Extended Essay
The study of obesity among primary school pupils in Szkola
Europejska
Research Question: Does calorific content, amount of proteins, carbohydrates and fats in
the school meals contribute to the abnormalities in body mass index among 9-12 aged
pupils of Szkola Europejska in Lodz?
IB Subject: Biology
by ……………………………
Candidate: ……………………
School: Szkoła Europejska (003065)
Łódź, Łódzkie, Poland
Diploma Session: May 2013
Word Count: 3936
Acknowledgments
I would like to thank my supervisor Mrs Marta Kamasińska for her continuous support,
guidance and providing me with valuable insight into this work. I would like to thank the
school nurse for letting me use her medical equipment in this research.
1
ABSTRACT:
The experiment was conducted to study the obesity among primary school pupils in
Szkola Europejska. The research question was formulated as: Do calorific content,
amount of proteins, carbohydrates and fats in the school meals contribute to the
abnormalities in body mass index among 9-12 aged pupils of Szkola Europejska in
Lodz?
The data was collected by measuring height and weight among 9-12 years old children
and giving them a questionnaire to fill. Also school meals menus throughout a week
were collected.
The data collected for height and weight was calculated into BMI values and then
subjected to two-tailed t-test. Subsequently, calorific content of school meals and their
amount of proteins, carbohydrates and fats were calculated and their relation to the
daily demand was determined. Those results were then compared to the number of
hours children spent on sports. Afterwards, the time required to burn average energy
value of a school meal was calculated.
The calculations of BMI value among 9-12 aged children showed that average BMI varies
between 5th percentile and 85th percentile, which is categorized as healthy weight. The
comparison of the t-test values proved no significant difference between children’s BMI
on average. Furthermore, it was showed that the daily breakfast demand for calories is
met only in 48%, and in the case of lunches is met in 89%. While the average content of
carbohydrates and fats in school meals is normal, the average protein content in school
meals exceeds 10% of the daily demand. Moreover, the calories burned during normal
activity exceed the average number of calories consumed in school meals.
The results indicated that school meals do not contribute to the BMI abnormalities
among 9-12 aged children and they do not exceed the daily demand for calories.
Nonetheless, the tendency to consume low-calories breakfasts and high-calories lunches
was manifested.
Word count: 302
2
CHAPTER 1: INTRODUCTION……..………………………………..................................................6
1.1 Research question……..………………………………..................................................……………6
1.2 Genesis of the work..………..………..………..………..………..………..………..………..………..…6
1.3 Theoretical background………..………..………..…………..………..………..…………..…………7
CHAPTER 2: METHODOLOGY………..………..………..…………..………..………..…………..….11
2.1 Objectives of the study………..………..………..…………..………..………..…………..…………11
2.2 Hypothesis………..………..………..…………..………..………..…………..………..………..………..11
2.3 Variables………..………..………..…………..………..………..…………..………..………..…………..11
2.4 Materials………..………..………..…………..………..………..…………..………..………..…………..12
2.5 Procedures………..………..………..…………..………..………..…………..………..………..………..12
2.6 Statistical analysis………..………..………..…………..………..………..…………..………..………13
CHAPTER 3: DATA COLLECTION AND PROCESSING………..………..………..…………14
3.1 Raw data for children………..………..………..…………..………..………..…………..………..…14
3.2 Raw data for school meals………..………..………..…………..………..………..…………..……15
3.3 Raw data for practiced sports………..………..………..…………..………..………..…………..18
CHAPTER 4: ANALYSIS AND INTERPRETATION:………..………..………..…………..…...19
4.1 BMI calculations:………..………..………..…………..………..………..…………..………..…………19
4.2 Food calculations:………..………..………..…………..………..………..…………..………..………..24
4.3 Sport calculations:………..………..………..…………..………..………..…………..………..……….27
CHAPTER 5: CONCLUSION AND EVALUATION………..………..………..…………..………29
5.1 Hypothesis I………..………..………..…………..………..………..…………..………..………..………29
5.2 Hypothesis II………..………..………..…………..………..………..…………..………..………..……..29
5.3 Caloric content of school meals ………..………..………..…………..………………..…………30
5.4 BMI………..………..………..…………..………..………..…………..………..………..…………..……….30
5.5 Sport………..………..………..…………..………..………..…………..………..………..…………..……..30
5.6 Evaluation………..………..………..…………..………..………..…………..………..………..…………32
3
BIBLIOGRAPHY………..………..………..…………..………..………..…………..………..………..………33
Appendix 1………..………..………..…………..………..………..…………..………..………..……………..34
Appendix 2………..………..………..…………..………..………..…………..………..………..……………..35
Appendix 3………..………..………..…………..………..………..…………..………..………..……………..36
CHAPTER 1: INTRODUCTION
1.1 Research question:

Does calorific content, amount of proteins, carbohydrates and fats in the
school meals contribute to the abnormalities in body mass index among 9-12
aged pupils of Szkola Europejska in Lodz?
1.2 Genesis of the work:
According to recent research, the number of overweight children in Poland has
increased three times over the past 20 years. It was estimated that the scale of the
obesity problem in Polish schools is coming closer to the one in America. While in
the United States, the percentage of children suffering from obesity is over 20%, in
Poland the issue applies to 18% children1. Furthermore, the consequences of
obesity among Polish children slowly begin to emerge: the majority of them suffer
from respiratory distress, hypoxia, hypertension, high cholesterol and dysfunction
of glucose metabolism. They eat too much salt, saturated fats and sugar, and not
enough fibre and unsaturated fats2. Under the influence of these studies, I began to
contemplate what is the determining factor of obesity among children. When
I started to look for the reasons behind this problem, I came across a large amount
of articles3 that suggested that one of the factors causing obesity among children is
the food served in schools. I was intrigued whether in my school, the school meals
contribute to weight problems among children of the primary school. Therefore,
1 http://zdrowie.dziennik.pl/profilaktyka/artykuly/408809,trzykrotnie-wzrosla-liczba-otylych-dzieci-w-polsce-
warszawa-chce-walczyc-z-nadwaga-i-otyloscia-w-szkolach.html
2 http://www.farmacjaija.pl/zdrowie/co-powinny-jesc-dzieci.html
3 http://children.webmd.com/news/20100315/school-lunches-linked-to-kids-obesity
4
a thorough study of the relationship between the consumption of meals at school
and the tendency to be overweight should be done.
1.3 Theoretical background:
Body Mass Index
Body Mass Index (BMI) or Quetelet index, is an estimate of body composition used
extensively as an indicator of whether an individual is clinically classified as obese.
The Body Mass Index is defined as weight in kilograms divided by the square of
their height in metres4.
𝐵𝑀𝐼 =
𝑚𝑎𝑠𝑠 [𝑘𝑔]
(ℎ𝑒𝑖𝑔ℎ𝑡 [𝑚])2
Estimating the BMI for children slightly differs from the one for adults, given that a
child’s BMI changes while they mature. In children, the child’s age is necessary in
order to compare the obtained result to typical values for children of the same age.
Instead of fixed thresholds for underweight and overweight such as those used for
adults, the BMI percentile indicates the relative position of …………., etc
Importance of breakfast and lunch consumption
Eating breakfast is the most optimal way to meet the energy needs of the body. Daily
consumption of breakfasts provides a better functioning of the digestive and circulatory
system and improves the ability to concentrate. If an individual does not provide the
body with food in a breakfast, in their empty stomachs hypersecretion of acid occurs,
therefore causing mucous membrane irritation and disruption of the digestive system.
Resistance to cold decreases and the concentration of glucose in the blood decreases,
which can lead to dizziness or even fainting. For this reason, some people may prove
themselves to be less efficient at work or school. The research that was carried out on a
group of several hundreds of British has confirmed that regular breakfast consumption
improves mood and well-being5. Two experimental groups were set up, both of which
4 Michael Kent, Oxford Dictionary of Sports Science & Medicine Second Edition, page 74
5
http://www.masaz.toskar.info/sniadanie-najwazniejszym-posilkiem-dnia.php
5
ate according to their previously calculated energy requirements. The only difference
between the two groups lied in the fact that one group ate their entire portion of calories
in the morning (provided in a large breakfast), and the other group, for dinner. The
group that ate in the evening gained weight, whereas the other group that ate in the
morning lost weight, even though they all ate as much as their body theoretically
needed. Therefore, in order to maintain a constant weight, the amount of food consumed
is as essential as the way it affects the metabolism. The sooner the body is provided with
food, the more the body is set to burn the energy supplied to it, however, the later there
is a greater tendency of body fat deposition. Daily breakfast consumption increases the
metabolism from 3 to 10%, consequently, we can gain or lose 10 pounds on an annual
basis6.
The benefits of regular breakfast consumption:

Better resistance to stress

Immune system is more efficient

Nervous system is more efficient

Helps in maintaining healthy weight

Controls hunger throughout a day

Reduces the likelihood of overeating
In Poland, the tendency to eat low-calories breakfasts and high-calories lunches is
manifested. According to recent research conducted in Poland, 22% of parents claimed
that their children do not eat breakfast three out of five days a week. Only slightly more
than half of the parents make sure that their children do not come to school hungry.
Moreover, 95% of children between 6 and 11 years old, do not consume lunch at school,
and one in five Poles do not eat breakfast at all7.
Daily demand for calories and the role of essential nutrients in the human body

Calories
The recommended food ration is deliberately chosen set of products, including their
amount in order to cover the body’s daily requirement for all nutrients. The
6
http://www.masaz.toskar.info/sniadanie-najwazniejszym-posilkiem-dnia.php
7http://metromsn.gazeta.pl/Lifestyle/1,126513,12818816,Polacy_nie_jedza_sniadan__To_niezdrowo__Jak_ich_zacheci
c.html
6
recommended daily calories intake for children aged 9-12 years is 2300 cal. Depending
on the number of meals per day, breakfast should coincide 25-35% and lunches 15-30%
of total daily caloric intake8.

Proteins
Protein is the basic structure of all living cells. It is an important part of cell membranes,
blood (haemoglobin) and enzymes. Proteins determine the growth of young organisms
and support the growth of hair, nails and help in reconstruction of damaged skin
epithelium and healing of wounds. Antibodies are made up of proteins, therefore they
play protective role in the organism. The effects of protein deficiency include……., etc

Carbohydrates
Carbohydrates are the main source of energy to the body, providing approximately 5060% of the energy. Deficiency of carbohydrates in a diet is harmful to the body and
reveals itself primarily as a feeling of hunger, general weakness, fainting, muscle tremor
and convulsions. The symptoms of hypoglycemia are related to the shortage of sugar as
the basic energy material for muscles and nerve cells. At least one third of daily calories
should come from energy supplied by carbohydrates. It is estimated that ………, etc

Fats
Fats play important role in the human body. They provide a significant amount of energy
(20 to 35%). One gram of fat gives the body 37.7 kJ of energy; approximately twice as
much as proteins and saccharides. Fats are also a major source of essential fatty acids
and fat-soluble vitamins (A, D, E and K). Some fatty acids are involved in the synthesis of
certain hormones tissues, such as prostaglandin. Fats in moderate amounts are the
essential human nutrients. They are the main source of ………………, etc
CHAPTER 2: METHODOLOGY
2.1 Objectives of the study:

To calculate the caloric content of school meals.
Wiesław Graban, Witold S. Gomułka, Encyklopedia Zdrowia, Wydawnictwo Naukowe PWN, Warszawa 2001, page
383
8
7

To estimate the average number of hours spent by children on sport activities.

To verify how much exercise is needed to burn the average school meal

To check whether school meals are appropriate for pupils of particular age.
2.2 Hypothesis:

HYPOTHESIS 1: School meals exceed the daily breakfast and lunch demand for
calories and daily demand for proteins, carbohydrates and fats.

HYPOTHESIS 2: School meals have too many calories to be burnt during the
pupil’s normal activity.
2.3 Variables:
Table 2.1 – Independent, dependent and controlled variables in the experiment
Independent Variables

Subjects

School meals

The number of hours
Dependent Variables
Controlled Variables


Body
mass
index
(BMI)

The
between 9 and 12
amount

proteins,
children
carbohydrates

Weight [kg]
fats in school meals

Height [m]
[g]

Age

Gender
Caloric
years old)
of
spent on sports by

Age group (children
and
content
Length
of
experiment (5 days)
of
school meals [kcal]
2.4 Materials:

Stadiometer

Medical Scale

CDC Body Mass Index-For-Age Percentiles for boys (2 to 20 years) (Appendix 1)
8
the

CDC Body Mass Index-For-Age Percentiles for girls (2 to 20 years) (Appendix 2)

Texas Instruments TI-84 Plus

Food calorie table

Questionnaire (Appendix 3)

Letter to parents asking for permission to conduct research on their children
(Appendix 4)
2.5 Procedures:
Procedure 1 – Medical examination of the children
1. Before the experiment begins, ask the parents for permission to conduct the
research on their children.
2. Having a parental consent, collect a group of children between the ages of 9 to 12
years (five or more in each age group).
3. Measure the height and weight of each child using stadiometer and medical scale.
4. Give them previously prepared questionnaire about sports they practice.
5. Having collected all the data, calculate each child’s BMI and plot it on CDC Body
Mass Index-For-Age Percentiles growth chart for either boys or girls, in order to
find out the percentile range and weight status category of a particular child.
6. Calculate the amount of …………………., etc
Procedure 2 – School meals
1. Everyday for one week, collect the school meals menu of food that children
consume.
2. Once all the data is collected calculate the caloric content of school meals using
food calorie table.
3. Calculate how much protein, fats and carbohydrates those meals contain.
4. Compare the obtained results with daily food intake for various calorie demands.
5. Evaluate the results.
2.6 Statistical analysis
Mean:
𝑥=
Σ𝑥
𝑁
Standard deviation:
9
𝜎=√
∑(𝑥 − 𝑥)2
𝑁
T-test:
𝑡=
(𝑥𝑚𝑒𝑎𝑛1 − 𝑥𝑚𝑒𝑎𝑛2 )
2
2
√ 𝑆1 + 𝑆2
𝑛1 𝑛2
CHAPTER 3: DATA COLLECTION AND PROCESSING
…………………………………………………………………………..……..
………………………………………………………………………………….
CHAPTER 4 – ANALYSIS AND INTERPRETATION
4.1 BMI calculations
As it can be seen in tables 4.1-4.4, information about BMI of children aged 9-12
years old, is presented. BMI was calculated using the following formula:
𝑚𝑎𝑠𝑠 [𝑘𝑔]
𝐵𝑀𝐼 = (ℎ𝑒𝑖𝑔ℎ𝑡 [𝑚])2 . The obtained values were then marked on the CDC Body Mass
Index-For-Age Percentiles growth charts in order to receive a percentile ranking
and weight status category of children.
Table 4.1 – BMI, percentile range and weight status category for 9 years old children
9 year old
children
1
2
3
4
5
Average
SD
BMI
Percentile range
Weight status
category
17
20
14
15
15
16
2.17
5th percentile up to the 85th percentile
85th to less than the 95th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
Healthy weight
At risk of overweight
Healthy weight
Healthy weight
Healthy weight
Healthy weight
10
Table 4.2 – BMI, percentile range and weight status category for 10 years old children
10 year old
children
1
2
3
4
5
6
Average
SD
BMI
Percentile range
Weight status
category
15
20
20
16
17
17
15
6.66
5th percentile up to the 85th percentile
85th to less than the 95th percentile
85th to less than the 95th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
Healthy weight
At risk of overweight
At risk of overweight
Healthy weight
Healthy weight
Healthy weight
Healthy weight
Table 4.3 – BMI, percentile range and weight status category for 11 years old children
11 year old
children
1
2
3
4
5
6
Average
SD
BMI
26
20
17
15
15
17
18
3.88
Percentile range
Weight status
category
Greater than or equal to the 95th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
Overweight
Healthy weight
Healthy weight
Healthy weight
Healthy weight
Healthy weight
Healthy weight
Table 4.4 – BMI, percentile range and weight status category for 12 years old children
12 year old
children
1
2
3
4
5
6
7
Average
SD
BMI
Percentile range
Weight status
category
18
19
18
20
21
18
20
19
1.22
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
85th to less than the 95th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
5th percentile up to the 85th percentile
Healthy weight
Healthy weight
Healthy weight
Healthy weight
At risk of overweight
Healthy weight
Healthy weight
Healthy weight
In order to establish if the difference between children’s BMI is significant, a two-tailed
Student’s t-test is performed. Based on BMI values of 9 and 10 years old children, a test
of comparing the mean and standard deviation of two sets of samples to see whether
11
they are equivalent or different, is conducted. A value for t is calculated using
a statistical formula:
𝑡=
(𝑥𝑚𝑒𝑎𝑛1 − 𝑥𝑚𝑒𝑎𝑛2 )
2
2
√ 𝑆1 + 𝑆2
𝑛1 𝑛2
The result of t-test for BMI values of 9 and 10 years old children came out as follows:
Table 5 – Example calculations for the t-test
Body Mass Index
(𝑥 − 𝑥̅ )2
𝑥
𝑥 − 𝑥̅
9 year old 10 year old 9 year old 10 year old 9 year old 10 year old
children
children
children
children
children
children
17
15
1
-3
1
9
20
20
4
2
16
4
14
20
-2
2
4
4
16
-1
-2
1
4
15
15
17
-1
-1
1
1
17
-1
1
2
23
23
∑(𝑥 − 𝑥̅ )
𝑛9 = 5
𝑛10 = 6
Figure 2 – Example calculations for the t-test
1. State the null and alternative hypothesis
𝐻0 = 𝜇𝐵𝑀𝐼 𝑜𝑓 9 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 = 𝜇𝐵𝑀𝐼 𝑜𝑓 10 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛
𝐻𝐴 = 𝜇𝐵𝑀𝐼 𝑜𝑓 9 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 ≠ 𝜇𝐵𝑀𝐼 𝑜𝑓 10 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛
2. Calculate the variances
𝑆92 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑
Σ(𝑥 − 𝑥̅ )29 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑
=
𝑛9 − 1
2
𝑆10
𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 =
2
Σ(𝑥 − 𝑥̅ )10
𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑
𝑛10 − 1
12
23
= 5.75
5−1
23
=
= 4.60
6−1
𝑆92 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 =
2
𝑆10
𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑
3. Calculate the actual difference between means
(𝑥9 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 − 𝑥10 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑) = 5.75 − 4.60 = 1.15
4. Calculate the t value
𝑡=
(𝑥𝐵 − 𝑥𝐴 )
2
2
√ 𝑆9 + 𝑆10
𝑛9 𝑛10
=
1.15
√5.75 + 4.60
6
5
= 0.83
5. Determine degrees of freedom
d.f. (𝑛9 + 𝑛10 − 2) = (5 + 6 − 2) = 9
6. Consult the t-table
For the calculation of Body Mass Index, the calculated value of t=0.83 is lower than the
critical value=2.26, therefore there is no significant difference between BMI of 9 years
13
old children and 10 years old children on average and we do not reject 𝐻0 =
𝜇𝐵𝑀𝐼 𝑜𝑓 9 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 = 𝜇𝐵𝑀𝐼 𝑜𝑓 10 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 .
Average Body Mass Index (BMI)
Graph 4.1 – Average Body Mass Index (BMI) for 9-12 years old children.
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
18
18
19
16
9 years old children
10 years old children 11 years old children 12 years old children
Age group
Average BMI value in children aged 9 years is 16, which is 5th percentile up to the 85th
percentile in percentile range and it is categorized as healthy weight. In the case of 10
and 11 year-olds, average BMI value is estimated to be 18, which is also classified as
healthy weight. In 12 year-old children, average BMI value is 19 and it is categorized as
healthy weight as well. Among the 24 children examined, subject 1 (11 years old) is the
only one whose BMI percentile is greater than or equal to the 95th percentile, which is
categorized as overweight in weight status category. In the case of subject 2 (9 years
old), subject 2 and 3 (10 years old) and subject 5 (12 years old) BMI percentile is 85th to
less than the 95th percentile in percentile range, which is classified as at risk of
overweight. Those children who deviate from the average represent 21% of all
examined children and a child, whose BMI is in the extreme value of 10% on the upper
side of the CDC BMI growth charts (above the 95th percentile) require careful
observation.
14
4.2 Food calculations
Average energy value of food, proteins, carbohydrates and fats obtained from both
breakfasts and lunches was calculated using the following formula: 𝑥 =
Σ𝑥
𝑁
Table 4.5 – Average energy value of food, proteins, carbohydrates and fats
Day of the week
Monday
Tuesday
Wednesday
Thursday
Friday
Average
SD
Graph
4.2
–
Energy value of food
[cal] (±0.01)
949.50
1075.48
1054.26
963.81
956.39
999.89
53.67
The
daily
demand
Proteins
[g] (±0.01)
48.09
57.67
41.06
44.73
58.54
50.02
6.97
for
proteins,
Carbohydrates [g]
(±0.01)
110.08
83.06
104.37
76.09
120.26
98.77
16.63
carbohydrates
Fats [g]
(±0.01)
33.77
59.34
54.20
52.81
30.05
46.03
11.79
and
fats.
The percent daily value for essential nutrients (%)
120%
110%
100%
90%
80%
70%
60%
50%
110%
40%
72%
30%
20%
34%
10%
0%
Proteins
Carbohydrates
Essential nutrients
Fats
As it can be seen on the graph above, average protein content in school meals exceeds
10% of the daily demand for proteins. Daily requirement for carbohydrates is met in
34% and in the case of fats, the daily demand is met in 72%.
15
Graph 4.3 – The percent daily demand for calories
The percent daily caloric value for school
meals (%)
100
90
80
70
60
50
40
30
20
47
41
46
42
42
10
0
Monday
Tuesday
Wednesday
Thursday
Energy value of food [cal]
Friday
The graph 4.3 presents the percent daily demand for calories in comparison to the
percent caloric content of food served in school. The values are roughly approximate to
each other, ranging between 40 and 50%. On Monday, daily demand for calories is met
in 41%, which makes it the lowest value, whereas on Tuesday, it is met in 47%, which
makes it the highest value.
Graph
4.4
–
The
percent
daily
demand
for
breakfasts
The percent daily demand for breakfasts and
lunches (%)
160
140
120
100
80
134
60
40
67
20
0
Breakfasts
Lunches
16
and
lunches
The graph 4.4 demonstrates the average percent daily demand for breakfasts and
lunches obtained from school meals. The daily breakfast demand for calories is met in
48% and the daily lunch demand for calories is met in 89%.
4.3 Sport calculations
As it can be seen in graphs 4.5 and 4.6 energy balance of the body is calculated. Energy
balance is the difference between the amount of energy delivered to the body in food in
the form of carbohydrates, fats and proteins, and the amount of energy expended by the
body in the form of work and heat, in the same period of time.
Graph 4.5 – Comparison of the average number of calories burned through physical activity with
an average caloric content of meals.
1014
1012
1010
Calories [cal]
1008
1006
1004
1012
1002
1000
998
1000
996
994
Average calories burned through
physical activity
Average calories consumed in a school
meal
As it can be seen on the graph 4.5 the average number of calories burned through a
physical activity exceeds the average number of calories consumed in school meals.
Therefore, energy balance is balanced because both sides are approximately equal.
17
Graph 4.6 – The time required to burn average energy value in a school meal.
Brisk walking
550
Swimming
210
Cycling (20 km/h)
140
0
100
200
300
400
Time in minutes
500
600
The graph above shows how much an individual has to spend on a particular sport in
order to burn average caloric content of a school meal (999.89 cal). To burn the calories
consumed in shortest time possible, a child has to spend 140 minutes cycling at the
speed of 20 km/h, whereas, brisk walking takes the longest time to burn the energy
value of food.
CHAPTER 5: CONCLUSION AND EVALUATION
5.1 Hypothesis I
The hypothesis I states that school meals exceed the daily breakfast and lunch demand
for calories and the daily demand for proteins, carbohydrates and fats. The graphs and
the processed data demonstrate that the daily breakfast demand for calories is met only
in 48%, therefore children obtain only half of the calories needed for their bodies to
function properly. In the case of lunches, the daily demand for calories is met in 89%,
which is fairly close to meeting the daily requirement. Therefore, the statement that in
Poland there is a tendency to eat low-calories breakfasts also applies to children, who go
to Szkoła Europejska. However, as far as the daily demand for proteins, carbohydrates
and fats is concerned, presented data clearly show that average protein content in
school meals exceeds 10% of the daily demand. Once again it must be emphasized that it
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is not known whether children exceed this limit even further consuming more proteins
at home. The excessive consumption of proteins is as harmful as its deficiency and it
results in metabolic disorders, such as acidosis and it also increases the risk of obesity.
Therefore, school ought to reduce the amount of proteins in the school meals and
increase the amount of carbohydrates intake, which as the data demonstrate, meets the
daily demand only in 34%. From a health point of view, reducing the consumption of
carbohydrates is incorrect and unhealthy. Carbohydrates are not only a source of energy
for neurons but also facilitate fat burning. As far as fats are concerned, the daily demand
is met in 72% and it seems to be in sufficient quantity. Therefore, the hypothesis that
school meals exceed the daily breakfast and lunch demand for calories and the daily
demand for proteins, carbohydrates and fats must be rejected for calories,
carbohydrates and fats, but accepted for proteins.
5.2 Hypothesis II
The hypothesis II states that school meals have too many calories to be burnt during the
pupil’s normal activity. The graphs and the processed data demonstrate that calories
burned during the pupil’s normal activity exceed the average number of calories
consumed in school meals. Therefore, the hypothesis must be rejected. However, the
data are not entirely accurate given the fact that some of the children examined in a
particular week did not practice sport at all and children who practiced a large amount
of sport made up that average. If the data for each child was calculated separately,
whether the hypothesis is either accepted or rejected would be different for each child.
5.3 Caloric content of school meals
The graphs and the processed data demonstrate that the daily demand for calories is
met approximately in 41-47%, therefore children get only half of the calories they need
in order for their body to function properly. Nonetheless, the experiment involved only
the food consumed in the school cafeteria and did not include meals consumed outside
of school. Consequently, it is not know whether children generally exceed or fall within
the limit of the daily demand for calories, however, the school meals certainly do not
exceed this limit.
5.4 BMI
19
Considering children’s BMI value, the average BMI is in 5th percentile up to the 85th
percentile range for each age group, which is categorized as healthy weight.
Furthermore, the t-test showed that there is no significant difference between children’s
BMI values of each age group on average. Nonetheless, there are four subjects that
deviate from the average. However, it is unlikely that school meals have contributed to
the abnormalities in their Body Mass Index. As I have mentioned before, it is not known
what children consume outside the school and what time of day they eat, therefore, it is
possible that home-prepared food could affect their BMI. Furthermore, the experiment
did not include whether children have health conditions such as hypothyroidism, which
contribute to weight gain, thus it is not known precisely what factors could affect their
BMI. Moreover, health weight range of BMI is in a fairly wide range, in order to take into
account people of different physical characteristics. Nonetheless, like in any other
mathematical formula, BMI calculations have some limitations; people with genetically
determined thick bones tend to have overestimated value of BMI and it does not include
muscle and water mass.
5.5 Sport
Calculations concerning time required to burn average energy value in a school meal are
approximate and in most cases not much useful if they are not verified in practice. It is
due to the fact that every human body is different and they differ from each other in
number of factors, in which the greatest impact is the error in the calculations of the rate
of metabolism and the composition of other body tissues. All the calculations above are
purely theoretical and tentative. Only exercise in controlled laboratory conditions,
where calorimetric energy change, the composition of exhaled air and a number of other
factors are tested, can give accurate values. Counting and burning calories predictions
are useful in the initial planning stage of exercising, but then all of the calculations
should be verified in practice by observing increase and decrease of both fat and lean
body mass, and on this basis, the amount of exercise should be controlled.
5.6 Evaluation
Factor
BMI calculations
Effect on Experiment
Improvement
Due to the fact that BMI Use
20
other
body
fat
calculation does not include measurement methods,
bones, muscle and water mass, such as bioelectrical
it is possible that it gave impedance analysis.
overestimated values.
Children
School meals
Children’s approach towards
the questionnaire was trivial,
and consequently it gave
inaccurate results, therefore
children had to re-answer the
questionnaire.
Weight of each product was
given by those preparing
meals, which then affected the
accuracy of calculations of the
amount of calories a particular
product had and therefore the
whole amount of calories in
school meals.
Perform a study on
children in adolescence.
Measure the weight of
each product using
weighting scales in
order to obtain accurate
values.
Bibliography
1. Wiesław Graban, Witold S. Gomułka, Encyklopedia Zdrowia, Wydawnictwo
Naukowe PWN, Warszawa 2001
2. Michael Kent, Oxford Dictionary of Sports Science & Medicine Second Edition,
Oxford University Press 1998
3. http://metromsn.gazeta.pl/Lifestyle/1,126513,12818816,Polacy_nie_jedza_sniad
an__To_niezdrowo__Jak_ich_zachecic.html
4. http://zdrowie.dziennik.pl/profilaktyka/artykuly/408809,trzykrotnie-wzroslaliczba-otylych-dzieci-w-polsce-warszawa-chce-walczyc-z-nadwaga-i-otyloscia-wszkolach.html
5. http://www.farmacjaija.pl/zdrowie/co-powinny-jesc-dzieci.html
6. http://children.webmd.com/news/20100315/school-lunches-linked-to-kidsobesity
7. http://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/about_childr
ens_bmi.html#What%20is%20BMI%20percentile
21
Appendix 1
22
Appendix 2
23
Appendix 3
1. Did you practice sport throughout the week? If so, please specify.
☐Yes: ____________
☐No*
2. How much time have you devoted your time to practice the aforementioned
sport?
☐______________
3. Did you attend physical education classes this week?
☐Yes
☐No
*If you have chosen this answer, you are not obliged to answer next questions.
Appendix 4
Dear __________,
My name is Eleonora U. …………….. and I am a student of International
Baccalaureate program in Szkola Europejska in Lodz. Under this program, I am obliged
to write a research paper of a topic of my interest, which in my case is The Study of
Obesity Among Primary School Pupils in Szkola Europejska. In order to conduct my
research,
I need your permission for your child to be medically examined. It would
involve measuring the height and weight of your child and launching of a questionnaire.
All information will be anonymous.
If you agree to have your child examined, please put your signature in
a designated area.
I give my permission for my child to undergo medical examination.
Signature:__________________________________
24