In the last chapter, we learned how the medical profession’s and the public’s understanding of how poor diet can be an important risk factor for silent heart disease and coronary heart disease in general has dramatically increased over the last fifty years. The same is true with exercise. When I first began my cardiology practice, any discussion of how activity might influence the development of cardiovascular disease focused on how too much exercise or physical exertion might trigger a heart attack. If you didn’t physically exert yourself—at all—then you were minimizing your chance of a heart attack.
How the times are a-changin’ (apology to Bob Dylan!). Today, a wide body of research shows that a sedentary lifestyle—in which the majority of your daily routine consists of sitting or sleeping—is not only not alright but downright dangerous. That’s not to say that the opposite is necessarily true—that exercise fanatics automatically decrease their risk of coronary heart disease. (More on this later in the chapter.) But there’s little doubt that moderate activity multiple times per day does significantly reduce your risk of heart disease.
Even if your weight is normal and you exercise intensely once or twice a week, if the majority of your waking hours on all the other days is spent sitting, you’re still living the kind of sedentary lifestyle that the American Heart Association (AHA) is ringing alarm bells about. This is from a recent “scientific advisory” from the AHA, which issues such reports on important issues in order to inform physicians: “There is now a substantial body of prospective data on associations of sedentary behavior with risk of developing cardiovascular disease as well as with overall mortality. Several (mainly cross-sectional) studies have also found significant associations of sedentary time (deleterious) and breaks from sedentary time (protective) with risk biomarkers.”
In short, inactivity equals death. Dramatic? Yes, but as we dig deeper into the science behind these latest findings, we now understand that the human body is meant to move. Inactivity not only fails to maximize the body’s health potential but, even more importantly, can actually promote a whole cascade of illnesses, including silent heart disease.
In our last chapter, you met my patient Nathan, the thirty-six-year-old, overweight video game programmer. Part of the reason for his high-risk profile for coronary heart disease was his diet. We solved that problem by switching him from a diet consisting largely of fast and frozen foods to a healthful Mediterranean diet, which emphasized fresh fruits and vegetables, fresh fish, whole grains, and olive oil. But diet was only part of Nathan’s health problem, the other being his sedentary lifestyle.
You know, being a Beverly Hills cardiologist, I’ve run into my share of entertainment industry professionals—actors, editors, producers, directors, and so forth—and actually have visited some of them at their work. The public perception of a movie set is an intense beehive of activity. Lights, camera, action!—right? Indeed, there is a certain creative energy that’s buzzing all around on a TV or movie set, but the reality is that there’s a good deal of just sitting around and waiting—for both the cast and the crew. For the most part, it’s sedentary.
With video games, where even the set is virtual, not to mention the cast, the level of inactivity reaches new heights. Like most professionals in his industry, Nathan sits in front of a computer monitor during his working day, with typing on his keyboard or moving his computer mouse the only regular activity that he engages in.
“Aren’t you proud of me, Doc? I’ve lost twenty-five pounds on the Mediterranean diet and I’m feeling and looking better than ever,” said Nathan on a recent visit.
“Yes, congratulations. The results are impressive. But we’ve only just begun,” I said.
“Wait! I thought the Mediterranean diet was the end game?”
“Let me ask you this, Nathan. How often do you exercise?
“Ah, I got you there, Doc. I am a weekend warrior to the ninja degree. I mean, I go to the gym either on Saturday or Sunday for at least two hours, sometimes three hours. Weights, cycling, the whole nine yards,” he said proudly.
“And otherwise during the week, how often are you active?”
“Not much, but, you see, I bank all my good physical activity on the weekends so I can just cruise through the week.” he said.
“Unfortunately, it doesn’t work that way. Maintaining good cardio health means being active on a daily basis,” I advised. “The good news is just a little activity goes a long way.”
A fairly recent innovation in the measurement of good health has been the body mass index (BMI). This value, derived from the weight of the person cross-referenced with his or her height, is a convenient rule of thumb used to broadly categorize a person as underweight, normal weight, overweight, or obese, based on tissue mass (muscle, fat, and bone) and height. So far, so good. However, this weight-to-height ratio can lull people into believing that a “normal” BMI means they’re the picture of perfect health.
In reality, BMI is a crude marker of sedentary behavior. It doesn’t predict whether a person is engaging in enough daily activity to sustain a heart-healthy lifestyle. In a study published in 2019 in the American Journal of Cardiology, researchers at the University of Florida in Gainesville found that a lifestyle characterized by daily physical inactivity can put healthy-weight adults at the same risk for cardiovascular disease as adults who are overweight. “Our study demonstrates that a sedentary lifestyle counters the benefit of being at a normal weight when it comes to heart disease risk,” said lead investigator Arch G. Mainous III, PhD, in an interview published in Cath Lab Digest. “Achieving a body mass index, or BMI, in the normal range shouldn’t give people a false sense of confidence they’re in good health. If you’re not exercising, you’re not doing enough.”
Researchers examined participants’ fat in the gut region as well as waist circumference. In addition, they calculated participants’ Atherosclerotic Cardiovascular Disease (ASCVD) risk score, based on an algorithm devised by the American College of Cardiology and the American Heart Association. The ASCVD risk score uses weighted variables, including age, sex, race/ethnicity, smoking status, diabetes status, cholesterol level, blood pressure, and blood pressure medication status, to determine individuals’ risk of having a heart attack or stroke within the next ten years. A score of 7.5 percent or higher is considered high risk.
What did the research find? Two things that are counterintuitive and actually quite shocking:
•The rate of high ASCVD risk score among overweight people was similar to the rate among people who had a normal BMI but had indicators of a sedentary lifestyle.
•30 percent of U.S. adults of normal weight are at increased risk of heart attack or stroke.
The test subjects in the Gainesville study had higher levels of belly fat, shortness of breath upon exertion, unhealthy waist circumference, or less than recommended levels of physical activity, but again their weight scale and their BMI measurement indicated a clean bill of health.
As we learned earlier, silent heart disease is a special kind of coronary heart disease in that it’s asymptomatic. Thus, patients who are seemingly healthy based on their BMI might think that they have a very low risk of silent heart disease when, in fact, they might have a whole range of factors increasing their risk of heart disease … including a sedentary lifestyle.
Let’s dig a little deeper into the study. The investigators analyzed data from the National Health and Nutrition Examination Survey, a nationally representative study that collects data from a combination of interviews, physical examinations, and laboratory tests. The study focuses on participants ages forty to seventy-nine with no previous diagnosis of coronary heart disease, stroke, or heart attack.
“We have traditionally thought that people with a normal BMI are healthy and at low risk for heart disease, but increasingly we are finding that how much you weigh is not necessarily a measure of good health,” said Mainous, the lead researcher. “Sedentary lifestyle markers may play a better role in predicting cardiovascular disease risk.”
Exactly!
According to the American Heart Association, sedentary jobs have increased 83 percent since 1950. Physically active work now makes up less than 20 percent of U.S. jobs, down from roughly half of jobs in 1960.
So what the heck happened to the fitness craze that emerged in the 1980s with the likes of Jane Fonda and aerobics and Jim Fixx and jogging? What happened was that even as average Americans joined in more sports activities than their parents, they were becoming more and more tied to a desk. The advent of computer technology and the Information Age in the 1990s sealed the deal.
The end result was Americans’ striving to be more physically active but eventually losing the battle. And as I discussed with my patient Nathan earlier, it’s not as if you can bank your physical activity and use its benefits later on in the week. If you’re crazy active during the weekends but essentially inactive during the workweek, you’re not improving your heart health. To reframe this paradox, sedentary behavior can coexist with high levels of total physical activity.
A large review of studies published in 2015 in the Annals of Internal Medicine found that even after adjusting for physical activity, sitting for long periods was associated with worse health outcomes, including heart disease, but also type 2 diabetes, which, as we discussed in Chapter 9, is also a risk factor for cardiovascular disease.
Historically, research on physical activity focused on the relationship between energy expenditure and health benefits. The resulting physical activity guidelines were largely oriented toward increasing physical activity levels in the population rather than reducing sedentary behavior. To be clear, we have known for millennia that physical activity improves overall health. None other than Hippocrates and Siddhartha sang the praises of exercise. But it was a British epidemiologist, Jeremy N. Morris, who first proved in the 1950s that the opposite was also true—that inactivity or sedentary behavior wasn’t benign but was actually bad for you.
Who were the subjects of his study? Employees of the London transport department. Morris had a hunch that prolonged inactivity was an important risk factor for coronary disease, but how could he show it? He happened upon the idea while riding one of London’s iconic double-decker buses. He noticed that drivers of the buses sat continually, never moving from their perch behind the wheels. On the other hand, the conductors who took the tickets were constantly on the move, walking up and down the aisles and even up and down the buses’ circular staircases. To be precise, the drivers sat for 90 percent of their shifts; the conductors climbed about six hundred stairs each working day.
So, all things considered, here were two sets of test subjects who worked in exactly the same environment, and the only thing that differentiated them was their job description. If there was a discrepancy in the risk of cardiovascular disease between the active and inactive in their daily work routine, it should reveal itself here on London’s buses.
Morris studied thirty-one thousand employees aged thirty-five to sixty-four during two years from 1949 to 1950. So, what did he find? The research was conclusive. When compared with conductors, bus drivers had about double the age-adjusted rate of fatal coronary heart disease. This was the first indication that sedentary behavior could markedly increase cardiovascular heart disease risk.
Ever the careful scientist, Morris set out to replicate the study. After all, maybe an unforeseen factor was influencing the results. For example, maybe people with certain body types were more prone to seek jobs with little activity (like driving a bus). The London transport department provided him with the trouser sizes of its workers. His data indicated that while conductors’ waistbands were smaller, their protection against heart attack could not be explained by a lean body type. The conductors had a lower risk of heart attack whether they were slim, average size, or portly.
Then, to corroborate his findings further, Morris turned his inquisitive mind toward London’s postal workers. He compared those who delivered the mail by walking or riding a bicycle with the window clerks at the post office and the telephone operators. And the results? (Drum roll, please.) The constantly on the move deliverers had a far lower risk of heart attack than their sedentary counterparts, the clerks and operators.
Morris would go on to show in subsequent studies that inactivity was also bad for those who had already had a heart attack. Prior to his research, heart attack victims were prescribed a regimen of as little physical exertion as possible. His continuing research showed the opposite was warranted: exercise reduced the risk of heart attack. (Morris, who followed his own prescriptive advice about staying active on a daily basis, lived until he was 99.5 years old.)
Now, you may ask, if inactivity is bad, are some kinds worse than others? As turns out, the answer is yes, according to the latest research.
An analysis of data from several thousand US participants aged fifty to seventy-one years in a study conducted by the National Institutes of Health and the AARP showed that the risk of cardiovascular disease rose progressively in lockstep with time spent watching television or videos. Participants’ time spent watching television or videos was assessed with the question “During a typical 24-h period over the past 12 months, how much time did you spend watching television or videos?” Among participants who watched one hour versus seven hours of television or videos per day, the heavy TV watchers had almost double the incidence of coronary heart disease.
These findings were validated in a subsequent study, published in 2019 in the Journal of the American Heart Association, which focused on binge TV watching compared to the effects of occupational sitting, such as at desk jobs. Over eight years researchers studied 3,592 adults enrolled in the Jackson Heart Study, a large, ongoing, community-based study following adults living in Jackson, Mississippi. With all other factors (e.g., age, occupation, gender) considered, those who watched the most television in their hours of inactivity had disproportionately higher rates of heart disease and stroke and faced a greater risk of cardiovascular disease at all ages of life. Even sustained and regular exercise proved not to offset the results.
You can almost hear the collective groan from Hollywood TV executives that, once again, they’ve been made the scapegoats for society’s ills. TV watching is blamed for everything from mental illness to gun violence; why not add to the list increased risk of coronary heart disease?
It turns out, however, there’s a simple explanation. According to the study’s lead researcher, Jeanette Garcia, PhD, a professor of kinesiology and physical therapy at the University of Central Florida in Orlando,
“TV watching may be associated with heart health risks more than sitting at work [because] TV watching occurs at the end of the day where individuals may consume their biggest meal, and people may be completely sedentary with hours of uninterrupted sitting until they go to bed. Eating a large meal and then sitting hours at a time could be a very harmful combination.” Snacking may also be an issue and, unfortunately, individuals typically are not snacking on fresh fruits and vegetables, but rather potato chips or other sweet or salty, high-calorie foods. At a desk job, workers are often getting up, going to a copy machine, talking with a colleague, going to a meeting or to the break room. It’s not hours of uninterrupted sitting.
So, if some sedentary behavior is worse than other kinds, how about exercise? Is some better in preventing cardiovascular heart disease?
There continues to be considerable controversy about the optimal dose of physical activity. However, substantial evidence suggests that any level of physical exercise and activity is better than none. Current federal guidelines call for a minimum of 150 minutes per week of moderate aerobic physical activity or 75 minutes per week of vigorous physical activity. The majority of Americans do not meet these guidelines, with only 10 percent meeting this minimum recommended level of activity.
Runners have the best results, according to studies. However, interesting findings emerge when we assess running dosing by dividing runners into quintiles of exercise volumes, such as miles per week, times per week, and minutes per week. Research shows that those who run less than six miles per week, one to two times per week, had the same benefits in preventing coronary heart disease as those who ran much more and more often.
There’s even some evidence that those who ran the most actually decreased the effects of their exercise in preventing cardiovascular disease. In other words, even though moderate levels of exercise have been found to be consistently associated with a reduction in coronary disease risk, there is evidence to suggest that continuously high levels of exercise (e.g., marathon running) could have detrimental effects on cardiovascular health.
Alright, so excessive and regular inactivity is bad. But what is the physiological mechanism by which exercise imparts it remarkable benefits to cardiovascular health and conversely causes sustained inactivity to be so perilous?
The short answer is that we don’t know for sure. However, many studies have tested whether regular engagement in physical activity may lower the risk of cardiovascular disease by affecting the levels of circulating lipoproteins. These studies have found that endurance training is associated with elevated levels of circulating high-density lipoprotein (HDL) and, to a lesser extent, a reduction in triglyceride levels—both changes that can reduce the risk of coronary heart disease.
Also, we know that blood flow increases in a standing versus a sitting position and is further increased during physical activity in response to increased oxygen requirements in muscle. There are clearly physiological changes that occur when physically active individuals become inactive. Reduced insulin sensitivity is found during prolonged sedentary behavior that can be mitigated with short bouts of physical activity.
Despite the extensive body of knowledge documenting the unequivocal health benefits of exercise, a vast majority of Americans do not engage in sufficient physical activity. Nonetheless, mortality risk reduction appears with even small bouts of daily exercise and peaks at fifty to sixty minutes of vigorous exercise each day.
However, the question remains as to how much exercise is optimal for cardiovascular health benefit. Studies in endurance runners show that the frequency of adverse cardiovascular events in marathoners is equivalent to that in a population with established coronary heart disease, suggesting that too much exercise may be detrimental. An upper limit for the cardiovascular benefits of exercise is further supported by a recent study showing that individuals who completed at least twenty-five marathons over a period of twenty-five years had higher than expected levels of coronary artery calcification (CAC) and calcified coronary plaque volume compared with sedentary individuals. (CAC scoring, also called a coronary calcium scan, is a test that measures the amount of calcium in the walls of the heart’s arteries. A coronary calcium scan is one way to estimate someone’s risk of developing heart disease or having a heart attack or stroke.)
Another recent investigation also showed that individuals who maintain very high levels of physical activity (three times recommended levels) have higher odds of developing CAC, particularly white males. In contrast, other studies report greater plaque stability due to calcification in exercisers, indicating that with higher levels of physical activity, plaque quality may be favorably impacted to lower the risk of cardiovascular events, despite a higher incidence of plaques and abnormal CAC scores.
An immediate result of a change from a highly physical active state to a highly sedentary state is a reduction in muscle and systemic insulin sensitivity, and if the resulting energy imbalance is sustained, adipose or fat tissue will expand. The consequences of energy surplus, adiposity, and insulin resistance for inflammation and cardiovascular disease risk have been well established. A decrease in insulin sensitivity that results from becoming sedentary can occur independent of increased adiposity or energy surplus.
To summarize, researchers believe there is a sweet spot between enough and too much exercise. It appears that both too little activity and too much activity can trigger physiological inflammation, which is in and of itself a well-known risk factor for cardiovascular disease.
For most of us, running twenty-five marathons is a distant likelihood, and so exercising too much shouldn’t be a concern for 90 percent of adult Americans. But here’s the best part: even a nominal increase in activity—for example, only sitting five hours instead of ten—results in a decreased risk of fatal and nonfatal coronary heart disease.
For those looking to increase to an optimum activity level, the Centers for Disease Control and Prevention has published physical activity guidelines, which recommend at least 150 minutes of moderateintensity exercise a week for adults. Exercise should include a combination of aerobic activity and strength training. I recommended such an activity regimen for my patient Nathan.
“Continue Mediterranean diet, check. Two-plus hours of moderate exercise but spread out throughout the week. Anything else, Doc?” said Nathan.
“Yes, get up and walk around,” I said.
“You mean now?”
“No, at work. Every hour, I want you to leave whatever virtual world you’re creating and reconnect with reality—get up from your desk and go get a glass of water, say hi to a colleague, stretch and touch your toes. Do you think your digital menagerie of creatures can let you be away for that long? Remember, there’s a great deal of benefit to light activity during the day but only if you do it throughout the day.”
“Got it. The body—at least the human body—is designed to keep moving.”