[Paleopsych] Skeptical Inquirer: Obesity: Epidemic or Myth?
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Obesity: Epidemic or Myth?
http://www.csicop.org/si/2005-09/obesity.html
New evidence shows that the obesity epidemic is not as bad as we have
been led to believe. However, that doesnt mean that we should dismiss
the problem either.
PATRICK JOHNSON
_________________________________________________________________
You have probably heard that we are in the midst of an obesity
epidemic. The Centers for Disease Control and Prevention (CDC) have
been fervently warning that we are in imminent danger from our
expanding waistlines since the beginning of this decade. However,
evidence has recently emerged indicating that the CDCs warnings were
based on questionable data that resulted in exaggerated risks.
This new evidence has led to a hostile backlash of sorts against the
CDC. The editors of the Baltimore Sun recently called the earlier
estimates the Chicken Little Scare of 2004. The Center for Consumer
Freedom, a group that has long been critical of the CDC, declared
unequivocally on its Web site and in print ads in several newspapers
around the country that the obesity scare was a myth (figure 1). Even
Jay Leno poked fun at the CDC in one of his Tonight Show monologues,
making the observation that not only are we fat. . . . We cant do math
either. Not everybody believes the new data, however. Cable talk show
host Bill Maher commented during an episode of his show Real Time with
Bill Maher about it being a shame that lobbyists were able to
manipulate the CDC into reducing the estimated risk.
So which is it? Are we in imminent danger, or is the whole concept a
myth? Looking at the scientific evidence it is clear that the extreme
views on either side of the argument are incorrect. There is no doubt
that many of our concerns about obesity are alarmist and exaggerated,
but it is also apparent that there is a real health risk associated
with it.
The Controversy
Between 1976 and 1991 the prevalence of overweight and obesity in the
United States increased by about 31 percent (Heini and Weinsier 1997),
then between 1994 and 2000 it increased by another 24 percent (Flegal
et al. 2002). This trend, according to a 2004 analysis, shows little
sign of slowing down (Hedley et al. 2004). The fact that more of us
are getting fatter all the time raises a significant public health
concern. The Centers for Disease Control and Prevention (CDC) began
calling the problem an epidemic in the beginning of this decade as the
result of research that estimated 280,000 annual deaths as a
consequence of obesity (Allison et al. 1999). Since then there has
been a strong media campaign devoted to convincing Americans to lose
weight. In 2003, Dr. Julie Gerberding, the director of the CDC, made a
speech claiming that the health impact of obesity would be worse than
the influenza epidemic of the early twentieth century or the black
plague of the Middle Ages. In 2004 the campaign reached a fever pitch
when a report was released that increased the estimate of
obesity-related deaths to 400,000 (Mokdad et al. 2004). Finally, in
March of this year, a report appeared in the New England Journal of
Medicine that predicted a decline in life expectancy in the United
States as a direct result of obesity (Olshansky, et al. 2005).
Despite the assertions that obesity is causing our society great harm,
however, many scientists and activist groups have disputed the level
of danger that it actually poses. Indeed, a recent analysis presented
in the Journal of the American Medical Association (JAMA) by Katherine
Flegal of the CDC and her colleagues calls the severity of the dangers
of excess body fat into question, indicating that the number of
overweight and obesity-related deaths is actually about 26,000about
one fifteenth the earlier estimate of 400,000 (Flegal et al. 2005).
There is little argument about the fact that, as a nation, more of us
are fatter than ever before; the disagreement lies in the effect that
this has on our health. The campaign to convince us to lose weight
gained much of its momentum in 2004; not only were there high-profile
public health initiatives devoted to stopping the obesity epidemic,
but the idea had pervaded popular culture as well. Movies like Morgan
Spurlocks Super Size Me were the topic of many a discussion, and there
were regular news reports about the dangers of too much fat.
During this campaign, however, there were some notable dissenters.
Paul Ernsberger, a professor of nutrition at Case Western Reserve
University, has been doing research since the 1980s that led him to
assert that obesity is not the cause of ill health but rather the
effect of sedentary living and poor nutrition, which are the actual
causes. Another prominent researcher, Steven Blair, director of the
Cooper Institute of Aerobics Research in Dallas, Texas, has been an
author on several studies indicating that the risks associated with
obesity can be significantly reduced if one engages in regular
physical activity, even if weight loss is not present. According to
Blair, weight loss should not be ignored but a greater focus should be
placed on physical activity and good nutrition. Both Ernsberger and
Blair indicated to me that they thought the new research by Flegal and
her colleagues provides a more accurate picture of the mortality risk
associated with obesity.
[Obesity-Poster.jpg]
Figure 1. This advertisement, paid for by the Center for Consumer
Freedom (CCF), ran in magazines and newspapers across the country. The
ad was issued in response to the study in the Journal of the American
Medical Association that found obesity-caused death rates had been
exaggerated. However, CCF, an advocacy group for restaurants and food
companies, has its own agenda.
While scientists like Ernsberger and Blair have been presenting their
conclusions in the scientific forum, others have taken a more
inflammatory approach. In his 2004 book, The Obesity Myth, Paul Campos
argues that the public health problem we have associated with obesity
is a myth and further claims that our loathing of fat has damaged our
culture (see Benjamin Radfords review on page 50). The most
antagonistic group, however, is the Center for Consumer Freedom (CCF)
(www.consumerfreedom.com), which implies that the obesity epidemic is
a conspiracy between the pharmaceutical industries and the public
health establishment to create a better market for weight-loss drugs.
Numerous articles on the organizations Web site bash several of the
most prominent obesity researchers who have disclosed financial ties
to the pharmaceutical industries. Paul Ernsberger echoed this
sentiment. He told me that the inflated mortality statistics were all
based on the work of David Allison, a well-known pharmacoeconomics
expert. These experts create cost-benefit analyses which are part of
all drug applications to the FDA. These self-serving analyses start by
exaggerating as much as possible the cost to society of the ailment to
be treated (obesity in the case of weight-loss drugs). The risks
associated with the new drug are severely underestimated, which
results in an extremely favorable risk-benefit analysis, which is
almost never realized once the drug is on the market. Experts who can
produce highly favorable risk-benefit analyses are very much in
demand, however.
The claims made by the CCF are given some credence by Ernsbergers
corroboration; however, there is a noteworthy problem with their own
objectivity. On their Web site they present themselves as a
consumer-minded libertarian group that exists to promote personal
responsibility and protect consumer choices. Upon closer examination,
however, it becomes evident that the CCF is an advocacy group for
restaurants and food companies, who have as much to gain by the threat
of obesity being a myth as the pharmaceutical industry does by the
danger being dire.
It is clear that there are agenda-determined interests on both sides
of the issue. Therefore, the best way to discern what is necessary for
good health is to shift our focus away from the sensational parts of
the controversy and look at the science itself.
Current Science and Obesity Risks
In their recent article, Katherine Flegal and her colleagues (2005)
point out that the earlier mortality estimates were based on analyses
that were methodologically flawed because in their calculations the
authors used adjusted relative risks in an equation that was developed
for unadjusted relative risk. This, according to Flegals group, meant
that the old estimates only partially accounted for confounding
factors. The older estimates, furthermore did not account for
variation by age in the relation of body weight to mortality, and did
not include measures of uncertainty in the form of [standard errors]
or confidence intervals. These authors also point out that the
previous estimates relied on studies that had notable limitations:
Four of six included only older data (two studies ended follow-up in
the 1970s and two in the 1980s), three had only self-reported weight
and height, three had data only from small geographic areas, and one
study included only women. Only one data set, the National Health and
Nutrition Examination Survey I, was nationally representative (Flegal
et al. 2005). In their current investigation, Flegals group addressed
this problem by using data only from nationally representative samples
with measured heights and weights. Further, they accounted for
confounding variables and included standard errors for the estimates.
Obesity was determined in this analysis using each subjects body mass
index, which is a simple height-to-weight ratio. A BMI of 18 to 24 is
considered to be the normal weight, 2529 is considered overweight, and
30 and above is considered obese. The data from this study indicated
that people who were underweight experienced 33,746 more deaths than
normal-weight people, and that people who were overweight or obese
experienced 25,814 more deaths than the normal-weight folks. This
estimate is being reported in the popular media as being one-
fifteenth the earlier estimate of 400,000. However, conflating the
categories of overweight and obesity this way is misleading.
At first glance, it appears that underweight poses a bigger threat to
our health than overweight and obesity, and that the earlier estimates
were profoundly exaggerated. However, in this study the people who fit
into the obese category actually experienced 111,909 excess deaths
compared to normal-weight subjects. In contrast, those who were
categorized as overweight experienced 86,094 fewer deaths than those
who were normal weight. The figure of 25,815 is the difference between
the obesity deaths and the overweight survivals. In the original study
by David Allison and his colleagues (Allison et al. 1999) it is
actually estimated that 280,000 deaths result from overweight and
obesity and that 80 percent, or 224,000, of these deaths occurred in
people who were in the obese category. However, the study by Mokdad
and colleagues (2004), using the same methods developed by Allison et
al., estimated 400,000 obesity-related deaths, and subsequently fueled
much of the recent fervor surrounding the obesity epidemic. In this
study, no distinction was made between overweight and obesity and the
authors failed to distinguish between obesity, physical inactivity,
and poor diet. All of these variables were simply lumped together.
A few things become clearer after examining the data. First, it
appears that our categories are mislabeled; being classified as
overweight appears to give one an advantage (statistically, anyway)
over those who are in the ideal weight range. [1] Moreover, it is
inappropriate to consider overweight and obese as one group. Despite
the current hype, the initial overestimation by Allison and his group
was not as exaggerated as is being publicized; compared to that study,
the new estimate is actually about half of the old number. Finally, it
is apparent that many at the CDC were simply confirming their own
biases when they accepted the estimate by Mokdad et al. The categories
in that studythat was, intriguingly, co-authored by CDC director Julie
Gerberding, which may provide some insight into why it was so readily
acceptedwere far too broad to provide useful information. The fact
that this flaw was ignored shows how easy it is to accept evidence
that supports our preconceived notions or our political agendas.
There is another problem inherent in all of the above mortality
estimates. They are based on epidemiological data that show
correlation but leave us guessing as to causation. Various factors are
interrelated with increased mortalityobesity, inactivity, poor
nutrition, smoking, etc. Yet, without carefully controlled
experiments, it is hard to determine which factors causeand which are
symptoms ofpoor health. This is a difficult limitation to overcome,
however, because we cant recruit subjects and have them get fat to see
if they get sick and/or die sooner. Most institutional review boards
would not approve that sort of research, and furthermore I cant
imagine that there would be a large pool of subjects willing to
participate. There are, however, observational data that were
collected with fitness in mind, which help to clarify the picture
somewhat.
In 1970 researchers at the Cooper Institute for Aerobics Research in
Dallas, Texas, began to gather data for a longitudinal study that was
called, pragmatically enough, the Aerobics Center Longitudinal Study
(ACLS). This study looked at a variety of different variables to
estimate the health risks and benefits of certain behaviors and
lifestyle choices. What set this study apart from other large-scale
observational studies, however, was that instead of relying on
self-reporting for variables like exercise habits, they tested fitness
levels directly by way of a graded exercise test (GXT). A GXT requires
a person to walk on a treadmill as long as he or she can with
increases in speed and incline at regular intervals. This is the most
reliable way we know of to assess a persons physical fitness.
With an accurate measure of the subjects fitness levels, researchers
at the Cooper Institute have been able to include fitness as a
covariate with obesity. Analysis of the data obtained in the ACLS
shows that there is a risk associated with obesity, but when you
control for physical activity, much of that risk disappears (Church et
al. 2004; Katzmarzyk et al. 2004; Katzmarzyk et al. 2004; Lee et al.
1999). One study showed that obese men who performed regular exercise
had a lower risk of developing cardiovascular disease than lean men
who were out of shape (Lee et al. 1999).
Steven Blair, who runs the Cooper Institute and was an author on all
four of the above-mentioned studies, however, does not think obesity
should be ignored. I do think obesity is a public health problem,
although I also think that the primary cause of the obesity epidemic
is a declining level of average daily energy expenditure . . . it will
be unfortunate if it is now assumed that we should ignore obesity. I
do not think that the [health] risk of obesity is a myth, although it
has been overestimated. Blair believes that a focus on good nutrition
and increased physical activity rather than on weight loss will better
serve us.
In spite of the fact that there are virtually no controlled clinical
trials examining the effects of obesity in people, we can make some
inferences from animal research. Investigations performed by
Ernsberger and his colleagues have shown that, over time, weight
cycling (temporary weight loss followed by a regain of that weight,
otherwise known as yo-yoing) in obese laboratory animals increases
blood pressure, enlarges the heart, damages the kidney, increases
abdominal fat deposits, and promotes further weight gain (Ernsberger
and Koletsky 1993; Ernsberger et al. 1996; Ernsberger and Koletsky
1999). This indicates that the yo-yo effect of crash dieting may be
the cause of many of the problems we attribute to simply being fat.
Even though there is a health risk from being too fat, you can
eliminate much of the potential risk by exercising. Moreover, it is
probably a bad idea to jump from diet to diet given the negative
consequences the yo-yo effect can have. According to another study
published in JAMA, the risk of cardiovascular disease has declined
across all BMI groups over the past forty years as the result of
better drugs (Gregg et al. 2005).
None of this means, however, that we should simply abandon our
attempts to maintain a healthy weight; obese people had twice the
incidence of hypertension compared to lean people and, most
significantly, there has been (according to the above study) a 55
percent increase in diabetes [2] that corresponds to the increase in
obesity. So while we are better at dealing with the problem once it
occurs, it is still better to avoid developing the problem in the
first place.
Condemning the CDC
Whatever side of the argument you are on, it is apparent that many in
the CDC acted irresponsibly. However, despite the fact that the
initial, exaggerated estimate came from people at the CDC, we should
keep in mind that so did the corrected number. While this can be
frustrating to the casual observer, it is also a testament to the
corrective power of the scientific method.
Science is about provisional truths that can be changed when evidence
indicates that they should be. The fact that scientific information is
available to the public is its greatest strength. Most of us, for
whatever reasonwhether its self-interest or self-delusiondont view our
own ideas as critically as we should. The fact that scientific ideas
are available for all to see allows those who disagree to disprove
them. This is what has happened at the CDC; the most current study has
addressed the flaws of the earlier studies. It is true that many of
those in power at the CDC uncritically embraced the earlier estimates
and overreacted, or worse simply accepted research that was flawed
because it bolstered their agendas. But that failure lies with the
people involved, not with the CDC as an institution or with the
science itself.
The evidence still shows that morbid obesity is associated with an
increased likelihood of developing disease and suffering from early
mortality, but it also shows that those who are a few pounds
overweight dont need to panic. Whats more, it is clear that everyone,
fat or thin, will benefit from regular exercise regardless of whether
they lose weight.
The lesson to be learned from this controversy is that rational
moderation is in order. Disproving one extreme idea does not prove the
opposite extreme. As Steven Blair told me, It is time to focus our
attention on the key behaviors of eating a healthful diet (plenty of
fruits and veggies, a lot of whole grains, and not too much fat and
alcohol) and being physically active every day.
Notes
1. This is not the first time this has been shown. The following
studies are also large-scale epidemiological studies that have found
the overweight category is where the longest lifespan occurs: Waaler
H.T. 1984. Height and weight and mortality: The Norwegian experience.
Acta Medica Scandinavica Supplementum 679, 156; and Hirdes, J.,
Forbes, W. 1992. The importance of social relationships,
socieoeconomic status and health practices with respect to mortality
in healthy Ontario males. Journal of Clinical Epidemiology 45:175182.
2. This is for both diagnosed and undiagnosed individuals.
References
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Blair, Steven, and James Morrow, Jr. 2005. Comments on U.S. dietary
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Campos, Paul. 2004. The Obesity Myth. New York, New York: Gotham
Books.
Church, T., et al. 2004. Exercise capacity and body composition as
predictorof mortality among men with diabetes. Diabetes Care 27(1):
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Ernsberger, Paul, and Richard Koletsky. 1993. Biomedical rationale for
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About the Author
Patrick Johnson is a biology instructor at Washtenaw Community College
in southeast Michigan and a clinical exercise physiologist who writes
frequently about health, nutrition, and fitness claims. He lives with
his wife and his eight-year-old son. E-mail: johnsonp @wccnet.edu.
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