Special article
The new engl and jour nal of medicine
n engl j med 368;5  nejm.org  january 31, 2013446
Myths, Presumptions, and Facts
about Obesity
Krista Casazza, Ph.D., R.D., Kevin R. Fontaine, Ph.D., Arne Astrup, M.D., Ph.D.,
Leann L. Birch, Ph.D., Andrew W. Brown, Ph.D., Michelle M. Bohan Brown, Ph.D.,
Nefertiti Durant, M.D., M.P.H., Gareth Dutton, Ph.D., E. Michael Foster, Ph.D.,
Steven B. Heymsfield, M.D., Kerry McIver, M.S., Tapan Mehta, M.S.,
Nir Menachemi, Ph.D., P.K. Newby, Sc.D., M.P.H., Russell Pate, Ph.D.,
Barbara J. Rolls, Ph.D., Bisakha Sen, Ph.D., Daniel L. Smith, Jr., Ph.D.,
Diana M. Thomas, Ph.D., and David B. Allison, Ph.D.
From the Departments of Nutrition Sciences
(K.C., M.M.B.B., D.L.S., D.B.A.),
Health Behavior (K.R.F.), Pediatrics
(N.D.), Medicine (G.D.), Health Care Organization
and Policy (E.M.F., N.M.,
B.S.), and Biostatistics (T.M., D.B.A.)
and the School of Public Health, Office of
Energetics, Nutrition Obesity Research
Center (A.W.B., D.B.A.), University of
Alabama at Birmingham, Birmingham;
the OPUS Center and the Department of
Nutrition, Exercise, and Sports, University
of Copenhagen, Copenhagen (A.A.);
the Departments of Development and
Family Studies (L.L.B.) and Nutritional
Sciences (B.J.R.), Pennsylvania State University,
University Park; Pennington Biomedical
Research Center, Baton Rouge,
LA (S.B.H.); Children’s Physical Activity
Research Group, Department of Exercise
Science, Arnold School of Public Health,
University of South Carolina, Columbia
(K.M., R.P.); the Departments of Pediatrics
and Epidemiology, Program in Graduate
Medical Nutrition Sciences, and Program
in Gastronomy, Culinary Arts, and
Wine Studies, Boston University, Boston
(P.K.N.); and the Center for Quantitative
Obesity Research, Montclair State University,
Montclair, NJ (D.M.T.). Address
reprint requests to Dr. Allison at the University
of Alabama at Birmingham, Department
of Biostatistics, Birmingham,
AL 35294, or at dallison@uab.edu.
This article was updated on June 6, 2013,
at NEJM.org.
N Engl J Med 2013;368:446-54.
DOI: 10.1056/NEJMsa1208051
Copyright © 2013 Massachusetts Medical Society.
ABSTR ACT
BACKGROUND
Many beliefs about obesity persist in the absence of supporting scientific evidence
(presumptions); some persist despite contradicting evidence (myths). The promulgation
of unsupported beliefs may yield poorly informed policy decisions, inaccurate
clinical and public health recommendations, and an unproductive allocation of research
resources and may divert attention away from useful, evidence-based infor-
mation.
METHODS
Using Internet searches of popular media and scientific literature, we identified,
reviewed, and classified obesity-related myths and presumptions. We also examined
facts that are well supported by evidence, with an emphasis on those that have
practical implications for public health, policy, or clinical recommendations.
RESULTS
We identified seven obesity-related myths concerning the effects of small sustained
increases in energy intake or expenditure, establishment of realistic goals for
weight loss, rapid weight loss, weight-loss readiness, physical-education classes,
breast-feeding, and energy expended during sexual activity. We also identified six
presumptions about the purported effects of regularly eating breakfast, early childhood
experiences, eating fruits and vegetables, weight cycling, snacking, and the
built (i.e., human-made) environment. Finally, we identified nine evidence-supported
facts that are relevant for the formulation of sound public health, policy, or
clinical recommendations.
CONCLUSIONS
False and scientifically unsupported beliefs about obesity are pervasive in both
scientific literature and the popular press. (Funded by the National Institutes of
Health.)
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Myths, Presumptions, and Facts about Obesity
n engl j med 368;5  nejm.org  january 31, 2013 447
P
assionateinterests,thehumantendency
to seek explanations for observed
phenomena, and everyday experience appear
to contribute to strong convictions about
obesity, despite the absence of supporting data.
When the public, mass media, government agencies,
and even academic scientists espouse unsupported
beliefs, the result may be ineffective
policy, unhelpful or unsafe clinical and public
health recommendations, and an unproductive
allocation of resources. In this article, we review
some common beliefs about obesity that are not
supported by scientific evidence and also provide
some useful evidence-based concepts. We define
myths as beliefs held to be true despite substantial
refuting evidence, presumptions as beliefs
held to be true for which convincing evidence
does not yet confirm or disprove their truth, and
facts as propositions backed by sufficient evidence
to consider them empirically proved for
practical purposes.
When standards for evidence are considered, it
is critical to distinguish between drawing conclusions
from scientific evidence and making decisions
about prudent actions. Stakeholders must
sometimes take action in the absence of strong
scientific evidence. Yet this principle of action
should not be mistaken as justification for drawing
conclusions. Regardless of the urgency of
public health issues, scientific principles remain
unchanged. We find the language of the Federal
Trade Commission to be apt: its standard for making
claims is “competent and reliable scientific
evidence,” defined as “tests, analyses, research,
studies, or other evidence .  .  . conducted and
evaluated in an objective manner .  .  . using procedures
generally accepted .  .  . to yield accurate
and reliable results.”1
The scientific community recognizes that
randomized experiments offer the strongest evidence
for drawing causal inferences. Nevertheless,
at least since the 1960s, when Sir Austin
Bradford Hill spearheaded the scientific activities
that led to the acceptance of the claim that
smoking causes lung cancer and to his classic
writing on association and causation,2 the scientific
community has acknowledged that under
some circumstances (i.e., when it is unethical or
unfeasible to conduct a randomized study and
when observed associations are not plausibly due
to confounding), inferring causality in the absence
of data from randomized, controlled trials
is necessary and appropriate. However, the fact
that the appropriateness of inferring causality
holds only under certain circumstances is sometimes
discounted by those who are eager to
garner support for a proposal in the absence of
strong data from randomized studies.
Notably, the circumstances that justify drawing
a conclusion of causation from nonexperimental
data are rarely met in clinical and public
proposals regarding obesity. It is possible to
conduct randomized studies of even the most
sensitive and invasive obesity procedures, as exemplified
by recent articles in the Journal. Moreover,
observational associations germane to the
causes, treatment, and prevention of obesity are
subject to substantial confounding, fraught with
measurement problems, and typically small and
inconsistent.3 Such observational associations
are often found to differ from those later obtained
by more rigorously designed studies.4
Hence, in the present discussion, we generally
conclude that a proposition has been shown to
be true only when it has been supported by confirmatory
randomized studies. References to published
studies are used sparingly herein, with a
more comprehensive listing provided in the Supplementary
Appendix, available with the full text
of this article at NEJM.org.
MYTHS
We review seven myths about obesity, along with
the refuting evidence. Table 1 provides anecdotal
support that the beliefs are widely held or stated,
in addition to reasons that support conjecture.
SMALL SUSTAINED CHANGES IN ENERGY INTAKE
OR EXPENDITURE
Myth number 1: Small sustained changes in energy
intake or expenditure will produce large,
long-term weight changes.
Predictions suggesting that large changes in
weight will accumulate indefinitely in response to
small sustained lifestyle modifications rely on the
half-century-old 3500-kcal rule, which equates a
weight alteration of 1 lb (0.45 kg) to a 3500-kcal
cumulative deficit or increment.5,6 However, applying
the 3500-kcal rule to cases in which small
modifications are made for long periods violates
the assumptions of the original model, which
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were derived from short-term experiments predominantly
performed in men on very-low-energy
diets (<800 kcal per day).5,7 Recent studies have
shown that individual variability affects changes
in body composition in response to changes in
energy intake and expenditure,7 with analyses predicting
substantially smaller changes in weight
(often by an order of magnitude across extended
periods) than the 3500-kcal rule does.5,7 For example,
whereas the 3500-kcal rule predicts that
a person who increases daily energy expenditure
by 100 kcal by walking 1 mile (1.6 km) per day
will lose more than 50 lb (22.7 kg) over a period
of 5 years, the true weight loss is only about
10 lb (4.5 kg),6 assuming no compensatory increase
in caloric intake, because changes in mass
concomitantly alter the energy requirements of
the body.
SETTING REALISTIC WEIGHT-LOSS GOALS
Myth number 2: Setting realistic goals for weight
loss is important, because otherwise patients will
become frustrated and lose less weight.
Although this is a reasonable hypothesis, empirical
data indicate no consistent negative association
between ambitious goals and program
completion or weight loss.8 Indeed, several studies
have shown that more ambitious goals are
sometimes associated with better weight-loss
outcomes (see the Supplementary Appendix).8
Furthermore, two studies showed that interventions
designed to improve weight-loss outcomes
by altering unrealistic goals resulted in more realistic
weight-loss expectations but did not improve
outcomes.
RATE OF WEIGHT LOSS
Myth number 3: Large, rapid weight loss is associated
with poorer long-term weight-loss outcomes,
as compared with slow, gradual weight loss.
Within weight-loss trials, more rapid and
greater initial weight loss has been associated
with lower body weight at the end of long-term
follow-up.9,10 A meta-analysis of randomized,
controlled trials that compared rapid weight loss
(achieved with very-low-energy diets) with slower
Table 1. Seven Myths about Obesity.*
Myth Basis of Conjecture
Small sustained changes in energy intake or expenditure will produce
large, long-term weight changes
National health guidelines and reputable websites advertise that
large changes in weight accumulate indefinitely after small sustained
daily lifestyle modifications (e.g., walking for 20 minutes
or eating two additional potato chips)
Setting realistic goals in obesity treatment is important because otherwise
patients will become frustrated and lose less weight
According to goal-setting theory, unattainable goals impair performance
and discourage goal-attaining behavior; in obesity treatment,
incongruence between desired and actual weight loss is
thought to undermine the patient’s perceived ability to attain
goals, which may lead to the discontinuation of behaviors necessary
for weight loss
Large, rapid weight loss is associated with poorer long-term weight
outcomes than is slow, gradual weight loss
This notion probably emerged in reaction to the adverse effects of
nutritionally insufficient very-low-calorie diets (<800 kcal per day)
in the 1960s; the belief has persisted, has been repeated in textbooks
and recommendations from health authorities, and has
been offered as a rule by dietitians
Assessing the stage of change or diet readiness is important in helping
patients who seek weight-loss treatment
Many believe that patients who feel ready to lose weight are more
likely to make the required lifestyle changes
Physical-education classes in their current format play an important
role in preventing or reducing childhood obesity
The health benefits of physical activity of sufficient duration, frequency,
and intensity are well established and include reductions
in adiposity
Breast-feeding is protective against obesity The belief that breast-fed children are less likely to become obese
has persisted for more than a century and is passionately de-
fended
A bout of sexual activity burns 100 to 300 kcal for each person
involved
Many sources state that substantial energy is expended in typical
sexual activity between two adults
*	We define myths as beliefs held true despite substantial evidence refuting them. A list of articles in which these myths are espoused is provided
in the Supplementary Appendix.
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Myths, Presumptions, and Facts about Obesity
n engl j med 368;5  nejm.org  january 31, 2013 449
weight loss (achieved with low-energy diets —
i.e., 800 to 1200 kcal per day) at the end of shortterm
follow-up (<1 yr) and long-term follow-up
(≥1 year) showed that, despite the association of
very-low-energy diets with significantly greater
weight loss at the end of short-term follow-up
(16.1% of body weight lost, vs. 9.7% with lowenergy
diets), there was no significant difference
between the very-low-energy diets and low-energy
diets with respect to weight loss at the end of
long-term follow-up.10 Although it is not clear
why some obese persons have a greater initial
weight loss than others do, a recommendation
to lose weight more slowly might interfere with
the ultimate success of weight-loss efforts.
DIET READINESS
Myth number 4: It is important to assess the
stage of change or diet readiness in order to help
patients who request weight-loss treatment.
Readiness does not predict the magnitude of
weight loss or treatment adherence among persons
who sign up for behavioral programs or who
undergo obesity surgery.11 Five trials (involving
3910 participants; median study period, 9 months)
specifically evaluated stages of change (not exclusively
readiness) and showed an average weight
loss of less than 1 kg and no conclusive evidence
of sustained weight loss (see the Supplementary
Appendix). The explanation may be simple —
people voluntarily choosing to enter weight-loss
programs are, by definition, at least minimally
ready to engage in the behaviors required to lose
weight.
IMPORTANCE OF PHYSICAL EDUCATION
Myth number 5: Physical-education classes, in
their current form, play an important role in reducing
or preventing childhood obesity.
Physical education, as typically provided, has
not been shown to reduce or prevent obesity.
Findings in three studies that focused on expanded
time in physical education12 indicated
that even though there was an increase in the
number of days children attended physical-education
classes, the effects on body-mass index
(BMI) were inconsistent across sexes and age
groups. Two meta-analyses showed that even
specialized school-based programs that promoted
physical activity were ineffective in reducing
BMI or the incidence or prevalence of obesity.13
There is almost certainly a level of physical
activity (a specific combination of frequency, intensity,
and duration) that would be effective in
reducing or preventing obesity. Whether that
level is plausibly achievable in conventional school
settings is unknown, although the dose–response
relationship between physical activity and
weight warrants investigation in clinical trials.
BREAST-FEEDING AND OBESITY
Myth number 6: Breast-feeding is protective
against obesity.
A World Health Organization (WHO) report
states that persons who were breast-fed as infants
are less likely to be obese later in life and
that the association is “not likely to be due to
publication bias or confounding.”14 Yet the WHO,
using Egger’s test and funnel plots, found clear
evidence of publication bias in the published literature
it synthesized.15 Moreover, studies with
better control for confounding (e.g., studies including
within-family sibling analyses) and a
randomized, controlled trial involving more than
13,000 children who were followed for more
than 6 years16 provided no compelling evidence
of an effect of breast-feeding on obesity. On the
basis of these findings, one long-term proponent
of breast-feeding for the prevention of obesity
wrote that breast-feeding status “no longer
appears to be a major determinant” of obesity
risk17; however, he speculated that breast-feeding
may yet be shown to be modestly protective,
current evidence to the contrary. Although existing
data indicate that breast-feeding does not
have important antiobesity effects in children, it
has other important potential benefits for the
infant and mother and should therefore be en-
couraged.
SEXUAL ACTIVITY AND ENERGY EXPENDITURE
Myth number 7: A bout of sexual activity burns
100 to 300 kcal for each participant.
The energy expenditure of sexual intercourse
can be estimated by taking the product of activity
intensity in metabolic equivalents (METs),18 the
body weight in kilograms, and time spent. For
example, a man weighing 154 lb (70 kg) would,
at 3 METs, expend approximately 3.5 kcal per
minute (210 kcal per hour) during a stimulation
and orgasm session. This level of expenditure is
similar to that achieved by walking at a moderate
pace (approximately 2.5 miles [4 km] per hour).
Given that the average bout of sexual activity
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lasts about 6 minutes,19 a man in his early-tomid-30s
might expend approximately 21 kcal
during sexual intercourse. Of course, he would
have spent roughly one third that amount of
energy just watching television, so the incremental
benefit of one bout of sexual activity with
respect to energy expended is plausibly on the
order of 14 kcal.
PRESUMPTIONS
Just as it is important to recognize that some
widely held beliefs are myths so that we may
move beyond them, it is important to recognize
presumptions, which are widely accepted beliefs
that have neither been proved nor disproved,
so that we may move forward to collect
solid data to support or refute them. Instead of
attempting to comprehensively describe all the
data peripherally related to each of the six presumptions
shown in Table 2, we describe the
best evidence.
VALUE OF BREAKFAST
Presumption number 1: Regularly eating (versus
skipping) breakfast is protective against
obesity.
Two randomized, controlled trials that studied
the outcome of eating versus skipping breakfast
showed no effect on weight in the total sample.20
However, the findings in one study suggested
that the effect on weight loss of being
assigned to eat or skip breakfast was dependent
on baseline breakfast habits.20
EARLY CHILDHOOD HABITS AND WEIGHT
Presumption number 2: Early childhood is the
period in which we learn exercise and eating
habits that influence our weight throughout life.
Although a person’s BMI typically tracks over
time (i.e., tends to be in a similar percentile
range as the person ages), longitudinal genetic
studies suggest that such tracking may be primarily
a function of genotype rather than a
persistent effect of early learning.21 No randomized,
controlled clinical trials provide evidence
to the contrary.
VALUE OF FRUITS AND VEGETABLES
Presumption number 3: Eating more fruits and
vegetables will result in weight loss or less weight
gain, regardless of whether any other changes to
one’s behavior or environment are made.
It is true that the consumption of fruits and
vegetables has health benefits. However, when
no other behavioral changes accompany increased
consumption of fruits and vegetables,
weight gain may occur or there may be no
change in weight.22
WEIGHT CYCLING AND MORTALITY
Presumption number 4: Weight cycling (i.e., yo-yo
dieting) is associated with increased mortality.
Although observational epidemiologic studies
Table 2. Presumptions about Obesity.*
Presumption Basis for Conjecture
Regularly eating (vs. skipping) breakfast is protective against obesity Skipping breakfast purportedly leads to overeating later in the day
Early childhood is the period during which we learn exercise and eating
habits that influence our weight throughout life
Weight-for-height indexes, eating behaviors, and preferences that are
present in early childhood are correlated with those later in life
Eating more fruits and vegetables will result in weight loss or less
weight gain, regardless of whether one intentionally makes any
other behavioral or environmental changes
By eating more fruits and vegetables, a person presumably spontaneously
eats less of other foods, and the resulting reduction in
calories is greater than the increase in calories from the fruit
and vegetables
Weight cycling (i.e., yo-yo dieting) is associated with increased
mortality
In observational studies, mortality rates have been lower among
persons with stable weight than among those with unstable
weight
Snacking contributes to weight gain and obesity Snack foods are presumed to be incompletely compensated for at
subsequent meals, leading to weight gain
The built environment, in terms of sidewalk and park availability,
influences obesity
Neighborhood-environment features may promote or inhibit physical
activity, thereby affecting obesity
*	We define presumptions as unproved yet commonly espoused propositions. A list of articles in which these presumptions are implied is
provided in the Supplementary Appendix.
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Myths, Presumptions, and Facts about Obesity
n engl j med 368;5  nejm.org  january 31, 2013 451
show that weight instability or cycling is associated
with increased mortality, such findings are
probably due to confounding by health status.
Studies of animal models do not support this
epidemiologic association.23
SNACKING AND WEIGHT GAIN
Presumption number 5: Snacking contributes to
weight gain and obesity.
Randomized, controlled trials do not support
this presumption.24 Even observational studies
have not shown a consistent association between
snacking and obesity or increased BMI.
BUILT ENVIRONMENT AND OBESITY
Presumption number 6: The built environment,
in terms of sidewalk and park availability, influences
the incidence or prevalence of obesity.
According to a systematic review, virtually all
studies showing associations between the risk
of obesity and components of the built environment
(e.g., parks, roads, and architecture) have
been observational.25 Furthermore, these observational
studies have not shown consistent
associations, so no conclusions can be drawn.
FACTS
Our proposal that myths and presumptions be
seen for what they are should not be mistaken as
a call for nihilism. There are things we do know
with reasonable confidence. Table 3 lists nine
such facts and their practical implications for
public health, policy, or clinical recommendations.
The first two facts help establish a framework
in which intervention and preventive techniques
may work. The next four facts are more
prescriptive, offering tools that can be conveyed
Table 3. Facts about Obesity.*
Fact Implication
Although genetic factors play a large role, heritability is not destiny;
calculations show that moderate environmental changes can
promote as much weight loss as the most efficacious pharmaceutical
agents available26
If we can identify key environmental factors and successfully influence
them, we can achieve clinically significant reductions in obesity
Diets (i.e., reduced energy intake) very effectively reduce weight, but
trying to go on a diet or recommending that someone go on a
diet generally does not work well in the long-term27
This seemingly obvious distinction is often missed, leading to erroneous
conceptions regarding possible treatments for obesity;
recognizing this distinction helps our understanding that energy
reduction is the ultimate dietary intervention required and approaches
such as eating more vegetables or eating breakfast
daily are likely to help only if they are accompanied by an overall
reduction in energy intake
Regardless of body weight or weight loss, an increased level of exercise
increases health28
Exercise offers a way to mitigate the health-damaging effects of obesity,
even without weight loss
Physical activity or exercise in a sufficient dose aids in long-term
weight maintenance28,29
Physical-activity programs are important, especially for children, but
for physical activity to affect weight, there must be a substantial
quantity of movement, not mere participation
Continuation of conditions that promote weight loss promotes
maintenance of lower weight30
Obesity is best conceptualized as a chronic condition, requiring ongoing
management to maintain long-term weight loss
For overweight children, programs that involve the parents and the
home setting promote greater weight loss or maintenance31
Programs provided only in schools or other out-of-home structured
settings may be convenient or politically expedient, but programs
including interventions that involve the parents and are provided
at home are likely to yield better outcomes
Provision of meals and use of meal-replacement products promote
greater weight loss32
More structure regarding meals is associated with greater weight
loss, as compared with seemingly holistic programs that are
based on concepts of balance, variety, and moderation
Some pharmaceutical agents can help patients achieve clinically
meaningful weight loss and maintain the reduction as long as
the agents continue to be used33
While we learn how to alter the environment and individual behaviors
to prevent obesity, we can offer moderately effective treatment
to obese persons
In appropriate patients, bariatric surgery results in long-term weight
loss and reductions in the rate of incident diabetes and mortality34
For severely obese persons, bariatric surgery can offer a life-changing,
and in some cases lifesaving, treatment
*	We classify the listed propositions as facts because there is sufficient evidence to consider them empirically proved.
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n engl j med 368;5  nejm.org  january 31, 2013452
to the public as well established. The last three
facts are suited to clinical settings.
IMPLICATIONS
Myths and presumptions about obesity are common.
Several presumptions appear to be testable,
and some of them (e.g., effects of eating breakfast
daily, eating more fruits and vegetables, and
snacking) can be tested with standard study designs.
Despite enormous efforts promoting these
ideas, research often seems mired in the accrual
of observational data. Many of the trials that have
been completed or are in progress do not isolate
the effect of the presumed influence and the
findings are therefore not definitive.
Many of the myths and presumptions about
obesity reflect a failure to consider the diverse aspects
of energy balance,35 especially physiological
compensation for changes in intake or expenditure.36
Some myths and presumptions involve an
implicit assumption that there is no physiological
compensation whatsoever (i.e., the 3500-kcal rule)
or only minimal compensation (e.g., a reduction in
snacking as a means of reducing weight). In other
cases, there is an implicit assumption of overcompensation
(e.g., eating breakfast daily or increasing
the intake of fruits and vegetables as a means of
reducing weight). Proponents of other unsupported
ideas fail to consider that people burn some
amount of energy even without engaging in the
activity in question (e.g., increased sexual activity).
In addition, interested parties do not regularly
request the results from randomized, longterm
studies that measure weight or adiposity as
an outcome. Therefore, the presented data are rife
with circumstantial evidence, and people are not
informed that the existing evidence is not compelling
(e.g., breakfast consumption). Furthermore,
some suggested treatment or prevention
strategies may work well (e.g., increasing the
consumption of fruits and vegetables) but only as
part of a multifaceted program for weight reduction.
Yet such a strategy is often presented as
though it will have effects in isolation and even
among persons not participating in weight-loss
programs. We must recognize that evidence that
a technique is beneficial for the treatment of obesity
is not necessarily evidence that it will be helpful
in population-based approaches to the prevention
of obesity, and vice versa.
KNOWING AND NOT KNOWING
Why do we think or claim we know things that
we actually do not know? Numerous cognitive
biases lead to an unintentional retention of erroneous
beliefs.37,38 When media coverage about
obesity is extensive, many people appear to believe
some myths (e.g., rapid weight loss facilitates
weight regain) simply because of repeated
exposure to the claims.39 Cognitive dissonance
may prevent us from abandoning ideas that are
important to us, despite contradictory evidence
(e.g., the idea that breast-feeding prevents obesity
in children). Similarly, confirmation bias may
prevent us from seeking data that might refute
propositions we have already intuitively accepted
as true because they seem obvious (e.g., the value
of realistic weight-loss goals). Moreover, we may
be swayed by persuasive yet fallacious arguments
(Whately provides a classic catalogue40) unless
we are prepared to identify them as spurious.
Fortunately, the scientific method and logical
thinking offer ways to detect erroneous statements,
acknowledge our uncertainty, and increase
our knowledge. When presented with an
alleged truth, we can pause to ask simple questions,
such as, “How could someone actually
know that?” Such a simple question allows one
to easily recognize some beliefs as spurious (e.g.,
300 kcal is burned during sexual intercourse).
Moreover, we often settle for data generated with
the use of inadequate methods in situations in
which inferentially stronger study designs, including
quasi-experiments and true randomized
experiments, are possible, as recently illustrated
(see the Supplementary Appendix). In addition,
eliminating the distortions of scientific information
that sometimes occur with public health
advocacy would reduce the propagation of mis-
information.
The myths and presumptions about obesity
that we have discussed are just a sampling of the
numerous unsupported beliefs held by many
people, including academics, regulators, and
journalists, as well as the general public. Yet
there are facts about obesity of which we may be
reasonably certain — facts that are useful today.
While we work to generate additional useful
knowledge, we may in some cases justifiably
move forward with hypothesized, but not proved,
strategies. However, as a scientific community,
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Myths, Presumptions, and Facts about Obesity
n engl j med 368;5  nejm.org  january 31, 2013 453
we must always be open and honest with the
public about the state of our knowledge and
should rigorously evaluate unproved strategies.
The views expressed in this article are those of the authors
and do not necessarily represent the official views of the National
Institutes of Health.
Supported in part by a grant (P30DK056336) from the National
Institutes of Health.
Dr. Astrup reports receiving payment for board membership
from the Global Dairy Platform, Kraft Foods, Knowledge Institute
for Beer, McDonald’s Global Advisory Council, Arena Pharmaceuticals,
Basic Research, Novo Nordisk, Pathway Genomics,
Jenny Craig, and Vivus; receiving lecture fees from the Global
Dairy Platform, Novo Nordisk, Danish Brewers Association,
GlaxoSmithKline, Danish Dairy Association, International Dairy
Foundation, European Dairy Foundation, and AstraZeneca;
owning stock in Mobile Fitness; holding patents regarding the
use of flaxseed mucilage or its active component for suppression
of hunger and reduction of prospective consumption (patents
EP1744772, WO2009033483-A1, EP2190303-A1, US2010261661A1,
and priority applications DK001319, DK001320, S971798P,
and US971827P); holding patents regarding the use of an alginate
for the preparation of an aqueous dietary product for the
treatment or prevention of overweight and obesity (patent
WO2011063809-A1 and priority application DK070227); and
holding a patent regarding a method for regulating energy balance
for body-weight management (patent WO2007062663-A1
and priority application DK001710). Drs. Brown and Bohan
Brown report receiving grant support from the Coca-Cola Foundation
through their institution.  Dr. Mehta reports receiving
grant support from Kraft Foods. Dr. Newby reports receiving
grant support from General Mills Bell Institute of Health and
Nutrition. Dr. Pate reports receiving consulting fees from Kraft
Foods. Dr. Rolls reports having a licensing agreement for the
Volumetrics trademark with Jenny Craig. Dr. Thomas reports
receiving consulting fees from Jenny Craig. Dr. Allison reports
serving as an unpaid board member for the International Life
Sciences Institute of North America; receiving payment for
board membership from Kraft Foods; receiving consulting fees
from Vivus, Ulmer and Berne, Paul, Weiss, Rifkind, Wharton,
Garrison, Chandler Chicco, Arena Pharmaceuticals, Pfizer, National
Cattlemen’s Association, Mead Johnson Nutrition, Frontiers
Foundation, Orexigen Therapeutics, and Jason Pharmaceuticals;
receiving lecture fees from Porter Novelli and the Almond
Board of California; receiving payment for manuscript preparation
from Vivus; receiving travel reimbursement from International
Life Sciences Institute of North America; receiving other
support from the United Soybean Board and the Northarvest
Bean Growers Association; receiving grant support through his
institution from Wrigley, Kraft Foods, Coca-Cola, Vivus, Jason
Pharmaceuticals, Aetna Foundation, and McNeil Nutritionals;
and receiving other funding through his institution from the
Coca-Cola Foundation, Coca-Cola, PepsiCo, Red Bull, World
Sugar Research Organisation, Archer Daniels Midland, Mars,
Eli Lilly and Company, and Merck. No other potential conflict of
interest relevant to this article was reported.
Disclosure forms provided by the authors are available with
the full text of this article at NEJM.org.
We thank Drs. Kyle Grimes and S. Louis Bridges for their suggestions
on an earlier version of the manuscript.
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