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Editorials
body weight may stay the same despite a
reduction in high risk visceral fat as a result
of increased muscle mass.
CURRENT EVIDENCE FOR PHYSICAL
ACTIVITY AND OBESITY
The Malhotra editorial challenges the
effectiveness of physical activity for weight
loss in obese individuals. The guidelines
and reports highlighted above present
much of the evidence base and include a
specific Cochrane systematic review by
Shaw et al,7 which was ignored by the
Malhotra editorial. This review included 43
studies reporting results from 41 randomised controlled trials including a total of
3476 participants. The duration of included
studies ranged from 3 to 12 months (61%
less than 4 months), including follow-up.
Although methodological quality for
included studies was variable according a
risk of bias assessment, the Cochrane
review authors report that exercise combined with diet resulted in greater weight
reduction than diet alone (mean difference
−1.0 kg; 95% CI, −1.3 to −0.7). They also
note the finding that increasing exercise
intensity increased the magnitude of weight
loss (mean difference −1.5 kg; 95% CI
−2.3 to −0.7). An additional finding was
that exercise improved a range of secondary
outcomes even when weight loss did not
occur. The authors conclude exercise was
an effective weight loss intervention, particularly when combined with dietary interventions, but make no inference to the
poor quality of included trials and little reference to the fact that diet alone appeared
better than exercise alone (mean difference
−3.6 kg, 95% CI −4.3 to −3). These
outcome and quality findings are repeated
in a more recent systematic review assessing
treatment (including diet, exercise or diet
and exercise) for overweight and obesity in
adult populations.8 Whether these differences are meaningful requires good clinical
judgement and open, honest discussion.
However, when objectively assessing the
best available evidence, for which we
acknowledge the majority is of low quality,
it would appear that diet alone (mainly low
fat) is better than exercise alone but better
than either are diet and exercise together. A
further key point is that improvements in
important health risk factors are observed
with exercise even without weight loss.
There is little doubt that diet is key in the
management of the obesity epidemic.
Indeed, Malhotra and colleagues could be
congratulated for taking on the ‘food industry’s public relations machinery’ and they
helpfully point out that more care is needed
in relationships between sport and celebratory endorsements of junk food or sports
drinks. What is less helpful, and does no
one, including the public and patients, any
favours, is the production of opinion pieces
that use evidence poorly or not at all.
970
To cite Mahtani KR, McManus J, Nunan D. Br J
Sports Med 2015;49:969–970.
Accepted 28 May 2015
Published Online First 18 June 2015
▸ http://dx.doi.org/10.1136/bjsports-2015-094911
Br J Sports Med 2015;49:969–970.
doi:10.1136/bjsports-2015-095005
REFERENCES
1
Twitter Follow Kamal Mahtani at @krmahtani
Acknowledgements The authors would like to thank
Jeffrey Aronson and Meena Mahtani for editorial
comments.
Competing interests KRM is an NHS general
practitioner who supports and advises patients to lose
weight through a healthy balanced diet and regular
physical activity. He holds NHS National Institute of
Health Research (NIHR) grant funding for some of his
research. JMcM is Director of Public Health for
Hertfordshire, and a member of the Academy of
Medical Royal Colleges Health Inequalities Forum. He is
a member of the International Scientific Advisory Group
for the Centre for Diet and Activity Research at the
University of Cambridge. DN is a senior research fellow
and tutor of evidence-based medicine, with a
background and research interest in exercise physiology
and physical activity. He holds NHS National Institute of
Health Research (NIHR) grant funding for some of his
research. The views expressed are those of the author
Steven N Blair,1 Gregory A Hand,2 James O Hill3
Department of Exercise Science, Department of
Epidemiology and Biostatistics, Arnold School of Public
Health, University of South Carolina, South Carolina,
USA; 2School of Public Health, West Virginia University;
3
Anschutz Health and Wellness Center, University of
Colorado
Correspondence to Professor Steven N Blair,
Department of Exercise Science, Department of
Epidemiology and Biostatistics, Arnold School of Public
Health, University of South Carolina, SC 29208, USA;
[email protected]
Provenance and peer review Not commissioned;
internally peer reviewed.
CONCLUSIONS
Energy balance: a crucial issue for
exercise and sports medicine
1
(s) and not necessarily those of the NHS National
Institute of Health Research (NIHR) or employing
institutions.
The recently published issue of British
Journal of Sports Medicine (http://bjsm.
bmj.com/content/49/4.toc) includes articles on several important topics in exercise science and sports medicine. We are
grateful to the many leading clinicians and
scientists who have made these contributions. This editorial will address another
relevant topic that requires focused attention—energy balance.
2
3
4
5
6
7
8
Malhotra A, Noakes T, Phinney S. It is time to bust
the myth of physical inactivity and obesity: you
cannot outrun a bad diet. Br J Sports Med 2015;49:
967–8.
Balshem H, Helfand M, Holger J, et al.
GRADE guidelines: 3. Rating the quality of
evidence. J Clin Epidemiol 2011;64:
401–6.
Luke A, Cooper RS. Physical activity does not influence
obesity risk: time to clarify the public health message.
Int J Epidemiol 2013;42:1831–6.
http://www.who.int/mediacentre/factsheets/fs311/en/
(accessed 28 Apr 2015).
http://www.nice.org.uk/guidance/cg43/resources/
guidance-obesity-pdf (accessed 28 Apr 2015).
http://www.aomrc.org.uk/general-news/exercise-themiracle-cure.html (accessed 28 Apr 2015).
Shaw KA, Gennat HC, O’Rourke P, et al. Exercise for
overweight or obesity. Cochrane Database Syst Rev
2006;(4):CD003817.
Peirson L, Douketis J, Ciliska S, et al. Treatment for
overweight and obesity in adult populations:
a systematic review and meta-analysis. CMAJ Open
2014;2:E306–17.
BACKGROUND
Non-communicable
chronic
diseases
(NCDs), such as cardiovascular disease,
cancer, obesity and type 2 diabetes, are
clearly the leading public health problems
facing the world in the 21st century.1 The
causes of NCDs are predominately
unhealthful lifestyles such as physical inactivity, poor diets, smoking, unhealthful sleep
habits and not managing stress effectively.1
In recent years, obesity rates have increased
in most countries, and this problem receives
enormous attention, in both the popular
media and scientific press. The fundamental
cause of increasing rates of obesity is too
many people being in a positive energy
balance on too many days; but the problem
is very complex.2 From a simple perspective,
Br J Sports Med August 2015 Vol 49 No 15
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Editorials
energy balance is the ratio of energy intake
and energy expenditure, and if more calories
are consumed than are expended, a person
will be in positive energy balance. This
excessive energy will be stored in the body,
mostly as body fat. Of course maintaining
energy balance is a much more complex
issue than this simple statement, with
numerous environmental, social and physiological factors having a role. Extensive
reviews of the energy balance concept have
been published in recent years.3 4
ENERGY FLUX—A RECENT CONCEPT
Energy flux refers to the rate of energy
flow through a system. Recently this
concept has been applied to the rate of
energy flow in the human body.5 Mayer
et al6 postulated that individuals with a
high rate of energy flow through the body
(ie, high intake matched by high expenditure) were better able to maintain energy
balance than those with a low rate of
energy expenditure. It should be noted
that at a very sedentary level, the participants had energy intake similar to that of
the highly active individuals. Blundell7
referred to a low energy flux as the
unregulated zone where energy intake and
expenditure were not well matched and
where the likelihood of positive energy
balance was high. He referred to a moderate and high energy flux as the regulated
zone where energy intake was well
matched to level of energy expenditure
(eg, better appetite control). Energy
balance at a high energy flux is seen typically in those with high levels of physical
activity. A low energy flux may be an
unstable situation that is resolved by
increasing body mass, which in turn
increases energy expenditure and energy
flux. This last point reinforces the ‘drive’
to maintain a relatively high energy intake
which requires either equivalent energy
expenditure or energy storage. To maintain a high energy flux in the face of a
sedentary lifestyle, there is no option
other than significant energy storage.
The fact that food restriction has not
proven to be an effective means of longterm weight control is consistent with the
flux hypothesis. People need to be in the
regulated zone to be better able to match
caloric intake to caloric expenditure over
long time periods. In addition, drastic
caloric restriction by sedentary individuals
in an effort to lose body weight creates a
number of health concerns including cachexia, reduction in bone density, impaired
immune function and fatigue. Finally, the
Br J Sports Med August 2015 Vol 49 No 15
reduced resting metabolic rate resulting
from excessive caloric restriction reduces
the likelihood of sustained weight management at a lower body weight over time.
IMBALANCE IN ENERGY BALANCE
INFORMATION
Energy balance is an important public
health issue, and we have focused on this
issue for the past few years. We are
obtaining detailed information on energy
intake, energy expenditure, energy storage
and other variables in a cohort of young
adults.8 The overall purpose is to provide
better information on how changes in
both sides of the energy balance equation
are related to changes in body weight and
composition.
There is enormous confusion about the
relation of energy intake and energy
expenditure to obesity. A Google search
on 1 January 2015 produced the following results:
▸ Physical inactivity and obesity—
966 000 hits;
▸ Diet and obesity—70 300 000 hits.
Of course Google hits are primarily from
public media, and it also is important to see
if a similar imbalance is present in the scientific literature, so we searched for these same
terms on PubMed. Here are the results:
▸ Physical inactivity and obesity—2176
manuscripts;
▸ Diet and obesity—44 584 manuscripts.
Both of these data searches show that
much more attention is focused on diet and
obesity than on physical inactivity and
obesity. We need more research that
focused on energy balance—not just a
single component of energy balance. As
indicated above, we are currently conducting research that will provide extensive data
on the contributions of the two sides of the
energy balance equation to weight change.
DEALING WITH UNBALANCED
INFORMATION ABOUT ENERGY
BALANCE
We clearly need a much more balanced
approach to discussing energy balance and
energy flux. We have created a not-forprofit organisation, the Global Energy
Balance Network that focuses attention on
making sound information about both sides
of the energy balance equation readily available to the public, clinicians and scientists.
The mission of the organisation can be
found at http://www.gebn.org. We invite
you to view the website and send us suggestions and information.
Competing interests The Global Energy Balance
Network has received support from private
philanthropy, the University of Colorado, the University
of South Carolina, the University of Copenhagen,
including an unrestricted education gift from The CocaCola Company. GEBN believes that finding workable
solutions to correcting energy imbalance will be
achieved faster by working with all sectors of society.
GEBN seeks support to continue our efforts from both
the public and private sectors.
Provenance and peer review Not commissioned;
externally peer reviewed.
Open Access
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distributed in accordance with the Creative Commons
Attribution Non Commercial (CC BY-NC 4.0) license,
which permits others to distribute, remix, adapt, build
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To cite Blair SN, Hand GA, Hill JO. Br J Sports Med
2015;49:970–971.
Accepted 14 February 2015
Published Online First 13 March 2015
Br J Sports Med 2015;49:970–971.
doi:10.1136/bjsports-2015-094592
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8
Murray CJL, Lopez AD. Measuring the global
burden of disease. N Engl J Med 2013;369:
448–57.
Shook RP, Blair SN, Duperly J, et al. What is causing
the worldwide rise in body weight? US Endocrinol
2014;10:44–52.
Hill JO, Wyatt HR, Peters JC. The importance of energy
balance. US Endocrinol 2013;9:27–31.
Hill JO, Wyatt HR, Peters JC. Energy balance and
obesity. Circulation 2012;126:126–32.
Hand GA, Blair SN. Energy flux and its role in
obesity and metabolic disease. US Endocrinol 2014;
10:59–64.
Mayer J, Roy P, Mitra KP. Relation between caloric
intake, body weight, and physical work: studies in an
industrial male population in West Bengal. Am J Clin
Nutr 1956;4:169–75.
Blundell JE. Physical activity and appetite control:
can we close the energy gap? Nutr Bull
2011;36:356–66.
Hand GA, Shook RP, Paluch AE, et al. The energy
balance study: the design and baseline results for a
longitudinal study of energy balance. Res Q Exerc
Sport 2013;84:275–86.
971
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Energy balance: a crucial issue for exercise
and sports medicine
Steven N Blair, Gregory A Hand and James O Hill
Br J Sports Med 2015 49: 970-971 originally published online March 13,
2015
doi: 10.1136/bjsports-2015-094592
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