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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 information. 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. 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. False and scientifically unsupported beliefs about obesity are pervasive in both scientific literature and the popular press. (Funded by the National Institutes of Health.).
Special article
new engl a nd jour nal
o f
n engl j med 368;5 january 31, 2013
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 Sci-
ences (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 Or-
ganization 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, Univer-
sity of Copenhagen, Copenhagen (A.A.);
the Departments of Development and
Family Studies (L.L.B.) and Nutritional
Sciences (B.J.R.), Pennsylvania State Uni-
versity, University Park; Pennington Bio-
medical 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 Pediat-
rics and Epidemiology, Program in Grad-
uate Medical Nutrition Sciences, and Pro-
gram in Gastronomy, Culinary Arts, and
Wine Studies, Boston University, Boston
(P.K.N.); and the Center for Quantitative
Obesity Research, Montclair State Uni-
versity, Montclair, NJ (D.M.T.). Address
reprint requests to Dr. Allison at the Uni-
versity of Alabama at Birmingham, De-
partment of Biostatistics, Birmingham,
AL 35294, or at
N Engl J Med 2013;368:446-54.
DOI: 10.1056/NEJMsa1208051
Copyright © 2013 Massachusetts Medical Society.
Many beliefs about obesity persist in the absence of supporting scientific evidence
(presumptions); some persist despite contradicting evidence (myths). The promulga-
tion of unsupported beliefs may yield poorly informed policy decisions, inaccurate
clinical and public health recommendations, and an unproductive allocation of re-
search resources and may divert attention away from useful, evidence-based infor-
Using Internet searches of popular media and scientific literature, we identified,
reviewed, and classified obesity-related myths and presumptions. We also exam-
ined facts that are well supported by evidence, with an emphasis on those that have
practical implications for public health, policy, or clinical recommendations.
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 child-
hood experiences, eating fruits and vegetables, weight cycling, snacking, and the
built (i.e., human-made) environment. Finally, we identified nine evidence-support-
ed facts that are relevant for the formulation of sound public health, policy, or
clinical recommendations.
False and scientifically unsupported beliefs about obesity are pervasive in both
scientific literature and the popular press. (Funded by the National Institutes of
Myths, Presumptions, and Facts about Obesity
n engl j med 368;5 january 31, 2013
assionate interests, the human ten-
dency to seek explanations for observed
phenomena, and everyday experience ap-
pear to contribute to strong convictions about
obesity, despite the absence of supporting data.
When the public, mass media, government agen-
cies, and even academic scientists espouse un-
supported 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 substan-
tial 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 evi-
dence to consider them empirically proved for
practical purposes.
When standards for evidence are considered, it
is critical to distinguish between drawing conclu-
sions from scientific evidence and making deci-
sions 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 draw-
ing 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 mak-
ing claims is competent and reliable scientific
evidence,defined as “tests, analyses, research,
studies, or other evidence . . . conducted and
evaluated in an objective manner . . . using pro-
cedures generally accepted . . . to yield accurate
and reliable results.
The scientific community recognizes that
randomized experiments offer the strongest evi-
dence for drawing causal inferences. Neverthe-
less, at least since the 1960s, when Sir Austin
Bradford Hill spearheaded the scientific activi-
ties that led to the acceptance of the claim that
smoking causes lung cancer and to his classic
writing on association and causation,
the scien-
tific 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 ab-
sence 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 some-
times 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 draw-
ing a conclusion of causation from nonexperi-
mental 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 ex-
emplified by recent articles in the Journal. More-
over, observational associations germane to the
causes, treatment, and prevention of obesity are
subject to substantial confounding, fraught with
measurement problems, and typically small and
Such observational associations
are often found to differ from those later ob-
tained by more rigorously designed studies.
Hence, in the present discussion, we generally
conclude that a proposition has been shown to
be true only when it has been supported by con-
firmatory randomized studies. References to pub-
lished studies are used sparingly herein, with a
more comprehensive listing provided in the Sup-
plementary Appendix, available with the full text
of this article at
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.
Myth number 1: Small sustained changes in en-
ergy 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.
However, ap-
plying 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 pre-
dominantly performed in men on very-low-energy
diets (<800 kcal per day).
Recent studies have
shown that individual variability affects changes
in body composition in response to changes in
energy intake and expenditure,
with analyses pre-
dicting substantially smaller changes in weight
(often by an order of magnitude across extended
periods) than the 3500-kcal rule does.
For ex-
ample, 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),
assuming no compensatory in-
crease in caloric intake, because changes in mass
concomitantly alter the energy requirements of
the body.
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, em-
pirical data indicate no consistent negative as-
sociation between ambitious goals and program
completion or weight loss.
Indeed, several stud-
ies have shown that more ambitious goals are
sometimes associated with better weight-loss
outcomes (see the Supplementary Appendix).
Furthermore, two studies showed that interven-
tions designed to improve weight-loss outcomes
by altering unrealistic goals resulted in more re-
alistic weight-loss expectations but did not im-
prove outcomes.
Myth number 3: Large, rapid weight loss is associ-
ated 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
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 pro-
duce large, long-term weight changes
National health guidelines and reputable websites advertise that
large changes in weight accumulate indefinitely after small sus-
tained daily lifestyle modifications (e.g., walking for 20 minutes
or eating two additional potato chips)
Setting realistic goals in obesity treatment is important because other-
wise patients will become frustrated and lose less weight
According to goal-setting theory, unattainable goals impair perfor-
mance and discourage goal-attaining behavior; in obesity treat-
ment, 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 neces-
sary 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 text-
books 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 help-
ing 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, fre-
quency, and intensity are well established and include reduc-
tions 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-
A bout of sexual activity burns 100 to 300 kcal for each person
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 pro-
vided in the Supplementary Appendix.
Myths, Presumptions, and Facts about Obesity
n engl j med 368;5 january 31, 2013
weight loss (achieved with low-energy diets
i.e., 800 to 1200 kcal per day) at the end of short-
term 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 low-
energy 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.
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.
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 per-
sons who sign up for behavioral programs or who
undergo obesity surgery.
Five trials (involving
3910 participants; median study period, 9 months)
specifically evaluated stages of change (not exclu-
sively 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
Myth number 5: Physical-education classes, in
their current form, play an important role in re-
ducing 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 ex-
panded time in physical education
that even though there was an increase in the
number of days children attended physical-edu-
cation 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 pro-
moted physical activity were ineffective in reduc-
ing BMI or the incidence or prevalence of obe-
There is almost certainly a level of physical
activity (a specific combination of frequency, in-
tensity, 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–re-
sponse relationship between physical activity and
weight warrants investigation in clinical trials.
Myth number 6: Breast-feeding is protective
against obesity.
A World Health Organization (WHO) report
states that persons who were breast-fed as in-
fants are less likely to be obese later in life and
that the association is “not likely to be due to
publication bias or confounding.
Yet the WHO,
using Egger’s test and funnel plots, found clear
evidence of publication bias in the published lit-
erature it synthesized.
Moreover, studies with
better control for confounding (e.g., studies in-
cluding within-family sibling analyses) and a
randomized, controlled trial involving more than
13,000 children who were followed for more
than 6 years
provided no compelling evidence
of an effect of breast-feeding on obesity. On the
basis of these findings, one long-term propo-
nent of breast-feeding for the prevention of obe-
sity wrote that breast-feeding status “no longer
appears to be a major determinant” of obesity
; however, he speculated that breast-feed-
ing may yet be shown to be modestly protective,
current evidence to the contrary. Although exist-
ing 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-
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),
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,
a man in his early-to-
mid-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 incremen-
tal benefit of one bout of sexual activity with
respect to energy expended is plausibly on the
order of 14 kcal.
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 be-
liefs that have neither been proved nor dis-
proved, 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 pre-
sumptions shown in
Table 2
, we describe the
best evidence.
Presumption number 1: Regularly eating (ver-
sus skipping) breakfast is protective against
Two randomized, controlled trials that studied
the outcome of eating versus skipping breakfast
showed no effect on weight in the total sam-
However, the findings in one study sug-
gested that the effect on weight loss of being
assigned to eat or skip breakfast was dependent
on baseline breakfast habits.
Presumption number 2: Early childhood is the
period in which we learn exercise and eating
habits that influence our weight throughout life.
Although a persons 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 pri-
marily a function of genotype rather than a
persistent effect of early learning.
No random-
ized, controlled clinical trials provide evidence
to the contrary.
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 in-
creased consumption of fruits and vegetables,
weight gain may occur or there may be no
change in weight.
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 eat-
ing 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 sponta-
neously 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
In observational studies, mortality rates have been lower among
persons with stable weight than among those with unstable
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.
Myths, Presumptions, and Facts about Obesity
n engl j med 368;5 january 31, 2013
show that weight instability or cycling is associ-
ated with increased mortality, such findings are
probably due to confounding by health status.
Studies of animal models do not support this
epidemiologic association.
Presumption number 5: Snacking contributes to
weight gain and obesity.
Randomized, controlled trials do not support
this presumption.
Even observational studies
have not shown a consistent association between
snacking and obesity or increased BMI.
Presumption number 6: The built environment,
in terms of sidewalk and park availability, influ-
ences 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 environ-
ment (e.g., parks, roads, and architecture) have
been observational.
Furthermore, these ob-
servational studies have not shown consistent
associations, so no conclusions can be drawn.
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 recommenda-
tions. The first two facts help establish a frame-
work in which intervention and preventive tech-
niques 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 pharma-
ceutical agents available
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-term
This seemingly obvious distinction is often missed, leading to erro-
neous conceptions regarding possible treatments for obesity;
recognizing this distinction helps our understanding that energy
reduction is the ultimate dietary intervention required and ap-
proaches 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 exer-
cise increases health
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 maintenance
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 weight
Obesity is best conceptualized as a chronic condition, requiring on-
going management to maintain long-term weight loss
For overweight children, programs that involve the parents and the
home setting promote greater weight loss or maintenance
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 loss
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 used
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 mortality
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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to the public as well established. The last three
facts are suited to clinical settings.
Myths and presumptions about obesity are com-
mon. Several presumptions appear to be testable,
and some of them (e.g., effects of eating break-
fast daily, eating more fruits and vegetables, and
snacking) can be tested with standard study de-
signs. 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 as-
pects of energy balance,
especially physiological
compensation for changes in intake or expendi-
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 overcom-
pensation (e.g., eating breakfast daily or increasing
the intake of fruits and vegetables as a means of
reducing weight). Proponents of other unsupport-
ed ideas fail to consider that people burn some
amount of energy even without engaging in the
activity in question (e.g., increased sexual activ-
ity). In addition, interested parties do not regu-
larly request the results from randomized, long-
term 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 com-
pelling (e.g., breakfast consumption). Further-
more, 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 reduc-
tion. 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 obe-
sity is not necessarily evidence that it will be help-
ful in population-based approaches to the preven-
tion of obesity, and vice versa.
Why do we think or claim we know things that
we actually do not know? Numerous cognitive
biases lead to an unintentional retention of er-
roneous beliefs.
When media coverage about
obesity is extensive, many people appear to be-
lieve some myths (e.g., rapid weight loss facili-
tates weight regain) simply because of repeated
exposure to the claims.
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 catalogue
) unless
we are prepared to identify them as spurious.
Fortunately, the scientific method and logical
thinking offer ways to detect erroneous state-
ments, acknowledge our uncertainty, and in-
crease our knowledge. When presented with an
alleged truth, we can pause to ask simple ques-
tions, 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, in-
cluding quasi-experiments and true randomized
experiments, are possible, as recently illustrated
(see the Supplementary Appendix). In addition,
eliminating the distortions of scientific infor-
mation that sometimes occur with public health
advocacy would reduce the propagation of mis-
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,
Myths, Presumptions, and Facts about Obesity
n engl j med 368;5 january 31, 2013
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 Na-
tional Institutes of Health.
Supported in part by a grant (P30DK056336) from the Na-
tional Institutes of Health.
Dr. Astrup reports receiving payment for board membership
from the Global Dairy Platform, Kraft Foods, Knowledge Insti-
tute for Beer, McDonald’s Global Advisory Council, Arena Phar-
maceuticals, 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, US2010261661-
A1, and priority applications DK001319, DK001320, S971798P,
and US971827P); holding patents regarding the use of an algi-
nate 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 bal-
ance for body-weight management (patent WO2007062663-A1
and priority application DK001710). Drs. Brown and Bohan
Brown report receiving grant support from the Coca-Cola Foun-
dation 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, Na-
tional Cattlemen’s Association, Mead Johnson Nutrition, Fron-
tiers Foundation, Orexigen Therapeutics, and Jason Pharmaceu-
ticals; receiving lecture fees from Porter Novelli and the Almond
Board of California; receiving payment for manuscript prepara-
tion from Vivus; receiving travel reimbursement from Interna-
tional 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
We thank Drs. Kyle Grimes and S. Louis Bridges for their sug-
gestions on an earlier version of the manuscript.
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... 16 There is also little evidence to suggest that the transtheoretical model of behavior change/readiness to change appropriately applies to weight loss management. 17 Further, results from other studies suggest that early non-responders have poorer adherence to intervention recommendations (e.g., lower session attendance, fewer days of self-monitoring) during the first 1-2 months of an intervention. 14,15,20 However, adherence metrics vary based on the intervention (i.e., number and type of sessions) and variability in early adherence is typically low. ...
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Objective There is substantial inter‐individual variability in response to weight loss interventions and emerging evidence suggests that weight loss during the early weeks of an intervention may be predictive of longer‐term weight loss. This secondary analysis of data from a commercial program therefore examined 1) the associations between early weight loss (i.e., week 4) with final visit weight loss and duration on the program, and 2) other predictors of lower weight loss at final visit. Methods Client charts of adults with overweight or obesity ( N = 748) were analyzed. Clients were stratified into categories of weight loss at the week 4 (< and ≥2%, 3% and 4%) and final visits (< and ≥5% and 10%). Multivariate logistic regression was used to assess predictors of <5% and <10% final visit weight loss. Results The odds ratios for losing <5% or <10% of weight at the final visit were higher (49.0 (95% CI: 13.84, 173.63) and 20.1 (95% CI: 6.96, 58.06)) for clients who lost <2% or <3% compared to those who lost ≥2% or ≥3% at week 4. Other predictors of not losing a clinically relevant amount of weight included female sex, use of higher calorie meal plans and shorter time in the program, among others. Those who lost ≥2% at week 4 also had a significantly greater percent program completion (109.2 ± 75.2% vs. 82.3 ± 82.4, p < 0.01) compared with those who did not meet the 2% threshold. Conclusions Lower 4‐week weight loss was identified as a strong predictor of not losing a clinically relevant amount of weight. These results may be useful for the early identification of individuals who can be targeted for additional counseling and support to aid in attaining weight loss goals.
... Obesity has a wide variety of underlying causes. These consist of the following [37]: ...
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Leptin, a hormone produced by fat cells, regulates energy balance and body weight by suppressing appetite and increasing energy expenditure. In obesity, there is often leptin resistance, reducing the hormone's effects due to factors such as inflammation and changes in leptin receptors. This resistance leads to an increased risk of weight gain and obesity. Leptin therapy shows promise in treating obesity and related metabolic disorders, such as dyslipidemia and type 2 diabetes mellitus. It can lower body weight, improve insulin sensitivity, and reduce blood glucose and lipid levels. However, its effectiveness may be limited by the development of leptin resistance. Leptin also exhibits anti-inflammatory and cardiovascular protective effects, with potential therapeutic value for obesity-related conditions. Nevertheless, further research is necessary to comprehend leptin's mechanisms and develop safe and effective therapies for these conditions, including those targeting dyslipidemia.
... One limitation of our study is missing data about family history of people with obesity [42]. We probably introduced some bias by assuming that cancer diagnosis was the start of the period of risk of obesity in adulthood for all patients. ...
Objective: The aim of this study was to identify risk factors for obesity in childhood cancer survivors (CCSs). Methods: The study included 3199 patients of the French Childhood Cancer Survivor Study cohort, with 303 patients with obesity who had returned the self-questionnaire. Analyses were adjusted for social deprivation index and sex. Results: CCSs were less likely to have obesity (9.5%; 95% CI: 8.5%-10.5%) than expected from the general French population rates (12.5%; p = 0.0001). Nevertheless, brain tumor survivors were significantly more likely to develop obesity than the general French population (p = 0.0001). Compared with patients who did not receive radiotherapy to the pituitary gland, those who received a dose >5 Gy had an increased risk of obesity: relative risk 1.9 (95% CI: 1.2-3.1), 2.5 (95% CI: 1.7-3.7), and 2.6 (95% CI: 1.6-4.3), respectively, for participants with 6 to 20 Gy, 20 to 40 Gy, and ≥40 Gy of radiation. Etoposide administration significantly increased the risk of obesity (relative risk 1.7; 95% CI: 1.1-2.6). High social deprivation index was also a risk factor, just like BMI at diagnosis. Conclusions: Long-term follow-up of CCSs should include weight follow-up during adulthood.
... The causal pathways to obesity are highly complex [7]. There is however a widespread, simplistic belief that obesity can be explained by high calorie intake and low physical activity alone [8,9]. Previous studies have found that a history of adverse childhood experiences (ACEs) is associated with adult obesity [10,11], but the role of ACEs on the life course development of body weight is incompletely understood. ...
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Objective: Investigate the association between adverse childhood experiences and pre-pregnancy body mass index (BMI) in a population-based cohort in Trøndelag county, Norway. Materials and methods: We linked data from the third (2006-2008) or fourth (2017-2019) survey of the Trøndelag Health Study (HUNT) and the Medical Birth Registry of Norway for 6679 women. Multiple logistic regression models were used to examine the association between adverse childhood experiences and pre-pregnancy BMI. Adverse childhood experiences were self-reported in adulthood and included perceiving childhood as difficult, parental divorce, parental death, dysfunctional family environment, bad childhood memories and lack of support from a trusted adult. Pre-pregnancy BMI was derived from the Medical Birth Registry of Norway or BMI measurement from the HUNT survey conducted within 2 years prior to the woman's pregnancy. Results: Perceiving childhood as difficult was associated with higher odds of pre-pregnancy underweight (OR 1.78, 95%CI 0.99-3.22) and obesity (OR 1.58, 95%CI 1.14-2.2). A difficult childhood was positively associated with obesity with an adjusted OR of 1.19, 95%CI 0.79-1.81 (class I obesity), 2.32, 95%CI 1.35-4.01 (class II obesity) and 4.62, 95%CI 2.0-10.65 (class III obesity). Parental divorce was positively associated obesity (OR 1.34, 95%CI 1.10-1.63). Bad childhood memories were associated with both overweight (OR 1.34, 95%CI 1.01-1.79) and obesity (OR 1.63, 95%CI 1.13-2.34). Parental death was not associated with pre-pregnancy BMI. Conclusions: Childhood adversities were associated with pre-pregnancy BMI. Our results suggest that the positive associations between childhood adversities and pre-pregnancy obesity increased with increasing obesity level.
Identifying cancer survivorship myths and presumptions perpetuated in survivorship circles.
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Objective: To assess the alignment of YouTube® videos providing dietary recommendations for gout with evidence-based guidelines targeted at the United Kingdom (UK) population and to establish their quality. Design: A content analysis of YouTube® videos providing dietary recommendations for gout was undertaken. Videos were categorised by video source. Each video's dietary recommendations for gout were compared with three evidence-based guidelines for gout, producing a compliance score. Presence of non-guideline advice was assessed. Understandability and actionability were evaluated using the Patient Education Material Assessment Tool for Audio-Visual Materials. Reliability was assessed using an adapted-DISCERN tool and educational quality using the Global Quality Score Five-Point Scale. Differences between video source and continuous variables were assessed using one-way Kruskal-Wallis H tests. For categorical variables, associations were investigated using Fisher-Freeman-Halton tests. Setting: Online, May-June 2020. Participants: 131 videos. Results: Alignment of videos with evidence-based guidelines was poor (median compliance score 27% (IQR 17-37%)). Additionally, 57% of videos contained non-guideline advice. The health professional source group had the fewest videos containing non-guideline advice, but this was only significantly lower than the naturopath group (31% vs 81%, p = 0.009). Almost 70% of videos were considered poorly actionable and 50% poorly understandable. Most videos were rated poor for reliability (79%) and poor to generally poor for educational quality (49%). Conclusions: YouTube® videos providing dietary recommendations for gout frequently fail to conform to evidence-based guidelines and their educational quality, reliability, understandability, and actionability is often poor. More high-quality, comprehensive, evidence-based YouTube® videos are required for UK gout patients.
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Rejeneratif tıp (RM), kas-iskelet yaralanmalarında tedavi amacı ile uygulanan proloterapi, trombositten zengin plazma tedavisi (PRP) ve kök hücre (SC) tedavisi gibi çeşitli tedavileri kapsayan bir genel terim olarak tanımlanmaktadır (DeChellis ve Cortazzo 2011, Reddy ve ark 2018). Son zamanlarda, rejeneratif kaliteye sahip tedaviler, potansiyel terapötik tedavi modelleri olarak yeniden ortaya çıkmakta ve kas-iskelet sisteminde yaygın olarak kullanılmaktadır. RM içerisinde değerlendirilen tedavi yöntemleri spesifik tedaviler olarak benzer birçok kavramı paylaşmalarına karşın, tedavi edici özelliklerinin arkasındaki mekanizma birbirinden oldukça farklıdır. Proloterapi formundaki RM, ilk olarak tendon ve bağ yaralanmalarını tedavi etmek için kullanılırken teknolojinin ilerlemesi ile PRP ve kök hücre tedavisine doğru genişletilmiştir. Farklı RM tedavilerinin yaygınlaşması, bağ ve tendon yaralanmaları, kas kusurları ve ayrıca osteoartrit ve dejeneratif disklerle ilişkili ağrılar için de uygulamada artışa yol açmıştır (DeChellis ve Cortazzo 2011). RM uygulamalarının iki farklı şekli olan kök hücre ve trombositten zengin plazma tedavileri bugün birçok hastalığın tedavisinde umut verici gelişmeler ortaya koyarak dikkatleri üzerlerine çekmektedirler.
The introduction to the chapter, which is perhaps also valid for the book, outlines the situation of pediatric obesity at the present time and the relationship with global and state organizations and especially with the direct care for obese children and young people and their families or those at risk of becoming obese. The Concept section also includes currently acceptable methods of assessment and where BMI-zs and broad-based comparative standards have a prominent place. The estimation of body fat and its distribution is also considered. Some historical milestones in this relatively young disease are described, while avoiding easy anecdotes. The Greco-Latin and Medieval stages have extremely limited dimensions, while some developments were made during the Renaissance and major medical contributions to obesity were achieved during the seventeenth and eighteenth centuries. The undeniable scientific development of the nineteenth century brought about the scientific bases on which this type of malnutrition due to excess is based. Thus, we reach the current stage where the ever shorter passage of time will reveal what is really history.KeywordsObesityOverweightPediatric age assessmentBMIBMI z-scoreGrowth standardsTruncal obesityHistorical milestonesPediatric obesity milestones
Unlabelled: Policy Points Between 1998 and 2016, 24 states and the District of Columbia passed laws meant to increase the time that children spent in physical education (PE) or other school-based physical activity (PA). Schools largely disregarded changes to PE/PA laws, which did not increase the time that children spent in PE or recess and did not reduce body mass index, overweight, or obesity. Closer oversight of schools would be needed to improve compliance with state PE and PA laws. Yet, even with better compliance, we estimate that PE and PA policies would be inadequate to reverse the obesity epidemic. Policies should also address consumption, both inside and outside of school. Context: To control childhood obesity, leading medical organizations have recommended increasing the time that children spend in physical education (PE) and other school-based physical activity (PA). Yet, it is unknown how many states have passed laws that codify these recommendations, and it is unknown what effect changing state laws has had on obesity or the time that children actually spent in PE and PA. Methods: We joined state laws to national samples of 13,920 children from two different cohorts of elementary students. One cohort attended kindergarten in 1998; the other attended kindergarten in 2010; both cohorts were followed from kindergarten through fifth grade. We estimated the effects of changes to state laws in a regression with state and year fixed effects. Findings: Twenty-four states and the District of Columbia increased the time that children were recommended or required to spend in PE or PA. These changes in state policies did not increase actual time spent in PE or recess, did not affect average body mass index (BMI) or BMI Z score, and did not affect the prevalence of overweight or obesity. Conclusion: Increasing the PE or PA time required or recommended by state laws has not slowed the obesity epidemic. Many schools have failed to comply with state laws. A back-of-the-envelope calculation suggests that, even with better compliance, the legislated changes in PE laws might not have changed energy balance enough to reduce obesity prevalence.
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The consensus often reported is that there is a modest but significant protective effect of breast-feeding on obesity risk. Numerous investigators have reported that “breast-feeding reduces childhood adiposity.” This article provides a brief review of the existing literature on breast-feeding and obesity, highlighting a number of factors that may have led to overstatement of positive effects. These include publication bias, confounding variables, and lack of long-term effects on obesity risk. Although the literature does not support the existence of a protective effect of breast-feeding, a definitive conclusion of no protective effect of breast-feeding on obesity is premature, and more research is needed.
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Objectives: We conducted a systematic review of the literature examining the relationship between built environments (e.g., parks, trails, sidewalks) and physical activity (PA) or obesity rates. Methods: We performed a 2-step inclusion protocol to identify empirical articles examining any form of built environment and any form of PA (or obesity rate) as the outcome. We extracted data from included abstracts for analysis by using a standard code sheet developed for this study. Results: Of 169 included articles, 89.2% reported beneficial relationships-but virtually all articles utilized simple observational study designs not suited for determining causality. Studies utilizing objective PA measures (e.g., pedometer) were 18% less likely to identify a beneficial relationship. Articles focusing on children in community settings (-14.2%), those examining direct measures of obesity (-6.2%), or those with an academic first author (-3.4%) were less likely to find a beneficial relationship. Conclusions: Policymakers at federal and local levels should encourage more rigorous scientific research to determine whether altered built environments will result in increased PA and decreased obesity rates.
Background: The evidence that breastfeeding protects against obesity and a variety of chronic diseases comes almost entirely from observational studies, which have a potential for bias due to confounding, selection bias, and selective publication. Objective: We assessed whether an intervention designed to promote exclusive and prolonged breastfeeding affects children's height, weight, adiposity, and blood pressure at age 6.5 y. Design: The Promotion of Breastfeeding Intervention Trial (PROBIT) is a cluster-randomized trial of a breastfeeding promotion intervention based on the WHO/UNICEF Baby-Friendly Hospital Initiative. A total of 17 046 healthy breastfed infants were enrolled from 31 Belarussian maternity hospitals and their affiliated clinics; of those infants, 13 889 (81.5%) were followed up at 6.5 y with duplicate measurements of anthropometric variables and blood pressure. Analysis was based on intention to treat, with statistical adjustment for clustering within hospitals or clinics to permit inferences at the individual level. Results: The experimental intervention led to a much greater prevalence of exclusive breastfeeding at 3 mo in the experimental than in the control group (43.3% and 6.4%, respectively; P < 0.001) and a higher prevalence of any breastfeeding throughout infancy. No significant intervention effects were observed on height, body mass index, waist or hip circumference, triceps or subscapular skinfold thickness, or systolic or diastolic blood pressure. Conclusions: The breastfeeding promotion intervention resulted in substantial increases in the duration and exclusivity of breastfeeding, yet it did not reduce the measures of adiposity, increase stature, or reduce blood pressure at age 6.5 y in the experimental group. Previously reported beneficial effects on these outcomes may be the result of uncontrolled confounding and selection bias.
• Heart rate, rate-pressure product, and Vo2 were measured in ten healthy men during four specified sexual activities: coitus with husband on top, coitus with wife on top, noncoital stimulation of husband by wife, and self-stimulation by husband. Foreplay generated slight, but statistically significant, increases above resting baseline in cardiac and metabolic variables. From stimulation through orgasm, average effort was modest for relatively short spans. Maximum exercise values occurred during the brief spans of orgasm, then returned quickly to near baseline levels. The two noncoital activities required lower expenditures than the two coital positions, with man-on-top coitus rating the highest. Large variations among subjects and among activities discourage use of a general equivalent activity for comparison, such as "two flights of stairs," to represent "sexual activity." (Arch Intern Med 1984;144:1745-1748)
The Swedish Obese Subjects Study is a prospective investigation involving obese subjects who underwent bariatric surgery or conventional treatment for obesity. This report documents follow-up data for subjects (mean age, 48 years; mean body mass index, 41 kg/m²) who were enrolled in the study for at least 2 years (4047 subjects) or 10 years (1703 subjects). The follow-up rate for laboratory examinations was 86.6% at 2 years and 74.5% at 10 years.
Despite Miller's (1969) now-famous clarion call to "give psychology away" to the general public, scientific psychology has done relatively little to combat festering problems of ideological extremism and both inter- and intragroup conflict. After proposing that ideological extremism is a significant contributor to world conflict and that confirmation bias and several related biases are significant contributors to ideological extremism, we raise a crucial scientific question: Can debiasing the general public against such biases promote human welfare by tempering ideological extremism? We review the knowns and unknowns of debiasing techniques against confirmation bias, examine potential barriers to their real-world efficacy, and delineate future directions for research on debiasing. We argue that research on combating extreme confirmation bias should be among psychological science's most pressing priorities. © 2009 Association for Psychological Science.
Why do so many people believe in mind reading, past-life regression therapy, abductions by extraterrestrials, and ghosts? What has led to the rise of "scientific creationism" and the belief that the Holocaust never happened? Why, in this age of supposed scientific enlightenment, do we seem to be more dangerously confused than ever? With a no-holds-barred assault on popular superstitions and prejudices, the author debunks these extraordinary nonsensical claims and explores the very human reasons we find otherworldly phenomena, conspiracy theories, and cults so appealing. The author shows how the eternal search for meaning and spiritual fulfillment often results in our thinking being led astray by incredible claims and controversial ideas. The author also reveals the more dangerous and fearful side of wishful thinking, including Holocaust denial, the effort to incorporate creationism into public school curricula, the recovered memory movement, the satanic ritual abuse scare and other modern witch crazes, extreme Afrocentrism, and ideologies of racial superiority. Finally, the author describes his confrontations with those who take advantage of people's gullibility to advance their own, often self-serving, agendas. (PsycINFO Database Record (c) 2012 APA, all rights reserved)