifters showed similar power and muscle features as 65-year-olds who did not engage in regular training in studies.

To achieve optimum improvement in muscle mass and strength, we should engage in resistance training 2-3 times per week per muscle group in addition to any aerobic exercises.

Resistance exercises that involve increasing load and speed should be done under supervision to ensure proper form and avoid injury.

2. Protein intake

Studies have shown that higher protein intake is associated with greater muscle mass and lower risk of developing frailty in older adults.

Protein intake should be individualized based on age, sex, activity level, and health status, but generally range from 1.6-2.2 grams per kilogram of body weight per day.

A systematic review and meta-analysis published in the British Journal of Nutrition in 2020 found that plant-based protein sources can be just as effective as animal-based sources for improving muscle health. It’s best to mix and match various plant-based sources of protein for optimum effect.

Consuming more than 35-50 grams of protein at one time does not provide any additional benefit for muscle growth, as excess protein is used for energy production. Therefore, it is best to spread protein intake out throughout the day rather than consuming the whole day’s amount in one sitting.

3. Supplements: Please see an excellent blog by Dr. Kaufman on this website to gain more knowledge about the safe use of supplements.

4. We all know to get good sleep and stay hydrated—more on these topics in future blog posts.

Why We Need Exercise: An Evolutionary Perspective

December 9, 2022/in Blog, Exercise /by Maya Shetty

By Maya Shetty

By now, we have all heard that exercise is good for us. But why is this true? And if it’s so good for us, why is it so hard to get up and do it? The Center for Disease Control (CDC) claims we need 150 minutes of moderate exercise and 2 days of muscle strengthening exercise a week to reduce our risk of chronic disease and other adverse health outcomes. However, nearly 80% of US adults are not meeting these guidelines, and 6 in 10 have one or more preventable chronic diseases. To understand this disconnect, we need to begin by examining the evolutionary perspective of exercise – why did humans evolve to exercise in the first place?

The first Homo Sapiens emerged around 200,000 years ago and their lives looked very different from our lives in the modern day. While we complain about having to take the escalators instead of the stairs or our food delivery taking too long, our ancient ancestors were running from predators and hunting for prey. Humans subsisted through hunting and gathering for food, and this was the primary way of life for 95% of human history. This means the majority of our evolution was spent living as nomadic hunter-gatherers. Therefore, our body and behavior is primarily adapted for this lifestyle.

Now, you may be wondering how this translates to exercise in today’s society. Well, as hunter-gatherers, our ancestors’ main advantage was endurance. We are not the strongest or fastest animals out there, so survival was dependent on our ability to outrun our predators and prey. Evolutionarily, we are endurance athletes adapted for consistent, long bouts of physical activity. If this is the case, then why does the average American spend most of their time relatively immobile? This is because we are also adapted for inactivity and energy conservation whenever possible. Thinking again about the hunter-gatherer lifestyle, our ancestors were constantly trying to maintain their energy balance – food intake vs. energy expenditure. It made sense to exercise only when necessary for survival, and conserve energy whenever possible. In today’s society, however, this biological tendency no longer serves us, as our environment has been engineered for an extremely positive energy balance: excess food with little energy expenditure. Now we must go against our biological tendencies and make the decision to exercise, even when our body is telling us not to, in order to maintain good health.

We can see just how much our physical activity differs from our hunter-gatherer ancestors by studying the few modern day hunter-gatherer communities. These populations are often used as models in public health due to their remarkably low rates of chronic disease and disability with age, a stark difference from modern day America. Researchers analyze the behaviors of these populations to have a better understanding of the evolutionary causes of chronic diseases – Why are they so common now vs. then? The most commonly studied population is the Hadza, a hunter-gatherer population in Tanzania. Decades of research has quantified their daily physical activity and how it changes throughout the lifetime. Most notably, the Hadza people average 15,800 steps, about 6 to 9 miles, per day. Meanwhile, Americans average less than 4,800 steps, about 2 miles, per day – about ⅓ the steps of modern hunter-gatherers. On top of this, the average American reduces the amount of steps they take per day by about half between the ages of 40 to 70. The Hadza people, on the other hand, barely change their physical activity levels with age. These behaviors have measurable effects on our physiology. By the age of 60, most Americans walk 33% slower, have less muscle mass, and their VO2max – an indicator of cardiovascular health – decreases by 25%. These functional losses are seen at a significantly lesser rate, if at all, in hunter-gatherer populations. These findings align with the theory of disuse and aging brought forth by Walter Bortz II, a Professor of Medicine at the Stanford University School of Medicine, and one of America’s most distinguished scientific experts on aging and longevity. Dr. Bortz claims the changes commonly associated with aging, such as loss of muscle mass and decreased maximum oxygen consumption (VO2max), are due to disuse with age, rather than aging itself. The differences in physical capabilities with age seen between the modern American and the Hadza people suggest our sedentary lifestyle may contribute to accelerated aging. By being sedentary, we oppose the evolutionary history encoded in our genes for periodic activity, leading to accelerated physiologic loss with age due to disuse.

Regular physical activity stimulates our body to allocate energy toward repair and maintenance, slowing cellular senescence and aging. It has also been seen to have dose dependent effects on the risk of several chronic conditions.

These include:

-Cardiovascular disease and hypertension

-Type 2 diabetes

-Arthritis

-Osteoporosis

-Stroke

-Lung disease

-Many cancers

-Alzheimer’s disease and dementia of any type

Many theories have been suggested about how exercise is able to elicit such powerful health effects. It is widely accepted that many benefits stem from the prevention of excessive weight gain, maintenance of normal blood pressure, decreased levels of unhealthy triglycerides, increased levels of healthy lipoproteins, decreased blood sugar levels, reduced systemic inflammation, and decreased stress levels. However, how these effects come about is still debated.

Studies have also found that regular physical activity stimulates brain growth and improves cognitive function, counteracting the loss of memory and cognition seen with age. Specifically, running has been shown to stimulate the production of neurotrophic factors, or biomolecules that support the growth and survival of neurons. Brain-derived neurotrophic factor (BDNF), for instance, strengthens neuron synapses, increases the production of new nerve cells, and promotes the growth of dendrites. BDNF expression directly increases in response to exercise and is an exciting example of how exercise attenuates cognitive loss.

The World Health Organization suggests that about 150 minutes per week of moderate exercise or 75 minutes per week of vigorous exercise reduces the risk of all-cause of mortality by ~50% in otherwise sedentary individuals (1). Aside from reducing risk of mortality, regular physical activity has been shown to improve functionality, cognition, mood, and healthspan – the amount of time spent in good health- without the functional losses of aging. Despite the extensive benefits of exercise, most of us do not routinely exercise and spend the majority of the day sedentary. Our drive to not exercise, however, is as encoded into our genes as our necessity to exercise. As difficult as it is to find the time and energy to exercise, we as humans are genetically selected for lifelong physical activity and, because of this, regular exercise is synonymous with good health. Our world has been engineered for our convenience, not our health, and for this reason we need to make the personal decision each day to walk more, sit less, and make physical activity a regular habit. Something is better than nothing, so find something that brings you joy! Identify activities that you like and can see yourself consistently doing throughout your life. When you are short on time, taking the stairs instead of the elevator or a short walk after a stressful day can still have tremendous benefits. Whether it be running, dancing, boxing, walking, pilates, biking, etc., just remember to find joy in it and be proud of yourself for putting in the effort. Your health will thank you later.