Asia Pacific J Clin Nutr (1994) 3, 141-143 141
Asia Pacific J Clin Nutr (1994) 3, 141-143
Body composition of Chinese compared with data from North America
Zhu-ming Jiang MD,
Nai-fa Yang, Marc R. Scheltinga MD
and Douglas W. Wilmore MD
Departments of Surgery, Peking Union Medical College Hospital, Beijing,
China; and Brigham and Women's Hospital, Harvard Medical School, Boston,
Massachusetts, USA
A multiple tracer dilution method measuring total body water
(TBW) and extra cellular water (ECW) was used to study body composition.
Healthy Chinese were compared to a group of healthy Americans
evaluated by similar dilutional methods. Compared to the American
subjects, Chinese subjects were less heavy (body weight was 62.1
± 2.0 kg vs 72.5±
4. 1, P<0.05), leaner (body fat was 19.6 ±
1.8% of body weight vs 25.8 ±
1.9, P<0.005), wetter (total body water was 58.9 ±
1.3% vs 54.3 ± 1.4, P<0.005)
and had a greater percentage of body cell mass (50.9 ±
1.7% vs 44.2 ± 1.4, P<0.001).
The multidilution method using deuterium oxide and sodium bromide
to assess body composition is accurate but expensive and laborious.
Therefore, equally precise but more economical bedside methods
are needed for routine compositional analysis.
Introduction
Body compositional data obtained from healthy North American subjects
studied with various techniques are widely available. The effect of
disease on intercompartmental relationships has been studied in main
western societies1-3. Less is known about body composition
of Asian populations such as the Chinese or Japanese. The genome of
Oriental people is derived from a different 'genetic pool', and Asian
people have different dietary customs compared to North Americans.
The principal energy source in China is rice or wheat which contains
much less fat calories than the usual American diet4. Since
food intake influences body composition, long-term differences in
dietary intake may be reflected in differences in body composition.
Although it is acknowledged that Chinese people have a lower mean
body weight and less fat compared to North American Caucasians, it
is not known whether all body compartments are proportionally decreased.
A group of Chinese subjects in Taiwan studied using densitometric
and anthropometric methods showed lower fat percentages compared to
Americans.
In the present study, body composition data were obtained from a
group of healthy male and female individuals and from surgical patients
in the Beijing area of China. These data were then compared to compositional
data previously obtained in a North American population1.
Subjects and methods
Subjects
The healthy Chinese group consisted of 22 subjects; physical examinations
and routine laboratory tests showed no abnormalities.
The protocol was approved by the Academic Committee of the Peking
Union Medical C 1000 ollege Hospital serving as the Institutional
Review Board for the hospital. Consent to participate in the study
was obtained from all subjects. The American data (n = 10) had been
reported in a publication from authors at the Harvard Medical School1.
Methods
If a known amount of a substance ('tracer') is injected into the
body and allowed to equilibrate within the compartment in which the
tracer is known to distribute exclusively, the volume of this compartment
can be calculated from a venous blood sample. Multiple tracers were
simultaneously injected and allowed to equilibrate in various body
fluid compartments. The concentrations of these tracers were then
determined and the volume of the various compartments calculated1-14.
Tracers.
1. Pyrogen-free deuterium oxide (D2O, 99.6%
purity, 40-50 ml, autoclave sterilized solution, Sigma, St Louis,
MO, USA) was used for measurement of total body water. 2. Pyrogen-free
sodium bromide (4% NaBr, 20ml, autoclave sterilized solution, GR grade
E. Merck, Germany) was used for extracellular water (ECW) measurement.
Sampling
procedure. Deutrium oxide and sodium bromide were simultaneously
injected intravenously within a 15-minute time period using a syringe
pump. The volume of the tracers injected was determined by subtracting
the weight of the empty syringes from the original weight of the syringes
containing the tracers (Mettler Balance, Model AE 163, Basle, Switzerland).
For TBW venous blood samples (2 ml) were taken at two and three hours
after injection of the D2O. The serum samples underwent
double vacuum distillation at -70 °C to obtain the pure water fraction.
The content of D2O in this sample was determined using
the 'falling drop technique' as described by Schloerb5.
A 125-litre thermal static water bath was used while the temperature
variation was kept within ± 0.0005
°C . The accuracy of the 'falling drop method' is ±
0.5%. The error of repeated determination of TBW is 2.2%6.
For ECW blood samples (4 ml) were taken at two and three hours after
injection of NaBr. Serum was heated in a nickel cruicible at 600 °C
for a half hour to remove the organic matter which could interfere
with the bromide determination as described by Hunter7,8.
The method is based on the conversion of bromide into tetrabromorosaniline,
which is measured calorimetrically. The accuracy is ±
1%; the total error of repeated determination is ±
2.3%2.
Abbreviations.
BW = Body weight; TBW = Total body water; ECW = Extracellular water;
ICW = Intracellular water; TBF = Total body fat; LBM = Lean body Mass;
V = Volume (tracer); V' = Volume (measured compartment); C= Concentration;
C' = Concentration in blood.
Data
analysis. Personal computers (Macintosh) using standard
statistical software (StatView) were used to analyse data. Student
t-tests were applied to evaluate differences between groups. Significance
was accepted at the P<0.05 level. The results were expressed as
means ± sem.
Results
When body composition in the healthy Chinese males and females were
examined, most of the compartments were larger in males than in females
(Table 1). In contracts, when the percent of body fat was calculated,
the males were lower compared to the females (TBF %BW = 19.6±
1.8 vs 25.5± 1.4, P<0.05). Also, the relative ECW was significantly
lower in males than in females (23.3±
0.5% vs 25.6± 0.7, P<0.05). The
relative plasma volume was not statistically different between groups.
Table 1. Comparison of healthy Chinese males and females.
|
|
Male Chinese (n= 15)
|
Female Chinese (n=7)
|
P
|
|
Age (yr)
|
36± 3
|
26± 5
|
= 0.05
|
|
Height (cm)
|
170± 1
|
155± 1
|
< 0.001
|
|
Body weight (kg)
|
62.1± 2.0
|
46.4± 1.8
|
< 0.001
|
|
TBW (I)
|
36.4± 1.0
|
25.4± 1.3
|
< 0.001
|
|
TBW (% BW)
|
58.9± 1.3
|
54.6± 1.1
|
< 0.05
|
|
ECW (I)
|
14.4± 0.5
|
11.8± 0.4
|
< 0.005
|
|
ECW (% BW)
|
23.3± 0.5
|
25.6± 0.7
|
<0.02
|
|
ECW (% TBW)
|
39.7± 0.9
|
47.1 ± 1.8
|
< 0.001
|
|
ICW (I)
|
22.0± 0.8
|
13.5± 1.1
|
< 0.001
|
|
ICW (% BW)
|
35.6± 1.2
|
29.0± 1.4
|
< 0.005
|
|
ICW (% TBW)
|
60.3± 0.9
|
52.9± 1.8
|
< 0.001
|
|
BCM (kg)
|
31.4± 1.1
|
19.3± 1.5
|
< 0.001
|
|
BCM (% BW)
|
50.9± 1.7
|
41.4± 2.0
|
& 1000 lt;0.01
|
|
LBM (kg)
|
49.7± 1.4
|
34.6± 1.8
|
< 0.001
|
|
LBM (%BW)
|
80.4± 1.8
|
74.5± 1.4
|
< 0.05
|
Table 2 shows data of healthy Chinese males, as well as data on American
males published by Moore1. The groups were similar with
respect to age (35.7 yrs vs 36.8). Chinese males were lighter (BW
was 62.1± 2.0kg vs 72.5±
4.1, P<0.05), wetter (TBW was 58.9±
1.3% vs 54.3± 1.4, P<0.05) and
leaner (TBF was 19.6± 1.8% vs 25.8±
1.9, P<0.05). Since ECW was not different between the two groups,
the difference in TBW was due to an expansion of the ICW (35.6±
I .2% vs 30.9± 3.0, P<0.01).
Table 2. Differences between healthy Chinese and American
males.
|
|
Chinese (n= l5)
|
American (n= 10)
|
P
|
|
Age (yr)
|
36± 3
|
37± 4
|
= 0.9
|
|
Body weight (kg)
|
62.1 ± 2.0
|
72.5± 4.1
|
< 0.02
|
|
TBW (I)
|
36.4± 1.0
|
39.0± 1.8
|
= 0.2
|
|
TBW (% BW)
|
58.9± 1.3
|
54.3± 1.4
|
< 0.05
|
|
ECW (I)
|
14.4± 0.5
|
16.8± 0.8
|
< 0.02
|
|
ECW (% BW)
|
23.3± 0.5
|
23.4± 0.7
|
= 0.9
|
|
ECW (% TBW)
|
39.7± 0.9
|
43.1 ± 0.7
|
< 0.02
|
|
ICW (I)
|
22.0± 0.8
|
22.2± 1.1
|
= 0.8
|
|
ICW (% BW)
|
35.6± 1.2
|
30.9± 3.0
|
<0.01
|
|
ICW (% TBW)
|
60.3± 0.9
|
56.9± 0.7
|
< 0.02
|
|
BCM (kg)
|
31.4± 1.1
|
31.8± 1.6
|
= 0.8
|
|
BCM (% BW)
|
50.9± 1.7
|
44.2± 1.4
|
< 0.01
|
|
LBM (kg)
|
49.7± 1.4
|
53.3± 2.5
|
= 0.2
|
|
LBM (%BW)
|
80.4± 1.8
|
74.2± 1.9
|
< 0.05
|
Similar results were found with Chinese and American females (Table
3). Chinese females were lighter (BW was 46.4±
1 .8kg vs 59.3± 3. 1, P< 0.01 )
and wetter (54.6± 1 .1% vs 48.6±
1.5, P<0.01) than their American peers. Unlike the males, the difference
in TBW was composed of both ICW and ECW. Healthy Chinese females had
less fat (25.5± 1.4% vs 33.6±
2.0, P<0.01 ).
Table 3. Comparison between healthy Chinese and American females.
|
|
Chinese (n=7)
|
American (n=10)
|
P
|
|
Age (yr)
|
26± 0.5
|
34± 3
|
= 0.2
|
|
Body weight (kg)
|
46.4± 1.8
|
59.3± 3.1
|
< 0.01
|
|
TBW (I)
|
25.4± 1.3
|
28.5± 0.9
|
= 0.06
|
|
TBW (% BW)
|
54.6± 1.1
|
48.6± 1.5
|
<0.01
|
|
ECW (I)
|
11.8± 0.4
|
13.4± 0.5
|
<0.05
|
|
ECW (% BW)
|
25.6± 0.7
|
22.7± 0.6
|
< 0.01
|
|
ECW (% TBW)
|
47.1± 1.8
|
46.9± 0.5
|
=0.9
|
ICW (I)
13.5± 1.1
|
15.1± 0.5
|
=0.2
|
|
ICW (% BW)
|
29.0± 1.4
|
25.9± 1.0
|
= 0.01
|
|
ICW (% TBW)
|
52.9± 1.8
|
53.1± 0.5
|
=0.9
|
|
BCM (kg)
|
19.3± 1.5
|
21.6± 0.7
|
=0.2
|
|
BCM (% BW)
|
41.4± 2.0
|
37.0± 1.4
|
= 0.1
|
|
LBM (kg)
|
34.6± 1.8
|
38.9± 1.3
|
= 0.06
|
|
LBM (%BW)
|
74.5± 1.4
|
66.4± 2.0
|
< 0.01
|
Discussion
In this study, various fluid compartments were measured using a multitracer
dilution method. Results were used to calculate relatively 'solid'
compartments such as fat. However, the standard for determining absolute
composition is the use of direct analytical techniques following cadaver
desiccation. All other methods use various assumptions and therefore
introduce potential errors which may eventually generate inaccurate
compositional data. Equations derived from animal studies or healthy
populations1 should be ideal in predicting body composition
in corresponding populations. However, these equations may not be
applicable in other (patient) populations. Deuterium oxide is a naturally
occurring isotope of waterl4 and is considered an accurate
dilution indicator for the measurement of TBW. After intravenous or
oral administration, D2O equilibrates with all body water
after two hours15. Although the 'falling drop' method to
measure D2O is accurate, it is time consuming and therefore
not the ideal method. Recently nuclear magnetic resonance (NMR) has
proven to be an accurate and rapid method of measurement of D2O
concentrations in body fluids16. Sodium bromide is also
a nonradioactive substance and used as a dilutional indicator to measure
the extracellular phase of body waterl7. The multitracer
dilution method used in this study is accurate but time consuming
and laborious. More inexpensive and precise methods are needed so
that compositional analysis can be applied as a clinical tool.
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Copyright © 1994 [Asia Pacific Journal of Clinical
Nutrition]. All rights reserved.
Please note: this article has been scanned and reformatted.
Please contact lshirven@ozemail.com.au if any errors are suspected.
Revised: March 30, 2000.
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