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Ecological factors affecting body size of Japanese adolescents.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 91:299-303 (1993)
Ecological Factors Affecting Body Size of Japanese Adolescents
AKIRA ENDO, KATSUHIKO OMOE, AND HITOSHI ISHIKAWA
Department of Hygiene and Preventive Medicine, Yamagata University
School of Medicine, Yamagata, 990-23, Japan
KEY WORDS
Environmental temperature, Daily energy intake,
Annual per capita income, Bergmann’s rule
ABSTRACT
Prefectural data of 17-year-old Japanese adolescents’ body
size were excerpted from the annual series of Reports on School Health Statistics (Ministry of Education) for the last 35 years, and were correlated with the
mean annual temperature of prefectural capitals. A negative correlation was
found for both height and weight. Thus, it can be stated that children in colder
climates conform to Bergmann’s rule that they are larger in their height and
weight than children growing up in warmer climates. Partial correlation
coefficients indicate that body weight is primarily related to the temperature.
Further, the results of a multiple regression analysis, using temperature,
daily energy intake (National Nutrition Surveys), and annual per capita income (Annual Reports of Prefectural Accounts) as the independent variables
among the 12 districts (groups of prefectures) for the last 25 years, suggest
that the observed Bergmann’s phenomenon is related to geographical differences in nutrition; people in colder regions consume more calories than those
in warmer regions. 0 1993 Wiley-Liss, Inc.
The development of human body size is
influenced by various ecological factors.
Bergmann’s rule holds that within any
warm-blooded species, body size should be
greater in colder climates for the maximum
retention of body heat. The applicability of
this rule to humans has been tested in several populations (Schreider, 1950; Newman,
1953; Roberts, 1953; Newman and Munro,
1955; Walter, 1976), mostly confirming this
phenomenon. However, some of the populations studied were not homogeneous
enough, either genetically (different breeding populations) or socioeconomically (different countries) to afford a reliable test of
the rule. Further, some investigators (Walter, 1976; Riesenfeld, 1980) have speculated
that this phenomenon in humans is t o be
interpreted as the result of geographical differences in nutritional factors such as protein and energy intake, rather than as reflecting genetic differences produced by
natural selection.
Japan provides a good test case. Japan’s
prefectures vary greatly in latitude (more
0 1993 WILEY-LISS, INC.
than 15”in north-south range), and the Japanese are relatively homogeneous genetically. Also, the data from several annual series of governmental surveys such as the
National School Health Survey and National Nutrition Survey are available €or
Japanese populations. In the present communication, we report how environmental
temperatures and nutritional and socioeconomic factors have been related to geographical variation in the body size of Japanese adolescents over the course of the last
three decades.
MATERIALS AND METHODS
Japan comprises 47 administratively autonomous units (hen, or prefecture). Statistics on the height and weight of senior highschool children (males and females) of 17
years of age for each prefecture were excerpted from annual series of Reports on
School Health Statistics (Ministry of Educa-
Received October 22,1991; accepted January 19, 1993.
300
A. END0 ET AL.
tion, 1955-1989) from 1955-1989. In this
annual survey, from 300-500 children for
each sex for each age were selected from the
prefectural populations by a stratified random sampling. To smooth the data, we calculated 5-year averaged figures and used
them throughout the analysis.
The mean annual temperature (averages
of years 1951-1980) and the latitude of each
prefectural capital were taken from tables
(National Astronomical Observatory, 1989)
supplied by the Meteorological Agency of Japan. The temperatures of the prefectural
capitals ranged from 8.0"C to 17.3"C.For the
last 30 years in Japan, these temperatures
of each prefectural capital have changed little (0.9"Cincrease at most), and the amount
of change differed only slightly (by 0.7"C or
less) among the prefectural capitals. The
mean annual temperature was highly correlated with other temperature indices such
as the coldest annual temperature and the
mean temperature of January (r > 0.95).
Data from the annual series of the National Nutrition Survey (Ministry of Health
and Welfare of Japan, 1965-1989) were also
incorporated in the present study. This survey contains nutritional data for more than
50,000 Japanese sampled throughout Japan, and data were available for 12 districts
(groups of prefectures). Districts divide this
country from the most northeast to the most
southwest, each comprising several prefectures (Fig. 1). Data on daily total energy intake (Kcal)for each of these districts (5-year
averages) were utilized. Although no specific data were available for schoolchildren
alone, we assumed that these data are representative of the entire population and can
be used to estimate quantitative differences
in nutritional intake of schoolchildren
among the districts. Young people (less than
20 years old) comprised about one fourth of
the overall sample in the nutrition survey.
The annual per capita income (5-year averages) for each prefecture, taken from the
Annual Report on Prefectural Accounts
(Economic Research Institute, 1991), was
utilized as an index of socioeconomicfactors
during the study period. From these data,
the averages for 12 districts were calculated.
During our study period, prefectural annual
per capita income increased more than 20
times nominally. However, the magnitude of
regional differences was much less (coefficients of variation: 14%for the period 19551959 vs. 11%for the period 1985-1989).
The relationships between the body size
and the prefectural temperature were analyzed using Pearson product-moment correlation coefficients and partial correlation coefficients (Snedecor and Cochran, 1980) for
the last 35 years. Then, using multiple regression analysis (Snedecor and Cochran,
1980), we examined how body height and
body weight are related to the mean annual
temperature, daily energy intake, and annual per capita income among the 12 districts during the last 25 years. The data
from one prefecture (Okinawa) were excluded from the analysis, because of the incompleteness of the data from this island
(which was not returned to Japan until
1972) and its geographical remoteness from
other prefectures.
RESULTS AND DISCUSSION
Table 1 shows how 17-year-old male and
female schoolchildren's height and weight
are correlated with the mean annual temperature. The temperatures of 46 capitals
were highly correlated with latitude
(r = - 0.95). Negative correlation was
present for both height and weight. Thus, it
can be stated generally that Japanese adolescents in colder climates are larger in their
height and weight than in warmer climates.
Figure 1 is a map of Japan demonstrating
how body weights of female adolescents
were distributed from north to south for the
years of 1985-1989. Partial correlation coefficients in Table 1 also indicate that body
weight is primarily related to the temperature. Newman and Munro (1955) obtained
similar statistical results using the same
partial correlation analysis.
In Japan, an annual nationwide survey of
schoolchildren's physical growth and health
status has been carried out for decades by
the Ministry of Education (Reports on
School Health Statistics), and various studies have been published utilizing these data.
Takaishi (1980) showed, using prefectural
data for 1979, that 12-year-old schoolchildren were larger in the north and smaller in
the south. Sato (1988) demonstrated that
ADOLESCENTS BODY SIZE AND ECOLOGICAL FACTORS
301
body weight, 17-year-old females, 1985-1989
c
4 4."N
N
c
--
1
53.6 (M+lSD)-52.9 - 53.6 (M+ISD)
52.1 (M-1SD)- 52.9
52.1 (M-1SD)
Fig. 1. Prefectural differences in body weight of 17-year-old female adolescents in Japan (for the
year-period of 1985-1989) (M, mean; SD, standard deviation). Japan is divided into 46 prefectures (thin
lines) and 12 districts (thick lines) in this map.
TABLE I . Correlation between the mean annual temperature, and the height and weight
Japanese adolescents in 46 prefectures
1955-1959
1960-1964
1965-1969
1970-1974
1975-1979
1980-1984
19x5-19x9
rth
-0.10
0.05
-0.05
-0.28*
-0.37*
-0.43**
-0.41**
17-year-old
Female
Male
Height
Year-period
of
Height
Weight
Weight
rth.w
rtw
rtw h
rth
rth.w
rtw
rtw h
0.14
0.36*
0.40**
0.35*
0.18
0.12
0.14
-0.56***
-0.54***
-0.59***
-0.64***
-0.62***
-0.67***
-0.69***
-0.57***
-0.62***
-0.67***
-0.66***
PO.%***
-0.58***
-0.63***
-0.23
-0.01
-0.01
-0.22
-0.38**
-0.34*
-0.32''
-0.08
0.34*
0.43**
0.24
-0.07
0.04
0.06
-0.84***
-0.72***
-0.72***
-0.74***
-0.70***
-0.71***
-0,70***
-0.83***
-0.76***
-0.78***
-0.75***
-0.65***
-0.66***
-0,66***
'rth or rtw,simple correlation coefficients;rth w, partial correlation coefficients with weight held constant; rtwhi partial correlation coefficients
with height held constant.
*P < 0.05, **P < 0.01, ***P < 0.001.
the body height and weight of 17-year-old ture of the prefectures, and concluded that
Japanese adolescents were correlated sig- Bergmann's rule obtains in this case. Hownificantly with the mean annual tempera- ever, he used data €or the year of 1985 alone.
302
A. END0 ET AL.
TABLE 2. Multiple regression analysis on the relation of body size of 17-year-old adolescents with the mean
annual temperature, daily energy intake, and annual per capita income in 12 districts
(groups of perfectures) of Japan for the last 25 years
Body height
p coefficients2
Temp3
Energy intake4
Year-period
Males
1965-1969
1970-1974
1975-1979
1980-1984
1985-1989
Females
1965-1969
1970-1974
1975-1979
1980-1984
1985-1989
0.87**
0.49*
0.32
0.40
0.72**
0.82**
0.60*
0.20
0.39
0.60*
Income'
R'
Body weight
p coefficients'
Energy intake4
Temp3
Income'
0.08
0.24
0.14
0.22
0.63
0.44
0.59
0.39
0.85**
0.60**
0.75**
0.64*
0.50
0.35
0.47*
0.47*
0.44
0.57"
0.77""
-0.11
-0.47
-0.13
-0.52
-0.43"
0.59
0.32
0.65
0.35
0.59**
0.32
0.47
0.33
0.25
0.25
0.85**
0.12
0.15
0.16
0.10
0.81**
0.43
0.50
0.48
0.651~
0.69*
OH**
0.58
0.58*
0.52'
0.70**
0.31
0.62*
0.67**
0.73**
-0.10
-0.41
-0.20
-0.15
-0.30
0.77*
0.40
0.71*
0.77**
0.72**
0.16
0.26
0.16
-0.13
-0.13
0.60**
Coefficients of determination (adjusted).
'Standardized partial regression coefficients
Mean annual temperature.
4Daily energy intake.
' ~ n n u a lper capita income.
* P < 0.05.. **P < 0.01.
The present study, in which the relation was
examined more extensively using more
data, shows that such a phenomenon has
been observable for the last 35 years.
Table 2 shows the results of multiple regression analysis among 12 districts of Japan for the last 25 years, taking body height
and body weight as criteria variables, and
the mean annual temperature, daily energy
intake, and annual per capita income as explanatory variables. Although we have to be
prudent in interpreting the partial regression coefficients (Snedecor and Cochran,
1980; Zar, 1984))we may use these as rough
measures of the relative importance of these
three explanatory variables within each period of observation. Generally speaking, it
seems that body height is more closely correlated with annual per capita income than
with the other two variables, and, especially
in females, body weight is more closely correlated with daily energy intake than with
the other two variables. The temperature
seems to be not a prime determinant of body
size. These findings are useful in explaining
the phenomenon observed in Table 1.
Among the 12 districts, the annual mean
temperature is correlated with daily energy
intake (r = - 0.5-0.7), while it has no correlation with annual per capita income
(r < 0.1). Also, little correlation exists between daily energy intake and annual per
capita income (r = 0.05-0.15). Therefore the
apparent phenomenon of larger body size in
colder climates probably comes from the
consumption of more calories per capita in
colder regions than in warmer regions. This
supports the nutritional theory that Bergmann's phenomenon in humans is to be interpreted in terms of geographical differences in nutritional factors rather than the
temperature itself (Walter, 1976; Riesenfeld, 1980). It may be that cold weather necessitates more energy intake, or that it
stimulates the appetite (Newman and Munro, 1955),resulting in larger body size. However, an alternative possibility, that larger
body size demands more daily energy intake, cannot be negated completely by the
present multiple regression analysis alone.
For illustrative purposes, Figure 2 shows
graphically the patterns of correlation of
daily energy intake with body weight in the
12 districts for female adolescents for yearperiods of 1965-1969, 1975-1979, and
1985-1989 (total energy intake has ceased
increasing since 1970 in Japan).
In conclusion, we found that body size of
Japanese adolescents (senior high-school
children) is correlated with the environmen-
ADOLESCENTS BODY SIZE AND ECOLOGICAL FACTORS
2500
LITERATURE CITED
17-year-old-females
1965-69, r=.87
2450
2400
2350
c
m
Y
2300
.:
Y
a,
.-x
9
2250
p
2200
E
a,
x
/1975-79.
I
2150
0
2100
2050
2000
50
303
51
52
53
54
55
Body weight (kg)
Fig. 2. Correlation of daily energy intake with body
weight of 17-year-old female adolescents in the 12 districts (for three year-periods of 1965-1969, 1975-1979,
and 1985-1989). Numbers accompanying each mark are
those for the districts shown in Figure 1. The “r”indicates simple correlation coefficients.
tal temperature, daily energy intake, and
annual per capita income among the prefectures or districts of their residence. The observed Bergmann’s phenomenon may be primarily related to regional differences in
nutritional characteristics.
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Prefectural Accounts. Tokyo: Economic Planning
Agency.
Ministry of Education (1955-1989) Report on School
Health Statistics. Tokyo: Ministry of Finance Printing
Bureau (in Japanese).
Ministry of Health and Welfare (1965-1989) Present
Status of National Nutrition (National Nutrition Survey). Tokyo: Daiichi-shyuppan (in Japanese).
National Astronomical Observatory (1989) Chronological Scientific Tables. Tokyo: Maruzen (in Japanese).
Newman MT (1953) The application of ecological rules
to the racial anthropology of the aboriginal New
World. Am. Anthropol. 55r311-327.
Newman RW, and Munro EH (1955) The relation of
climate and body size in U.S. males. Am. J . Phys.
Anthropol. 13tl-17.
Riesenfeld A (1980) Body build and temperature tolerance: An experimental analysis of ecological ‘rule’.
Acta Anat. 107t3545.
Roberts DF (1953)Body weight, race and climate. Am. J .
Phys. Anthropol. 11:533-558.
Sat0 H (1988) Secular changes in body physiques and
physical strength. In M Tanaka and Y Kikuchi (eds.):
Kinmirai no Ningenkagaku Jiten (Textbook of Human Sciences for Near Future). Tokyo: Asakurashoten, pp. 253-274. (in Japanese).
Schreider E (1950) Geographical distribution of the
body-weighUbody-surface ratio. Nature 165:286.
Snedecor GW, and Cochran WG (1980) Statistical Methods, 7th ed. Iowa: Iowa University Press.
Takaishi M (1980) Body physiques of schoolchildren. In
H Funakawa (ed.): Gakudou no Hoken (Health of
Schoolchildren). Tokyo: Nipponhyouronsha, pp. 7178. (in Japanese).
Walter H (1976) Korperbauform und Klima: Kritische
Uberlegungen zur Ubertragbarkeit der BERGMANNschen Regel auf den Menschen. Z. Morphol.
Anthropol. 67:241-263.
Zar J H (1984) Biostatistical Analvsis. 2nd Ed. Enelewood Cliffs: Prentice-Hall, Inc.
I
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Y
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