Effect of Genetic and Environmental Factors on
obesity in children
(Case Study: Qom city)
Seyede Marzie Fatemi Abhari
Assistant professor, Alborz University of Medical sciences, Karaj, Iran
E-mail: :marziefatemi@yahoo.com
Maysam Musai
Professor, University of Tehran, Tehran, Iran
E-mail: mousaaei@ut.ac.ir
Abstract
In this study we answer this main question: what extent genetic and environmental
factors affect children obesity?
Research methodology in this article is a survey method. For data collection, 384
children between 6-12 years old have been randomly selected from girl’s and boy’s
primary schools in Qom city. Descriptive and inferential statistics are used for
analysis.
Findings show that 19% of children under study are overweight and 13.2% are obese
and remaining has normal weight.
Overweight and obesity is observed more in boys than girls, also this study shows
that there is a significant relationship between genders, physical activity, fast food
consumption, sleep debt, parental BMI and rate of the prevalence of childhood
obesity, but there is not a significant relationship between age, family income and
mother education level.
So some effective factors that can be controlled must be considered like food type,
physical activity and quality and quantity of children’s sleep and necessary actions
must be taken under planning two main factors.
Keywords: Children, Obesity, Over Weight and BMI
1- Introduction
Nowadays obesity is one of the common diseases that unfortunately it causes
mortality and morbidity throughout adult life. The prevalence of childhood obesity
has increased, and the prevention and treatment of obesity has emerged as an
important focus of pediatric research and clinical care. [1].
According to WHO Europe report in European countries 20% of 13 years old children
and 33% of 11years old children have been overweight [2].
Based on WHO reports, from 43 million overweight and obese children throughout
the world 81% live in developing countries. The prevalence of obesity was 20.5% in
Egypt in year of 2008 and 22.4% in Libya in year of 2007. The high prevalence obesity
[6. million] in children in 2010 was at southern areas in central Asia [3].
1
In a study by Juan Angel Rivera 2001 in Latin America, the prevalence of
overweight/obesity among 5-11 years old children was 18.9% and 36.9% and among
12-19 years old young was 16.6% and 35.8%.[4]
Kerasas and colleagues (2001) by examining 6-10years old students in Greece have
reported over weight and obesity 25.3 and 5.6% respectively and in 11-17years old
students 19 and 2.6%. [5]
In a study conducted in China by zhangbin yu and colleagues 1981-2010, has been
shown that the prevalence of overweight /obesity has increased from 1.8% and 0.4%
respectively in 1981 -1985 to 13.1% and 7.5% in 2006-2010 and there was an annual
average increase rates of 8.3%-12.4% respectively. [6]
A research in Lebanon that their study samples included a total of 2004 subjects in the 1997
survey and 3636 in the 2009 survey, has shown the annual rates of change in the prevalence
of obesity have ranged between +4.1% in children and adolescents and +5.2% in adults.[7]
Janson and colleagues have reported the prevalence of overweight18.9% by
examining 17000 students in Florida. [8]
According to a study in America by Cunningham SA and colleagues from 1998 to
2007, it is presented that 14.9% of children in kindergarten were overweight and
12.4 of them were obese. From these children 17% had overweight at age of 14 and
20.08% were obese [9)
Based on a report by NCMP in England the latest figures, for 2012/13, show that 18.9% of
children in Year 6 (aged 10-11) were obese and a further 14.4% were overweight. Of children
in Reception (aged 4-5), 9.3% were obese and another 13.0% were overweight. This means
almost a third of 10-11 year olds and over a fifth of 4-5 year olds were overweight or obese
[10].
Studies in United States and Mexico show that overweight and obesity has increased
among children during 1980-2004. [11].
Studies also show that overweight prevalence in childhood in Canada is a public
problem. (1).
Different studies concerning the prevalence of obesity and overweight in Iran show
that our country is not exceptional.
Nabavi and colleagues’s studies (2011) in semnan and similar studies in Ahvaz and
Isfahan show that the prevalence of obesity and overweight has been from 4.4, 6.7%
to 12, 27.4%, respectively. [12, 13, 14].
Reports of Kelishadi in a research in 2008 show an increase rate of the prevalence of
overweight and obesity 8.82 and 4.5%,respectively in age of 6-18 in 23 provinces and
the highest rate of overweight has been in 12 year olds and the highest rate of
obesity in 6 year olds. Under her study there was no significant association between
gender and BMI but there was an age differences in BMI [15].
Reports of Mirmohammadi in a research in 2011 in Iran has shown the prevalence of
overweight and obesity among Iranian children 9.27% and 3.22% respectively
comparing international standards. The frequency of overweight and obesity was
higher in boys [16].
Afsoun Talaie in a research has reported that the overall prevalence of obesity and
overweight based on Iranian references was significantly higher than that of the CDC
reference. There was no statistically differences between girls and boys in the
prevalence of overweight as it was in the prevalence of obesity. [17]
Studies in Romania have shown that the prevalence of overweight and obesity in boys
has been higher than girls. [18]
2
The reports by Johnson SB in 2007 in Florida on 17000 children have indicated 36.2% of the
children were either overweight (18.9%) or at risk for overweight (17.4%). Approximately 30% of the
kindergarten children were overweight (14.0%) or at risk for overweight (15.5%). [8]
In a research in Iran by Taheri, the overall prevalence rates of overweight and
obesity has been 4.8% and 1.8%, respectively. Overweight prevalence has varied by age. [19]
Whereas non-genetic obesity is considered as one of diseases related to 20 and 21
century and results from urbanization and industrialization and it is related to life
style. Our country is under industrial development and life style is changing. More
studies must be conducted to remove this disease.
The present article examines mentioned matter.
The main question of this research is: effect of genetic and environmental factors on
the prevalence of obesity and overweight
Secondary questions include:
1- Is there any relationship between age , overweight and obesity?[genetic
factor]
2- Is there any relation between gender , overweight and obesity?[genetic
factor]
3- Is
there
any
relationship
between
physical
activity
and
overweight?[environmental factor]
4- Is there any relationship between dietary , overweight and
obesity?[environmental factor]
5- Is there any relationship between sleep debt , overweight and
obesity?[environmental factor]
6- Is there any relationship between obesity in children and obesity in their
parents?[genetic factor]
7- Is there any relationship between obesity in children and their mother
education level?[environmental factor]
8- Is there any relationship between obesity in children
and family
income?[environmental factor]
2- Methods
This study is a survey method that sectional data is used during years 20122013.Survey was designed to provide a random sample 384, 6-12 years old. For
collecting data we used a questionnaire designed by the researcher and samples
were selected randomly by using Cochran formula under correlation degree 95% as
Z . pq (1 / 96) 2 (0 / 5) (0 / 5)
 384
follows: n  2 
d
(0 / 05) 2
We increased number of samples to 410 that 26 questionnaires were removed after
fill questionnaires because of non-compliance of study conditions.
Samples must be 6-12 years old students and they should not suffer a chronic
disease and do not use any medicine for long term and there is no symptoms of
genetic syndromes.
3
Questionnaire is a tool of the data collection means including information related to
children like age, gender, height, weight, family income, mother education level,
BMI, physical activity and sleep rate.
BMI was calculated by dividing body weight (kg) by the square of the height
(m2).
Body weight was measured to 0.1 kg with Seca scale and height was measured to 0.1 cm.
Obesity criteria for children was defined based on the charts of BMI for-agepercentile of CDC.
Obesity criteria was defined as BMI>95% whereas overweight was defined as BMI
85-95% and obesity criteria for adults is more than 30 or equal it.
Statistics X2 under significant degree 5% is used for determining significant degree.
3- Conceptual Framework
Theoretical study concerning obesity shows that effective factors are divided into 2
categories:
- genetic factors;
Environmental factors determine levels of available food, preferences for
types of foods, levels of physical activity, and preferences for types of activities.
4- Findings
From 384 children under study 19% were overweight and 13.2% were obese. 19.8%
of boys and 18.2% of girls had overweight. Also 16.2% of boys and 10.4 of girls were
obese [table1]. There was a gender difference in obesity [p=0.008].
In examination of obesity prevalence in terms of age, the least rate of overweight
observed in the 12 –year-old group (13.6%) and the highest rate in the 9-year-old
group (22.2%) and the least rate of obesity was in the 10-year-old group(5.5%) and
the highest in the 12-year-old group(18.6%). But there were not a significant relation
between age and the prevalence of obesity 5% level. [p=0.13]
Children were classified in terms of physical activity into 3 groups:
Group with less activity:
In this group those children that spend their time at home after school, watch TV,
work with computer or play video games more than 3 hours each day.
Group with moderate activity:
Children that play with their peers for 2-3 hours, watch TV, work with computer or
play video games for less than 3hours and students that go to school by car 3 times a
week.
Group with high activity:
Children that play in sport club, watch TV, work with computer or play video games
for less than 2 hours, and go to school by walk every day.
Based on physical activity 39.3% of children with less activity were overweight
whereas 14.7% of children with average activity and 11.5% with high activity had
overweight. Also 25% of children with less activity were obese and 11.3%, 8.5% of
children with moderate activity and high activity respectively were obese.[table2].
Physical activity was significantly related to overweight and obesity. [p=0.0071].
In terms of dietary and fast food consumption, 14.9% of children that consume fast
food rarely were overweight and 9.4% of them were obese, whereas among children
4
that consume fast food once or twice a week 21.3% and 40.6% respectively, were
overweight and obese and among those children that consume fast food 3
times a week or more, 28.6% were overweight and 52.4% were obese.
[Table 4]. In general consumption fast food and its times were
significantly related to overweight and obesity. (Table5).
This study has shown a relation between sleeping rate and obesity,
overweight. 25.8% of children had sleep debt (sleep time less than
9hours in the 24h day). 21.2% of them were overweight and 15.25%
were obese (table5). Sleeping rate was significantly related to the
prevalence of obesity in level of 94%. [p=0.06].
Regarding relation between children obesity and parents’ BMI, 21.1% of
children with overweight father, were overweight. 3.7% of them were
obese and 75.2% were normal. Only 41.3% of children with obese father
were normal, 13% of them were overweight and 45.7% were obese.
While only 18.5% of children with normal father were overweight and
13.3% of them were obese.
24.1% of children with overweight mother were overweight and 15.1%
children with obese mother had obesity, but 20.9% of children with
obese mother were overweight and 34.9% of them were obese and only
13.7% of children with normal mother had overweight and 6.3% had
obesity. (Table 6).
In general, parent’s BMI was significantly related to children‘s BMI.
[p=0.001, 0.0001].
Regarding the effect of maternal education on the prevalence of obesity
we have shown, that 18.2%and 13% of children that their mother
education level was above diploma were overweight and obese
respectively. While 19% and 12.8% of children that their mother
education level was diploma were overweight and obese respectively.
19.8% and13.5% of children that their mother education level was
secondary school had overweight and obesity respectively.
18.8% and 15.6% of children with illiterate mothers were overweight
and obese [table 8]. Generally, BMI of children was not significantly
related to mother education level in level of 5% [p=0.316%].
Regarding family income 17.9% and 13.9% of children that their parents
have an income less than 1,000,000 toman had overweight and obesity.
18.10% and 13.8% of children with more family income 10000002,000,000 toman were overweight and obese. 23.2% and 11% of
children with family income more than 2,000,000 toman had overweight
and obesity [table9]. So family income was no significantly related to the
prevalence of obesity. [p=0.204]
5
5- Conclusions and Recommendations
This article is aimed at provide an answer this question: what is rate of the
prevalence of overweight and obesity among children of 6-12 years old in Qom city?
What are effective factors on it? How are their effects?
This study was a surveying research that showed us both genetic [eg. father and
mother obesity], and environmental factors [eg .diet, physical activity rate, sleep
rate] affect obesity. This finding conforms to what revealed in scientific reference
book [1]. Also this study emphasized on previous studies [nabavi2010]. However,
both genetic and environmental factors affect obesity but this disease is related to
life style in contemporary world [diet and activity rate, etc.] , These factors can be
controlled in contrary to genetic factors. So some suggestions are addressed for the
prevention of obesity:
- Whereas diet is significantly associated with obesity, necessary notices must
be given to families and children concerning healthy food. This matter can be
included in school text books and be taught to children at school.
- Activity rate is significantly related to obesity so sport must be considered
seriously at school. Increase of sport hours, development of sport facilities in
schools and scientific training relevant to effective sports must be
considered.
- Sleep debt is significantly related to obesity. Upon initial notices to parents
concerning sleep quality and quantity adjustment this problem can be
decreased.
- In addition to mentioned factors there is significantly relationship between
genetic factors and obesity. In fact, for children with obese father and
mother, possibility of overweight and obesity is high. In this regard it is
recommended that first special training is given to parents in order to
necessary actions is taken for environmental factors control from childhood
like physical activity rate, suitable nutrition and enough sleep.
Table 1- The prevalence of obesity in samples in terms of gender
Gender
Girl
Boy
Total
Number[percent] The
prevalence
obesity[number/percent]
Normal
Overweight
192[50]
137[71/4]
35[18/2]
192[50]
123[64]
38[19/8]
384[100]
260[67/8]
73[19]
Source: research findings
6
of P
obesity
20[10/4]
31[16/2]
51[13/2]
*
0.008
Table2- The prevalence of obesity in samples in terms of age
Age
7
8
9
10
11
12
13
Total
Number[percent] The
prevalence
obesity[number/percent]
Normal
Overweight
52[13/5]
35[67/3]
10[19/2]
51[13/2]
33[664/7] 10[19/6]
54[14/1]
35[64/8]
12[22/2]
55[14/1]
42[76/4]
10[18/2]
52[13/5]
34[65/3]
11[21/2]
59[15/4]
40[67/8]
8[13/6]
61[15/9]
42[68/9]
12[19/7]
384
260
73
100
67/8
19
of P
obesity
7[13/5]
8[15/7]
7[13]
3[5/5]
7[13/5]
11[18/6]
7[11/5]
51
13/2
0.13
Source: research findings
Table 3- The prevalence of obesity in samples in terms of physical activity
physical
activity
Less activity
Moderate
activity
High activity
percent
Number[percent] The
prevalence
of
obesity[number/percent]
P
Normal
Overweight obesity
84[21/8]
30[35/7]
33[39/3]
21[25]
170[44/3]
126[74/1] 25[14/7]
19[11/2]
0.0071
130[33/9]
104[80]
15[11/5]
11[8/5]
384[100]
260[67/8] 73[19]
51[73/2]
Source: research finding
Table4- The prevalence of obesity in samples in terms of dietary
Terms of consume fast Number[percent] The
prevalence
food
obesity[number/percent]
Normal
Overweight
Seldom
202[52/6]
153[75/7] 24[14/9]
Once or twice a week
161[42]
61/5[38/1] 43[21/3]
Three times a week or 21[5/5]
4[19]
6[28/6]
more
Total
384[100]
26[67/8]
73[19]
Source: research finding
7
of
p
obesity
25[9/4] 0.041
57[40/6]
11[52/4]
51[13/2]
Table5-The prevalence of obesity in samples in terms of sleep rate
Sleep
hour
condition
/ Number[percent] The
prevalence
of
obesity[number/percent]
P
Normal
Overweight obesity
Less than 9 hours
99[15/8]
63[63/6] 21[21/2]
15
0.06
9-11 hours
28[74/2]
197[69/1] 52[18/2]
36[12/7]
Total
384[100]
260[67/8] 730[19]
51[13/2]
Source: research finding
Table6- The prevalence of obesity in samples in terms of father obesity
Father
obesity
Number[percent] The
prevalence
of P
obesity[number/percent]
Normal
Overweight obesity
Natural
173[45]
118[68/2] 32[18/5]
23[13/3] 0.0001
Overweight 165[43]
124[75/2] 35[21/1]
6[3/6]
Obese
46[12]
19[41/3]
6[13]
21[45/7]
Total
384[100]
260[67/8] 73[19]
51[13/2]
Source: research findings
Table 7- The prevalence of obesity in samples in terms of mother obesity
mother
obesity
Number[percent]
Natural
Overweight
Obese
Total
175[45/6]
166[43/2]
43[11/2]
384[100]
The
prevalence
obesity[number/percent]
Normal
Overweigh obesity
t
140[80]
24[13/7]
11[6/3]
101[60/8] 40[24/1]
25[15/1]
19[44/2]
9[20/9]
15[34/9]
260[67/8
73[19]
51[13/2]
Source: research findings
8
of P
0.001
384[1
00]
Table 8- The prevalence of obesity in samples in terms of mother education
mother
education
Number[percen
t]
Illiterate
, 32[8/3]
primary school
Guidance
96[25]
school
Diploma
179[46/6]
Higher diploma 77[20/1]
Total
384[100]
Source: research findings
The
prevalence
obesity[number/percent]
Normal
Overweigh obesity
t
21[65/6]
6[18/8]
5[15/6]
64[66/6]
19[19/8]
of P
13[13/5]
0.316
122[68/2]
53[68/8]
260[67/8]
34[19]
14[18/2]
73[19]
23[12/8]
10[13]
51[13/2]
Table 9- The prevalence of obesity in samples in terms of family income
family income
Number[percen
t]
Less
than
1milion toman
1-2milion
toman
More 2milion
toman
Total
151[39/3]
The
prevalence
obesity[number/percent]
Normal
Overweigh obesity
t
103[68/2] 27[17/9]
21[13/9]
160[41/7]
109[68/1]
29[18/1]
22[13/8]
73[19]
48[65/8]
17[23/2]
8[11]
384[100]
260[67/8]
73[19]
51[13/2]
of P
0.204
Source: research findings
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