Nutric’ión

Nutr Hosp 2013;28(Supl. 5):89-98
ISSN (Versión papel): 0212-1611


ISSN (Versión electrónica): 1699-5198


CODEN NUHOEQ
S.V.R. 318


Nutric’ión
Hospitalaria


Sedentarism, active lifestyle and sport: impact on health and obesity prevention
Marcela González-Gross“ andAgustín Meléndez‘
’ ImFINE Research Group. Department ofHealth and Human Performance. Faculty ofPhysical Activity and Sport Sciences-
INEF. Technical University ofMadrid. Spain. ZCIBEROÍJH (Fisiapatología de la Obesidady la Nutrición CBI2/03/30038),
Instituto de Salud Carlos III. Spain.


Abstract


The benefits of regular physical activity have been known
since ancient Greek. But in the last Century the scientific
knowledge around this topic has progressed enormously,
starting with the early studies of JN Morris and RS Paffen-
berger, who demonstrated that physical activity at work
reduced incidence of cardiovascular disease and mortality.
In the Harvard alumni study, the lowest risk was associated
with a weekly output of 1000 to 2000 kcal performing vi-
gorous activities. Further studies in all age groups have
supported these findings and have added that even moderate
levels of physical activity provide considerable benefits to
health, including lower prevalence ofoverweight and obesity
at all ages. Metabolic fat oxidation rate is highest at exercise
intensities between 45 and 65% ofVOzmax. This means that
people must be active regularly and force physiological
mechanisms at certain intensities. All this body of evidence
has contributed to current WHO physical activity recom-
mendations of 150 min/week ofmoderate to vigorous phys-
ical activity (MVPA) in adults and elderly, and 60min/day of
MVPA in children and adolescents, with additional strength
training,apart fromadopting an active lifestyle.
In the last 50 years, occupational physical activity has


been reduced for about 120 kcal/day, and sedentarism
has emerged as an additional risk factor to physical inac-
tivíty. Even if less than 60 min of TV time in adults have
been related to lower average BMI, there is still a need for
research to determine the appropriate dose of exercise in
combination with sedentary behaviours and other activi-
ties in the context of our modern lifestyle in order to
prevent obesity at all ages. As public health measures have
failed to stop the obesity epidemic in the last 3 decades,
there is clearly a need to change the paradigm. The inclu-
sion of sport scientists, physical education teachers and
other professionals in the multidisciplinary team which
should be responsible for drawing the road map to pre-
vent the increase of the obesity epidemic effectively is a
“must” from our point of view.


Nutr Hosp 2013,‘ 28 (Supl. 5):89—98
Key words: Fitness. Health. Physical activity. Obesity.


Prevention.


Correspondence: Marcela González-Gross.
ImFINE Research Group.
Departamento de Salud y Rendimiento Humano.
Facultad de CC de la Actividad Física y del Deporte-INEF.
Universidad Politécnica de Madrid.
Martín Fierro, 7.
E-28040 Madrid.
E-mail: marcelagonzlaezgross@upm.es


SEDENTARISMO, VIDA ACTIVA Y DEPORTE:
IMPACTO SOBRE LA SALUD Y PREVENCION


DE LA OBESIDAD


Resumen


Los beneficios de la práctica regular de actividad física
se conocen desde la antigua Grecia. En el siglo XX, el
avance del conocimiento científico fue enorme, empe-
zando con los estudios de JN Morris y RS Paffenberger,
que demostraron que la actividad física en el trabajo redu-
cía la incidencia de morbilidad y mortalidad por enferme-
dad cardiovascular. En el estudio de los ex alumnos de
Harvard, el menor riesgo se asoció a gastos semanales de
1000 a 2000 kcal realizando actividades vigorosas. Estu-
dios posteriores en todos los grupos de edad han verificado
estos resultados. Además, se ha observado que incluso
actividades a intensidades moderadas aportan beneficios
importantes para la salud, incluyendo una menor preva-
lencia de sobrepeso y obesidad a todas las edades. La tasa
metabólica de oxidación de las grasas es máxima a intensi-
dades entre el 45 y el 65% del VO2max, que se alcanzan
únicamente con entrenamientos mantenidos en el tiempo,
con en fin de forzar los mecanismos fisiológicos a determi-
nadas intensidades. Toda esta evidencia científica llevó a la
OMS a formular sus recomendaciones de 150 min/semana
de actividad física de moderada a vigorosa (MVPA) en
adultos y mayores, y de 60 min/día de MVPA en niños y
adolescentes, además de entrenamiento de la fuerza y en el
contexto de un estilo de vida activo.


En los últimos 50 años, la actividad física laboral se ha
reducido en unas 120 kcal/día, y el sedentarismo surge
como un factor de riesgo adicional a la inactividad fisica.
Aunque se han relacionado tiempos de menos 60 min de
TV en adultos con menor tasa de IMC, aun es necesario
profundizar en la dosis apropiada de ejercicio físico en
combinación con comportamientos sedentarios en el con-
texto de nuestro estilo de vida moderno para prevenir la
obesidad a todas las edades. Consideramos necesario un
cambio de paradigma, ya que las medidas de Salud Pública
no han conseguido frenar el progreso de la epidemia de la
obesidad en las últimas 3 décadas. La inclusión de los cien-
tíficos y profesionales del deporte, de los profesores de edu-
cación física en el equipo multidisciplinar que debería ser
el responsable de trazar las líneas maestras para prevenir y
frenar la epidemia de la obesidad de forma efectiva es algo
imprescindible desde nuestro punto de vista.


NutrHosp 2013; 28 (Supl. 5):89—98
Palabras clave: Condición física. Salud. Actividadfísica.


Obesidad. Prevención.


89




Abbreviations


AVENA: Alimentación y valoración del estado
nutricional en adolescentes.
EXERNET: Red de investigación en ejercicio físico


y salud para poblaciones especiales.
EYHS: European Youth Heart Study.
HBSC Study: Health and behaviour in school-aged


children.
HELENA: Healthy Lifestyle in Europe by Nutrition


in Adolescence.
MVPA: Moderate to Vigorous physical activity.
NHANES: National health and Nutrition Exarnina-


tion Survey.
PRONAF: Programas de nutrición y actividad física


para el tratamiento de la obesidad.


Introduction


The human being is meant to move. Our ancestors
had to move to hunt animals, gather fruit or cultivate
their fields. Since the industrial revolution, human mo-
vement has been reduced constantly and sedentarism
has increased progressively. It has been estimated that
in the 1960’ s, around half of the jobs in private industry
in the U.S. required at least moderate intensity physical
activity, in contrast to less than 20% of the jobs curren-
tly.‘ A worrying trend as inactivity is accompanied by a
tendency towards dysfunction, and in some cases in-
creased morbidity as lack of movement produces pro-
gressive atrophy and physical weakness in the whole
organism. At the end of the 1950s and beginning of the
l960s, Kraus and Raab’ had already introduced the
term hypokinetic to refer to a series of changes associ-
ated with physical activity and those diseases which
could be provoked or worsened as a consequence of
physical inactivity.


Modern technology and the development of motor-
based transport systems, of machines which take over
former high-energy demanding activities both at home
and at the workplace, as well as in commuting, have
reduced the intensity of, and time spent in, physical
activity in our daily living,‘ turning us into a “Homo
sedentarius”. In fact, sedentary behaviour has begun to
be used to describe prolonged sitting (sedére in Latin =
to sit), instead of the absence of physical activity. The
word “sedentary” has begun to be applied to people
who spend most of the day sitting down? There is a
rapidly expanding body of evidence suggesting that
time spent in sedentary behaviours is associated adver-
sely with health risks and can be a factor which is inde-
pendent of the protective action ofphysical activity}


Energy balance, which has been considered funda-
mental for avoiding overweight and obesity, has puzzled
scientists for a long time. In the 16"‘ century, Sanctorio in
Padua built a scale for himself in order to understand
weight maintenance in adulthoodí‘ It was in the late 18"‘
Century with the studies of Lavoisier and his collea-


gues that science started to understand heat production,
oxygen consumption and energy output; and at the end
ofthe 19"‘ and beginning of the 20"‘ Century interest grew
regarding the physiological and biochemical adaptations
to training“. In the last five decades, daily energy output
due to the reduction in occupational physical activity has
been estimated to have decreased among US men and
women by 140 and 124 kcal, respectively‘, probably
affecting energy balance.


Physical activity and cardiovascular health


The belief that people who are physically active in
their daily life both because of their occupation and
through their recreation, exercise and sports activities
have a lower level of morbidity and mortality are not
new ideas, and can be traced back to the writings of di-
fferent authors in ancient Greece or Rome.“ However,
for a long time these ideas have come up against the
scepticism of health professionals. A change in menta-
lity was brought about as a result of a series of impor-
tant epidemiological studies.


The famous articles by J.N. Morris and colleagues
published in 1953 examined the incidence of coronary
heart disease among the bus drivers who spent more
than 90% of their working hours sitting down, and bus
conductors, who spent their working days going up and
down the stairs on the famous London double-decker
buses. They found a lower incidence of coronary heart
disease among the conductors and postulated that
“physically active” work provided a certain amount of
protection against sudden death due to cardiac prob-
lems as a first manifestation of disease. Further data
obtained from post office employees, comparing those
who had to deliver the post by walking or by riding a bi-
cycle with those working at the post office that carried
out more sedentary work like sorting letters, confirmed
the protective effect ofphysical activity?
In this line of epidemiological research, R.S. Paffen-


barger and colleagues“ published the results of their
research studying the stevedores at the San Francisco
port. The researchers found out that in the group of the
most active stevedores, who expended an additional
4,200 kJ/week (1,000 kca]/week) cardiovascular morta-
lity was clearly lower than in the less active workers.


Other epidemiological studies from the same re-
search group which have been critical for confirming
the relationship of exercise and cardiovascular health
and mortality were the college alunmi of the University
of Harvard studies, initiated by Paffenberger. After a
follow-up of 6 to lO years, it was concluded that there
was an inverse relationship between the levels of phys-
ical activity and the risk of suffering coronary heart
disease. After 12 to 16 years, the researchers showed
that an extra energy expenditure of 8,400 kJ/week
(2,000/kcal/week), was associated with a decrease of
28% in all cause mortality, and that the decrease was
even more with regard to cardio-respiratory problems.


90




Specifically in the cohort of alumni from Harvar “v7
it was demonstrated that those subjects who performed
regular physical activity of certain intensity reduced to
half the risk of suffering from coronary heart disease
compared to sedentary ones. The lowest risk was asso-
ciated with a weekly energy output of between 4,200
and 8,400 kJ/week (1000 to 2000 kcal) despite the fact
that 8,400 kJ/week seems to be a critical point for men.
There were benefits with 4,200kJ for women and a
dose-response for the levels of exercise training sho-
wing a lower risk with a higher energy output and addi-
tional benefits with vigorous activities.“ Older men
should expend at least 4200 kJ/week in total physical
activity to potentially reduce their risk for CHD in a
statistically significant way (about 20%); however,
when expending 2, 100 to 4, 100 kJ/week, a value slightly
lower than the one recommended by the Surgeon Ge-
neral, a 10% reduction was observed. This reduction
was not statistically significant but can have an impor-
tant practical value.’ Interesting findings of the above-
mentioned studies were that the benefits of regular and
vigorous physical activity seemed to be irrespective of
body composition; in other words, they also applied to
obese subjects. Some exercise is better than none, while
more is better than some“, and cardiovascular adapta-
tions to training have a positive influence on the many
pathophysiological conditions associated with obesity,
and better fitness facilitates the tasks ofdaily living.’


More recently, the work of S.N. Blair and others has
confirmed these findings in relation to a lower all cause
mortality underlining the fact that even moderate levels
of physical activity, and an improved fitness level used
as amore objective marker ofphysical activity, provide
considerable benefits for health in general? And while
the benefits may be more dramatic in a sedentary 45
year-old like Dr Paffenberger himself, benefits can be
derived regardless of age as shown in 80-year-olds who
can improve the quality of their life significantly,“
something possible in even older people.”


Physical activity, obesity and health


Obesity (BMI > 30, high body fat) as a risk factor for
health has recently been the focus of research, due to
the increase in its prevalence in all age groups in devel-
oped, and currently also, in developing countries. Age-
adjusted prevalence of obesity in the U.S. has shifted
from 10%-15% in the l960s up to 35% in 2008. Over
the last 50 years in the U.S. there have been progressive
decreases in the percentage of individuals employed in
occupations that require moderate intensity physical
activity. It has been estimated that daily occupation-
related energy expenditure has decreased by more than
100 kcal per day, and that this reduction in energy
expenditure could account for a significant portion of
the increase in mean U.S. body weight for women and
men in the U.S.‘ The estimation of this reduction of 100
kcal/day or even more would have been adequately


compensated for by meeting the 2008 U.S. Department
ofHealth and Human Services Federal Physical Activi-
ties Recommendation of 150 minutes per week of
moderate intensity or 75 minutes per week of vigorous
intensity activity or the 2010 WHO Global recommen-
dations on physical activity for health'° (table I).
If data on children and adolescents are taken sepa-


rately, prevalence of overweight has shifted from
around 4% in the l960s up to 20% in 2008." As age-
adjusted prevalence of overweight has been quite stable
since the l970s (around 28% for women and 40% for
men), prevalence of overweight and obesity together is
currently around 64% for women and 72% for men in
the U.S." Currently, data seem to indicate that preva-
lence is starting to plateau in both children and adults".


Trends in Europe have been less consistent. In Spain,
prevalence of overweight and obesity has increased
steadily.” Median total body fat of 14-y old boys was
7.5% in 1985 and 14% in 1995 and mean waist circum-
ference increased significantly from 72.75 i678 cm in
1995 to 77.90i 1 1.89 cm in 2002. Currently, prevalence
data are tending to stabilize.“ In Europe, prevalence in
children and adolescents varies from less than 10% in
some of the Nordic countries up to more than 25% in the
Mediterranean countries and the UK.” In the analysis
performed by Church et al.', increases of obesity rates in
the US adults over the last 5 decades have been related to
the decrease in occupation-related physical activity.
Interestingly, estimated increase in body weight (since
1960) by means of the energy balance model closely
matches measured body weight of the National Health
and Nutrition Examination Surveys (NHANES) data
form 2003-2006.


There is quite a huge amount of supporting evidence
that trained people have less body fat percentage at all
ages than non-trained people." In the study by Kohrt et
al.," healthy older endurance-trained men and women
had similar body fat percentages (17% and 25%) to
healthy young sedentary subjects (18 and 24%, respec-
tively). For comparison, it is interesting to indicate that
older sedentary males and females had 28% and 38%
body fat, respectively. In the EXERNET study, a repre-
sentative study of Spanish elderly performed on non-
institutionalized subjects of both sexes, those who
walked regularly had a lower prevalence of overweight
and obesity than the sedentary ones. 14


European adolescents from the Healthy Lifestyle in
Europe by Nutrition in Adolescence (HELENA) study
who performed more than 60 minutes of moderate to
vigorous physical activity (MVPA) had less total and
abdominal fat (%) than their less active counterparts.“ In
the Spanish cohort of the European Youth Hearth Study
(EYHS) the risk of developing overweight/obesity was
nearly 4-fold in children who practiced less than
60 minutes of MVPA per day than their more active
counterparts. 1°


Exercise intensity has also been proposed as a main
factor influencing stem cell differentiation.” Based on
animal studies it has been hypothesised that vigorous


91




Table I
Physical activity recommendations by age group. Adaptedfrom WHO 2010"’


Age Group Physical activity recommendation Additional comments


5-17 years - Children and youth aged 5-17 should accumulate at least 60 minu-
tes ofmoderate- to vigorous-intensity physical activity daily.
Amounts ofphysical activity greater than 60 minutes provide addi-
tional health benefits.
Most of the daily physical activity should be aerobic. Vigorous-
intensity activities should be incorporated, including those that
strengthen muscle and bone*, at least 3 times per week.


For this age group, bone-loading activities
can be performed as part of playing
games, running, turning or jumping.
In order to improve cardiorespiratory and
muscular fitness, bone health, and cardio-
vascular and metabolic health biomarkers.


18-74 years ' Adults aged 18-64 should do at least 150 minutes of moderate-
intensity aerobic physical activity throughout the week or do at
least 75 minutes of vigorous-intensity aerobic physical activity
throughout the week or an equivalent combination of moderate-
and vigorous-intensity activity.
Aerobic activity should be performed in bouts of at least 10 minu-
tes duration.
For additional health benefits, adults should increase their mode-
rate-intensity aerobic physical activity to 300 minutes per week, or
engage in 150 minutes of vigorous-intensity aerobic physical acti-
vity per week, or an equivalent combination of moderate- and
vigorous-intensity activity.
Muscle-strengthening activities should be done involving major
muscle groups on 2 or more days a week.


For this age group, physical activity inclu-
des leisure time physical activity (for
example: walking, dancing, gardening,
hiking, swimming), transportation (e.g.
walking or cycling), occupational (i.e.
work), household chores, play, games,
sports or planned exercise, in the context
ofdaily, family, and community activities.
In order to improve cardiorespiratory and
muscular fitness, bone health, reduce the
risk ofNCDs and depression.


> 65 years ' Older adults should do at least 150 minutes of moderate-intensity
aerobic physical activity throughout the week or do at least 75
minutes of vigorous-intensity aerobic physical activity throughout
the week or an equivalent combination ofmoderate- and vigorous-
intensity activity.
Aerobic activity should be performed in bouts of at least 10 minu-
tes duration.
For additional health benefits, older adults should increase their
moderate-intensity aerobic physical activity to 300 minutes per
week, or engage in 150 minutes of vigorous-intensity aerobic phy-
sical activity per week, or an equivalent combination of moderate-
and vigorous-intensity activity.
Older adults, with poor mobility, should perform physical activity
to enhance balance and prevent falls on 3 or more days per week.
Muscle-strengthening activities, involving major muscle groups,
should be done on 2 or more days a week.
When older adults cannot do the recommended amounts of physi-
cal activity due to health conditions, they should be as physically
active as their abilities and conditions allow.


For this age group, physical activity inclu-
des leisure time physical activity (for
example: walking, dancing, gardening, hi-
king, swimming), transportation (e.g. wal-
king or cycling), occupational (if the indi-
vidual is still engaged in work), household
chores, play, games, sports or planned
exercise, in the context of daily, family,
and community activities.
In order to improve cardiorespiratory and
muscular fitness, bone and functional
health, reduce the risk of NCDs, depres-
sion and cognitive decline.


physical activity produces a sufficient mechanical stim-
ulation of the tissues in order that stem cells are turned
preferably into fat-free mass cells. In contrast, the ab-
sence of moderate-intensity physical activity or an
excessive energy intake favours stem cells turning into
fat mass cells.” There are two periods during growth in
which noticeable increases in adipocytes occur: infancy
and adolescence which are viewed as “critical” for the
enlargement of the adipose tissue and in turn for devel-
opment or prevention of obesity during growth. The
above-mentioned theory could be “crucial” to apply in
these periods in which it is also important to provoke a
higher accretion of bone mass, one of the aspects con-
sidered in the theory that is important for growth.
Professor Claude Bouchard had already proposed in


1990 that physical fitness is the main determinant of
health in the broad sense as defined byWHO.


Regarding metabolic risk, cardio-respiratory fitness
has been defined as a powerful market of health at all
ages.” Healthy children aged 9 and 10 years from the
EYHS study and adolescents aged 13 to 18 years from the
AVENA study with high cardio-respiratory fitness (clas-
sified in quartiles) had a significantly and progressively
better metabolic profile (index based on fasting trigly-
cerides, LDL-cholesterol, HDL-cholesterol and glucose
concentrations) than those with lower cardio-respiratory
fitness?“ But even in overweight subjects, cardio-respira-
tory fitness can make the difference. Separating the
adolescents from the AVENA study according to their
body composition, those overweight adolescents with high


92




Metabolic


profile


Unfavourable


Favourable


Low


Cardiorespiratory fitness
(quartiles)


¡:1 Overweight


I Non—overweight


* P < 0.05


High


Fig. I .—Relationship between cardiorespiratory fitness, body composition and metabolic risk in Spanish adolescents from the AVENA
study. Modifiedfrom". Footnote: Association between metabolic profile (computed with age- gender specific standardized values of
triglyeerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol andfasting glycaemia) and cardiorespiratoryfit-
ness quartiles in non—overweight and overweight Spanish adolescents. The higher is the metabolic profile the healthier. Weight catego-
ries were constructedfollowing the International Obesity Task Force-proposed gender- and age-adjusted body mass index cutofi
points. Data shown as mean and standard error of the mean. *Pfor trend in both overweight and non-overweight categories.


respiratory fitness had the same metabolic profile as the
normal weighted adolescents With 10W cardio-respiratory
fitness” (fig. l). The cardio-metabolic effects of exercise
in overweight and obese children (boys and girls) aged 9.4
years have been confirmed in the randomized control trial
mentioned below,“ and appear to be able to be general-
ized regardless of race (black and white), of pre-diabetes
or a family history ofdiabetes.
Trying to get a deeper understanding of the dose-res-


ponse of exercise in overweight and obese children, a
randomized control trial over 13 weeks was performed
in sedentary children in Georgia (U.S.).2' Children had
to perform 20 or 40 minutes of aerobic training daily
after school and were compared to a control group. Ge-
neral and visceral body fat, among other variables, was
reduced significantly in a dose-response gradient. The
increment of benefit between the control and low-dose
exercise conditions was larger than the additional be-
nefits observed between the loW- and the high-dose
exercise and both groups showed similar effects on
insulin resistance. As has been observed in several
studies, the lower the baseline physical activity status,
the greater will be the health benefit associated with a
given increase in physical activity (fig. 2).


Several studies have proposed that muscular strength
influences cardio-metabolic health independently and
reduces the risk of metabolic syndrome in addition to
cardio-respiratory fitness.” As We get older, bothVOzmax
and strength diminish. Regular exercise can at least


slow down this process. Both the percentage of body
fat and total body fat are more similar among trained
young and old people than among the un-trained.
Studies indicate that trained older people have a similar
fat mass to young un-trained people, and one that is
much lower than older un-trained people.


Regular daily physical activity contributes to energy
balance in several Ways. There is no doubt about that
every activity the human body performs is linked to
energy output. The higher the intensity and duration,
the more energy is spent. Additionally, adaptations to
training, i.e. increases in muscle mass, in capillaries,
etc, also contribute to raising the basal metabolic rate;
and after exercise, oxygen consumption (and conse-
quently energy output) remains high for a while until
the body has again reached homeostasis.”


Adipose tissue increases With age and obesity itself
has been proposed as a barrier for being physically
active. In a recent prospective study performed on
middle-aged women, both mean weekly physical
activity and MVPA measured by accelerometry
decreased significantly more in obese women over a
20-month period than in non-obese Women.“ Low
levels of growth hormone have been linked to obesity.”
Growth hormone is one of the hormones involved in
FFAmetabolism during exercise.


Several studies have shown that at all ages, boys are
more active than girls,” which tracks also into adult-
hood, adult men being more active than adult women in


93




DAILY ACTIWTIES


Diatributa your time!


I,
L’, _,,_ L


7% Sleep/Rest


All activltícs ore mccssnry,


HEALTHY LIFESTYLE PYRAMID


4 FACES + BASE
1.- Daily intake
2.- Daily activities
3.- Food pyramíd
4.- Hygiene and health
Base.- Healthy growth


School/Study ‘h,


CHILDREN AND ADOLESCENTS AGED 6 TO 18 YEARS


Fig. 2.—The importance of
the daily Schedule including
physical activity within a
healthy lifestyle for children
and adolescents."


all WHO Regions.“ In accordance, cardiorespiratory
fitness and strength values are higher in boys than in
girls, with more homogenous fitness levels among girls
than boys.” In Europe, data from the HELENA study
have revealed that 61% of the adolescent boys and 57%
of the girls presented a healthy cardio-respiratory
fitness (CRF) level,” a similar prevalence as found for
U.S. adolescents. There is consistency among the
studies that with increasing age there is a tendency in
both sexes to abandon physical activities and sports
(i.e. HBSC Study, AVENA study, HELENA Study).
According to the “Study of sport habits among school-
age children in Spain”? the main cause of not prac-
ticing physical activity is lack of time, a cause which
increases with increasing age (10% at ages 6-7 up to
32% at ages 16- l 8). It is essential to educate children in
learning how to distribute their time in order that
MVPA is included in their daily schedule,“ as it is
specifically indicated in the Healthy Lifestyle Pyramid
for children and adolescents (fig. 3). Additionally,
some other factors have been identified in relationship
to physical activity in youth. A physically active mother


(i.e. AVENA study) positively influences both boys and
girls. Lower physical activity among female friends
and perceived lack of safety in the neighbourhood re-
presents a negative influence among the girls.“
In relationship to relative risk reduction of coronary


heart disease, currently the evidence suggests that any
type of physical activity contributes to reducing the
risk, but that a high level of physical fitness reduces the
relative risk even more.”
In relation to body fat reduction, both strength and


aerobic exercise have been demonstrated to be effec-
tive, though aerobic exercise has a much higher impact
on body fat and body fat distribution.”
In relation to the improvement ofblood lipid profiles


and glucose metabolism, both types of exercise have
demonstrated similar efficacy” (table II).


Substrate utilization during exercise


The human body functions in accordance with the
laws of thermodynamics. If total food calories consu-


94




Benefit


\
Dose-
Response
Curve


Fig. 3 .—The dose-response
he best esti-A Z Sedem curse represents .


B Z Modeflïcïy Active mate af the relationship bet-
C Z Active ween physical activity (dose)and health benefit (respon-


B
Low


Baseline Activity Status


se). The lower the baseline
physical activity status, the


High greater will be the health be-
nefit associated with a given
increase in physical activity
(arrows A, B, and C).


med exceed daily energy expenditure, excess calories
accumulate and are stored as fat in the adipose tissue.”
In this situation, there are three ways to recover the
energy balance: increasing physical activity, decrea-
sing food intake or a combination of the two.


The energy expenditure for an activity depends on
its intensity and duration. Greater intensity will de-
mand greater energy expenditure per unit of time, and
longer duration greater total energy expenditure. These
aspects should be taken into account when a certain
amount of energy expenditure is required. Brooks and
Mercier” pointed out that the crossover point is the
power output at which energy from carbohydrate deri-
ved fuels predominates over energy from lipids, with
further increases in power eliciting a relative increment
in carbohydrate utilization and a decrement in lipid
oxidation. During rest and mild- to moderate intensity
exercise, lipids predominate as energy sources, espe-
cially in an endurance-trained state. Exercise at low
intensities (about 45% of V02 max) is accomplished
with lipids as the main substrate. In contrast, in hard
intensity exercise (about 75% of V02 max) carbohy-
drates become the predominant substrate. Lipids also
become the predominant substrate during recovery
from exercise that results in glycogen depletion.”


There is a consensus that in endurance trained
athletes fat oxidation rate is the highest in those activi-
ties performed at intensities around 65% of V02 max.“
This intensity corresponds to a value of approximately
70-75% of maximal heart rate, a value commonly re-
commended in exercise prescriptions for programmes


to improve cardiovascular fitness, but this intensity is
difficult to reach or to maintain for overweight or obese
untrained people. This was recently confirmed in the
PRONAF study, in which untrained overweight and
obese adult subjects followed a supervised training
protocol of 22 weeks. At the end of the study, even
after losing weight and body fat and improving their
fitness status, they were not able to perform at the
target intensity of 65%VO2max.27


There is a belief that to increase the use of fats as the
energy source, exercise intensity should be moderate or
low because the higher the exercise intensity the
greater the body’ s reliance on carbohydrates as an
energy source," but to reach a determined energy expen-
diture for maintaining or losing body weight, untrained,
overweight or obese people, should emphasize exercise
duration and progress to higher intensity exercise increa-
sing the energy expenditure which will also bring them
additional cardiovascular benefits.


sedentary or Sitting time as a risk factor
for health


The relationship between physical activity and
sedentary behaviour is still not clear in adults accor-
ding to the systematic review by Rhodes et al”. There
seems to be some evidence for a negative association
between TV viewing and general screen viewing with
physical activity, but no relationship is apparent for
computer use or general screen behaviour. Few studies


95




Table H
Effects ofaerobic training and strength training


on selected health parameter


. Aerobic ResistanceVariable . .exercise exercise


Bone mineral density TT TT


Body composition
% body fat ‘L‘L ‘L
Fat free mass H TT


Strength H TTT


Glucose metabolism
Insulin response to glucose ‘L‘L ‘L‘L
challenge
Basal insulin levels ‘L ‘L
Insulin sensitivity TT TT


Blood lipid levels
HDL—cholesterol T TH
LDL—cholesterol ‘L ‘LH


Heart rate at rest ‘L‘L H


Stroke volume TT H


Blood pressure at rest
Systolic ‘LH H
Diastolic ‘LH ‘LH


V02 max TTT TT


Endurance performance TTT TT


Basal Metabolic rate T TT


Footnote: The Arrows indicate the change produced by training. T =
increase; ‘L = decrease; H = little or no change. The more arrows, the
greater the effect. Modified from l l.


have analysed the combined influence of sedentary
behaviour and physical activity on obesity. In a recent
study on adults from the NHANES, low MVPA was
consistently associated with a higher risk of obesity,
regardless ofTV time or total sedentary behaviour?” Inter-
estingly, small differences in dailyMVPA (5-10 minutes)
were associated with relatively large differences in the
risk of obesity. Another study found that the strength of
the association between certain types of sedentary
behaviour and BMI was influenced by the time spent
performing physical activity. More than 60 minutes of
MVPA and less than 60 minutes of TV time per day
resulted in lower average BMI than the same TV time
but less than 60 minutes of MVPA.“ As data are still
scarce and even contradictory when analysing the same
subjects?!“ the combined effect of sedentary beha-
viour (and here differentiating between several ones like
TV time, reading, learning, etc) and physical activity
(here also differentiating betweenMVPA, active trans-
portation, etc.) deserves further study.


Currently, many common forms of behaviour in our
daily life involve sitting, for example, driving a car,
working at a desk, eating ameal at a table, playing video
games, watching TV, listening to music, etc, and they
can occupy a large part of our day, a tendency which is
predicted to increase further in the near future.” Seden-
tarism has begun to be studied as an independent risk
factor in the last decade. A recent study performed on
222,497 adults in Australia, concluded that prolonged
sitting is a risk factor for all-cause mortality even for
people who engage in the recommended 150 min/week
ofphysical activity, suggesting that what happens in the
remaining 6500 minutes of the week one is awake is
important for health.” Shorter sitting time and physical
activity are independently protective against all-cause
mortality not just for healthy individuals but also for
those with cardiovascular disease, diabetes, overweight
and obesity. In contrast, sitting periods of 4 to less than
8 hours/day, 8 to less than ll hours/day, and 1 l or more
hours/day, increased the mortality hazard ratios (1.02,
1.15, 1.4, respectively) after an average follow-up pe-
riod of 2.8 years. The association between sitting time
and all-cause mortality appeared consistent across the
sexes, age groups, body mass index categories, and
physical activity levels and across healthy participants
comparedwith subjects with pre-existing cardiovascular
disease or diabetes mellitus.”


General practitioners participating in the health care
system should be involved in a population-based inter-
vention to increase physical activity in the population?“
But the percentage of primary care physicians who in-
clude physical activity together with nutrition in a
combined lifestyle guidance to their patients is low, and
therefore we are possibly missing additional opportuni-
ties for obesity prevention.” Other settings such as
schools, workplaces and sports clubs have been proposed
for increasing physical activity in all age groups by
providing Optimal conditions for each subpopulation.“
These authors also express the urgent need of a coordi-
nated population-based intervention program for im-
proved health and reduced health expenses through
increased physical activity in the entire population,
which should be implemented at the national and interna-
tional level.


Conclusions and future prospects


There is scientific evidence that regular physical ac-
tivity reduces total mortality risk, mortality risk from
cardiovascular disease and other causes (independently
of weight loss). Physically active people have a lower
body fat percentage than inactive people, at all ages and
in both sexes. Overweight people who have a good
fitness level have better cardio-metabolic health than
non-fit overweight people and similar to lean but unfit
people. Physical activity and physical fitness seem to
exert synergic but independent effects on health-related
parameters. Sedentarism and hours ofphysical inactivity


96




seem to act as independent risk factors for health.
Aerobic exercise should be complemented with strength
training in both sexes and all age groups. An active life is
fun and helps in socialization. Several studies have
shown that it is never too late to start doing physical
activity; this means that intervention programmes
should focus on people of all ages, including the elderly.
Gender aspects should also be taken into account.


There is still a need for research to determine the
appropriate dose of exercise (time, duration and inten-
sity) in combination with sedentary behaviours and
other physical activities (i.e. transport) in the context of
ourmodern lifestyle in order to prevent obesity at all ages.
As has been mentioned above, obesity prevention has not
been a target issue of sport sciences until quite recently.
As public health measures have failed to stop the obesity
epidemic in both developed and developing countries in
the last 3 decades, there is clearly a need to change the
paradigm. The inclusion of sport scientists, physical
education teachers and otherprofessionals in themultidis-
ciplinary team Which should be responsible for drawing
the road map to prevent the increase of the obesity
epidemic effectively is a “must” from our point ofview.


Acknowledgments


We would like to acknowledge the support of the
Spanish Ministry of Health and Consumption Affairs
(CIBERobn CB 12/03/30038) and of the European
Comission funded project Active Age (EAC/S06/20l2).
Our thanks to the CEU San Pablo University, the Spanish
Nutrition Foundation and Coca Cola Iberia for organizing
the Obesity workshop in Segovia on November 30"‘ and
December 15‘, 2012 and contributing to the debate to find
solutions to the obesity epidemic. The ImFINE research
group belongs to the EXERNET network.


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