2009-08-07 09:27:25
By JOHN CLOUD John Cloud 1 hr 24 mins ago
As I write this, tomorrow is Tuesday, which is a cardio day. I'll spend five
minutes warming up on the VersaClimber, a towering machine that requires you to
move your arms and legs simultaneously. Then I'll do 30 minutes on a stair
mill. On Wednesday a personal trainer will work me like a farm animal for an
hour, sometimes to the point that I am dizzy - an abuse for which I pay as much
as I spend on groceries in a week. Thursday is "body wedge" class, which
involves another exercise contraption, this one a large foam wedge from which I
will push myself up in various hateful ways for an hour. Friday will bring a
5.5-mile run, the extra half-mile my grueling expiation of any gastronomical
indulgences during the week.
I have exercised like this - obsessively, a bit grimly - for years, but
recently I began to wonder: Why am I doing this? Except for a two-year period
at the end of an unhappy relationship - a period when I self-medicated with
lots of Italian desserts - I have never been overweight. One of the most widely
accepted, commonly repeated assumptions in our culture is that if you exercise,
you will lose weight. But I exercise all the time, and since I ended that
relationship and cut most of those desserts, my weight has returned to the same
163 lb. it has been most of my adult life. I still have gut fat that hangs over
my belt when I sit. Why isn't all the exercise wiping it out? (Read "The Year
in Medicine 2008: From A to Z.")
It's a question many of us could ask. More than 45 million Americans now belong
to a health club, up from 23 million in 1993. We spend some $19 billion a year
on gym memberships. Of course, some people join and never go. Still, as one
major study - the Minnesota Heart Survey - found, more of us at least say we
exercise regularly. The survey ran from 1980, when only 47% of respondents said
they engaged in regular exercise, to 2000, when the figure had grown to 57%.
And yet obesity figures have risen dramatically in the same period: a third of
Americans are obese, and another third count as overweight by the Federal
Government's definition. Yes, it's entirely possible that those of us who
regularly go to the gym would weigh even more if we exercised less. But like
many other people, I get hungry after I exercise, so I often eat more on the
days I work out than on the days I don't. Could exercise actually be keeping me
from losing weight? (Watch TIME's video "How to Lose Hundreds of Pounds.")
The conventional wisdom that exercise is essential for shedding pounds is
actually fairly new. As recently as the 1960s, doctors routinely advised
against rigorous exercise, particularly for older adults who could injure
themselves. Today doctors encourage even their oldest patients to exercise,
which is sound advice for many reasons: People who regularly exercise are at
significantly lower risk for all manner of diseases - those of the heart in
particular. They less often develop cancer, diabetes and many other illnesses.
But the past few years of obesity research show that the role of exercise in
weight loss has been wildly overstated. (Read "Losing Weight: Can Exercise
Trump Genes?")
"In general, for weight loss, exercise is pretty useless," says Eric Ravussin,
chair in diabetes and metabolism at Louisiana State University and a prominent
exercise researcher. Many recent studies have found that exercise isn't as
important in helping people lose weight as you hear so regularly in gym
advertisements or on shows like The Biggest Loser - or, for that matter, from
magazines like this one.
The basic problem is that while it's true that exercise burns calories and that
you must burn calories to lose weight, exercise has another effect: it can
stimulate hunger. That causes us to eat more, which in turn can negate the
weight-loss benefits we just accrued. Exercise, in other words, isn't
necessarily helping us lose weight. It may even be making it harder.
The Compensation Problem
Earlier this year, the peer-reviewed journal PLoS ONE - PLoS is the nonprofit
Public Library of Science - published a remarkable study supervised by a
colleague of Ravussin's, Dr. Timothy Church, who holds the rather grand title
of chair in health wisdom at LSU. Church's team randomly assigned into four
groups 464 overweight women who didn't regularly exercise. Women in three of
the groups were asked to work out with a personal trainer for 72 min., 136
min., and 194 min. per week, respectively, for six months. Women in the fourth
cluster, the control group, were told to maintain their usual physical-activity
routines. All the women were asked not to change their dietary habits and to
fill out monthly medical-symptom questionnaires.
See the most common hospital mishaps.
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The findings were surprising. On average, the women in all the groups, even the
control group, lost weight, but the women who exercised - sweating it out with
a trainer several days a week for six months - did not lose significantly more
weight than the control subjects did. (The control-group women may have lost
weight because they were filling out those regular health forms, which may have
prompted them to consume fewer doughnuts.) Some of the women in each of the
four groups actually gained weight, some more than 10 lb. each.
What's going on here? Church calls it compensation, but you and I might know it
as the lip-licking anticipation of perfectly salted, golden-brown French fries
after a hard trip to the gym. Whether because exercise made them hungry or
because they wanted to reward themselves (or both), most of the women who
exercised ate more than they did before they started the experiment. Or they
compensated in another way, by moving around a lot less than usual after they
got home. (Read "Run For Your Lives.")
The findings are important because the government and various medical
organizations routinely prescribe more and more exercise for those who want to
lose weight. In 2007 the American College of Sports Medicine and the American
Heart Association issued new guidelines stating that "to lose weight ... 60 to
90 minutes of physical activity may be necessary." That's 60 to 90 minutes on
most days of the week, a level that not only is unrealistic for those of us
trying to keep or find a job but also could easily produce, on the basis of
Church's data, ravenous compensatory eating.
It's true that after six months of working out, most of the exercisers in
Church's study were able to trim their waistlines slightly - by about an inch.
Even so, they lost no more overall body fat than the control group did. Why
not?
Church, who is 41 and has lived in Baton Rouge for nearly three years, has a
theory. "I see this anecdotally amongst, like, my wife's friends," he says.
"They're like, 'Ah, I'm running an hour a day, and I'm not losing any weight.'"
He asks them, "What are you doing after you run?" It turns out one group of
friends was stopping at Starbucks for muffins afterward. Says Church: "I don't
think most people would appreciate that, wow, you only burned 200 or 300
calories, which you're going to neutralize with just half that muffin." (Read
"Too Fat? Read Your E-mail.")
You might think half a muffin over an entire day wouldn't matter much,
particularly if you exercise regularly. After all, doesn't exercise turn fat to
muscle, and doesn't muscle process excess calories more efficiently than fat
does?
Yes, although the muscle-fat relationship is often misunderstood. According to
calculations published in the journal Obesity Research by a Columbia University
team in 2001, a pound of muscle burns approximately six calories a day in a
resting body, compared with the two calories that a pound of fat burns. Which
means that after you work out hard enough to convert, say, 10 lb. of fat to
muscle - a major achievement - you would be able to eat only an extra 40
calories per day, about the amount in a teaspoon of butter, before beginning to
gain weight. Good luck with that.
Fundamentally, humans are not a species that evolved to dispose of many extra
calories beyond what we need to live. Rats, among other species, have a far
greater capacity to cope with excess calories than we do because they have more
of a dark-colored tissue called brown fat. Brown fat helps produce a protein
that switches off little cellular units called mitochondria, which are the
cells' power plants: they help turn nutrients into energy. When they're
switched off, animals don't get an energy boost. Instead, the animals literally
get warmer. And as their temperature rises, calories burn effortlessly. (See
TIME's health and medicine covers.)
Because rodents have a lot of brown fat, it's very difficult to make them
obese, even when you force-feed them in labs. But humans - we're pathetic. We
have so little brown fat that researchers didn't even report its existence in
adults until earlier this year. That's one reason humans can gain weight with
just an extra half-muffin a day: we almost instantly store most of the calories
we don't need in our regular ("white") fat cells.
All this helps explain why our herculean exercise over the past 30 years - all
the personal trainers, StairMasters and VersaClimbers; all the Pilates classes
and yoga retreats and fat camps - hasn't made us thinner. After we exercise, we
often crave sugary calories like those in muffins or in "sports" drinks like
Gatorade. A standard 20-oz. bottle of Gatorade contains 130 calories. If you're
hot and thirsty after a 20-minute run in summer heat, it's easy to guzzle that
bottle in 20 seconds, in which case the caloric expenditure and the caloric
intake are probably a wash. From a weight-loss perspective, you would have been
better off sitting on the sofa knitting.
See pictures of what makes you eat more food.
Watch a video about fitness gadgets.
Self-Control Is like a Muscle
Many people assume that weight is mostly a matter of willpower - that we can
learn both to exercise and to avoid muffins and Gatorade. A few of us can, but
evolution did not build us to do this for very long. In 2000 the journal
Psychological Bulletin published a paper by psychologists Mark Muraven and Roy
Baumeister in which they observed that self-control is like a muscle: it
weakens each day after you use it. If you force yourself to jog for an hour,
your self-regulatory capacity is proportionately enfeebled. Rather than
lunching on a salad, you'll be more likely to opt for pizza.
Some of us can will ourselves to overcome our basic psychology, but most of us
won't be very successful. "The most powerful determinant of your dietary intake
is your energy expenditure," says Steven Gortmaker, who heads Harvard's
Prevention Research Center on Nutrition and Physical Activity. "If you're more
physically active, you're going to get hungry and eat more." Gortmaker, who has
studied childhood obesity, is even suspicious of the playgrounds at fast-food
restaurants. "Why would they build those?" he asks. "I know it sounds kind of
like conspiracy theory, but you have to think, if a kid plays five minutes and
burns 50 calories, he might then go inside and consume 500 calories or even
1,000." (Read "Why Kids' Exercise Matters Less Than We Think.")
Last year the International Journal of Obesity published a paper by Gortmaker
and Kendrin Sonneville of Children's Hospital Boston noting that "there is a
widespread assumption that increasing activity will result in a net reduction
in any energy gap" - energy gap being the term scientists use for the
difference between the number of calories you use and the number you consume.
But Gortmaker and Sonneville found in their 18-month study of 538 students that
when kids start to exercise, they end up eating more - not just a little more,
but an average of 100 calories more than they had just burned.
If evolution didn't program us to lose weight through exercise, what did it
program us to do? Doesn't exercise do anything?
Sure. It does plenty. In addition to enhancing heart health and helping prevent
disease, exercise improves your mental health and cognitive ability. A study
published in June in the journal Neurology found that older people who exercise
at least once a week are 30% more likely to maintain cognitive function than
those who exercise less. Another study, released by the University of Alberta a
few weeks ago, found that people with chronic back pain who exercise four days
a week have 36% less disability than those who exercise only two or three days
a week.
But there's some confusion about whether it is exercise - sweaty, exhausting,
hunger-producing bursts of activity done exclusively to benefit our health -
that leads to all these benefits or something far simpler: regularly moving
during our waking hours. We all need to move more - the Centers for Disease
Control and Prevention says our leisure-time physical activity (including
things like golfing, gardening and walking) has decreased since the late 1980s,
right around the time the gym boom really exploded. But do we need to stress
our bodies at the gym?
Look at kids. In May a team of researchers at Peninsula Medical School in the
U.K. traveled to Amsterdam to present some surprising findings to the European
Congress on Obesity. The Peninsula scientists had studied 206 kids, ages 7 to
11, at three schools in and around Plymouth, a city of 250,000 on the southern
coast of England. Kids at the first school, an expensive private academy, got
an average of 9.2 hours per week of scheduled, usually rigorous physical
education. Kids at the two other schools - one in a village near Plymouth and
the other an urban school - got just 2.4 hours and 1.7 hours of PE per week,
respectively.
To understand just how much physical activity the kids were getting, the
Peninsula team had them wear ActiGraphs, light but sophisticated devices that
measure not only the amount of physical movement the body engages in but also
its intensity. During four one-week periods over consecutive school terms, the
kids wore the ActiGraphs nearly every waking moment.
And no matter how much PE they got during school hours, when you look at the
whole day, the kids from the three schools moved the same amount, at about the
same intensity. The kids at the fancy private school underwent significantly
more physical activity before 3 p.m., but overall they didn't move more. "Once
they get home, if they are very active in school, they are probably staying
still a bit more because they've already expended so much energy," says Alissa
Fr meaux, a biostatistician who helped conduct the study. "The others are more
likely to grab a bike and run around after school."
Another British study, this one from the University of Exeter, found that kids
who regularly move in short bursts - running to catch a ball, racing up and
down stairs to collect toys - are just as healthy as kids who participate in
sports that require vigorous, sustained exercise.
See nine kid foods to avoid.
Read "Our Super-Sized Kids."
Could pushing people to exercise more actually be contributing to our obesity
problem? In some respects, yes. Because exercise depletes not just the body's
muscles but the brain's self-control "muscle" as well, many of us will feel
greater entitlement to eat a bag of chips during that lazy time after we get
back from the gym. This explains why exercise could make you heavier - or at
least why even my wretched four hours of exercise a week aren't eliminating all
my fat. It's likely that I am more sedentary during my nonexercise hours than I
would be if I didn't exercise with such Puritan fury. If I exercised less, I
might feel like walking more instead of hopping into a cab; I might have enough
energy to shop for food, cook and then clean instead of ordering a satisfyingly
greasy burrito.
Closing the Energy Gap
The problem ultimately is about not exercise itself but the way we've come to
define it. Many obesity researchers now believe that very frequent, low-level
physical activity - the kind humans did for tens of thousands of years before
the leaf blower was invented - may actually work better for us than the
occasional bouts of exercise you get as a gym rat. "You cannot sit still all
day long and then have 30 minutes of exercise without producing stress on the
muscles," says Hans-Rudolf Berthoud, a neurobiologist at LSU's Pennington
Biomedical Research Center who has studied nutrition for 20 years. "The muscles
will ache, and you may not want to move after. But to burn calories, the muscle
movements don't have to be extreme. It would be better to distribute the
movements throughout the day."
For his part, Berthoud rises at 5 a.m. to walk around his neighborhood several
times. He also takes the stairs when possible. "Even if people can get out of
their offices, out from in front of their computers, they go someplace like the
mall and then take the elevator," he says. "This is the real problem, not that
we don't go to the gym enough." (Read "Is There a Laziness Gene?")
I was skeptical when Berthoud said this. Don't you need to raise your heart
rate and sweat in order to strengthen your cardiovascular system? Don't you
need to push your muscles to the max in order to build them?
Actually, it's not clear that vigorous exercise like running carries more
benefits than a moderately strenuous activity like walking while carrying
groceries. You regularly hear about the benefits of exercise in news stories,
but if you read the academic papers on which these stories are based, you
frequently see that the research subjects who were studied didn't clobber
themselves on the elliptical machine. A routine example: in June the
Association for Psychological Science issued a news release saying that
"physical exercise ... may indeed preserve or enhance various aspects of
cognitive functioning." But in fact, those who had better cognitive function
merely walked more and climbed more stairs. They didn't even walk faster;
walking speed wasn't correlated with cognitive ability.
There's also growing evidence that when it comes to preventing certain
diseases, losing weight may be more important than improving cardiovascular
health. In June, Northwestern University researchers released the results of
the longest observational study ever to investigate the relationship between
aerobic fitness and the development of diabetes. The results? Being aerobically
fit was far less important than having a normal body mass index in preventing
the disease. And as we have seen, exercise often does little to help heavy
people reach a normal weight. (Read "Physical Fitness [EM] How Not to Get
Sick.")
So why does the belief persist that exercise leads to weight loss, given all
the scientific evidence to the contrary? Interestingly, until the 1970s, few
obesity researchers promoted exercise as critical for weight reduction. As
recently as 1992, when a stout Bill Clinton became famous for his jogging and
McDonald's habits, the American Journal of Clinical Nutrition published an
article that began, "Recently, the interest in the potential of adding exercise
to the treatment of obesity has increased." The article went on to note that
incorporating exercise training into obesity treatment had led to
"inconsistent" results. "The increased energy expenditure obtained by training
may be compensated by a decrease in non-training physical activities," the
authors wrote.
Then how did the exercise-to-lose-weight mantra become so ingrained?
Public-health officials have been reluctant to downplay exercise because those
who are more physically active are, overall, healthier. Plus, it's hard even
for experts to renounce the notion that exercise is essential for weight loss.
For years, psychologist Kelly Brownell ran a lab at Yale that treated obese
patients with the standard, drilled-into-your-head combination of more exercise
and less food. "What we found was that the treatment of obesity was very
frustrating," he says. Only about 5% of participants could keep the weight off,
and although those 5% were more likely to exercise than those who got fat
again, Brownell says if he were running the program today, "I would probably
reorient toward food and away from exercise." In 2005, Brownell co-founded
Yale's Rudd Center for Food Policy and Obesity, which focuses on food marketing
and public policy - not on encouraging more exercise.
Some research has found that the obese already "exercise" more than most of the
rest of us. In May, Dr. Arn Eliasson of the Walter Reed Army Medical Center
reported the results of a small study that found that overweight people
actually expend significantly more calories every day than people of normal
weight - 3,064 vs. 2,080. He isn't the first researcher to reach this
conclusion. As science writer Gary Taubes noted in his 2007 book Good Calories,
Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health,
"The obese tend to expend more energy than lean people of comparable height,
sex, and bone structure, which means their metabolism is typically burning off
more calories rather than less."
In short, it's what you eat, not how hard you try to work it off, that matters
more in losing weight. You should exercise to improve your health, but be
warned: fiery spurts of vigorous exercise could lead to weight gain. I love how
exercise makes me feel, but tomorrow I might skip the VersaClimber - and skip
the blueberry bar that is my usual postexercise reward.