The Impact of Nutrition and Exercise on the Academic Performance and the Physical Development of Adolescents Based on the Data of 165 Students Senior Project Zemplen Pataki European School of Luxembourg European Schools Science Symposium March 2012
Abstract This research investigated the impact of nutrition, exercise and other lifestyle habits on the academic performance and the physical development of adolescents. The factors that determine academic performance are primarily attitude, motivation, genetic mental ability and learning, but this research showed that lifestyle also has an impact. Students who did more than four hours of aerobic exercise a week, ate fish, and drank more than one litre of water a day had a better average-mark in school than those who did less. Staying hydrated and having a good oxygen supply are essential for brain function. Oxygen supply to the brain can be improved by increasing the basal metabolic rate through exercise. Fish is a source of Omega-3 fatty acids, which are building blocks for cell membranes and are used in the production of brain and nerve tissue. Small quantities of fish consumed had the same positive impact on academic performance as larger quantities. Conversely, those who were physically less active, smoked and drank a lot of colas did worse in school. This study seems to support the hypothesis that improvement can be made in academic performance by simply living a balanced life overall, eating and drinking healthily and exercising regularly. Exercise, eating habits and water intake also had an impact on the physical development of students participating in this research. Those students who exercised more had greater muscle mass and greater lung capacities. Students who drank more than one litre of water per day, exercised and ate dairy products regularly had higher bone calcium levels. Analysis of the different age-groups demonstrated that there was in fact a cumulatively greater incorporation of calcium into the bones of those boys who exercised more. Dairy product consumption in girls had a positive impact on their bones, but it also seemed to cause higher levels of body fat because of the fat these products naturally contain. 1
1. Aim The aim of my research is to demonstrate that exercise and good nutrition has a beneficial impact on the academic performance and the physical development of adolescents between the ages of 15 and 19. Based on what I have learned so far, exercise and a balanced diet should have a positive impact on the overall health, and the physical and mental fitness of adolescents. I assumed that students who do more exercise and eat healthier would have a greater muscle mass, relatively less fat, more calcium in their bones and better marks in school. I decided to test whether the assumed impacts of lifestyle could be demonstrated on a group of students using a questionnaire, spirometry and bioelectric impedance analysis. 2. Apparatus The Body Composition Monitor (see image 1) uses bioelectric impedance analysis (BIA) to estimate the fat content of the body, hydration level, calcium content of the bones and muscle mass. BIA works by passing a small electric current through the body. Different tissues conduct electricity differently, so their resistance or "bioelectric impedance" can be used to identify the type of tissue. The monitor also measures weight and can deduce the mass of each type of tissue. The spirometer (see image 2) is a device that measures the vital capacity of the lungs. The spirometer does this by measuring how much air is blown into it. I prepared a questionnaire in three languages with 20 questions primarily concerned with the amount of exercise the participants do and their diets. Other questions were also asked, such as how much water they drink, whether or not they smoke and what their average-mark in school was. 3. Method Students taking part in the research fill in the questionnaire. They take a few deep breaths and blow as much air out of their lungs and into the spirometer as possible. They can try this three times and the best result is taken. I enter their gender and height into the Body Composition Monitor. 2
They step barefoot onto the Body Composition Monitor and their body composition is measured. The data are entered into an excel spreadsheet and analysed using regression analysis and various groups of students are compared. 165 students participated in total: 101 students from various language sections of the European School of Luxembourg and 64 students from local sports clubs. 4. Challenges and Solutions during the Research: Firstly, I had to learn to use the equipment and to handle people during the experiment. I practised sharing and discussing their personal body measurements with them. Secondly, I had difficulties finding students at school to participate in my research. I started measurements at a school fair, but only adults participated voluntarily, so I realised that I needed help from teachers to convince students to take part in my research. My biology teacher spoke to the Director of the School and asked her for support. I could not skip lessons to do measurements, but it was arranged that during the Christmas exams, when I did not have lessons to attend, I could measure students in the 7th Year who still had lessons. It was challenging and required good timemanagement on my part to be able to prepare for and take exams whilst also gathering data for my research. I measured 63 students during the week of the exams. I needed more observations to see a clear trend. My biology teacher helped me during teaching time to get more data. The challenge this time was to not miss my lessons, but to still measure others while they were in school. I arranged to enter classes when I had free lessons to get more measurements. I thereby obtained data on a further 49 students. Gathering data outside school was even more problematic. My school tried to help by sending a letter to the local medical sports-exam centre and to the largest sports complex near our school. Neither of these approaches materialised. They suggested that I contact the various sports federations and coaches and measure athletes during their trainings. I took their advice and measured 64 people in my target age category during their practices with various sports-clubs. 3
Fourthly, I had difficulties analysing and interpreting all the data I gathered. I have not studied statistics at school and did not know how to run regressions. I read books, "help" menus on excel and talked to my biology and mathematics teachers and a professor of medical science. Finally, I had difficulty understanding why I was getting some results and why I was not getting other ones. I went to some academic book-stores and libraries to read and I also did research on the internet. I learned a lot in the process about research methods, biology and the human body and brain. 5. Results and conclusions regarding academic performance 101 European School students were taken when analysing the impact of lifestyle on acedemic performance. The average-mark of students in school was taken as a proxy for academic performance. The distributions of 101 students by average year-mark is illustrated in graph 1. Students from other schools were not included for this part of the analysis, because the marking methods of different schools are not comparable. First, average year-mark was analysed against six lifestyle factors using regression analysis. Regression analysis is a technique for modelling and analysing a dependent variable against one or more independent variables, where the variables are normally distributed. Linear regression estimates an equation of the following type: y = m 1 x 1 + m 2 x 2 + m 3 x 3 +... + m n x n + c. In this case, the dependent variable y stood for average year mark out of 10. The independent variables x 1 to x 6 stood for hydration level (%), colas (l/week), fish (servings/week), exercise (hours/week), water (l/day), and smoking (yes/ no). m 1... m 6 were coefficients of the x variables. The following overall result was obtained (see table 1). Multiple R is the measure of how accurate the line of best fit from the data is. It can vary from 0 to 1. The closer Multiple R is to 1, the stronger the relationship is between the dependent and independent variables. Multiple R in this regression was 0.32, which means that the x-variables in this analysis do not explain the y-variable very well. This was to be expected, since genetic factors, attitude, time spent studying etc. are clearly the most important factors. Furthermore, most of variables were not normally distributed, so regression analysis may not have been the appropriate analysis technique. 4
The details of the coefficients for each x-variable are shown in table 2. The greater the t Stat and the lower the P-value, the stronger the relationship is between the dependent variable and the particular x-variable. "The lower the P-value, the less likely it is that the difference happened by chance and so the higher the significance of the finding." 1 For most of the x-variables, the t Stat and P-value shows little statistical significance. Nevertheless, there is some relationship with the y- variable for colas intake (coefficient -0.144, p-value 0.077), fish servings (coefficient 0.133, p-value 0.12) and water intake (coefficient 0.128, p-value 0.199). Starting with these three, I analysed with a different method their impact on academic performance. 5.1 The impact of colas on academic performance Half the students reported that they drink colas and the other half reported they never do. I took the average of the average-marks of the two groups and compared them (see table 3). The result showed that there was virtually no difference as far as the average of the average-marks are concerned between those who drank colas and those who did not. However, when looking at those who drank a lot of colas, more than or equal to two litres a week, the average mark dropped significantly by 0.4. My questionnaire did not specify whether the colas intake included diet colas. Presumably those who drank a lot of colas also drank some diet colas. It is known that diet colas contains aspartame which is a mild neurotoxin that has damaging effects when consumed regularly. This may have been impairing the academic performance of the students. 5.2 The impact of fish on academic performance 85 students in this study reported that they ate fish regularly and 16 reported that they never ate fish. I took the average of the average-marks of the two groups and compared them. Students who ate fish at least once a week had better marks at school by 0.25 on average. Interestingly, students who ate fish more than once a week had no better results. Small quantities of fish consumed had the same positive impact as larger quantities (see table 4). 1 Medical Statistics Made Easy by M. Harris and G.Taylor, page 25 5
A lot has been written about the benefits of fish on the brain. First of all, "eating protein increases the supply of neurotransmitters, which are essential for mental alertness..." 2 Secondly, Omega-3 fatty acids can be found in fish. Omega-3 fatty acids are considered essential fatty acids, which "are building blocks for our cell membranes. They are used in the production of brain and nerve tissue." 3 Omega-3 fatty acids stimulate brain activity and "are necessary for the normal function of the eyes and the cerebral cortex. The cerebral cortex is the brain region that handles higher functions of reasoning and memory" 4, both essential for doing well in tests. In 2004, L. Steve and J. Burgess, researchers at the National Institute of Health in Washington D.C., found that children with higher scores in mathematics had higher amounts of long-chain fatty acids omega-3 and omega-6 in their blood." 5 In another study "of nearly 100 boys, those with lower levels of omega-3 fatty acids had more learning and behavioral problems (such as temper tantrums and sleep disturbances) than boys with normal omega-3 fatty acid levels." 6 Students in this research who ate fish were also more hydrated (see table 4). The average hydration level of those who ate fish more than once a week was 60.5% compared to 58.4% for those who did not eat fish. This might be because fish also contains hyaluronic acid, which is "one of the most hydrophilic (water-loving) molecules in nature" 7, so it binds readily to a lot of water. 5.3 The impact of water intake and hydration level on academic performance 65 students in this study reported that they drank more than one litre of water per day and 36 reported that they drank less than or equal to one litre. I took the average of the average-marks of the two groups and compared them (see table 5). 2 Train Your Brain by Terry Horne and Simon Wootton, page 4. 3 Power Up by Peter Albrecht, page 248. 4 The Omega-3 Miracle by Garry Gordon, page83. 5 Train Your Brain, page 5. 6 http://www.umm.edu/altmed/articles/omega-3-000316.htm 7 http://www.baxyl.net/ 6
Staying hydrated is vital for health and brain function. "You can improve mental performance by avoiding dehydration." 8 Students who drank more than one litre of water per day achieved better marks (8.1) than students who drank only one litre or less (7.8) (see table 6). There is little difference in the academic performance between those whose hydration level was higher and those whose was lower. This might be because "although body water content varies greatly between individuals, but the body strives to maintain 'water balance' - the water content of various tissues is maintained relatively constant." 9 5.4 The impact of smoking on academic performance 79 students in this study reported that they did not smoke and 22 reported that they did. I took the average of the average-marks of the two groups and compared them (see table 7). Cigarettes contain hundreds of toxins which can harm all human organs and smoking also affects academic performance in this research. Students who smoked had worse marks at school (7.76) than students who did not (8.03). 5.5 The impact of aerobic exercise on academic performance 67 students in this study reported that they did less than or equal to four hours of aerobic exercise per week and 34 reported that they did more than four hours. The highest number of hours a student exercised per week was 12.5 (see table 8). Based on what I have read, aerobic exercise should enhance thinking performance. "Brain activity is fuelled by oxygen and aerobic exercise increases the supply of oxygen to the brain." 10 "During exercise there is increased oxygen demand. Oxygen consumption during intense exercise can rise up to 15-fold resting levels and more importantly, oxygen flux in an active muscle can increase up to 100-fold..." 11 "Oxygen is carried to your brain in your blood and the rate at which it is 8 Train Your Brain, page 24. 9 Nutrition and Sport 10 Train Your Brain, page 10. 11 Nutrition and Sport by Don MacLaren 7
supplied depends, among other things, on the resting metabolic rate at which your heart pumps your blood. This can be raised by periodic aerobic exercise...the increased supply of oxygen to your brain will enable you to process information faster and to assess problems more quickly." 12 Many researchers have shown that groups who exercised aerobically achieved higher reasoning and thinking scores than those who did not. My study also shows that aerobic exercise enhances academic performance. Students who did more than four hours of aerobic exercise a week did better in school on average (by 0.13). This is not a big difference, but this might be due to the fact that the reported number of hours of aerobic exercise did not reflect the intensity of the exercise. 6. Results and conclusions regarding muscle mass The distribution of students by muscle mass is illustrated in graph 2. Boys had a greater muscle mass on average (54.7kg) than girls (42.8 kg). Gender and the muscle mass of one's parents have big impacts, but exercise is also significant in building muscle. Boys who exercised more tended to have a greater muscle mass (see graph 3 and tables 9 and 10). This relationship is statistically significant, because the probability that this happened by chance was only five percent. On average, boys who exercised 6 hours or more per week had 3.4 kg more muscle mass than boys who exercised less than 6 hours (56.5 kg and 53.1 kg respectively). The difference for girls was smaller: those who exercised 5 hours or more had 1.2 kg more muscle mass on average than those who did less than 5 hours (43.2kg and 42 kg of muscle respectively). Some exercises are more intense than others. Those who exercised more intensely, for example swimmers, had a greater lung capacity and a greater muscle mass than table tennis players. Tables 13 and 14 show lung capacities by sports for boys and girls. Those with a greater lung capacity had a greater muscle mass. This was a particularly strong relationship for boys (graph 4). 12 Train Your Brain, pages 11 and 23. 8
Lung capacity tends to increase with increased amount and intensity of exercise. Muscles need a lot of oxygen, so those who do more intense exercise breathe deeper, and over time lung capacity increases. In this sense, lung capacity reflects the quality of exercise. This is why the relationship between lung capacity and muscle mass was greater than between exercise and muscle mass. In this research, table tennis players trained more in terms of time than swimmers, but swimmers still had larger lung capacities on average. Even with less training, swimmers did more valuable exercise for their physical development than table tennis players. They worked their muscles more, and therefore had a greater muscle mass on average. Consuming dairy products also had some positive impact on boys (m=0.16, p-value: 0.08). Surprisingly for girls, it wasn't exercise that had the greatest impact, but drinking water (m=1.9, p- value: 0.02, see table 12), eating dairy products (m=0.2, p-value: 0.02) and most interestingly of all, drinking colas (m = 2.8, p-value: 0.00007). This is a very significant impact because the probability that it happened by chance is less than 0.01%! 7. Results and conclusions regarding fat percentage The distribution of students by fat percentage is illustrated in graph 5. Gender plays a very important role. Girls had a higher fat percentage than boys on average: 24% compared to 15.7%. I expected that those who exercised more would have a lower fat percentage. My study has not confirmed this hypothesis (see the statistically insignificant results in tables 15 and 16 for boys and in tables 17 and 18 for girls). I expected that those who ate more would have a higher percentage of fat. I had no way of finding out the daily calorie intake of the people in my research, but I investigated whether there was a relationship between fat percentage and the consumption of dairy products which are high in fat. Girls who ate more than or equal to 10 servings of dairy products per week had a higher body fat percentage (24.7% on average) than girls who ate less than 10 servings per week (20.7% on average) (see table 19). In this research, eating more had a greater impact on fat percentage than more exercise. 9
8. Results and conclusions regarding the mass of bone calcium The distribution of students by mass of bone calcium is illustrated in graph 6. Boys had a greater mass of bone calcium on average (2.9kg) than girls (2.3kg). Genetics are expected to be the most important factors determining bone calcium levels. For example, taller people have bigger bones and therefore also tend to have greater mass of bone calcium. Amongst lifestyle factors, I expected that consuming dairy products would have the greatest impact on bone calcium formation. Surprisingly, for boys, dairy product consumption had hardly any impact (see tables 20 and 21), whilst more than 5 hours of exercise per week had a clear impact on boys when analysing each of the age groups separately: 0.22 kg increase in bone calcium on average. Exercising more than 5 hours per week increased bone calcium in 15-16 year old boys by 5.6% compared to a more than 10% increase in 17-18 year old boys, from 2.9kg to 3.2kg (see tables 24 and 25). This shows that exercise had a significant cumulative impact on bone development in boys. For girls, the impact of exercise on bone formation was negligible (see tables 22 and 23). Dairy product consumption and drinking water had small, but statistically significant impacts. The bone calcium of girls who consumed more than 8 servings of dairy products per week was slightly higher (2.33kg) than for girls who ate less than that (2.25kg). Even though milk contains more calcium than water does, in this research drinking water had a greater impact than drinking milk: drinking more than 1 litre of water per day increased bone calcium by 0.15kg for boys and drinking more than 1.5 litres per day increased bone calcium by 0.11kg for girls. The coefficient was 0.098 for water compared to 0.012 for milk, both being statistically significant with p-values of 0.02 (see table 23.). It seems that the body absorbs calcium better from water than from milk. In this research, exercising seemed to aid the absorption and incorporation of calcium into bones. This might be because chemical reactions in the body speed up as a result of exercise, and the body tries to adapt to the strain of exercise by developing stronger bones. 10