Differences in dietary patterns between overweight and normal-weight adolescents

Różnice w zachowaniach żywieniowych młodzieży z nadwagą i prawidłową masą ciała

Maria Jodkowska, Anna Oblacińska, Izabela Tabak, Katarzyna Radiukiewicz
Department of Child and Adolescent Health
Head of Department: dr hab. med. prof. IMiD K. Mikiel-Kostyra
Institute of Mother and Child, Warsaw
Director: S. Janus

* Acknowledgments. The OLAF study was supported by a grant from Iceland, Liechtenstein and Norway through the EEA Financial Mechanism and the Norwegian Financial Mechanism, and the Ministry of Science and Higher Education of Poland; grant number: PL0080.


Abstract

The aim of the study: To investigate the dierences in the dietary patterns of Polish overweight and normal weight adolescents.
Materials and methods: The study was carried out on a group of 1906 pupils from gymnasium (lower secondary school) aged 13-15 years, of whom 953 were overweight and 953 had normal body mass. The sample was taken from a representative group of 8386 pupils. Their height and body weight were measured, and their BMI was calculated. Overweight was dened as BMI 385 percentile for gender and age. Using the method of "selection in pairs", each overweight pupil was paired with a pupil with normal body weight. The research tool was a self-reported questionnaire, containing questions regarding how often selected food products were usually consumed during the week, how regularly basic meals (breakfast, lunch, supper) were eaten, and data on snacking.
Results: Overweight adolescents consumed unhealthy products such as sweets and crisps significantly less often than their peers with appropriate body mass. Overweight girls ate dark bread significantly more often, and consumed soft drinks less often than their peers with normal weight. Overweight adolescents had more irregular meals than those with normal weight: only 44% overweight adolescents had breakfast every day, significantly less than adolescents with normal weight. Nevertheless, overweight teenagers snacked significantly less often than young people with normal body mass. The overweight teenagers also less often chose snacks with high fat content, sugar and salt, and more often vegetables, fruits, as well as yoghurt and kefir.
Conclusions: 1. Our study shows that compliance of low energy diet alone does not ensure the maintenance of normal body weight. Irregularity of meals and breakfast skipping play an important role in developing overweight and obesity in adolescents. 2. In future studies on dietary patterns in a larger sample of adolescents, emphasis should be placed on adding questions about portion size, food preparation and meal time. Eating behaviours of parents should be also examined in relation to their body weight.

Key words: dietary patterns, overweight, normal body weight, adolescents

Streszczenie
Cel: Celem pracy było zbadanie róznic w sposobie zywienia polskich nastolatków z nadwaga i bez nadwagi w zakresie czestosci spozywania wybranych produktów zywnosciowych, regularnosci spozywania posiłków oraz pojadania miedzy posiłkami.
Materiał i metoda: Badania przeprowadzono w grupie 1906 uczniów gimnazjów w wieku 13-15 lat (953 z nadwaga i 953 z prawidłowa masa ciała), wyłonionych z reprezentatywnej próby 8386 uczniów. Dokonano u nich pomiarów wysokosci i masy ciała oraz obliczono wskaznik BMI. Za nadwage i otyłosc przyjeto wartosci BMI równe i powyzej 85 centyla, odpowiedniego dla płci i wieku. Stosujac metode „doboru w parach”, do kazdego ucznia z nadwaga i otyłością dobrano ucznia o prawidłowej masie ciała.
Narzedziem badawczym był kwestionariusz ankiety, zawierajacy miedzy innymi pytania dotyczace czestosci spozywania wybranych produktów zywnosciowych w tygodniu, regularnosci spozywania podstawowych posiłków (sniadanie, obiad, kolacja) oraz pojadania miedzy posiłkami.
Wyniki: Nastolatki z nadwaga istotnie rzadziej spozywały produkty niesprzyjajace zdrowiu: słodycze i chipsy niz ich rówiesnicy z prawidłowa masa ciała. Dziewczeta z nadwaga istotnie czesciej spozywały.
ciemne pieczywo, a rzadziej słodkie napoje gazowane niz rówiesniczki bez nadwagi. Młodziezy z nadwaga czesciej nieregularnie spozywała codziennie podstawowe posiłki niz rówiesnicy z prawidłowa masa ciała. Tylko 44% nastolatków z nadwaga codziennie spozywało sniadanie, istotnie mniej niz nastolatków z prawidłowa masa ciała. Nastolatki z nadwaga istotnie rzadziej pojadały miedzy posiłkami niz młodziez z prawidłowa masa ciała. Rzadziej takze wybierali przekaski o wysokiej zawartosci tłuszczu, cukru oraz soli, czesciej za to warzywa, owoce oraz jogurty i kefiry.
Wnioski: 1. Nasze badanie wskazało, ze samo przestrzeganie diety niskoenergetycznej nie gwarantuje utrzymania naleznej masy ciała. Wydaje sie, ze nieregularnosc posiłków i opuszczanie sniadan odgrywa istotna role w rozwoju nadwagi i otyłosci u nastolatków. 2. W przyszłych badaniach zachowan zywieniowych w wiekszej grupie młodziezy, korzystne byłoby dodanie pytan dotyczacych sposobu przyrzadzania potraw, ich objetosci, czasu poswiecanego na spozywanie posiłków oraz zbadanie zachowan zywieniowych rodziców, takze w kontekscie ich masy ciała.

Słowa kluczowe: zachowania żywieniowe, nadwaga, prawidłowa masa ciała, młodzież

INTRODUCTION
In recent decades, the growing global epidemic of obesity among children, adolescents and adults has resulted in a significant increase in research into the causes of this phenomenon. Generally, it is considered that the main risk factors for obesity include inappropriate eating behaviour and too low level of physical activity (1, 2). Nutritional behaviour consists of many factors, including the content of the meal, the size of the products’ portions and the frequency of their consumption, the number, regularity and duration of the meals during the day, their preparation and their consumption, family meals (3, 4).
Puberty is the critical period for the development of overweight and obesity. Overweight adolescents are likely to become overweight or obese adults. Adolescence witnesses sudden acceleration in physical development, changes in the body’s build associated with the redistribution of fatty tissue, as well as changes in the psycho-emotional sphere. Teenagers take independent decisions on what they will eat and how they will spend their leisure time. They often eat unhealthy meals associated with an excessive intake of energy (the consumption of fast-food ‘energy’ snacks, drinking sweet drinks). Also they had too low energy expenditure (avoiding physical education lessons in school, watching television and using computers for several hours a day) (5-7).
In addition to the already mentioned consumption of high-energy products, excessive body weight is also associated with irregular consumption habits and too little consumption of vegetables and fruits. Regularity of eating, including the daily consumption of breakfast (8), is an important factor affecting not only the maintenance of appropriate body weight, but also children’s and young people’s disposition to learn, and their overall well-being (9). Skipping meals and too long gaps between them cause people to eat larger servings or to consume high energy snacks. This leads to accumulation of fatty tissue. To stay healthy, including the proper maintenance of body mass one should eat no less than four meals during the day, at intervals of not more than 4 hours; and where possible, at about the same time of day (6). In regard to children and young people, the recommended number is 5 daily meals, as one element in the prevention of obesity (10). Accurate knowledge of how the overweight adolescents eat could allow us to discover the common errors in this area. The vast majority of dietary irregularities can be modified. This, therefore, is the starting point for the application of appropriate strategies to prevent obesity.

THE AIM OF THE STUDY
The aim of the study was to investigate the differences in the dietary habits of Polish adolescents who were overweight and those who were of normal weight, in the following respects:
- how often selected food products were consumed,
- the regularity of the meals,
- snacks eaten between meals.

SUBJECTS AND METHODS
The study design and participants
The study was conducted in the autumn of 2005 on 1906 pupils. They were taken from a representative sample of 8384 lower secondary school (gimnazjum) pupils aged from 13 to 15 years (from the 1st, 2nd and 3rd grades), in 5 provinces (województwa) in Poland (11). School nurses measured the subjects’ body weight and height in accordance with the standard screening test for the detection of physical development disorders (12). The pupils’ BMI (Body Mass Index) was calculated and their growth chart established in accordance with their gender and age, according to the tables of BMI values developed by A. Krzyzaniak (13) for the Polish population in 2004. Overweight was defined as a BMI value equal to or above 85 percentiles, according to gender and age. All the pupils who met this criterion were invited to participate in the self-reported questionnaire survey.
Using the method of "selection in pairs", each overweight pupil was paired with a pupil of normal body weight (standard) – the next one in the class register, or another who was closest to meeting the following criteria: the same sex, with a difference in age no greater than ±9 months, BMI ranging between 15 and 75 percentiles, and displaying no chronic diseases. Pupils from both groups participated in a questionnaire study concerning health, lifestyle (including nutritional behaviour), their relationship with their peers, and their social environment. The study was carried out by the school nurses. Questionnaires were received from 998 pupils from the obese group and 1015 from the control group. 79 surveys were rejected due to selection errors of pairs, or the absence of responses to questions on gender and age. In further analyses, data from 1906 questionnaires was included (953 from each group, 400 boys and 553 girls).
In the presented study, questions regarding the frequency of weekly consumption of selected food products, basic meals (the regularity of their consumption) and snacks between meals were used*:
- How many times a week do you usually eat or drink the following products (fruits, vegetables, sweets, chocolate, Coca-Cola or other sweet drinks, yellow cheese, dark bread, crisps)? Possible answers: never, less than once a week, once a week, 2-4 days per week, 5-6 days per week, once a day, more often than once a day. In the analyses conducted, the three combined response categories were: once a week or less frequently, 2-6 days a week, every day (7 days a week).
- How often do you usually eat breakfast, lunch (midday meal) and supper (evening meal) on school days and weekends? Possible answers in relation to schooldays: one day, two days, three days, four days, five days and in relation to weekends: never, only one day (Saturday or Sunday), both days (Saturday and Sunday). For the purpose of this study, these replies were added together for the whole week.
- Do you snack between meals on school days and on weekends? Possible answers: never, seldom, sometimes, often.
- How often do you snack between meals on the following products: sweets, chocolate bars; cakes or pastries; crisps; sandwiches; vegetables; fruit; fruit yoghurt; kefir or natural yoghurt? Possible answers: never, seldom, sometimes, often. The significance of differences between the groups was tested using the t-Student test and the ?2 test. The statistical analysis of the data was carried out using the SPSS v. 14. statistical package.

* Health Behaviour in School – Aged Children; a WHO Cross – National Study. Research Protocol for the 2001/2002 Survey.

RESULTS
The anthropometric characteristics of the groups surveyed
Table I displays the mean values of body mass, height, and BMI of the overweight adolescents and those of normal body mass. Statistically significant differences concerning body mass and BMI are shown in both the girls’ and boys’ groups (p<0.001).

Consumption of selected food
The frequency of adolescents’ consumption of selected food products is shown in table II. Overweight adolescents consumed substantially fewer unhealthy products (sweets and crisps (both boys and girls) and sweet Coca-Cola-type drinks (only girls)) than their peers with the normal body mass.
Regarding products which are essential for health, it was confirmed that both the adolescents with excess body weight and those of normal weight consumed vegetables, fruits and dark bread too rarely. Analysis of the data indicated that the overweight girls ate dark bread significantly more often than their peers of normal weight. However, no significant differences were noted in the frequency of fruit consumption between the two groups of adolescents.
Moreover, it was observed that compared to overweight boys, overweight girls drank substantially less sweet drinks (p<0.001), while they consumed fruits (p<0.01) and vegetables (p<0.05) considerably more often.

Regularity of meals during the week
Regularity of the consumption of basic meals is presented in tables III and IV. Table III shows the average number of days in the week in which the young people consumed the three basic meals of breakfast, lunch and supper. Table IV shows the percentages of adolescents who daily consumed basic meals.
The analysis showed that of the three main meals, lunch was eaten most regularly, both by overweight adolescents and those with normal body mass. Overweight teenagers (both boys and girls) ate substantially less often during all three basic meals (p<0.001) than their peers of normal weight. At the same time, the percentages of teenagers with excess body weight who ate main meals daily were significantly smaller. Special attention should be paid to the fact that only slightly over 40% of the overweight adolescents (50% of the boys and 39% of the girls) ate daily breakfast, compared with 60% of their peers of normal weight (67% of boys and 56% of girls). Irregular consumption of all meals was noted considerably more often among overweight girls than overweight boys (tab. IV).

Snacking
The percentages of overweight teenagers who often snacked between meals were half those of their peers of normal weight (p<0.001), both on school days and weekends (see figure 1). The obese also chose snacks with high fat content, sugar and salt (such as candy bars, biscuits, crisps and sandwiches) substantially less often than their peers of normal weight (tab. V). However, this group often snacked on vegetables, fruits and yoghurt and kefir more often (the difference was statistically significant only for vegetables, p=0.008).
The analyses also showed that girls with excess body mass chose vegetables and fruits as snacks significantly more often, and cakes less frequently, compared with the overweight boys.

DISCUSSION
The study has shown that the greatest differences in the dietary pattern of adolescents with excess body weight and those of normal weight concern the regularity of meals. Overweight teenagers more frequently skipped the main meals than their peers with normal body mass. This problem concerned girls more than boys. It can be assumed that obese adolescents consider skipping meals (mostly breakfast) as a kind of weight-reduction diet. Special emphasis must be placed on the fact that in a study conducted 12 years previously (in 1996), among adolescents in Warsaw, aged between 11 and 17 who were overweight and of normal weight, it was also shown that the main imbalance in their dietary behaviour was omitting breakfast (14, 15). These results indicate that educational activities on meals regularity may not be getting through to the young people’s awareness. Certainly the organisation of the normal school day, including a long period of time spent away from home, makes it more likely that meals will be skipped during the day and moved to the late hours of the afternoon or the evening. It does happen that some young people consume their first meal of the day only after returning from school. Such a lifestyle promotes the development of obesity.
Consuming meals irregularly means not only the risk of consuming more calories by increasing portions and snacking during the day, but also the risk of the body expending less energy. According to some studies, people eating meals irregularly or more rarely have lover metabolism after meal (specific dynamic action of food), and are thus more likely to show a positive energy balance (16).
The overweight problem also involves the phenomenon of snacking between main meals. There is nothing wrong in eating two snacks during the day, if they consist of fruit, vegetables, or dairy products low in sugar and fat. Studies indicate the positive impact of increasing the frequency of meals consumed, while maintaining the same energy value of the daily diet (9). Eating high-energy crisps, cakes or sweet drinks, however, may constitute an obesity risk.
The young people in the study who were overweight stated clearly that they ate different types of snacks less frequently than their peers of normal weight. A positive phenomenon which the research revealed is that when overweight young people decided to eat snacks, then they selected products which are beneficial for health (vegetables or fruits) more often than their peers with normal body mass. Other beneficial differences in diet between overweight teenagers and those of normal weight include less frequent consumption of products unfavourable to health, such as sweets, crisps and sweet carbonated drinks (although the latter is true only for girls). These observations may indicate that overweight young people are sufficiently aware of which products are good or bad for their health. Similar results were obtained by Norwegian researchers during tests on pre-pubertal children (aged 9-10); the obese children ate varied Norwegian food more often, and the children with normal body weight often ate processed foods (“junk/convenient” eating pattern) (17).
It should be noted that the reliability of the adolescents’ response to our test is difficult to verify. It cannot be ruled out that these answers were intended to please, despite the survey being conducted on the basis of anonymous responses. Studies have shown that the use of a questionnaire on how frequently products were consumed, as used in this work, may lead to statements (especially by overweight young people) which underestimate how often they consume the discussed products (18). However, this fact does not affect the reliability of the resulting conclusions about the adolescents’ level of awareness and knowledge.
The questionnaire used in the survey on the frequency of food product consumption only presents how often within a specified time (e.g. one week) the selected products are eaten. The results based on our analysis showed also that regularity of meals is very important for healthy weight and not only the type of food consumed.
The questionnaire used in this survey does not contain questions on volume, the number of servings consumed or their method of preparation, which may substantially affect the energy value of the product consumed (e.g. whether it is cooked or fried). It says nothing about how the dishes are prepared, or at what time of day the meals are consumed (19). These issues and confirmation of the important role of meals irregularity in frequency of overweight in adolescents will form the main areas of interest for successive studies planned in the coming years, in a representative group of children and adolescents aged 10–18 years.

CONCLUSIONS
1. Differences in dietary behaviour which adversely affect obese teenagers, compared with those of normal weight, relate primarily to the regularity of consumption and the omission of breakfast. Among Polish teenagers at puberty, problems concerning the regularity of consumption have persisted for over 10 years.
2. The awareness and knowledge which adolescents with excess body weight have of the energy value of products and snacks seems to influence their declared, significantly less frequent consumption of sweets, sweet drinks and salt snacks, in contrast to their peers with normal body mass.
3. Our study shows that compliance of low energy diet alone does not ensure the maintenance of healthy body weight. Irregularity of meals and skipping breakfast play an important role in overweight and obesity development in adolescents.
4. In health education concerning nutrition, greater emphasis should be placed on the importance of eating meals regularly and not skipping them from the daily schedule, and not just on the quality of the products consumed and their energy value.
5. In the future studies on dietary patterns in a larger sample of adolescent, emphasis should be placed on adding questions about portion size, food preparation and meal time. Eating behaviours of parents should be also examined in the relation to their body weight.

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Adres do korespondencji / Address for correspondence:
Maria Jodkowska
Department of Child and Adolescent Health
Institute of Mother and Child
ul. Kasprzaka 17a, 01-211 Warsaw, Poland
tel. (+48 22) 32-77-310
[email protected]