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Monthly changes in the gain and loss of growth in weight of children living in Guatemala.

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Monthly Changes in the Gain and Loss of Growth in Weight
of Children Living in Guatemala
BARRY BOGIN
Department of Anthropology, Wayne State Uniuerslty, Detroit. MLchigan 48202
K E Y WORDS Seasonal growth
. Weight growth . Guatemala
ABSTRACT
Monthly increments of weight growth for a sample of 246
Guatemala City private school children are analyzed for the presence of a seasonal pattern in rates of growth. Neither a seasonal pattern nor any other periodic rhythm is found. It is observed that a significantly greater number of
children aged 5.0 to 6.9 years experience their minimum annual growth rate
during the dry season, with up to 60% of them losing or not gaining weight in
any one month. Patterns of diet, exercise and disease cannot explain this trend.
A possible association between minimum weight growth and maximum growth
in height is discussed.
In a n earlier publication (Bogin, '781, a seasonal pattern in the rate of growth in height
was described for a sample of children and
youths living in Guatemala. It was found that
preadolescent boys and girls and male youths
aged 14 years and older grew a t a faster rate
during the dry season, and a t a slower rate
during the rainy season. These findings parallel those from previous investigations, conducted throughout the world, which find that
the maximum annual rate of height growth
usually coincides with the season of maximum
sunlight availability (but see Marshall, '75,
for an exception).
The literature on seasonal variation in
growth also reports t h a t weight gain and loss
follow a seasonal pattern. Of the 29 studies reviewed by Bogin ('771, 22 find that fall or
winter are the seasons of maximum gain. Four
studies report summer to be the season of
greatest growth and three find no seasonal
variation. No study finds spring to be the season of maximum growth. Indeed, most report
spring and summer to be the seasons of
minimal growth. Several find actual weight
loss to occur during the spring. Most of these
investigations are based on samples of healthy, well nourished children living a t temperature latitudes north or south of the equator.
In the tropical regions the traditional seasons-summer, fall, winter, spring-have little climatic meaning or biological relevance.
AM. J. PHYS. ANTHROP. (1979) 51: 287-292.
Dry and rainy seasons are more meaningful
classifications.
The three studies of seasonal differences in
weight growth of children in the tropics report
conflicting results. Vincent and Dierickx ('60)
find the dry season to be the period of maximum gain for African and European children
living in Leopoldville. This is also the season
of maximum gain in height. Eveleth ('67-'68)
also reports maximum gain in weight during
the dry season for United States children living in Rio de Janeiro, Brazil. But, most of
these children spent part of the Brazilian dry
season vacationing in the U.S.A., so the seasonal effect on weight is difficult to interpret.
Conversely, Billiwicz ('67) finds maximum
weight gain of a group of rural Gambian
children to occur in the rainy season. In this
case diet may be the factor responsible for the
seasonal pattern. Both minimal weight gain
and food shortages occur during the dry season.
Since the seasonal weight growth studies
conducted in the tropics are not directly comparable with those from the temperate latitudes, a new study of tropical children was
carried out and the results are reported in this
paper.
MATERIALS A N D METHODS
The sample and research design used for
this study are exactly the same as those used
287
288
BARRY BOGIN
TABLE 1
Descriptive statistics for subsample size and age distributions
Subsample code
Subsample size
Age range
Mean age
Standard deviation
Boys
Girls
Boys
M1
43
F1
42
M2
41
6.9
0.31
Boys
Girls
F2
39
11.0-13.9
12.3
12.0
0.46
0.44
5.0-6.9
6.0
0.36
Girls
M3
46
F3
35
14.0-17.9
16.0
16.0
0.71
0.38
TABLE 2
Mean total gain in hezght and weight for each subsample, September, 1974-October, 1975
Height (cm)
Subsample
Meangain
Standard
deviation
Minimum
Maximum
M1
6.47
F1
6.38
0.76
5.2
8.1
0.77
4.4
7.8
M2
Weight ckg)
F1
F2
6.56
M3
1.83
F3
0.31
M1
3.46
3.20
2.16 1.91
3.9
3.0
12.1 10.4
1.32
0.0
6.4
0.48
0.0
1.7
1.47
1.4
7.9
1.05
1.3
6.3
7.17
for the study of seasonal variation in height
growth described in Bogin (’78).Briefly, these
are children of European, North American,
and Guatemalan families living permanently
in Guatemala. All are from the upper socioeconomic levels of Guatemala City and all are
free of significant nutritional or disease
stress. Six subsamples of children divided by
age and sex were measured. Subsample structure is described in table 1.
Three age groups were purposefully selected
for study. Few researchers have considered
age as a variable in either the design or analysis of seasonal growth studies. Marshall (‘15)
measured preadolescent children so that the
rapid acceleration and deceleration of growth
during the adolescent “spurt” in growth would
not mask the seasonal effect. Conversely,
Thompson (’42) presents data in which the
seasonal differences in rate of height growth
are most pronounced during the adolescent
years. No data for weight growth is given.
Kemsley (’53) reports that seasonal variation
in body weight, independent of diet and exercise, persists into adult life. Due t o the conflict
of opinion and the lack of sufficient data in
the literature it was decided to measure rates
of growth at several different ages.
The data consist of 13 monthly increments
of weight (from September, 1974 t o October,
1975). Weight was taken immediately following the height measurement. All measurements were taken by the author using a
Health-0-Meter balance capable of recording
t o the nearest half pound. The pound measure-
M2
6.21
FZ
6.63
M3
3.45
F3
1.25
2.28
3.16
1.4 -4.0
10.7
15.3
2.37
-2.1
9.9
2.74
-6.4
7.5
ments were converted t o kilograms for analysis. The subjects were weighed barefoot,
dressed in minimal indoor clothing. An assistant recorded and checked all measurements
for reliability. Any individual missing more
than one measurement was excluded from the
study.
RESULTS
Table 2 presents descriptive statistics for
the mean total gain in height and weight of
the children in each of the subsamples during
the 14 months of study. Growth for the M1 and
F1 subsamples is relatively homogeneous and
representative of the annual growth rate expected for clinically healthy children of this
age (Tanner and Whitehouse, ’76). Growth of
the youths in the M2 and F2 subsamples is
heterogeneous. The range of variability is due
to the inclusion of both preadolescent and adolescent individuals in the age group. Similar
heterogeneity in growth of the M3 and F3 subsamples is due to the inclusion of adolescent
and post-adolescent youths and some individuals who have stopped growing in height. But,
weight growth, both positive and negative, is
still pronounced, and seasonally related fluctuations may still be discernible.
The total gain in weight was divided between the mean amounts achieved during the
dry and rainy seasons. Table 3 presents these
data. During the time of study the dry season
began in October and the rainy season began
in April (Bogin, ’78). Weight growth during
the dry season is greater than the rainy season
in every subsample. A test for the significance
MONTHLY CHANGES IN WEIGHT GROWTH
TABLE 3
Mean gain in weight achieued during the dry semon
and rainy season
~
Dry season
~~
Rainy season
Subsample
M1
F1
M2
F2
M3
F3
n
jigain
s.d.
n
.?gain
41
38
40
37
46
35
2.09
1.90
3.11
3.78
2.27
0.80
0.94
0.95
1.83
2.86
1.85
2.88
33
33
35
33
42
33
1.42
1.20
3.08
2.46
1.37
0.51
8.d.
1.27
1.56
1.87
1.53
1.61
1.93
' The difference &tween dry and rainy season means is significant
at the 0.05 level.
of the difference for all subsamples combined
is highly significant (F,.,,, = 121.38, p <
0.001), but post-hoc comparisons of the means
indicate signficance only for the F2 and M 3
subsamples.
Since the growth rates of individual children may differ markedly from the mean seasonal trend (Bransby, '45; Marshall, '711, individual sequences of monthly changes were examined. Table 4 presents the month in which
individual children, expressed as a percentage
of the total subsample size, attained their
maximum or minimum rate of growth.
As can be seen the timimg of the maximum
or minimum rates is variable and no obvious
pattern emerges. To look for a pattern the
monthly growth rates were analyzed by season. The growth rates, grouped by dry and
rainy season, are presented in table 5. The
number and percentage of individual children
reaching maximum or minimum growth rate
2 89
in each season is given for each subsample.
The statistical test for the difference between
seasonal percentages for all subsamples combined it-test for percentages, Snedecor, '56) is
not significant for maximum weight growth
but is highly significant for minimum weight
growth. Comparisons of the seasonal percentages of minimum growth for each subsample
indicates significant differences for the M1,
F1, M2 and F3 subsamples. Some of these
minimum weight gains were negative. Other
children experienced zero gains. Table 6 presents the percentage of children losing or
not gaining weight during each month. The
youngest children (subsamples M1 and Fl)
show the strongest relation of zero or negative
gain with the dry season. The relation is weak
in the M2 subsample and absent in the others.
It is also apparent that zero or negative gain is
not confined to either season for any subsample. Table 5 also shows that many children
experience both maximum and minimum
growth rates in the same season. This is especially apparent for the dry season percentages; approximately half the children experience maximum weight gains and three
quarters their minimum gain. However, since
minimum growth rates do cluster into significant groupings for some subsamples it is possible the maximum growth rates also cluster,
but not according to season of the year. In an
effort to detect other patterns for maximum
weight growth a periodic regression and harmonic analysis (Bliss, '70) was performed. The
value of this analysis is that the complete
month to month data for each child are
TABLE 4
Percentage of mmimum and minimum growth rates of weight observed each month
Subsamples
M1
Month
October
November
December
January
February
March
April
May
June
July
August
September
October
F1
F2
M2
Max
Min
Max
Min
Max
Min
7.0
20.9
7.0
7.0
14.0
2.3
2.3
0
7.0
20.9
2.3
2.3
7.0
0
2.3
2.3
4.7
4.7
18.6
16.3
37.2
0
0
4.7
2.4
19.0
7.1
14.3
16.7
2.4
2.4
0
4.8
7.1
4.7
2.3
2.3
14.3
4.8
17.1
17.1
4.9
9.8
14.6
2.4
2.4
7.3
0
14.6
2.4
7.3
0
2.4
9.8
4.9
4.9
19.5
12.2
12.2
7.3
4.9
7.3
4.9
4.9
4.9
4.8
7.1
2.4
7.1
7.1
11.9
9.5
26.5
4.8
2.4
7.1
7.1
7.1
Max
5.1
10.3
10.3
7.7
10.3
5.1
2.6
12.8
7.7
7.7
5.1
5.1
10.3
F3
M3
Min
Max
Mln
Max
Min
5.1
15.4
2.6
2.6
17.9
5.1
10.3
5.1
7.7
2.6
7.7
5.1
12.8
6.5
13.0
6.5
2.2
6.5
4.3
4.3
6.5
19.6
2.2
23.9
2.2
2.2
4.3
10.9
4.3
6.5
13.0
15.2
6.5
8.7
6.5
6.5
2.2
8.7
6.5
0
8.6
14.3
8.6
20.0
2.9
8.6
2.9
2.9
5.7
11.4
8.6
5.7
0
20.0
2.9
5.7
8.6
11.4
11.4
11.4
5.7
8.6
0
5.7
8.6
290
BARRY BOGIN
TABLE 5
sonal rhythm absent, but that no other periodic rhythm for weight growth was present.
Number and percentage of individuals attaining
maximum or minrmum velocities in monthly
rates of weight growth during the
dry and rainy seasons ’
Subsample
Dry seaeon
n
,
a
F2
M3
F3
M1
F1
M2
F2
M3
F3
Minimum growth rates
6
18.0
37
90.2
30
78.9
12
38.4
12
34.3
29
72.5
16
48.5
23
62.2
30
65.3
16
38.1
10
30.3
25
71.4
312
p
%
Maximum growth rates
23
56.1
20
60.6
26
68.4
16
48.5
24
60.0
17 48.6
23
62.1
16
48.5
20
43.5
16
38.1
12
36.4
23
65.7
M1
F1
I
Y
Rainy season
DISCUSSION
0.001
0.001
0.05
0.50
0.10
0.001
Overall test of significance: maximum growth rates t
= 5.72, p = 0.001.
=
1.66,
p = 0.10;minimum growth rates t
TABLE 6
Percentage of children losing or not gaining weight
during each month of study
Subsamples
Month
M1
October
November
December
January
February
March
April
,May
June
July
August
September
October
FI
M2
F2
M3
F3
11
8
5
11
30
45
7
5
10
22
30
32
55
17
11
14
16
31
42
60
12
12
20
42
32
32
14
18
14
12
19
13
12
6
30
16
29
32
37
14
25
49
37
31
38
47
38
50
5
8
19
21
16
19
10
13
15
25
14
12
18
6
3
18
9
15
20
33
22
35
22
51
51
34
36
45
6
3
treated separately to determine if a periodic
rhythm in growth rate exists. Each individual
is then compared with the mean trend of
growth for his or her subsample. Using this
technique both seasonal and non-seasonal periodic rhythms of growth for individual children can be detected. Because of its length a
full discussion of this procedure is not presented here (the reader is referred to Bogin, ’77).
The results of the analysis show that the only
significant pattern is that for the non-periodic
scatter of weight gains and losses from month
to month. This means that not only was a sea-
The mean gain in weight for each subsample
of children is greater during the dry season
then during the rainy season. For this group
pattern to be truly seasonal it is necessary
that the growth rates of individual children
conform to the mean trend and that each
child‘s rate of change in growth rate be periodic, regularly increasing to a maximum and
decreasing to a minimum (Luce, ’71; Bogin,
’77). When individual sequences of growth are
analyzed for the distribution of maximum and
minimum weight gains no seasonal rhythm is
found. In fact, i t is observed that between 25
and 50% of the children in all subsamples experience both maximum and minimum weight
gains during the dry season. Periodic regression and harmonic analysis suggest that the
observed monthly weight changes are essentially random when compared with the expected periodic pattern.
The observed weight fluctuations are probably not associated with obvious weight-influencing factors such as food availability, exercise or disease. It was previously shown that
food availability and exercise patterns are virtually constant throughout the year for these
children and that the influence of disease is
negligible (Bogin, ’77, ’78).
The apparent randomness in weight growth
of the older children and youths (subsamples
M2-F3) may be largely due to the effects of
adolescence. No attempt was made to assess
the developmental status of any child but i t is
reasonable to assume that some of these individuals, aged 11.0 to 17.0 years, would be experiencing the adolescent growth “spurt.” Included in this group would be some adolescents accelerating in growth rate, some a t or
near peak weight velocity, and others decelerating in growth velocity. For the American
School population the mean age of peak
weight velocity (PWV) is estimated to be 13.6
years for boys and 12.1 years for girls (Johnston et al., ’73). This is also an age when
weight reduction via “dieting” is a common
practice, and may have influenced the findings. The weight growth of the oldest females
(subsample F3) is further complicated by the
fact that about 75%of these young women did
not grow in height during the study. Thus
Thompson’s (’42) observation of a greater sea-
MONTHLY CHANGES IN WEIGHT GROWTH
sonal effect on growth rates during adolescence is not found in the present study for
growth in weight. Nor was it observed for
growth in height (Bogin, '78). Kemsley's ('53)
report of a seasonal rhythm in weight growth
after height growth has stopped was not repeated in the present study.
The non-periodic changes in growth of the
youngest children cannot be an effect of
adolescence. It is also unlikely that children
5.0 to 6.9 years old were significantly restricting their food intake in order to reduce weight.
The greater percentage of children at this age
losing or not gaining weight must be otherwise explained. The annual school holiday coincides with the beginning of the dry season,
but the largest number of zero or negative
weight gains occur four months after the
children return to school. Several sources from
the literature on seasonal growth suggest
that, for groups of children, rate of weight
growth is a t or near minimum when rate of
height growth is a t maximum (Nylin, '29; Orr
and Clark, '30; Fitt, '41; Bransby, '45, Takahashi, '66). Growth in height of the M1 and F1
subsamples follows a periodic rhythm with
about 75% of the individuals experiencing
maximum gains during the dry season and
minimum gains during the rainy season
(Bogin, '78). Although the weight growth of
these children is not seasonal or periodic, a
significantly greater number of individuals
experienced minimum gains during the dry
season. In the last three months of this season
between 30 and 60%of the children either lost
or did not gain weight. An association between
maximum growth in height and minimum
growth in weight is suggested by these data
for the youngest children. Detailed confirmation of this trend remains to be demonstrated.
ACKNOWLEDGMENTS
Research was supported in part by the
American School of Guatemala and the Universidad del Valle de Guatemala, and conducted while the author was a fellow with
the Latin American Teaching Fellowship
291
Program of Tufts University. The author
thanks the editor and referees of this journal
for helpful criticisms.
LITERATURE CITED
Billewicz, W. Z. 1967 A note on body weight measurements
and seasonal variation. Human Biology, 39: 241-250.
Bliss, C. I. 1970 Statistics in Biology. Vol. 2. McGraw-Hill,
New York.
Bogin, B. A. 1977 Periodic Rhythm in the Rates of Growth
in Height and Weight of Children and its Relation to Season of t h e Year. Doctoral dissertation. University
Microfilms, Ann Arbor.
1978 Seasonal pattern in the rate of growth in
height of children living in Guatemala. Am. J. Phys. Anthrop., 49: 205-210.
Bransby, E. R. 1945 The seasonal growth of children. Medical Officer, 73: 149-151.
Eveleth, P. B. 1967-68 Physical growth of American
children in the tropics. Revista de Antropologia. 1.5/26;
14-25.
Fitt, A. B. 1941 Seasonal Influence on Growth. Function
and Inheritance. New Zealand Council For Educational
Research, Wellington.
Johnston, F. E., M. Borden and R. B. MacVean 1973 Height,
weight and their growth velocities in Guatemalan private school children of high socioeconomic class. Human
Biology, 45: 627-641.
Kemsley, W. F. F. 1953 Changes in body weight from 19431950. Annals of Eugenics, 18; 22-42.
Luce, G. G. 1971 Biological Rhythms in Human and A n i ~
ma1 Physiology. Dover, New York.
Marshall, W. A. 1971 Evaluation in growth rates in height
over periods of less than one year. Archives of Disease in
Childhood, 46: 414-420.
1975 The relationship of variations in children's
growth rates to seasonal climatic variation. Annals of
Human Biology, 2: 243-250.
Nylin, G. 1929 Periodical variation in growth, standard
metabolism and oxygen capacity of the blood in children.
Acta Medica Scandinavia, 31: 1-207.
Orr, J. B., and M. L. Clark 1930 Seasonal variation i n t h e
growth of school children. Lancet, 2: 365-367.
Snedecor. G. W. 1956 Statistical Methods. Fifth ed. Iowa
State College, Ames.
Takahashi, E. 1966 Growth and environmental factors in
Japan. Human Biology, 38: 112-130.
Tanner, J. M., a n d R . H. Whitehouse 1976 Clinical longitudinal standards for height, weight, height velocity,
weight velocity and the stages of puberty. Archives of
Disease in Childhood, 51: 170-179.
Thompson, DArcy W. 1942 On Growth and Form. Second
ed. Cambridge University, London.
Vincent, M., and J. Dierickx 1960 Etude sur la croissance
saisonniere des ecoliers de Leopoldville. Annales de la
Societe Belge de Medecine Tropicale, 40: 837-844.
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