Many of us spend most of our time sitting. This sedentary lifestyle comes at a steep cost to our health. But there’s good news: Even small amounts of physical activity can dramatically reduce the risk of serious diseases.
We’ve brought together ideas from paleoanthropologist Daniel E. Lieberman, physician Peter H. Diamandis, neurosurgeon and biomedical scientist Robert Hariri, and coach Tony Robbins. Read on to learn about the crucial connection between exercise and disease prevention.
Table of Contents
The Power of Physical Activity
In their book Life Force, Robbins, Diamandis, and Hariri recommend moderate to vigorous exercise for good health and vitality. They explain that sedentary lifestyles—those that involve sitting for six or more hours per day with little to no exercise—put you at much higher risk for many different causes of premature death. Regular exercise can prevent diseases of the heart and kidneys, diabetes, dementia, and various types of cancer. The authors recommend making simple lifestyle changes that provide you with your personal optimal level of activity.
Daniel E. Lieberman offers a deeper explanation for why exercise is so crucial in his book Exercised. The absence of regular physical activity allows disease and faster aging because our bodies aren’t getting the signals they evolved to expect to activate crucial repair processes. Lieberman argues that many chronic diseases, including those commonly associated with aging, result from a lack of physical activity. He characterizes these diseases as the results of evolutionary mismatches: Our bodies are poorly adapted to aspects of modern life such as smoking, obesity, and sedentary lifestyles.
Lieberman supports this hypothesis with statistics showing how rare these conditions are among the elderly in modern-day hunter-gatherer societies. Exercise helps prevent and treat many modern diseases by activating the maintenance and repair mechanisms that evolved to respond to physical activity.
| Sedentary Lifestyles at Work and in Schools The prevalence of sedentary lifestyles is increasing globally. Research shows that around one-third of the world’s adult population gets insufficient exercise and that factors like a lack of access to exercise spaces and an increase in sedentary work like office jobs continue to limit people’s physical activity. Additionally, children are being given fewer opportunities for exercise at school than they had in the past several decades. Daily physical education classes used to be standard in most American schools, but recently the public education system’s push for academic achievement and budget cuts has led to a drop in such classes. Currently, less than 10% of American schools have daily PE, and nearly a quarter have no PE at all. This societal increase in sedentary behavior makes it all the more important to implement your own lifestyle changes that give you the right level of regular exercise. |
Simple Changes, Significant Benefits
The authors of Life Force contend that simple changes such as walking for two and a half hours a week can drastically reduce your risk of dying from a stroke or heart attack. These benefits increase if you choose a harder activity such as jogging, which can reduce your biological age by nearly a decade. (Your biological age is how old your body appears to be based on the condition of your cells and tissues—as opposed to chronological age, which is how many years you’ve been alive.)
(Shortform note: Research shows that you can get the benefits of exercise even from activities like housework and yard work. These activities can build muscle, flexibility, and cardiovascular strength just like regular exercise, with the added benefit of a clean house or a beautiful lawn.)
How Exercise Prevents Various Diseases
So, exactly how does exercise prevent disease? Lieberman identifies several conditions that he argues are the result of evolutionary mismatches. They’re virtually nonexistent in modern-day hunter-gatherers, but their numbers have increased exponentially in our modern societies. Let’s explore how exercise can help prevent or manage each condition.
Infectious Diseases
Lieberman argues that lack of exercise weakens our immune function and makes us more vulnerable to pathogens. By contrast, physical activity boosts our immune system by deploying immune cells to vulnerable areas such as the respiratory tract and improving vaccine response. Moderate cardio exercise appears most beneficial, with studies showing that 45 minutes of walking five times a week can reduce respiratory tract infections.
(Shortform note: To enhance the positive effect of exercise on preventing respiratory tract infections, breathe through your nose while exercising. In The Oxygen Advantage, Peter McKeown explains that breathing through your nose strips harmful germs out of the air before they enter your body. Mouth breathing, on the other hand, causes you to lose moisture every time you take a breath, increasing the likelihood of general dehydration and a dry mouth. With excessive mouth breathing, the bacteria-killing compounds in your saliva dry out, allowing bacteria to infect your mouth and airways. This can cause respiratory infections.)
Metabolic Disorders
Exercise is essential for preventing metabolic disorders such as obesity, type 2 diabetes, and cardiovascular disease. When we eat more calories than we expend, excess calories are stored as fat, leading to enlarged fat cells that disrupt our metabolism. Lieberman outlines how obesity, poor diet, stress, and inactivity can lead to insulin resistance, where cells fail to respond to insulin—the hormone that helps our body turn sugar into energy. This results in high blood sugar levels that, over time, can damage vital organs such as the heart and kidneys.
(Shortform note: Obesity is a modern problem, but it’s deeply intertwined with our evolutionary history. In 1962, anthropologist James Neel theorized that early humans had “thrifty genotypes” that stored food in the body as fat when food was plentiful, so it could be burned for energy later when food was scarce. Although most of us don’t face periods of famine today, our genes still tell our bodies to save fat—which leads to obesity. Neel’s theory might explain why we crave fatty foods: Eating these high-energy foods would have been an advantage in hunter-gatherer days.)
Lieberman explains that physical activity is crucial for maintaining a healthy weight and preventing the negative effects of obesity. In addition, regular exercise prevents diabetes and lowers blood pressure by improving your metabolism, including reducing organ fat and regulating blood sugar levels.
(Shortform note: While exercise helps maintain a healthy weight and prevent metabolic disorders, Lieberman doesn’t suggest it’s the only way to achieve these goals. That’s because a healthy diet is still a prerequisite for metabolic health. In The Obesity Code, Jason Fung explains that our metabolism falls out of balance when we eat the wrong foods and when we eat too frequently. Both of these activities increase insulin levels. To avoid metabolic disorders, follow Fung’s advice to avoid processed foods containing wheat and added sugars, industrial meat and dairy, trans fats, and refined vegetable oils. In addition, he argues you should avoid snacking and space your meals to allow your insulin to return to normal levels.)
Lieberman suggests spending at least 150 minutes a week on moderate-intensity exercise, emphasizing that a combination of cardiovascular and strength training is best. This approach not only helps prevent and manage diabetes but also lowers triglycerides and raises HDL (good cholesterol), significantly decreasing the risk of cardiovascular diseases.
(Shortform note: While moderate-intensity exercise improves cardiovascular health markers, it can be difficult to know what moderate-intensity means for you. One exercise expert suggests finding an activity that raises your heart rate and makes it challenging but still possible to engage in a conversation. According to a case study conducted by the same expert, an overweight patient was able to lower triglycerides and bad cholesterol, and raise good cholesterol, by walking briskly for 150 minutes per week for 11 weeks. The patient didn’t engage in strength training during this time. This suggests that if you have to choose between cardio and strength training, cardio should be your first choice for cardiovascular and, as Lieberman mentions, respiratory health.)
| Your Ancestors Called and Said You Need to Go for a Swim In Your Inner Fish, paleontologist Neil Shubin agrees that we can trace many of the ills and ailments we suffer to how our evolutionary history disagrees with our sedentary lifestyles. However, Shubin also believes that part of the problem is how complex our bodies evolved to be. For example, he explains that our arteries and veins evolved to have convoluted paths, making them rely on leg muscles to pump blood back up from the feet. The convoluted design of our cardiovascular system, plus our sedentary lifestyle, results in cardiovascular issues such as blood flow problems. When we don’t use our leg muscles enough, blood pools in our leg veins or around the rectum, creating varicose veins and hemorrhoids. While Lieberman points to hunter-gatherers for evidence of an evolutionary mismatch, Shubin goes even further back. By tracing our body’s evolution back to the first limbed animal—a fish that walked on land—he argues that our evolutionary history can help us understand some of our human weaknesses. Some of our current features were designed for other purposes, such as swimming or crawling. When you start with the body of a fish and turn it into a human mammal that walks on two legs, you get knee problems because limbs in fish were not originally developed to support walking upright on two legs. |
Musculoskeletal Disorders
Lieberman explains that exercise can prevent three major musculoskeletal conditions: sarcopenia (muscle loss), osteoporosis (weak bones), and osteoarthritis (degraded joints). Our muscles consume a lot of energy, so our body eliminates muscle cells if it suspects we don’t need them. Similarly, our bodies naturally deplete bone cells as we age. The best way to keep healthy muscle mass and bone density is to exercise our bones and muscles often with resistance training.
The authors of Life Force also counsel you to build muscle mass, which improves your metabolism and decreases the risk of falling as you age. They recommend static contraction exercises, which involve holding the maximum weight you can hold in a still position for several seconds. They also point out that rest is vital to building muscle, and that it’s necessary to give your muscles a few days of rest after exercising them intensely in order to get stronger.
(Shortform note: Muscle mass can be extremely beneficial in old age. Healthy diet and exercise throughout life can slow the emergence of sarcopenia, or reduction in muscle mass due to aging. Taking these steps can drastically reduce the risk of falls and the likelihood of breaking a bone from a fall, which is significant given that falling is the number one cause of injury in older Americans.)
Lieberman points out that exercise can also protect your joints by preventing excess body weight, which can inflame and degrade the cartilage. In The Body, Bill Bryson elaborates on this point, noting that all of your joints are lined with cartilage, which, unlike the rest of your bodily tissues, doesn’t have a blood supply. The only way your body can maintain the cartilage in your joints is by circulating the synovial fluid in your joints, and the only way you can make your synovial fluid circulate is by moving your joints. If the cartilage in your joints deteriorates too much, movement becomes painful and difficult, a condition known as osteoarthritis.
(Shortform note: Just as the cartilage in your joints needs movement to circulate synovial fluid, so does your lymph system. Lymph cells are part of your immune system. They identify and eliminate unwelcome cells, such as harmful bacteria and cells that have become cancerous. Instead of circulating through your body in your bloodstream, lymph cells are carried by lymph fluid through a separate circulatory system that relies on the movement of your body to move fluid through the system.)
| Humans Evolved to Be Smart and Productive—Not Strong Evolution can help explain why it’s so easy for the quality of our bones, joints, and muscles to degrade over time. In the case of bones and joints, researchers traced the drop in tissue density to the reduction in physical activity that occurred when humans transitioned from hunting-gathering to agriculture. One study found that modern human skeletons have 50-75% less dense spongy trabecular bone in their joints compared to other primates and ancient human ancestors. Another study examined archaeological remains and found that forager groups had thicker, higher-volume trabecular bone in the hip joint compared to farmer groups. In the case of muscles, we might have to go further back to understand why our muscles are prone to degrading. Some scientists speculate that human muscles evolved to be weaker to save energy for our brains. This allowed us to have bigger brains than our primate ancestors, but it made our muscles more susceptible to lifestyle changes. Primates are stronger than humans, even after weeks of little physical activity. However, humans need regular exercise to maintain their muscles because our body prioritizes sending energy to other parts of the body. |
Oncological Disorders
Cancer involves cells that mutate and divide uncontrollably, competing for resources with healthy cells. Lieberman argues that physical activity helps prevent cancer through multiple mechanisms, such as regulating reproductive hormones that trigger mutations, reducing blood sugar availability to cancer cells, and enhancing immune function to suppress cancer cells. In addition, higher levels of exercise generally show a stronger impact.
(Shortform note: Not only does exercise help prevent cancer, but it also plays a significant role in recovery. Studies involving survivors of breast, colon, and prostate cancer show that patients who exercised after their diagnosis had lower mortality rates than those who stopped (or never started) exercising. Besides improving chances of survival, exercise can also alleviate the side effects of cancer treatments and help patients recover following chemotherapy, radiation, and surgery.)
Explore Exercise & Disease Prevention Further
All four authors emphasize that regular physical activity is one of the most powerful tools we have for maintaining vitality throughout our lives. To understand the connection between exercise and disease prevention in the broader context of health, read Shortform’s guides to these books:
- Life Force by Tony Robbins, Peter H. Diamandis, and Robert Hariri
- Exercised by Daniel E. Lieberman
