Blood
Pressure
in Obese
Adolescents:
Effect
of Weight
Loss
Albert
P. Rocchini,
MD,
Victor
Katch,
EdD,
Judith
Anderson,
PhD,
Judith
Hinderliter,
MS,
Daniel
Becque,
MS,
Monica
Martin,
MD,
and
Charles
Marks,
MS
From the Section of Pediatric Cardiology, Department of Pediatrics, and the Department of Kinesiology, Division of Physical Education, University of Michigan, Ann Arbor, Michigan
ABSTRACT. The BP distribution of a group of 72 obese
adolescents was determined both before and after
weight loss. Weight loss was produced by a program of
caloric restriction and behavior change alone (n = 26)
or with a combination of caloric restriction, behavior
change, and exercise (n
=
25). It was demonstrated thatobese adolescents have a BP distribution that is skewed
1 SD to the right of normal (P < .01), and that with
weight loss this distribution was no longer different
from that of the general population. It was also shown
that a weight loss program that incorporates exercise
and caloric restriction produces the most desirable
ef-fect on BP reduction (ie, greatest decrease in resting systolic BP and greatest decrease in exercise diastolic
and mean BP ).Finally, it was demonstrated that obese
adolescents have structural changes present in the
fore-arm resistance vessels and that these structural
changes are reversed to the greatest extent in the
weight loss program that includes exercise. Pediatrics
1988;82:16-23; blood pressure, exercise, weight loss,
caloric intake restriction, diet, behavior change, adoles-cent obesity.
High BP has been associated with obesity in both children and adults. Lauer et al’ showed that, of those children in the upper decile of body weight, 29% had systolic BPs and 28% had dias-tolic BPs greater than the 90th percentile for age and sex. Similar results have been reported by Webber et al,2 Voors et al,3 and Aristimuno et al.4 Although all of these studies have been focused on evaluating the determinants of BP in the gen-eral population, there have been few studies in
Received for publication June 29, 1987; accepted Sept 9, 1987.
Reprint requests to (APR.) Pediatric Cardiology, Room
FillS, Box 0204, University ofMichigan Medical Center, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0204.
PEDIATRICS (ISSN 0031 4005). Copyright © 1988 by the
American Academy of Pediatrics.
which a direct evaluation of resting and exercise
BP in a group of obese adolescents has been
at-tempted. In addition, there is only limited infor-mation regarding whether weight loss in the
ad-olescent can reduce BP,5’6 and there is no
infor-mation regarding whether the method of
achiev-ing weight loss has any effect on the magnitude
of BP reduction associated with the weight loss. The present study was, therefore, undertaken to
determine the BP distribution of a group of obese
adolescents both before and after weight loss and
to determine whether weight loss produced by a program of caloric restriction, behavior change, and exercise causes a greater reduction in BP
than that which is associated with a weight loss
program composed of caloric restriction and behavior change alone.
MATERIALS
AND
METHODS
A total of 72 obese adolescents (34 boys and 38
girls) with a mean age of 12.6 years (range 10 to
17 years) and ten nonobese adolescents with a
mean age of 12.2 years (range 10 to 14 years) were
studied. All of the ten nonobese adolescents were
previously described by us, whereas only 30 of the
72 obese adolescents were previously described.7
Obesity was defined as weight for height
greater than the 75th percentile for age and sex and triceps and subscapular skin folds greater
than the 80th percentile for age and sex.8
To study the effect of weight loss on BP, the
subjects were randomly assigned to one of three
treatment groups. A group of26 obese adolescents were assigned to and 22 completed a 20-week weight loss program consisting of diet and behav-ior change (diet group). The diet was a
designed to produce a weight loss of
approxi-mately 2.2 kg (1 lb)/wk. The behavior change
com-ponent ofthe program was composed ofa one-hour
class each week for 20 weeks that consisted of
record keeping, stimulus control, changing eating behavior, and reinforcement of altered behavior.
A total of 25 obese adolescents were assigned
to and 23 completed a 20-week weight loss pro-gram composed of diet, behavior change, and
ex-ercise (exercise group). The diet and behavior
change were as previously described. The exercise program consisted ofthree 1-hour exercise classes per week for 20 weeks. Each class included warm-up exercise and aerobic activity. The warm-up
ex-ercises consisted of progressive stretching
tech-niques and muscle strengthening for ten minutes
at the beginning of each exercise class. Aerobic
activities were used for total body activities
de-signed to maintain heart rate for at least 40
mm-utes at greater than 70% to 75% of maximal
ex-ercise heart rate. The duration ofexercise was
mi-tially 15 minutes and was progressively increased
to 40 minutes. Specific activities included
walk-ing,jogging, swimming, aerobic dance, soccer, and
other recreational activities. To ensure adequate supervision and motivation, there were two to four adolescents per exercise leader.
A total of 22 obese adolescents were assigned
to the control group and 18 completed the 20-week
study and received no weight loss program for 20
weeks. There were no significant differences be-tween the three treatment groups with respect to age or gender. The 72 obese adolescents were
tested before and 63 were tested after the three
20-week programs. The ten nonobese adolescents were only tested once.
Experimental
Protocol
All subjects were admitted overnight to the
clinical research center at the University of
Mich-igan Hospitals. All adolescents fasted after 10 PM
the evening preceding the study and were main-tamed in a supine position after 4 AM the morning of the study. A heparin lock was inserted at 7:30
AM while the adolescents were supine. The heart
rate and arterial pressure during the 30-minute
rest period were the values recorded. Mean
ar-terial pressure also was calculated as diastolic
pressure plus one-third pulse pressure.
All adolescents also performed a multistaged
discontinuous exercise test in the sitting position
using an electronically braked bicycle ergometer.
The first two stages were done at 15 and 30 W.
Subsequent work stages were increased by 30-W
increments until the adolescent could no longer
turn the pedals at 60 rpm. Each work rate was
performed for five minutes and there was a
three-minute rest period between every other work
stage. The following measurements were taken
during each stage ofexercise: BP, heart rate, tidal
volume, oxygen uptake, and carbon dioxide pro-duction. Gas exchange was continuously moni-tored by an online measurement of ventilation rate (pneumotachometer), percentage of carbon dioxide (Beckman carbon dioxide analyzer), and percentage of oxygen (Applied Electrochemistry oxygen analyzer). Following the exercise test, all
adolescents were given lunch and then had body
composition (percentage of fat) measured by
hy-drostatic weighing as described by Katch et al.9 Finally, forearm blood flow was measured in the
right arm using a mercury in Silastic strain gauge
plethysmography and venous occlusion.’0 During
measurements of forearm blood flow, circulation
to the hand was arrested by inflating a cuff around the wrist to the point of suprasystolic pressure.
Initially, four blood flows were recorded every 10
seconds and an average value was calculated
while BP was measured in the left arm with a
Critikon monitor. Forearm vascular resistance
was calculated by dividing mean arterial pressure
by forearm blood flow (milliliters per minute per
100 mL of forearm volume). Minimum forearm vascular resistance was assessed by inflating the cuff on the upper arm to above systolic pressure
for ten minutes to occlude arterial flow while
hay-ing the adolescent squeeze a ball ten times. After
release of the arterial occlusion, forearm blood flow was measured after 5 seconds and every 10
seconds thereafter for three minutes. BPs were
measured at approximately 30-second intervals
after release of the arterial occluding cuff. The peak blood flow recorded after release of arterial occlusion was used to calculate the minimal fore-arm vascular resistance.
Laboratory
Procedures
Weight was measured in kilograms using a beam balance scale and height was measured to the nearest 0. 1 cm using a stabilometer.
Statistical Analysis
Statistical analysis was performed using an
analysis of variance to compare differences
be-tween the nonobese and obese adolescents. To compare differences among the three obese groups at the end of the randomized 20-week treatment,
a one-way analysis ofyariance with a Scheff#{233}pro-cedure for multiple comparisons on the pretest
minus posttest values was used. Systolic and
dias-tolic BP values were adjusted for age and sex by
30
PRE WEIGHT LOSS PROGRAM
N- 72
25
20
POST WEIGHT LOSS PROGRAM N=63
1J=diet z-1.O9 1.1
r-
exercise z-1.O6 .70EJcontroi z-1.03 .98
EJ=z-.451.1
= 2 =0.02 .72
L::J- =1.21 1.1
15
10
5
-2 -1 0 1 2 3 -2 -1 0 1 2 3
z SCORE z SCORE
Fig 1. Distribution of systolic BP in obese adolescents compared with those rates in
the Second National Health and Nutrition Examination Survey before and after
20-week weight loss program. All values presented are means ± SD. Diet, diet and
be-havior change group; exercise, diet, exercise, and behavior change group; control, obese
control group.
z
0
I-4 -J
0 I’-0
according to the formula z
=
x - i/SD, where x=
measured BP,=
mean ofthe expected BP for age and sex (the second National Health and Nu-trition Examination Survey data),8 and SD=
standard deviation of the expected BP for age and sex. Linear regression analyses were performed prior to the weight loss program using z score
sys-tolic and diastolic BP values as dependent van-ables with total body weight, percentage of fat, heart rate, and forearm blood flow and resistance
as the independent variables. Where appropriate,
nonparametnic for pairwise comparisons (the Wil-coxon, signed-rank test, and the Friedman two-way analysis of variance) were performed.
RESULTS
We observed that, when compared with the ten
nonobese adolescents, the 72 obese adolescents had significantly higher systolic, diastolic, and mean arterial pressures. Because BP is affected in childhood by both age and sex, to compare our group of obese adolescents with the adolescent population in general, a z score BP distribution was calculated for obese adolescents using data from the second National Health and Nutrition Examination Survey.8 We observed that the obese adolescents had both a systolic and diastolic BP distribution that was significantly skewed to the right (P < .01, Figs 1 and 2). Both the systolic and
diastolic BP distributions for the obese
adoles-TABLE 1. Anthropo morphic and Resting Hemodynamic Data*
Variables Adolescents
Nonobese (n = 10) Obese (n = 72)
Age (yr) 12.1 ± 3 12.6 ± 3
Wt (kg) 42.2 ± 13 75.4 ± 161
Height (cm) 148.2 ± 10.4 156 ± lit
%Fat 20±7 44± 71:
BP (mm Hg)
Systolic 104 ± 6 132 ± 131:
Diastolic 60 ± 7 78 ± 121:
Mean 74±8 97± 101:
z
scoreSystolic (mm Hg) 0.20 ± 0.54 1.06 ± 0.931:
Diatolic (mm Hg) 0.59 ± 0.78 0.94 ± 1.2
Heart rate (beats/ 77 ± 6 88 ± 121:
mm)
* Results are given as means ± SD.
tP < .05.
1:P < .01.
cents were skewed greater than 1 SD to the right
of the children in the second National Health and
Nutrition Examination Survey8 (systolic BP 1.06
±
0.93 and diastolic BP 0.94 ± 1.2). We alsoob-served a significant linear correlation between
the z score BP values and totaly body weight (r
=
.49 systolic; r=
.62 diastolic, P < .01) and fatweight (r
=
.62 systolic; r=
.77 diastolic, P <.01). No significant relationship was observed be-tween lean body weight and the z score BP (r
=
addi-25
J-diet z-.971.2
20
=exercise z=.941.O
D=control z=931.1
D-z-.41.2
D-z-.15.7
D-z= .931.2
-2 -1
15
10
5
z SCORE z SCORE
Fig 2. Distribution of diastolic BP in obese adolescents compared with those rates in
the Second National Health and Nutrition Examination Survey before and after a
20-week weight loss program. All values presented are means ± SD. Diet, diet and change
group; exercise, diet, exercise, and behavior change group; control, obese control group.
3
TABLE 2. Anthropomorphic and Hemodynamic Data Before and After 20-Week Weight Loss Program (n = 63)*
Variables Obese Control Group
(n = 18) Preprogram Postprogram
Obese Diet Group
(n = 22)
Preprogram Postprogram
Obese Exercise Group (n = 23)
Preprogram Postprogram
Wt (kg) 73 ± 14 77 ± 16 73 ± 14 70.5 ± 15t1: 72 ± 12 69.6 ± lltt Height (cm) 159 ± 12 162 ± i2t 157 ± 8 161 ± 8t 159 ± 10 163 ± 8t
%Fat 41±6 42±8 43±8 39±8t1: 41±6 35±4t1:
Right forearm 26.3 ± 2.9 26.6 ± 2.9 26.9 ± 2.2 26.6 ± 2.3 26.1 ± 1.1 25.7 ± 1.3
circumference (cm)
BP
126 ± 13 130 ± 14 127 ± 14 117 ± 8tt 129 ± 9 113 ± 6t1:
78±10 77±15 80±11 68±9t1: 79±11 66±7t1:
90±11 93±12 95±9 82±8tt 95±10 83±7t1:
84±14 85±10 88±12 79±11 88±13 72±iltt
30 PRE WEIGHT LOSS PROGRAM N#{149}72
POST WEIGHT LOSS PROGRAM N:63
z
0 4 -J
0.
0
0. U.
0
Systolic (mm Hg)
Diastolic (mm Hg)
Mean (mm Hg)
Heart rate (beats/mm)
* Results are given as means ± SD.
t P < .05, pre- v postprogram.
1:P < .05, Control group v obese diet or exercise group.
§P < .05, diet group v exercise group.
tion to having an elevated BP, the obese children
also had tachycardia when compared with our
nonobese group (P < .01, Table 1). There also was a significant positive correlation between resting
heart rate and z score systolic and diastolic BP
values (r = .39, P < .05 systolic; r = .48, P < .01 diastolic).
The effect of weight loss on BP and heart rate was evaluated by comparing the changes that oc-curred after 20 weeks of weight loss induced by either diet and behavior change alone or in
com-bination with exercise v that which occurred after
a 20-week control period. Of the 72 obese
adoles-cents who started in the program and were
mi-tially tested, there were 63 adolescents who
com-pleted both weight loss or control periods and had a posttest performed (Table 2). No significant
dif-ferences were noted between the three groups of
obese adolescents prior to the weight loss pro-gram. When compared with the obese control group, the two 20-week weight loss groups expe-nienced a modest but significant decrease in body
weight (P < .01, Table 2). The modest decrease in
body weight observed in the two weight loss groups was associated with a significant change
in body composition (P < .01, Table 2). Although
the exercise group tended to have a greater
de-crease in percentage of fat (measured by
hydro-static weighing), there were no significant
TABLE 3. Submaxim al and Maximal Bicycle Exerc ise Data Before and After 20- Week Weight Loss Program*
Exercise Obese Control Group Obese Exercise Group Obese Diet Group
(n = 18) (n = 22) (n = 23)
Preprogram Postprogram Preprogram Postprogram Preprogram Postprogram
Submaximal
Heart rate (beats/ 144 ± 19.7 148 ± 14 147 ± 21 128 ± l8t1: 144 ± 21 140 ± 21
mm)
Systolic BP (mm 135 ± 25 138 ± 20 138 ± 13 125 ± lit 140 ± 15 130 ± 14
Hg)
Diastolic BP (mm 80 ± 15 79 ± 16 81 ± ii 60 ± i3t1: 82 ± 13 69 ± lit
Hg)
Mean BP (mm Hg) 98 ± 17 98 ± 18 100 ± 12 81 ± i2t1: 101 ± 14 89 ± 12t
02 consumption (mid 1,225 ± 222 1,277 ± 252 1,349 ± 302 1,109 ± 2i6t1: 1,226 ± 189 1,200 ± 156 mm)
Maximal
Heart rate (beats/ 188 ± 15 188 ± 12 189 ± 14 182 ± 12 185 ± 14 184 ± ii
mm)
Systolic BP (mm 156 ± 18 160 ± 17 159 ± 20 148 ± 16 163 ± 22 154 ± 17
Hg)
Diastolic BP (mm 84 ± 16 85 ± 17 83 ± 16 70 ± i4t1: 81 ± 16 78 ± lit
Hg)
Mean BP (mm Hg) 108 ± 17 110 ± 17 108 ± 18 95 ± l5t1: 108 ± 19 103 ± 15
02 consumption (mL/ 2,019 ± 544 2,014 ± 538 2,236 ± 520 2,283 ± 557 2,188 ± 505 2,003 ± 719 mm)
Total time (mm) 22.2 ±5.5 22 ± 4.7 23 ± 4.8 25 ± 4.3 23.3 ± 4.8 22.9 ± 4.5
*Results are given as means ± SD.
t P < .05, preprogram v postprogram.
1:P < .05, obese exercise group v obese diet group and obese control group.
with respect to any of the anthropometnic van-ables measured.
The changes in cardiovascular fitness following the weight loss programs are summarized in Table 3. Prior to weight loss, the heart rate and oxygen consumption response to bicycle exercise were similar in all three groups of obese adoles-cents. After the 20-week program, both weight loss groups of children experienced a significant decrease in resting heart rate; however, this de-crease in heart rate was significantly greater in the weight loss group that exercised (P < .01). In addition, only the group ofchildren in the exercise group experienced a decrease in both heart rate and oxygen consumption at the 60-W submaximal exercise stage (P < .01). The exercise group also tended to have the largest increase in maximal oxygen consumption and endurance (Table 3). When compared with the obese control group, the two weight loss groups experienced significant decreases in systolic and diastolic mean and z
score BP values (Figs 1 and 2, Table 2). After the
20-week weight loss program, both weight loss
groups experienced a decrease in BP; however, when we performed an analysis of covaniance (with the change in body weight as the
concomi-tant variable), we observed that there was a
sig-nificantly greater decrease in resting systolic BP
in the exercise group than was observed in the diet group. In addition, differences between the two weight loss groups in their response to bicycle
exercise were also noted. As can be seen in Table 3, the increase in diastolic and mean BP that
oc-curs during both submaximal and maximal
ex-ercise were significantly less in the exercise group
following the 20-week weight loss program (P <
.01).
Finally, vascular reactivity was evaluated by measuring forearm blood flow and resistance at rest and following ten minutes of arterial
occlu-sion (Table 4). When compared with the nonobese
control subjects, the obese adolescents had
in-creased resting forearm blood flow and postis-chemic forearm vascular resistances and de-creased forearm vascular resistance and postis-chemic vascular blood flow (P < .01). In addition,
prior to weight loss, we observed in the obese group a significant correlation between z score
systolic and diastolic BP and the postischemic
vas-cular resistance (r = .36, P < .05 systolic, r =
.47, P < .01 diastolic). Following the 20-week
weight loss program, we observed that only the exercise group experienced a significant decrease
in resting forearm blood flow and a significant
TABLE 4. Resting and Postischemic Forearm Vascular Resistance and Blood Flow in Obese and Nonobese Ad-olescents
Group At Rest Postischemia
Forearm Blood Flow Forearm Vascular Resistance Forearm Blood Flow Forearm Vascular Resistance
Preprogram1 Postprogram Preprogram Postprogram Preprogramt Postprogram Preprogram Postprogram
Obese
Control 13.7 ± 7 13.1 ± 9 6.7 ± 4.5 7.1 ± 1.9 43.6 ± 15 44 ± 14 2.6 ± 1.0 2.6 ± 1.4
Diet 13.4 ± 8 11.2 ± 15 79 ± 2.0 7.8 ± 3.5 40.3 ± 19 42 ± 16 3.0 ± 1.7 2.2 ± 1.31:
Exercise 12.9 ± 8 9.2 ± 101:1 7.3 ± 2.4 9.1 ± 2.31:* 41.2 ± 16 54.2 ± 161: 2.9 ± 1.5 1.5 ± 0.61:i
Nonobese 5.6 ± 1.9 14.1 ± 3.6 65.2 ± 19 1.2 ± 0.5
Results are given as means ± SD. Forearm blood flow is given in mLIminIlOO mL offorearm volume; forearm vascular resistance
is given in mm Hg/mL/minIiOO mL of forearm volume. t P < .05, nonobese group v control, diet, or exercise group.
1:P < .05, preprogram v postprogram.
§P < .05, exercise group v diet group.
DISCUSSION
An association between obesity and
hyperten-sion has previously been reported in both
adults’1’3 and children.’6 In the present study,
we confirmed this association by demonstrating
that obese adolescents have a BP distribution that
is skewed 1 SD to the right of normal and that,
following weight loss, this distribution is no
longer different from that of the general
popula-tion (Figs 1 and 2). We also showed that the
method by which weight loss is accomplished is
important in determining the degree of BP
re-duction. Although both of our weight loss groups experienced a significant decrease in resting
sys-tolic and diastolic BP and heart rate, the weight
loss group that combined caloric restriction and
exercise experienced the greatest decrease in
rest-ing systolic BP and heart rate. Differences
be-tween the two weight loss groups in their BP
re-sponse to bicycle exercise were also observed.
Ab-solute systolic, diastolic, and mean BPs during
maximal and submaximal exercise were
signifi-cantly reduced in both weight loss groups.
How-ever, following the 20-week weight loss program,
only the exercise group experienced a
signifi-cantly smaller increase in diastolic and mean BP
during both submaximal and maximal exercise
testing. These differences in resting and exercise
BP and heart rate in the exercise group probably
reflect changes in the autonomic nervous system that occur after physical conditioning. Other have previously demonstrated that after physical
training sympathetic nervous system activity
de-creases, whereas parasympathetic nervous
sys-tem activity increases.’4”5
The present study also may provide some
in-sight into why there is a strong association
be-tween BP and body weight in obese adolescents.
Numerous studies involving obese adults have
demonstrated that obesity is associated with an
increased cardiac output and stroke volume and
a decreased systemic vascular resistance. 1619
Neither cardiac output nor total systemic
vascu-lan resistance were directly measured in our
study; however, because we observed that obese
adolescents had an elevated resting forearm blood
flow and a reduced nesting forearm vascular
re-sistance, our results are compatible with these
obese adolescents having an elevated cardiac
out-put and a reduced systemic vascular resistance.2#{176}
Our data also suggest that, although vascular
ne-sistance may be reduced, it is not reduced enough
to result in a normal BP.
Results of studies in children2’ and adults2023
have suggested that structural changes in the
ne-sistance vessels may occur in the presence of
hy-pertension. Structural changes in resistance
yes-sels can be assessed physiologically by measuring
vascular resistance during ischemia-induced maximal vasodilation. Several studies have doc-umented the fact that the minimal vascular
re-sistance measured at peak reactive hypenemia
can be used as an index of the structural
compo-nent of vascular nesistance.2024 As can be seen
in Table 3, at peak reactive hyperemia, forearm
vascular resistance was significantly greaten in
the obese adolescents as compared with the
non-obese control group. Thus, the elevated minimum
forearm vascular resistance suggests that
struc-tural changes were present in the forearm
resis-tance vessels of the obese adolescents. The exact
nature of these vascular changes are unknown
but might involve vascular smooth muscle hy-pertrophy with increased wall to lumen ratio, water logging, a decreased number of resistance
vessels, or decreased size of the vessels without
vascular hypertrophy. Egan and Julius24
dem-onstnated in children with essential hypertension
that minimal forearm vascular resistance
come-lates with increased sympathetic drive as
suggested that chronic sympathetic stimulation
may have produced vascular smooth muscle hy-pertrophy. For the following two reasons, our data also suggested that chronic increased sympathetic drive activity may also be responsible for the structural changes in the forearm resistance
yes-sels observed in obese adolescents.
First, unlike the previous reports concerning obese adults,’6”7 our results demonstrated that obese adolescents have an increased heart rate when compared with nonobese children. We also observed that, with weight loss, heart rate
sig-nificantly decreased. Others have also
demon-strated in obese adults that weight loss is asso-ciated with a reduction in heart rate.’8”9 Al-though we do not know why our obese adolescents have an elevated nesting heart rate, we believe that the increased heart rate probably reflects in-creased sympathetic nervous system activity. In many but not all studies of obese adults, it has been suggested that, based on plasma and/or
un-nary norepinephnine levels, increased
sympa-thetic activity may contribute to the increased BP observed in these patients.2527 Conversely, most
studies have also demonstrated that weight
re-duction during caloric restriction results in a
progressive decrease in circulating
catechola-mines.’8”9
Second, we observed that, with weight loss, minimum forearm vascular resistance decreased to the greatest extent in the exercise group. Al-though we do not have direct proof, we believe that the significant decrease in minimum forearm vascular resistance in the exercise group may be due to reversal of structural changes in the resis-tance vessels as a result of chronic attenuation of
sympathetic nervous constrictor influences on the
local resistance vessels of the forearm (either due to decreased sympathetic nervous system activity or decreased sensitivity of the peripheral affector
tissue to sympathetic nervous system
activ-ity).28’29
In summary, we have demonstrated that, like obese adults, obese adolescents have an elevated
BP that is reduced with weight loss. We have also
shown that a weight loss program that
inconpo-mates exercise with caloric restriction produces the most desirable effects in BP reduction. Finally, we have demonstrated that obese adolescents appear to have these structural changes present in the forearm resistance vessels and that these struc-tunal changes are reversible.
ACKNOWLEDGMENT
This work was supported, in part, by grants NIH
ROl-AM309-89, NIH MOi-RP00042-2i, and NIH 2ROi-HL-35743 from the Natiopal Institutes of Health.
REFERENCES
1. Lauer RM, Connor WE, Leaverton PE, et al: Coronary heart disease risk factors in school children: The Musca-tine study. J Pediatr 1975;86:697-708
2. Webber LS, Voors AW, Srinivasan SR, et al: Occurrence in children of multiple risk factors for coronary artery dis-ease: The Bogalusa heart study. Prey Med 1979;8:407-411 3. Voors AW, Webber LS, Frerichs RR, et al: Body weight
and body mass a determinants of basal blood pressure in children: The Bogalusa heart study. Am J Epidemiol
i977;106:101-115
4. Aristimuno GG, Foster TA, Voors AW, et al: Influence of persistent obesity in children on cardiovascular risk fac-tors: The Bogalusa heart study. Circulation 1984;69:895-904
5. Rames LK, Clarke WR, Conner WE, et al: Normal blood pressures and the evaluation of sustained blood pressure evaluation in childhood: The Muscatine study. Pediatrics
1978;61:245-253
6. Brownell KD, Kelman JH, Stunkad AJ: Treatment of
obese children with and without their mothers: Changes in weight and blood pressure. Pediatrics 1983;71:515-523 7. Rocchini AP, Katch VL, Grekin R, et al: Role for
aldoste-rone in blood pressure regulation ofobese adolescents. Am
J Cardiol 1986;57:613-618
8. National Center for Health Statistics: Plan, Operation, andResults ofa Program ofChildren’s Examination. Vital and Health Statics Series II, N 135, PHS No. 100. Gov-ernment Printing Office, 1973
9. Katch Fl, Michael ED, Hovath SM: Estimation of body volume by underwater weighing: Description of a simple method. J Appi Physiol 1967;23:811-813
10. Gidding 5, Rocchini A, Moorehead C, et al: Increased fore-arm vascular reactivity in patients with repaired coarc-tation of the aorta. Circulation 1985;71:495-499
11. Reisin E, Abel R, Modan M, et al: Effect of weight loss without salt restriction on the reduction of blood pressure
in overweight hypertensive patients. N Engl J Med
1978;298:1-6
12. Chiag BN, Penman LV, Epstein FH: Overweight and
hy-pertension: A review. Circulation 1969;39:403-421
13. Dornfield LP, Maxwell MH, Waks AU, et al: Obesity and hypertension: Long-term effects of weight reduction on blood pressure.
mt
J Obes 1985;9:381-38914. Euler USV: Sympatho-adrenal activity in physical exer-cise. Med Sci Sports Exerc 1974;6:165-173
15. Ekbolm B, Kilblom A, Soltysiak J: Physical training bradycardia, and autonomic nervous system. Scand J Clin Lab Invest i973;32:251-256
16. Messerli FH, Sundgaard-Riise K, Reisin E, et al: Disparate cardiovascular effects ofobesity and arterial hypertension. Am J Med i983;74:808-812
17. Messerli FH, Ventura HO, Reisin E, et al: Borderling hy-pertension and obesity: Two prehypertensive states with elevated cardiac output. Circulation 1982;66:55-60
18. Reisin E, Frohlich ED, Messerli FH, et al: Cardiovascular changes after weight reduction in obesity hypertension. Ann Intern Med 1983;98:315-319
19. Anderson OK, Fagerberg B, Hedner T: Importance of di-etary salt in the hemodynamic adjustment to weight
re-duction in obese hypertensive men. Hypertension
1984;6:8i4-8l9
20. Sullivan JM, Prewith RL, Josephs JA: Attenuation of the microcirculation in young patients with high-output bor-derline hypertension. Hypertension 1983;5: 1844-1851
21. Mahoney LT, Clarke WR, Mark AL, et al: Forearm
vas-cular resistance in the upper and lower quintiles of blood pressure in children: The Muscatine study. Pediatr Res
1982;16:163-165
22. Conway J: A vascular abnormality in hypertension: A
study of blood flow in the forearm. Circulation
1963;27:520-529
23. Takeshita A, Mark A: Decreased vasodilator capacity of forearm resistance vessels in borderline hypertension.
24. Egan B, Julius 5: Vascular hypertrophy in borderline hy-pertension: Relationship to blood pressure and sympa-thetic drive. Clin Exp Theory Pract 1985;A7:243-255 25. Sowers JR, Nyby M, Stern N, et al: Blood pressure and
hormone changes associated with weight reduction in the
obese. Hypertension 1982;4:686-691
26. Sowers JR, Whitefield LA, Catania RA, et al: Roles of
sym-pathetic nervous system in blood pressure maintenance in
obesity. J Clin Endocrinol Metab 1982;54:ll8l-1l86
27. Tuck ML, Sowers JR, Dornfeld L, et al: Reduction in
plasma catecholamines and blood pressure during weight
loss in obese subjects. Acta Endocrinol 1983;102:252-257 28. Bjorntrop P: Physiological and clinical aspects of exercise
in obese persons. Exerc Sport Sci Rev 1983;5:159-180 29. Clausen JP: Effect of physical training on cardiovascular
adjustments to exercise in man. Physiol Rev 1977;87:779-815
REFERENCES
DAVID
HUME,
THE SCOTTISH
PHILOSOPHER,
ON HOW A CHILD
LEARNS
NOT TO TOUCH
A BURNING
CANDLE
(1749)
David Hume (1711-1776), a Scottish philosopher, was one ofBritain’s lead-ing advocates of the philosophical doctrine of empiricism. This doctrine held
that all knowledge is derived from experience. This position is opposed to
rationalism in that it denies the existence of innate ideas.
Hume’s empiricism is evident in this description of how a child learns not to put his hand near a burning candle.’
It is certain that the most ignorant and stupid peasants-nay infants, nay even
brute beasts-improve by experience, and learn the qualities of natural objects, by
observing the effects which result from them. When a child has felt the sensation of
pain from touching the flame of a candle, he will be careful not to put his hand near
any candle; but will expect a similar effect from a cause which is similar in its sensible
qualities and appearance. Ifyou assert, therefore, that the understanding ofthe child
is led to this conclusion by any process of argument or ratiocination, I may justly
require you to produce that argument; nor have you any pretense to refuse so equitable
a demand. You cannot say that the argument is abstruse, and may possibly escape
your inquiry; since you confess that it is obvious to the capacity of a mere infant. If
you hesitate, therefore, a moment on if, after reflection, you produce any intricate or
profound argument, you, in a manner, give up the question, and confess that it is not
reasoning which engages us to suppose the past resembling the future, and to expect
similar effects from causes which are, to appearance, similar. . . . If I be right, I
pre-tend not to have made any mighty discovery. And if I be wrong, I must acknowledge
myselfto be indeed a very backward scholar; since I cannot now discover an argument
which, it seems, was perfectly familiar to me long before I was out of the cradle.
Noted by T.E.C., Jr, MD
1. Hume D: An Enquiry Concerning Human Understanding. Garden City, NY, Anchor Books,