1. EXERCISE IN SECONDARY PREVENTION AND
CARDIAC REHABILITATION 0733-8651/01 $15.00 + .OO
EXERCISE IN WEIGHT
MANAGEMENT OF OBESITY
Paul Poirier, MD, FRCP(C), and Jean-Pierre Despres, PhD
Obesity has become an important burden 1960.'" In the United States and in Europe,
for the health system of industrialized coun- the incidence of being overweight and obese
tries and must be regarded as a serious public have reached epidemic proportions.2,61 Fur-
health issue in our time. Obesity is associated thermore, in the past decade, the percentage
with reduced life expectancy,38 and it is now of overweight and obese individuals in the
well recognized that increased body fat is United States and in some countries in Eu-
associated with heart disease, stroke, hyper- rope has increased to over 50% of adults aged
tension, dyslipidemia, type 2 diabetes melli- 20 years or older.61* Childhood obesity is
lo4
tus, gallbladder disease, osteoarthritis, sleep also an alarming problem, and opportunities
apnea and respiratory problems and numer- for physical activity have been lost in the
ous cancers (endometrial, breast, prostate and ~011th.~ Obesity in the youth may, in part,
colon)?, The American Heart Association have been created by structural changes that
has stated that obesity is a major modifiable have reduced the ability to make healthy
risk factor for heart disease.40, This article choices (ie, it is unsafe for children to play
reviews basic regulatory aspects of human outside). As many clinicians have often ob-
adipose tissue metabolism with implications served, weight reduction is difficult to
for the cardiologist in terms of exercise pre- achieve and even more difficult to maintain.
scription and the role of exercise and aerobic The reduced-obesity state is a self-perpetuat-
physical training in the management of obe- ing condition, wherein homeostatic mecha-
sity. nisms attempt to restrain further weight
loss.4l Obesity is a very complex chronic dis-
EPIDEMIOLOGY order that results from the interaction of ge-
notypic versus environmental factors2,l9 and
The incidence of obesity in the United involves multifaceted interactions among nu-
States has increased progressively since merous potential determinants (humoral,
neural, metabolic, psychological etc). Of great
Support has been provided by grants from The Qu6bec consequence, the relative risk of diabetes in-
Heart Institute and Le Fond de Recherche en Sant6 du creases by approximately 25% for each addi-
Qu6bec (PP), the Canadian Institutes for Health Research tional unit of body mass index (BMI) over 22
(J-PD), the Natural Sciences and Engineering Research
Council (J-PD), the Canadian Diabetes Association (J-
kg/m2,23and the practice of regular physical
PD), and the Heart and Stroke Foundation of Canada activities has been associated with the pre-
(J-PD). vention of diabetes&, and decreased mortal-
78
From the Department of Pharmacy, Laval University School of Pharmacy (PI'); and the Departments of Human
Nutrition 0-PD) and Research 0-PD), Institut de Cardiologie et de Pneumologie, Laval Hospital, Sainte-Foy, Que-
bec, Canada
CARDIOLOGY CLINICS
~~
VOLUME 19 NUMBER 3 AUGUST 2001 459

2. 460 POIRIER & DESP&S
ity in obese individuals and those with type able metabolic h e t e r ~ g e n e i t y . ~ ~ - ~ ~
Thus, the
2 diabetes.62, Likewise, insulin resistance is
111 challenge for the health care professional and
frequently associated with obesity, and it the cardiologist is to identify the overweight/
should always be kept in mind that insulin- obese individuals "at high risk" of cardiovas-
resistant individuals are at increased risk of cular disease (CVD).84 this regard, abun-
In
heart disease. It was recently reported in three dant literature published over the last 20
European cohorts (>17,000 men) followed for years has emphasized that abdominal obesity
over 20 years that nondiabetic men with was more important than excess fatness as a
higher blood glucose had a significantly correlate of the complications that had been
higher risk of death from cardiovascular and in the past considered as the consequence of
coronary heart disease.14 Therefore, asymp- obesity per se.20, 59, 90 It has been shown that
26,
tomatic glucose intolerance should no longer waist circumference is positively correlated
be considered a benign metabolic condition, with abdominal fat content and that it is the
and features associated with the insulin resis- most practical anthropometric measurement
tance syndrome should be taken seriously by for assessing a patient's abdominal fat con-
the medical community. Indeed, data from tent.86 has been recently suggested that two
It
the Quebec Cardiovascular Study have sug- simple clinical variables, waist circumference
gested that hyperinsulinemia resulting from (290 cm) and fasting plasma triglyceride con-
insulin resistance might be an independent centrations (22.0 mmol/L), might be useful
risk factor for coronary artery disease.%This as screening tools to unmask men character-
observation further stresses the importance ized by an atherogenic profile characteristic
of exercise and aerobic physical training as of the insulin-resistance syndrome.@ Box 1
effective interventions to increase insulin sen- shows some of the atherogenic profile fea-
siti~ity.35,
87,93,102 tures associated with abdominal obesity.
Obesity is age-dependent, with most sub-
jects increasing their fat stores when they be-
come older. Aging is associated with a decline ADIPOSE TISSUE METABOLISM AND
in physical activity that contributes to de- CARDIAC ADAPTATION IN OBESITY
creased exercise tolerance, decreased lean
body mass, and increased fat mass, with alter- Numerous enzyme pathways and hor-
ations in glucose and lipoprotein metabolism. mones are implicated in adipose tissue me-
Therefore, while aging, our population is be- tabolism.= Lipoprotein lipase (LPL) is synthe-
coming obese. This trend has important pub- sized in adipose tissue and, by hydrolysing
lic health implications, and proper nonphar- circulating triglyceride-rich lipoproteins, is
macologic management of obesity and important in the provision of fatty acids for
associated comorbidities is mandatory to de- their uptake and storage as triglycerides
crease the burden of obesity on the health
system. Unfortunately, data from the 1998 Be-
havioral Risk Factor Surveillance System
(BRFSS) indicate that two thirds of over-
weight persons trying to lose weight reported Box 1. Abnormalities
Associated with "At Risk"
using physical activity as a strategy for
Obesity (Insulin Resistance
weight loss, but only one fifth reported being
Syndrome)
active at the recommended levels.4,79
t Triglycerides
1 HDL cholesterol
DEFINITION t Apolipoprotein B levels
t Proportion of small, dense LDL
Overweight is defined as a body mass in- t Ratio of cholesteroVHDL cholesterol
dex (BMI; weight in kilograms divided by the
t Insulin
square of height in meters) of 25 kg/m2 to
t Glucose intolerance
t Fibrinogen
29.9 kg/m2 and obesity as a BMI 230 kg/m2.2 1' Factor VII activity
All overweight and obese adults aged >18 t Factor Vlllc activity
years with a BMI 225 kg/m2 are considered t TPA antigen
at risk for developing cardiovascular comor- t PAL1 antigen and activity
bidities.@However, it is important to empha- t C-reactive protein
size that obesity is characterized by a remark-

3. EXERCISE IN WEIGHT MANAGEMENT OF OBESITY 461
(TG).39 Insulin increases adipose tissue LPL.83 concomitant increase in lean body mass in
There are site differences in the regulation of these individuals. Higher cardiac output from
lipolysis in vitro and in vivo in normal- increased stroke volume and expanded intra-
In
weight subjects.63 normal-weight men, adi- vascular volume are features of the higher
pose tissue LPL activity is higher in the ab- metabolic demands generated by 0besity.5~~ 74
dominal wall than in the gluteal/femoral In obesity, left ventricular filling pressure and
region1'; in women, the opposite has been volume increase, shifting left ventricular func-
reported.ll. 1 5 t a 9 This may be of clinical impor- tion to the left on the Frank-Starling curve. A
tance because these site differences are more decrease in central blood volume accompan-
marked in women than in men, and might ies weight reduction and, when present, relief
explain why women have more fat in periph- of edema and dyspnea accompanies this im-
eral sites than men. The most important lipo- p r ~ v e m e n t . ~Of, importance, because of the
56 ~
lytic hormones in men are the catechol- need to move excess body weight, at any
amines, and their lipolytic effect is dependent given level of activity, the cardiac workload
upon the balance between a and p adrenergic is greater for obese subjects than for nonobese
stimulation. The hormonal regulation of lipol- individuals.
ysis, in particular the action of catechol-
amines, is impaired in obesity, and in vivo
studies have shown blunted catecholamine
induced lipolysis in obese subjects." Thus, ADIPOSE TISSUE METABOLISM AND
resistance to the lipolytic effect of catechol- EXERCISE
amines and a greater antilipolytic effect of
insulin are found in subjects with peripheral Whereas a-adrenergic mechanisms regulate
as compared to abdominal obesity.24How- lipolysis at rest, P-adrenergic activity controls
ever, in obese womenm,114 and fasting the lipolytic rate during exercise.1° Free fatty
adipose tissue LPL activities have not been acid (FFA) availability is maximal at 25% to
shown to be different between the abdominal 40% of Vozmax, and shifts in energy substrate
wall and gluteal regions, and the regulation mobilization and utilization occur as exercise
of the enzyme by insulin114and exercisem is intensity increases, particularly at intensities
also similar. This is due to increased 01-2 adre- above 70% to 80% of V ~ ~ m a Therefore,x.~~
noceptor function and decreased P-adreno- above a certain degree of intensity, the muscle
ceptor expression in the gluteal/femoral fat preferentially operates on glycogen stored in
cells.63, 91 These results are in contrast to
71, situ. However, aerobic physical exercise in-
what has been reported in normal-weight in- volves respiratory and circulatory systems as
dividuals, in whom adipose tissue LPL differs well as the enzymatic machinery adaptations
between fat depots. Therefore, the alterations that facilitate the muscle to work more effec-
in lipolysis associated with obesity favor tively. When adaptation to endurance exercise
weight maintenance. has taken place, the muscle is characterized
The p-adrenoceptors that mediate vasodila- by more oxidative enzyme activity and is
tation in adipose tissue are mainly the pl- now better equipped to work at low intensity
type, whereas in skeletal muscle, the pz-sub- for long duration and to use FFA as the main
type is mainly responsible for vasodilatation. substrate. There are also changes occurring at
Although there are differences between blood the site of lipid mobilization in adipose tissue
flow in adipose tissue and other organs, the depending on the physical training fitness
increment in blood flow with increasing adi- status." These include a more sensitive mech-
posity is not proportional to the increment in anism for activation of hepatic sensitive lipase
adipose tissue mass.66Increases in total body (HSL)? and in untrained individuals, an in-
fat result in higher total blood flow secondary crease in the lipolytic response of adipose
to the enlarged vascular bed, but in line with tissue to catecholamines after exercise both in
this, it is important to keep in mind that the ~ i t r o98, log, and in vivo.al Lipolysis is any-
~~
adipose tissue is less vascularized than lean thing but rate limiting during exercise, and is
tissue with increasing obesity. Accordingly, probably in excess of that required.92 Even if
the increase in systemic blood flow seen in p-blockade reduces the release of FFA from
obesity74cannot solely be explained by in- adipocytes, this reduction in energy supply
creased requirements due to adipose tissue to the exercising muscle is probably not clini-
perfusion, but most probably occurs by the cally re1e~ant.l"~

4. 462 POIRIER & DESPRl%
COMMON RISK FACTORS patients with high blood pressure are over-
ASSOCIATED WITH OBESITY weight, and hypertension is about six times
more frequent in obese than in lean
Dyslipidemia Moreover, weight gain in young people is an
important risk factor for subsequent develop-
As we have alluded to previously, some ment of hypertension.84Weight reduction is
very obese individuals may nevertheless one of the rare antihypertensive strategies
show a fairly normal metabolic risk factor that decreases blood pressure in normoten-
profile, whereas others may present all the sive as well as hypertensive persons.2, As
features of an atherogenic and diabetogenic little as a 10% reduction in body weight can
metabolic p r ~ f i l e ~ ~ (see Box 1). Indeed,
64 - ~ ~ , decrease blood pressure among obese hyper-
there is remarkable metabolic heterogeneity tensive patients.18ra It has also been suggested
among obese subjects, and the presence of that an exaggerated blood pressure response
visceral obesity generally worsens the meta- to exercise may be a better predictor of tar-
bolic portrait. Accumulation of visceral fat get organ damage than resting blood pres-
has been associated with type 2 diabetes mel- sure.47, Again, it has been reported that
50
litus, hypertension, and coronary artery dis- weight loss could decrease blood pressure
ease.65For instance, disturbances in lipopro- and heart rate measured both at rest and at
tein metabolism, coagulation systems, plasma all exercise intensities.16 Interestingly, it has
insulin-glucose homeostasis and an elevated been shown that weight reduction induced
blood pressure have all been reported in sub- by a modest exercise prescription and by a
jects with visceral obesity=, =, 48, 67, 97, 97 (see hypocaloric diet could decrease left ventricu-
Box 1). The dyslipidemic profile commonly lar mass, which is a well-recognized CVD risk
associated with abdominal obesity has been factor, regardless of blood pressure in obese
shown to include high TG, low HDL choles- subjects."
terol and elevated apolipoprotein B concen-
trations as well as an increased proportion of
small, dense LDL. All these features of an
atherogenic dyslipidemic profile can be im- INFLUENCE OF PHYSICAL ACTIVITY
proved by the incorporation of regular exer- ON ADIPOSE TISSUE METABOLISM
cise in daily life activitie~.,~, 33 Fat loss
28,
through dieting and/or exercise produces There is an inverse relationship between
comparable and favorable changes in HDL the amount of daily physical activity and
cholesterol and its subfractions HDL, and body weight. Exercise requires energy, and
HDL, as well as in TG.43, Furthermore, the two main sources of fuel for muscle con-
long-term aerobic exercise training could traction are carbohydrates (CHO) and lipid.
even normalize the metabolic risk profile of The major source of lipid energy for muscle
obese subjects despite the fact that subjects is the TG stored in adipose tissue, but avail-
were still classified as "obese" at the end of able as FFA. Exercise is one of the most potent
the prograrn.'O0 In addition, the improvement physiological stimuli for lipolysis; it is higher
in the plasma lipid profile observed with the during exercise in trained subjects than that
use of aerobic exercise in patients with type 2 reported during critical illness57 even after
or
diabetes is also probably mediated mainly 84 hours of tarv vat ion.^^ In obesity, the ex-
through body fat lO9 Of interest, exercise panded adipose tissue mass provides abun-
seems to confer no additional benefit to dant lipid substrates to meet the needs of
weight loss when hemostatic factors are con- increased energy expenditure associated with
~idered.~~ exercise. For instance, an 80-kg man with 25%
body fat (20 kg) has stored in adipose tissue
approximately 180,000 calories. Thus, only 1
Hypertension kg of adipose tissue TG would be sufficient
to provide energy for several marathons. Nu-
Although it is well accepted that hyperten- merous factors associated with obesity, that
sion is a major CVD risk factor, an elevated is, gender, body fat mass, adipose tissue distri-
blood pressure is an underrecognized and bution, and number and size of adipose cells,
therefore an undertreated condition.' It is im- contribute to the eventual response to exercise
portant to keep in mind that obesity and training. For instance, in response to a 20-
hypertension often coexist; the majority of week exercise training program, Tremblay et

5. EXERCISE IN WEIGHT MANAGEMENT OF OBESITY 463
a199reported that men, matched for body fat kJ (500 kcal)/d. Although aerobic exercise
mass, with a high fat cell size, lost six times alone produces a modest weight reduction,
more body fat mass (loss of 4.4 kg) than men generally 2% to 3%, increased physical activ-
with small adipose cells (loss of 0.7 kg). Of ity is extremely important in sustaining the
note, women in this study with either high or weight-reduced state.36, lol An intervention
73,
low fat cell size did not lose body fat. There- combining behavior therapy, a low-calorie
fore, it seems that there might be a certain diet, and increased physical activity is proba-
morphology (size + number of cells + distri- bly the most successful management ap-
bution) that may explain, at least to a certain proach for weight loss and weight mainte-
extent, the susceptibility to lose weight in nance. In overweight/obese patients who
response to an exercise p r ~ g r a mDuring ex-
.~ have reached the proper ”readiness” state,
ercise, the lipolytic rate has been shown to be this approach should be emphasized and sus-
higher in abdominal subcutaneous than in tained for a few months before considering
gluteal/femoral subcutaneous adipose tissue, other strategies such as pharmacotherapy.
especially in women,’O whereas there is no Weight loss programs that result in a slow
gender difference at rest. Women also exhibit but steady weight reduction, eg, 1 pound to
less lipolysis during exercise than 32 2 pounds per week, may be more effective
and this phenomenon may help explain why long-term than those that result in rapid
men decrease body fat more efficiently with weight losses.1o5 Indeed, behavioral strategies
physical training than do women.30, Another
99 reinforcing changes in diet and physical activ-
important clinical issue that should be kept ity can produce weight loss in the range of
in mind is that when exercise is considered 10% over a period of 6 months in obese
in the management of obesity, the weight loss adult^.^ Unfortunately, long-term follow-up
may be accompanied by an increase in appe- results of patients undergoing behavior ther-
tite. Careful attention should be given to this apy show a return to baseline weight for the
adaptation that may compromise weight majority of subjects in the absence of contin-
10ss.37 ued behavior intervention.80, lo7These nega-
lo6,
tive results reinforce the importance of incor-
porating daily exercise in the lifestyle of
EXERCISE PRESCRIPTION overweight/obese patients. Because of the
presence of high left ventricular filling pres-
The minimal objectives of a weight loss and sure and, as in type 2 diabetes, left ventricular
management program are: to prevent further diastolic dysfunction, the usually recom-
weight gain, to reduce body weight, and to mended exercise prescription may be inap-
permanently maintain a lower body weight. propriate for the obese i n d i v i d ~ a l sObesity
.~~
Regular physical activity is a well-recognized is associated with persistence of elevated car-
tool for long-term weight maintenance be- diac filling pressures during exercise? l3 and
cause it contributes to increased energy ex- the average left ventricular filling pressure
penditure through a caloric deficit (although rises with exercise similarly (about 20 mm
generally small) contributing to weight loss.1o2 Hg) after weight loss. Of interest, reduced
Although epidemiologic studies have sug- ventricular compliance characterized by left
gested that weight cycling could be associ- ventricular diastolic dysfunction during exer-
ated with an elevated risk of death from cise does not always regress with weight
CVD,17,53 there is little evidence to support 10ss.5.13
the view that weight cycling could be related An important issue is whether one needs to
to an increased prevalence/risk of coronary focus on exercise intensity in order to achieve
artery disease.77Patients should have their metabolic improvements and reduce the risk
BMI and levels of abdominal fat measured of coronary heart disease in obese individu-
with goals of weight reduction established to als. Concomitant with diet therapy, low-inten-
favorably impact health outcomes, including sity training of 30% to 50% bo2max of long
the risk of a first or recurrent CVD event.loO, duration (90 minutes to 240 minutes) and
112 Simply stated, weight reduction depends high frequency has been proposed for losing
upon energy intake compared to energy ex- body fat. This recommendation is based on
penditure. Approximately 1 pound per week the premise that the dominant fuel for energy
can be lost with no change in physical activity during the first 20 minutes of exercise is gly-
if caloric intake can be reduced by only 2100 cogen; exercising more than 30 minutes will

6. 464 POIRIER & DESPRES
increase the usage of fat Of note, as (Borg scale) seem to predict the degree of
obese people have a lower mechanical effi- effort of walking.70In the clinical setting, it
ciency (defined by the relation between oxy- is most of the time impractical to measure
gen uptake and external work), the most ap- Vo,max before giving advice on physical ac-
propriate approach to prescribe exercise is to tivity. Nevertheless, measuring heart rate after
base work intensity on the oxygen cost rela- a 4- to 6-minute walk may be a simpler way
tive to Vo2max.46 This notion has clinical im- to judge the relative cost of walking. Heart
portance, since subjects with obesity usually rate exceeding 100 beats per minute during
get standard recommendations to lose weight walking is generally associated with an exer-
by decreasing food intake and increasing cise intensity of about 50% Vo,max (Fig. 1).
physical activities. For instance, normal- Obese individuals who enjoy walking and
weight subjects use about 35% Vo,max when who can tolerate this form of physical activity
walking at a self-selected, comfortable pace.', without too many unpleasant side effects
This activity is generally considered a conve- should certainly continue to do so. In general,
nient and mild form of training. It is accessi- however, recommendations should focus on
ble to everyone and carries a low risk of training regimens, not generating pain over
injuries, which are increased in obesity be- time, otherwise compliance will obviously be
cause of the burden of extra weight on the impaired. It is also important to keep in mind
joints. Joint considerations should, however, that various aerobic training modalities
not limit physical activity, since exercise com- (walking, cycling, swimming) may have a dif-
bined with diet leads to improvement in pain, ferent impact on weight loss. Notably, swim-
disability, performance and gait in obese ming protocols have generated rather disap-
older adults with knee osteoarthritis." pointing results regarding weight
However, individuals often find the exer- Health care professionals should also empha-
cise prescription difficult to follow, since they size that heart rate should be properly as-
get extremely tired while walking at the pace sessed at the wrist level, because the carotid
recommended by the clinician. Vozmax and pulsation may be difficult to find in obese
heart rate during brisk walking is higher in patients. It is also very important to inform
obese than in normal-weight i n d i v i d ~ a l s . ~ ~ patients about the results to be expected
the
Thus, even walking may represent a difficult from the recommended exercise regimen in
exercise modality for obese individuals, since order to avoid unrealistic expectations on
they can use as much as 56% Vo,max (some weight loss. Body weight normalization
using between 64% to 98% Vo,max) to meet should obviously not be the target, but rather
the demand of such an activity compared to some weight loss associated with improve-
only about 35% in normal-weight subjects. ments in the risk factor profile. As an exam-
Therefore, long and brisk walks should not ple, a working model of an algorithm for the
be regarded as low-intensity forms of training
for obese people in general. Since the average
work load during a day causes fatigue if it
100
exceeds 30% to 40% Vozmax,'2 it seems natu-
ral that walking for exercise may be too de-
manding for many obese patients. In addi- 80
tion, walking outdoors can be demanding
because of uneven or slippery surfaces, and ii
E
heavy outdoor clothes during the autumn ON
*>
and winter seasons add to body weight. s
Moreover, severe obesity may impair the abil-
ity to properly walk, especially when the obe-
sity is of the gynoid form. Gluteal fat in-
creases the friction on clothing and skin,
making it even more unpleasant to walk. This 80 90 100 110 120 130 140 150
common problem is often neglected in clinical Heart rate (beatslminute)
practice. Increasing obesity and age, abnor-
mal gait pattern, degenerative pain, friction Figure 1. Simple regression between percentage of
of clothes and skin problems may increase Vo2max and heart rate during walking in obese women.
r = 0.63; P < .0001. (Adapted from Mattsson E, Larsson
the relative oxygen cost. Clinical assessment UE, Rossner S: Is walking for exercise too exhausting for
may be difficult, because neither BMI, walk- obese women? Int J Obes Relat Metab Disord 21:380-
ing speed rate, perceived exertion nor pain 386, 1997; with permission.)

7. EXERCISE IN WEIGHT MANAGEMENT OF OBESITY 465
detection and management of the high-risk cutaneous abdominal and gluteal/ femoral
obese individuals is suggested in Figure 2. adipose tissue regions.7'j Thus, a reduction of
body weight to a level that would still be
considered as overweight is accompanied by
Reduced-0bese Individuals a decreased basal rate of lipolysis but by an
improved catecholamine-stimulated lipolysis
A better understanding of adipose tissue in vitros Insulin sensitivity is also increased
metabolism in weight-reduced obese subjects after weight reduction under isocaloric main-
is important because of the high recidivism. tenance of the reduced-obese state.l13,115 Al-
Weight loss by hypocaloric diet decreases li- though most of the in vivo action of insulin
polysis and fat oxidation, adaptations that is accounted for by its effect on the skeletal
may predispose individuals to weight re- the ability of increased insulin sensi-
gaining. The blunted utilization of fat as fuel tivity to predict weight regain in reduced-
during a 60-minute bout of exercise at 50% obese is partly explained by the
Vo,max contributes to a positive fat balance effects of insulin on adipose tissue. Suggested
and possibly weight gain in formerly obese risk factors for body weight regain include:
individuals.ssHowever, studies of adipose tis-
sue function in vitro have shown that the Increased insulin sensitivity
addition of exercise training to a hypocaloric Low resting metabolic rate for a given body
diet counteracts the decline in lipolytic re- size and composition
sponsiveness, fat oxidation and resting meta- Low ratio of fat to carbohydrate oxidation
bolic rate in weight-reduced postmenopausal (ie, high respiratory quotient)
women.76, Moreover, the lipolytic adapta-
88 Low levels of physical activity
tions are of the same magnitude between sub- Caloric intake
Risk factor
risk factor
according
Further assessment of the risk profile
BMI > 25 kg/m2
Low risk
1
High risk
I
I .
profile management
with emphasis on the
Figure 2. Working model for an algorithm allowing effective and
simple identification by health professionals of the high-risk form
of overweightness and obesity among individuals asymptomatic for
coronary artery disease (CAD). BMI = Body mass index; TG =
triglycerides.

8. 466 POIRIER & DESP&S
SUMMARY agement program that was designed for
obese children.",95
Obesity is a chronic metabolic disorder as- Thirty to 45 minutes of physical activity of
sociated with CVD and increased morbidity moderate intensity, performed 3 to 5 days a
and mortality. When the BMI is 2 30 kg/m*, week, should be encouraged. All adults
mortality rates from all causes, and especially should set a long-term goal to accumulate at
CVD, are increased by 50% to 100%. There is least 30 minutes or more of moderate-inten-
strong evidence that weight loss in over- sity physical activity on most, and preferably
weight and obese individuals improves risk all days.79Public health interventions pro-
factors for diabetes and CVD. Additional evi- moting walking are likely to be the most
dence indicates that weight loss and the asso- successful. Indeed, walking is unique be-
ciated diuresis reduce blood pressure in both cause of its safety, accessibility, and popular-
overweight hypertensive and nonhyperten- ity. It is noteworthy that there is a clear dis-
sive individuals, reduce serum TG levels, in- sociation between the adaptation of cardiore-
crease high-density lipoprotein cholesterol spiratory fitness and the improvements in the
levels, and may produce some reduction in metabolic risk profile that can be induced by
low-density lipoprotein cholesterol concentra- endurance training programs. It appears that
tions. Of interest, even if weight loss is mini- as long as the increase in energy expenditure
mal, obese individuals showing a good level is sufficient, low-intensity endurance exercise
of cardiorespiratory fitness are at reduced risk is likely to generate beneficial metabolic ef-
for cardiovascular mortality than lean but fects that would be essentially similar to
poorly fit subjects.62Insulin and catechola- those produced by high-intensity exercise.
mines have pronounced metabolic effects on The clinician should therefore focus on the
human adipose tissue metabolism. Insulin improvement of the metabolic profile rather
stimulates LPL and inhibits HSL; the opposite than on weight loss alone. Realistic goals
is true for catecholamines. There is regional should be set between the clinician and the
variation in adipocyte TG turnover favoring patient, with a weight loss of approximately
lipid mobilization in the visceral fat depots of 0.5 to 1pound per week. It should be kept
and lipid storage in the peripheral subcutane- in mind that since it generally takes years to
ous sites. The hormonal regulation of adipo- become overweight or obese, a weight loss
cyte TG turnover is altered in obesity and pattern of 0.5 or 1 pound per week will re-
is most marked in central obesity. There is quire time and perseverance to reach the pro-
resistance to insulin stimulation of LPL; how- posed target. However, the use of physical
ever, LPL activity in fasted obese subjects is activity as a method to lose weight seems
increased and remains so following weight inversely related to patients' age and BMI
reduction. Catechol- and directly related to the level of education?
amine-induced lipolysis is enhanced in vis- Thus, public health interventions helping
ceral fat but decreased in subcutaneous fat. these groups to become physically active re-
Numerous adaptive responses take place main a challenge61and further emphasize the
with physical training. These adaptations re- importance of the one-on-one interaction be-
sult in a more efficient system for oxygen tween the clinician/health care professional
transfer to muscle, which is now able to better with the obese individual "at risk" of CVD.
utilize the unlimited lipid stores instead of This notion is critical, as it has been shown
the limited carbohydrate reserves available. that less than half of obese adults have re-
In addition, the reduced adipose tissue mass ported being advised to lose weight under
represents an important mechanical advan- the guidance of health care professionals.",
tage, allowing better long-term work. Gender
differences have been reported in the adapta-
tion of adipose tissue metabolism to aerobic
exercise training. Physical training helps References
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ronment that predisposes reduced-obese sub- 1. The sixth report of the Joint National Committee on
jects to regain weight. An exercise program prevention, detection, evaluation, and treatment of
high blood pressure. Arch Intern Med 1572413-
using weight resistance modalities may also 2446, 1997
be included safely, and it improved program 2. Clinical Guidelines on the Identification, Evaluation,
retention in a multidisciplinary weight man- and Treatment of Overweight and Obesity in

9. EXERCISE IN WEIGHT MANAGEMENT OF OBESITY 467
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Health. Obes Res Suppl2:51S-209S, 1998 accumulation and its relation to plasma hemostatic
3. Executive summary of the clinical guidelines on the factors in healthy men. Arterioscler Thromb Vasc
identification, evaluation, and treatment of over- Biol 16368-374,1996
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