112
Physical activity
Physical activity
The evidence for a preventive effect of physical
activity against colon cancer is strong, while that
for an effect against breast cancer is somewhat
weaker. The mechanism appears to be partly
related to weight control, but high physical
activity also has independent effects on cancer
risk.
It is recommended that people should engage
in at least 30 minutes, but preferably 60 minutes, of physical activity of moderate intensity
(such as brisk walking) daily. The daily activity dose can be divided into shorter parts, such
as four times 15 minutes.
Increasing physical activity requires a combination of strategies at the level of the population and high-risk individuals.
In populations and communities, it is important
to improve factors that make physical activity
more accessible to individuals. Environmental
reorganization to increase safety and access to
a greater number of varied facilities for all segments of the community is an important consideration in planning for health and will involve
NGOs working in partnership with several
municipal sectors (e.g. health, urban planning,
transport, education, sports).
At the individual level, appropriate behaviour
modification techniques should be incorporated
into intervention strategies to increase efficacy.
113
Physical activity
Results of interventions
Methods and characteristics of interventions
Mikael Fogelholm
The UKK Institute for
Health Promotion
Research,
Tampere,
Finland
Physical activity and
cancer: scientific evidence
for disease etiology
activity was defined as that of
individuals in the highest category (tertile, quartile or quintile).
A considerable number of cohort
Because there are various ways
Missing information and research topics
and case–control studies have
of assessing physical activity
Conclusions and recommendations
evaluated the relationships be-
and
tween physical activity and risks
used, it has been difficult to
for developing various forms of
conclude whether a ‘minimal
cancer [1]. There is sufficient
effective dose’ exists. In their
evidence to conclude that a
review, Thune and Furberg [2]
high level of physical activity,
suggested that 20–25 ‘metabolic
when compared with low activity,
equivalent hours’ of activity
reduces the probability of get-
are needed to bring about a pre-
ting colon and breast cancer by
ventive effect on cancer. This dose
about 20%. The evidence is
of physical activity is equivalent
stronger for colon than for
to approximately 2.5 hours of
breast cancer. There is also
vigorous exercise (producing
some evidence that physical
marked
activity protects against endo-
sweating, as during running or
metrial cancer, but the evidence
aerobics) or 4–6 hours of mode-
is weaker than that for colon
rate physical activity (pro-
and breast cancer. Studies on
ducing little or insignificant
physical activity and rectal,
increase in breathing frequency
ovarian, prostate, lung and tes-
and sweating, as during brisk
ticular cancer do not clearly
walking) per week.
show any associations. In the
114
above studies, high physical
various
categories
breathlessness
are
and
Physical activity
Physical activity and cancer:
scientific evidence for disease etiology
115
One potential cancer-prevent-
long-term effects of regular
in the intervention areas in one
therefore that improved knowl-
objective of all of them was to
ing effect of physical activity is
exercise are less clear. Moderate
[12]. The residents of the inter-
edge, skills and positive attitudes
decrease deaths and morbidity
body weight control. Several
physical activity has also been
vention communities included
lead to changes in behaviour
from cardiovascular disease.
cross-sectional studies have
shown to improve immune
in the Minnesota Heart Health
and, further, to changes in disease
• The interventions were too
shown that physically active
function [5], and this could be
Study were somewhat more
variables. Health education was
general, and hence important
individuals have a lower body
another mechanism by which
physically active (self-reported)
carried out through the mass
subgroups may have been
mass index, relative fat content,
physical activity prevents some
by the end of follow-up [9]. In
media (e.g., local television and
lost. Interventions directed
waist circumference, waist:hip
forms of cancer.
the Stanford Five-city Project,
radio channels, newspapers,
towards high-risk individuals
ratio and visceral fat mass than
Although physical activity may
the intervention had a positive
print materials), by peer groups
(e.g., overweight individuals
sedentary
[3].
have independent effects on
effect on physical activity in
and by health professionals. In
or children of obese parents)
also
cancer risk, part of the protec-
independent,
cross-sectional
only one project were there de-
are therefore needed.
show that high or increased
tive effect seems to be mediated
samples but not in the cohort
liberate efforts to change the
• All the interventions had a
physical activity is linked to
through
survey [6,13].
physical environment by con-
strong emphasis on education.
better weight control both be-
control. Therefore, if physical
Although the results for physi-
struction of walking and fitness
There are clearly several unused
fore (as a primary prevention
activity is used effectively as a
cal activity were positive in
paths [15]. All interventions
possibilities
strategy)
weight
preventive strategy against can-
most projects, the effects of the
had elements that were distri-
environments to facilitate or
reduction [4]. Nevertheless, some
cer, it should at the same time
intervention on body weight
buted unselected to a wide
promote physical activity [16].
effects of physical activity seem
be used as a preventive mea-
change
audience,
These include increasing the
to be independent of obesity. A
sure against obesity. Because
Three projects found no effect
strong putative mechanism is
the scope of the present review
on body mass index [10,12,15].
alteration of the hormonal milieu
is prevention of cancer, the
Moreover, no change in the pre-
[4]. Many studies have shown
focus is on large-scale studies
valence of overweight (body
that strenuous physical activity
of increasing physical activity
mass index > 25 kg/m2) was
acutely (for 0–2 hours) decreases
at the community level and – at
seen in one project [14]. In the
The studies cited in this brief
as well as building stairways
plasma insulin and increases
the same time – preventing
Stanford Five-city project, body
review
positive
in public buildings and on
the serum concentration of sex
weight gain. Only five interven-
mass index increased less in
effects of physical activity in
work sites. New interventions
hormone-binding globulin and
tions, most reported in multiple
the intervention than in the
preventing weight gain are not
should identify and modify
total and free testosterone. In
publications, can be included
control communities, but this
easily demonstrated in (controlled)
settings used daily by a signif-
the longer term, an increase in
[6–15].
effect was observed only in the
interventions. There are several
icant proportion of the com-
independent,
potential explanations for the
munity. Moreover, behaviour
problems encountered in increasing
modification approaches might
physical activity in communities:
improve the efficacy of physical
• The focus has been on tradi-
activity
Observational
and
studies
after
improved
weight
physical activity lowers the fasting
plasma insulin concentration, but
Results of interventions
were
disappointing.
cross-sectional
surveys [8].
the effects on sex hormone-
116
Methods and characteristics of interventions
although
targeted
interventions were also used.
show
that
Of the four projects in which
physical activity was assessed,
Exercise also acutely increases
two [12,15] found no significant
the absolute concentrations of
effects
intervention,
Health education was the main
• Too little priority was given to
insulin growth factor-1 and
although there was a tendency
component of the community
physical activity in the inter-
binding proteins, but again the
for increased physical activity
interventions. The premise was
ventions, because the primary
Evidence-based Cancer Prevention: Strategies for NGOs - A UICC Handbook for Europe
safety and convenience of
munity residents and improving the safety and availability
of biking and walking paths,
or oestrogens are less clear.
the
modifying
exercise facilities for all com-
Missing information
and research topics
binding globulin and androgens
of
for
interventions
and
tional physical activity, rather
encourage long-term adherence
than usual daily activity.
to increased individual or
Evidence-based Cancer Prevention: Strategies for NGOs - A UICC Handbook for Europe
group activity [17].
Physical activity
individuals
117
effective in changing behaviour,
bilities for modifying environ-
and further work is needed to
ments to promote physical activ-
identify environmental facilities
ity. The actors in interventions
Evidence for the importance of
that will encourage increased
(e.g., NGOs) must therefore
physical activity in cancer aetiology
activity. Effective behavioural
work with several municipal
is becoming stronger, suggesting
programmes should be devel-
sectors (e.g. health, urban plan-
that increasing everyday activity
oped on the basis of theoretical
ning,
and exercise can reduce cancer
models from social psychology.
sports). Moreover, a combina-
risk. The increasing prevalence
Community interventions de-
tion of strategies for the general
of obesity (and its role in cancer
signed to increase physical activ-
population and high-risk indi-
development) highlights the need
ity should therefore use possi-
viduals should be used.
Conclusions and
recommendations
transport,
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minutes, of physical activity of
moderate intensity (such as
Health-enhancing
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a model of good practice
1–2
times a week
Further sports
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119
ical
activity
levels
suggests
that increases in all types of
activity (from stair climbing to
sports) should be addressed,
EVERYDAY
Increase incidental activity: park your car further away, take stairs
instead of the lift, walk to your job, do work around the house,
don’t use remote controls, play with your children, walk the dog
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devoted to high-risk groups,
such as children of obese parents.
Educational
118
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cross-country skiiing
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CUT DOWN ON
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