Prof. Dr. Raven Flores PhD.
Looking beyond poor eating habits and a couch-potato lifestyle, a group of researchers has found a new culprit in the obesity epidemic: the American workplace.
A sweeping review of shifts in the labor force since 1960 suggests that a sizable portion of the national weight gain can be explained by declining physical activity during the workday. Jobs requiring moderate physical activity, which accounted for 50 percent of the labor market in 1960, have plummeted to just 20 percent.
The remaining 80 percent of jobs, the researchers report, are sedentary or require only light activity. The shift translates to an average decline of about 120 to 140 calories a day in physical activity, closely matching the nation’s steady weight gain over the past five decades, according to the report, published Wednesday in the journal PLoS One.
Today, an estimated one in three Americans are obese. Researchers caution that workplace physical activity most likely accounts for only one piece of the obesity puzzle, and that diet, lifestyle and genetics all play an important role.
But the new emphasis on declining workplace activity also represents a major shift in thinking, and it suggests that health care professionals and others on the front lines against obesity, who for years have focused primarily on eating habits and physical activity at home and during leisure time, have missed a key contributor to America’s weight problem. The findings also put pressure on employers to step up workplace heath initiatives and pay more attention to physical activity at work.
“If we’re going to try to get to the root of what’s causing the obesity epidemic, work-related physical activity needs to be in the discussion,” said Dr. Timothy S. Church, a noted exercise researcher at the Pennington Biomedical Research Center in Baton Rouge, La., and the study’s lead author. “There are a lot of people who say it’s all about food. But the work environment has changed so much we have to rethink how we’re going to attack this problem.”
The report shows that in 1960, one out of two Americans had a job that was physically active. Now it is estimated that only one in five Americans achieves a relatively high level of physical activity at work. Dr. Church notes that because the research doesn’t factor in technological changes, like increasing reliance on the Internet and e-mail, many people in service and desk jobs that have always involved only light activity are now moving less than ever, meaning the findings probably understate how much physical activity has been lost during work hours.
While it has long been known that Americans are more sedentary at work compared with the farming and manufacturing workers of 50 years ago, the new study is believed to be the first in which anyone has estimated how much daily caloric expenditure has been lost in the workplace.
“It’s a light bulb, ‘aha’ moment,” said Barbara E. Ainsworth, the president-elect of the American College of Sports Medicine and an exercise researcher at Arizona State University. “I think occupational activity is part of that missing puzzle that is so difficult to measure and is probably contributing to the inactivity and creeping obesity that we’re seeing over time.”
For years, the role that physical activity has played in the obesity problem has been uncertain. Numerous studies suggest there has been little change in the average amount of leisure-time physical activity, posing a conundrum for researchers trying to explain the country’s steady weight gain. As a result, much of the focus has been on the rise of fast-food and soft drink consumption.
Other studies have suggested that changing commuting habits, declining reliance on public transportation and even increased time in front of the television have played a role in the fattening of America. But none of those issues can fully explain the complex changes in nationwide weight-gain patterns.
Some earlier research has hinted at the fact that workplace physical activity is associated with weight and health. One seminal set of studies of London bus drivers and conductors showed that the sedentary bus drivers had higher rates of heart disease than the ticket-takers, who moved around during the workday.
Dr. Church said that during a talk on the country’s obesity patterns, he was struck by the fact that Mississippi and Wisconsin both have high rates of obesity, despite having little in common in terms of demographics, education or even weather. It occurred to him that both states have waning agricultural economies, prompting him to begin exploring the link between changes in the labor force and declines in workplace physical activity.
He quickly discovered that a decline in farming jobs alone could not explain increasing obesity around the country and began exploring job shifts over several decades. Using computer models, Dr. Church and colleagues assigned metabolic equivalent values to various job categories and then calculated changes in caloric expenditure at work from 1960 to 2008.
“You see the manufacturing jobs plummet and realize that’s a lot of physical activity,” said Dr. Church. “It’s very obvious that the jobs that required a lot of physical activity have gone away.”
Ross C. Brownson, an epidemiologist at Washington University in St. Louis, said that both health professionals and the public needed to broaden the traditional definition of physical activity as something that occurs during planned exercise, like running or working out at the gym.
“We need to think about physical activity as a more robust concept than just recreational physical activity,” said Dr. Brownson, whose 2005 report on declining physical activity in the workplace is cited in the PLoS One report. “In many ways we’ve engineered physical activity out of our lives, so we’ve got to find ways to put it back into our lives, like taking walks during breaks or having opportunities for activity that are more routine to our daily lives, not just going to the health club.”
Researchers said it is unlikely that the lost physical activity can ever be fully restored to the workplace, but employers do have the power to increase the physical activity of their employees by offering subsidized gym memberships or incentives to use public transit. Some companies have set up standing workstations, and marketers now offer treadmill-style desks. Employers can also redesign offices to encourage walking, by placing printers away from desks and encouraging face-to-face communication, rather than e-mail.
“The activity we get at work has to be intentional,” said Dr. Ainsworth. “When people think of obesity they always think of food first, and that’s one side of it, but it’s high time to look at the amount of time we spend inactive at work.”
THURSDAY, May 26, 2011 (Health Day News) — As Americans sit — literally — in more sedentary jobs, they’re packing on the pounds, and it’s this inertia that’s a major contributor to the obesity epidemic, new research suggests.
Staring at the computer for hours rather than hoeing the fields means Americans are burning 120 to 140 fewer calories a day than they did 50 years ago.
So promoting any kind of physical activity needs to have an even greater emphasis in this war on weight, according to a study in the May 25 online edition of the journal PLoS ONE.
“It’s all about calories in and calories out, and we’re putting more calories in than we’re taking out,” said Dr. Robert Graham, a primary care physician at Lenox Hill Hospital in New York City.
A tilt towards calories in has resulted in two-thirds of U.S. adults now being overweight or obese.
Although both eating habits and exercise have been studied in relation to the obesity epidemic, these researchers, from the Pennington Biomedical Research Center in Baton Rouge, La., said much of the blame for the extra poundage has been placed on calorie intake.
That’s because the amount of leisure-time physical activity hasn’t really changed over the years.
But what about the physical demands of work, where so many people spend most of their waking hours?
These researchers cross-referenced U.S. Bureau of Labor Statistics on the prevalence of different jobs with a large national database that includes information on body weight.
Fifty years ago, about half of private-industry jobs in the United States involved some kind of physical activity, things such as farming, mining, construction and manufacturing. Today, that number is less than 20 percent, thanks to the dominance of jobs in retail, education and business.
The authors estimated that 100 fewer calories going out every day would result in a weight gain in line with what the U.S. population has seen since 1960.
Yet, if Americans were following federal guidelines for physical activity (150 minutes a week of moderate-intensity exercise or 75 minutes of more vigorous activity), those extra calories would have been evened out.
Only one in four Americans is doing the recommended level of exercise, the authors stated.
“We need to encourage physical activity even more, especially given that we sit more during the day than we did 100 years ago,” said Keri Gans, a spokeswoman for the American Dietetic Association and author of The Small Change Diet.
“The demands of everyday life are competing with exercise,” Graham added. “We just have to make time for it.”
Gans recommends that people move at work even if they have what amounts to a desk job. That could mean taking the stairs when you can, walking over to a co-worker’s desk when you can and going for a walk at lunchtime. And if your company happens to have a gym or exercise program, by all means, partake.
More information
The U.S. Centers for Disease Control and Prevention has more on how to get moving.
SOURCES: Keri M. Gans, R.D., spokeswoman, American Dietetic Association, and author, The Small Change Diet; Robert Graham, M.D., primary care physician, Lenox Hill Hospital, New York City; May 25, 2011, PLoS ONE, online
A 2006 University of Minnesota study found that from 1980 to 2000, the percentage of people who reported exercising regularly remained the, same-but the amount of time people spent sitting rose by 8 percent.
Now consider how much we sit today compared with, say, 160 years ago. In a clever study, Dutch researchers created a sort of historical theme park and recruited actors to play 1850s Australian settlers for a week. The men did everything from chop wood to forage for food, and the scientists compared their activity levels with those of modern office workers. The result: The actors did the equivalent of walking 3 to 8 miles more a day than the desk bound men. That kind of activity is perhaps even more needed in today’s fast-food nation than it was in the 1800s, but not just because it boosts calorie burn.
A 2010 study in the Journal of Applied Physiology found that when healthy men limited their number of footsteps by 85 percent for 2 weeks, they experienced a 17 percent decrease in insulin sensitivity, raising their diabetes risk. “We’ve done a lot to keep people alive longer, but that doesn’t mean we’re healthier,” says Hamilton.
Today’s death rate is about 43 percent lower than it was in 1960, but back then, less than 1 percent of Americans had diabetes and only 13 percent were obese. Compare that with now, when 6 percent are diagnosed with diabetes and 35 percent are obese.
The definition of an active life. Make no mistake: “Regularly exercising is not the same as being active,” says Peter Katzmarzyk, Ph.D., Hamilton’s colleague at Pennington, the nation’s leading obesity research center. Katzmarzyk is referring to the difference between official exercise activity, such as running, biking, or lifting weights, and so-called non exercised activity, like walking to your car, mowing the lawn, or simply standing. “A person may hit the gym every day, but if he’s sitting a good deal of the rest of the time, he’s probably not leading an overall active life,” says Katzmarzyk. You might dismiss this as scientific semantics, but energy expenditure statistics support Katzmarzyk’s notion.
In a 2007 report, University of Missouri scientists said that people with the highest levels of nonexercised activity (but little to no actual “exercise”) burned significantly more calories a week than those who ran 35 miles a week but accumulated only a moderate amount of non-exercise activity. “It can be as simple as standing more,” Katzmarzyk says. For instance, a “standing” worker-say, a sales clerk at a Banana Republic store—burns about 1,500 calories while on the job; a person behind a desk might expend roughly 1,000 calories. That goes a long way in explaining why people gain 16 pounds, on average, within 8 months of starting sedentary office work, according to a study from the University of North Carolina at Wilmington.
Why sitting too much is never a good thing
But calories aren’t the only problem. In 2009, Katzmarzyk studied the lifestyle habits of more than 17,000 men and women and found that the people who sat for almost the entire day were 54 percent more likely to end up clutching their chests than those who sat for almost none of the time. That’s no surprise, of course, except that it didn’t matter how much the sitters weighed or how often they exercised. “The evidence that sitting is associated with heart disease is very strong,” says Katzmarzyk. “We see it in people who smoke and people who don’t. We see it in people who are regular exercisers and those who aren’t. Sitting is an independent risk factor.”
This isn’t actually a new discovery. In a British study published in 1953, scientists examined two groups of workers: bus drivers and trolley conductors. At first glance, the two occupations appeared to be pretty similar. But while the bus drivers were more likely to sit down for their entire day, the trolley conductors were running up and down the stairs and aisles of the double-decker trolleys. As it turned out, the bus drivers were nearly twice as likely to die of heart disease as the conductors were. A more recent interpretation of that study, published in 2004, found that none of the participants ever exercised. But the two groups did sit for different amounts of time. The analysis revealed that even after the scientists accounted for differences in waist size-an indicator of belly fat-the bus drivers were still more likely to die before the conductors did. So, the bus drivers were at higher risk not simply because their sedentary jobs made them resemble Ralph Kramden, but also because all that sitting truly was making them unhealthy.
Hamilton came to call this area of science “inactivity physiology” while he was conducting studies to determine how exercise affects an enzyme called lipoprotein lipase (LPL). Found in humans as well as mice, LPL’s main responsibility is to break down fat in the bloodstream to use as energy. If a mouse (or a man) doesn’t have this enzyme, or if the enzyme doesn’t work in their leg muscles, the fat is stored instead of burned as fuel. Hamilton discovered that when the rodents were forced to lie down for most of their waking hours, LPL activity in their leg muscles plummeted. But when they simply stood around most of the time, the gene was 10 times more active. That’s when he added an exercise session to the lab-rat routine and found that exercise had no effect on LPL. He believes the finding also applies to people. “Humans sit too much, so you have to treat the problem specifically,” says Hamilton. “The cure for too much sitting isn’t more exercise. Exercise is good, of course, but the average person could never do enough to counteract the effect of hours and hours of chair time.”
“We know there’s a gene in the body that causes heart disease, but it doesn’t respond to exercise no matter how often or how hard you work out,” he says. “And yet the activity of the gene becomes worse from sitting—or rather, the complete and utter lack of contractile activity in your muscles. So the more non-exercise activity you do, the more total time you spend on your feet and out of your chair. That’s the real cure.”
“Your body adapts to what you do most often,” says Bill Hartman, P.T., C.S.C.S., a Men’s Health advisor and physical therapist in Indianapolis, Indiana. “So, if you sit in a chair all day, you’ll essentially become better adapted to sitting in a chair.” The trouble is, that makes you less adept at standing, walking, running, and jumping, all of which a truly healthy human should be able to do with proficiency.
“Older folks have a harder time moving around than younger people do,” says Hartman. “That’s not simply because of age; it’s because what you do consistently from day to day manifests itself over time, for both good and bad.”
Inactivity affects more than the heart
Do you sit all day at a desk? You’re courting muscle stiffness, poor balance and mobility, and lower-back, neck, and hip pain. But to understand why, you’ll need a quick primer on fascia, a tough connective tissue that covers all your muscles. While fascia is pliable, it tends to “set” in the position your muscles are in most often. So, if you sit most of the time, your fascia adapts to that specific position. Now think about where your hips and thighs are in relation to your torso while you’re sitting. They’re bent, which causes the muscles on the front of your thighs, known as hip flexors, to contract slightly, or shorten. The more you sit, the more the fascia will keep your hip flexors shortened. “If you’ve ever seen a guy walk with a forward lean, it’s often because of shortened hip flexors,” says Hartman. “The muscles don’t stretch as they naturally should. As a result, he’s not walking tall and straight because his fascia has adapted more to sitting than standing.”
This same effect can be seen in other areas of your body. For instance, if you spend a lot of time with your shoulders and upper back slumped over a keyboard, this eventually becomes your normal posture. “That’s not just an issue in terms of how you look; it frequently leads to chronic neck and shoulder pain,” says Hartman. Also, people who frequently cross their legs a certain way can experience hip imbalances. “This makes your entire lower body less stable, which decreases your agility and athletic performance and increases your risk for injuries,” Hartman says. Add all this up, and a person who sits a lot is less efficient not only at exercising, but also at simply moving from, say, the couch to the refrigerator.
There’s yet another problem with all that sitting. “If you spend too much time in a chair, your glute muscles will actually ‘forget’ how to fire,” says Hartman. This phenomenon is aptly nicknamed “gluteal amnesia.”
A basic-anatomy reminder: Your glutes, or butt muscles, are your body’s largest muscle group. So if they aren’t functioning properly, you won’t be able to squat or deadlift as much weight, and you won’t burn as much fat. After all, muscles burn calories. And that makes your glutes a powerful furnace for fat—a furnace that’s probably been switched off if you spend most of the day on your duff.
It gets worse. Weak glutes as well as tight hip flexors cause your pelvis to tilt forward. This puts stress on your lumbar spine, resulting in lower-back pain. It also pushes your belly out, which gives you a protruding gut even if you don’t have an ounce of fat. “The changes to your muscles and posture from sitting are so small that you won’t notice them at first. But as you reach your 30s, 40s, 50s, and beyond, they’ll gradually become worse,” says Hartman, “and a lot harder to fix.” So what’s a desk jockey to do?
Hamilton’s advice: Think in terms of two spectrums of activity. One represents the activities you do that are considered regular exercise. But another denotes the amount of time you spend sitting versus the time you spend on your feet. “Then every day, make the small choices that will help move you in the right direction on that sitting-versus-standing spectrum,” says Hamilton. “Stand while you’re talking on the phone. It all adds up, and it all matters.”
Of course, there’s a problem with all of this: It kills all our lame excuses for not exercising (no time for the gym, fungus on the shower-room floor, a rerun of The Office you haven’t seen). Now we have to redefine “workout” to include every waking moment of our days. But there’s a big payoff: more of those days to enjoy in the future. So, get up off your chair and start non-exercising.
Dr. Raven Flores PhD.
