This course proposes an overview of current global health challenges drawing on the insights of several academic disciplines including medicine, public health, law, economics, social sciences and humanities. This interdisciplinary approach will guide the student into seven critical topics in global health.
Physical Activity by Bengt Kayser
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Из курса от партнера University of Geneva
Global Health: An Interdisciplinary Overview
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Emerging Trends in Global Health: Non-Communicable Diseases and Disability
In this module we consider the rise of non-communicable (NCDs) diseases across countries, along with mental disorders and disability.
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Rafael Ruiz De CastañedaInstitute of Global Health - Faculty of Medicine
University of Geneva
Antoine FlahaultProfessor of Public Health and Director of the Institute of Global Health (Faculty of Medicine, University of Geneva) and co-Director of Centre Virchow-Villermé (Université Paris Descartes)
University of Geneva and Université Paris Descartes – Sorbonne Paris Cité
[MUSIC]
Hello, my name is Bengt Kayser I'm an MD medical doctor and
with a PhD in exercise physiology.
I'm interested in physical activity and health.
I just commuted here on my bike, as you can see.
I'm lucky to live in a place where this is possible.
Increasing number of bike lanes and
increasing number of cyclists make commuting possible in Geneva.
Not as good as in Denmark or Holland, but we're getting along.
But now enough on my physical activity patterns and behavior.
I am here to explain you about the relationship between physical activity and
health, and its importance with regard to non-communicable diseases.
In 2012, at the occasion of the Olympics in London, the Lancet,
one of the most prestigious journals, published a series of papers in a special
issue devoted totally to physical activity.
It showed the importance given by the editors and
by the scientists to this question.
And this series was announced by a press conference in London and
met by tremendous echo in the general press.
It showed the general awareness of this problem on a global level.
Generally one speaks about physical activity, but
perhaps it's better to speak about physical inactivity.
In a way physical inactivity is the abnormal behavior,
physical activity is the norm.
Our physiology needs regular physical activity to function properly.
Lack of physical activity is accompanied by increasing risk for
many chronic diseases, such as type two diabetes, cardio vascular disease,
several cancers, such as colon, breast, and prostate cancer, depression, etc.
The global burden of disease is about 60 to 70% from non communicable disease.
Of this proportion, it is pretty important,
comes from the lack of physical activity.
About 17% of the population globally is inactive and
a third is somewhat active, but does not reach the recommendation of of half and
hour a day of moderate physical activity.
This lack of physical activity globally is responsible for
6 to 10% of all deaths from non communicable disease.
About five million deaths would be preventable
if everybody would have been sufficiently active.
Of course, life is a deadly risk.
We will all die.
But what is at stake, is when one dies and what condition.
There's an interesting hypothesis that says that when one is sufficiently active
and eats a healthy diet, that there is tendency for
compression of morbidity at the end of the life span.
So then there will be less of a burden of disease for the individual and for
the collectivity vice versa bad nutritional habits,
lack of physical activity will be accompanied by a long period of increasing
the important health problems towards the end of life.
And a more important burden for the individual and the collectivity.
Last century,
two important changes took place that changed energy expenditure and intake.
The first change was due to the industrial revolution.
The mechanization of labor and mobility.
Today's environment is fully mechanized.
Cars, elevators, everything is moved my motors, and
it leads to physical inactivity.
100 years ago, our ancestors were working several hours a day.
2 million years ago we were hunter-gatherers, and
we were active all day to subsist.
Today, we don't have to be active anymore.
We can move about in mechanist ways and
have access to more energy in take than ever.
The second change is energy intake was ever further.
About 50 years ago with the changes in the industrialization of food processing,
and the availability of high density foods at all time, in all places,
specifically of course, initially in the rich income world, USA, Europe.
But now also increasingly happening in middle and low income parts of the world.
Taken together, the environment is increasingly imposing in a way,
lack of physical inactivity, and excess energy intake.
And one should consider this change in behavior as normal,
since imposed by an environment.
Remember, a phenotype is the result of interaction between genome
and environment.
Our genotype did not change over the last 100 years, but
the environment went through a radical change.
The pandemics of physical activity and
of obesity are therefore due to a change in environment.
The best way to change our behavior would therefore be to change the environment.
It's usefulness to context briefly review what is understood is by energy balance.
Energy balance is when energy intake is equal to energy expenditure.
There will be changes in body mass only when expenditure is higher or
lower than intake and vice versa.
Remember, every single gram of body mass comes through the mouth.
A positive energy balance is normal for
pregnant women and growing children, but not for adults.
As discussed before, today's environment imposes like a physical activity and
excess energy intake.
So it is the environment, in the large sense of the word,
that imposes energy balance.
Genes are important but they express in a given environment.
Some genetic predisposition certainly leads to more pathology given for
such an environment.
But once more, not the genes have changed,
it's the environment in which this genes express the genes.
This environmental determines physical, cultural and social economic damages.
Physical activity levels can be expressed in multiples of resting metabolic rates.
Even when one does nothing lying still in his bed,
there is still metabolic activity ongoing to keep the organism alive.
This is called basal metabolic rate and
amounts to about one kilogram per hour per kilogram of body mass.
Energy expenditure above this level is due to physical activity.
One can express the total energy expenditure as the sum
of the basic metabolic rate, physical activity related energy expenditure, and
some energy expenditure, about 10%, for the digestion of food.
Normally, this varies, this total energy expenditure,
between 1.2 times basic metabolic rate all the way up to several multiples.
It can reach about five for athletes who do the Tour de France.
Normally, for non athletes, it varies between 1.2 and, say, 2.2.
Now, for these ratios of total energy expenditure,
basal metabolic rates, between 1.8 and 2.5, the physiology works very well,
and energy the intake is matched by energy expenditure.
A certain increase or a certain decrease in activity
immediately will be matched with a change to intake in energy.
But below 1.8, this doesn't work anymore.
This is probably because evolution has never been confronted
with this type of low energy expenditure.
Our ancestors were always much more active than we are.
We are less physically active compared to ancestors, and
we also eat actually less than our ancestors.
But it's important to realize that there is an important body composition
independent health promoting effect of physical activity.
So even for people with excess body weight, 25 of body mass index,
or even 30 considered obese, good levels of fitness will protect
from certain health risks, usually related to having obesity.
Today, this is brought together under a statement which says,
it's rather be fat and fit, than not-fat but not-fit.
As explained before life results from the expression of
genes in a given environment.
There are genetic factors that contribute to the propensity to be physically active,
but the environment is the most important determinant
of our physical activity levels.
This environment, not only the physical one, includes cultural and
socio-economic dimensions, our modern environment
is radically different from that of our ancestors, with whom we share our genes.
So in high income countries, research intercorrelates, that is,
risk factors that are associated with activity, or determines those
with a causal relationship show that age, sex, health status, self-efficacy, and
motivation are associated with physical activity.
Ecological models take a broad view of health behavior representation
with the social and physical environment included as contributors to physical
activity, particularly those outside the health sector such as urban planning,
transportation systems, access to recreational areas such as parks.
A better understanding of this determines in low income and
middle income countries are needed.
We know quite a lot of it already in high income countries.
But when we speak about physical activity levels,
how much is needed and how much is enough?
The present evidence would suggest that about half an hour a day is good for
optimal health.
Possibly complemented with some higher intensity efforts a few times a day,
bringing on a sweat.
For children more is needed, up to 60 to 90 minutes.
The same goes for
adults who do not wish to gain weight over time during their life.
But it is important to realize that even below the recommendations,
there is a great benefit of being physically active,
the dose response curve is not linear.
This graph illustrates this nonlinear response of the health benefit from
increasing activity levels.
For a person inactive, the given increase in physical activity depicted in letter A,
leads to greater return on investment with regard to health benefits.
For a person already quite active, depicted in C, for the same absolute
increase there will be less health benefit for this fatter person.
So for insufficient, physically active individuals, any increase in physical
activity is of interest, even if it's less than 30 minutes a day.
For a long time and still today, behavioral determinants of health
are often considered to be a matter of personal responsibility.
Obesity, for instance, was and still often is regarded as a problem of individual.
However, it is now becoming increasingly clear that this is really unfair.
Given an environment with its physical, socio-economic and
cultural aspects, obesity is actually quite a normal outcome of
the interaction between genome and environment.
The same goes for physical inactivity.
It will therefore take changes of the environment to make it more adapted for
reaching adequate physical activity levels to change things.
This cannot be done without regulatory effort.
We need local, national, regional and global politics to be implicated in this.
The inclusion of physical inactivity is a major determinant
of non-communicable disease by the UN and
the WHO Shows that this awareness of this importancy is increasing.
This now leads,
of course, translation into local governmental regulatory efforts.
So what are some key messages you should take away from this short lecture?
I've added those from my colleague Cole and
coworkers published in one of the mentioned Lancet papers.
Physical inactivity is harmful with health and environmental consequences and
is a public health priority.
Public health and physical activity have become a new discipline together,
not yet fully recognized, but
allowing a multidisciplinary approach that is promising.
It needs now capacity building, work restraining and
a system approach to really start to change things.
Now what is the outlook for the future?
The publication of the Lancet series was met by huge media response.
It forebodes an increasing awareness also at national, regional, and
global political levels.
The recognition by the UN and WHO of physical activity
as a major determinant of non-communicable disease is promising.
There is also increased awareness generally, so
in principle the outlook is promising but it will need big,
big changes at many, many levels to really come to a big impact.
I hope to have convinced you of the importance of including
the promotion of physical activity levels in the population.
I also hope that you have understood that just trying to make individuals move by
playing on their personal responsibility will not be sufficient,
that a systemic, ecological approach is needed.
Bringing such change to the environment that the choice of physical activity
becomes the only possible but is actually induced.
But on an individual level, certainly change is possible too.
So what about you?
I invite you to reflect on your own physical activity patterns.
And I recommend you to look at the video by Dr. Mike Evans, 23 1/2 Hours,
for which you'll find the link in the material of the course.
Who very well explains what the use of the investment of just half
an hour of the 24 hours a day will bring you with regard to health.
Well, with that I conclude my lecture.
I hope you enjoyed it.
And don't forget to move.
[MUSIC]
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