text new page (beta)
English (pdf)
Article in xml format
Automatic translation
Cited by SciELO 
Cited by Google 
Similars in
SciELO 
Similars in Google 
Permalink
INTRODUCTION
The incidence of overweight and/or obesity in children and adolescents has increased significantly, principally in developed countries and certain segments of developing countries1. In Latin America, it is estimated that between 42,4 and 51,8 million children and adolescents suffer from excess body mass, representing 20-25% of this population2. In European countries, the prevalence of infant and juvenile obesity is over 20%3, while the figure is lower in Asian countries, estimated to be between 5% and 10%4. Obesity not only leads to an increase in the incidence of diseases, such as diabetes, hypertension, cerebrovascular accidents and cancer, but it can also cause psychological problems, such as a reduction in self-esteem and increasing depression in children and adolescents subject to strong socio-cultural pressure to possess a thin body5. Overweight children and adolescents are more likely to follow unhealthy diets to try to control their weight compared to those whose weight is normal6; in particular, overweight girls present a higher risk of developing eating disorders due to the socio-cultural pressure to be thin7.
Dietary behaviour is determined by demographic, nutritional and behavioural factors8. During their school years, young people are more prone to oscillating feelings and behaviours related with their bodies, for example in dietary habits and physical activity9,10. As a result of these factors, studies have reported a high prevalence of health-damaging dietary behaviour among school-age adolescentes9,11 principally girls12. Many characteristics of the environment may help to determine a child's physical activity (PA), including the parents’ attitude and the stimulus they provide to take part in sports, the percentage of time spent outdoors, the geographical location and the time of year13,14. Sedentarism, economic and socio-cultural influences and excessive passive eating are obesogenic factors which lead to an increase in the prevalence of child obesity15. Kruger et al.14 indicate the importance of applying assessment strategies in order to identify children who are prone to overweight/ obesity, since treating adults for obesity does not generally produce good results. Many studies have used instruments to measure specific behaviours, knowledge, attitudes and intentions in dietary behaviour and the practice of PA in adolescents and children, and their influence on body mass index (BMI) in this population. The aim of the present study was to carry out a literature review to analyze the influence of physical activity and dietary behavior on BMI in school-age children and adolescents.
MATERIAL AND METHOD
This study is characterised as a literature review involving a critical analysis of published literature on physical activity and dietary behaviour in schoolchildren.
A search was carried out of the PubMed and LILACS electronic databases. The key words used in Portuguese and English were: ‘physical activity OR physical exercise’ AND ‘teenagers or schoolchildren’ AND ‘overweight’ AND ‘obesity’ AND ‘dietary behaviors OR food behavior’. The bibliographic search was limited by date (2000-2017) and language (Portuguese, Spanish, and English).
The inclusion criteria were for original studies, in human beings, descriptive and analytical, which used instruments to analyse the impact of practising PA and dietary behaviour on the BMI of schoolchildren. The exclusion criteria excluded studies related with the topic outside the school environment, studies which analysed specific sports, studies carried out in periods outside the classroom routine, literature reviews, points of view/opinions of specialists, validation studies, monographs, dissertations and theses.
After the results had been obtained, duplicate articles were excluded and a preliminary selection was made by reading the titles and abstracts of the manuscripts. Titles and abstracts were selected independently by two investigators (F.N.M.U. and R.P.L.) to verify their eligibility. In cases of discrepancy, consensus was obtained by discussion or by consulting a third reviewer (N.A.). The references that appeared to fulfil the inclusion criteria were reviewed in full text by the same reviewers (F.N.M.U. and R.P.L.). The full texts of potentially eligible articles were then analysed.
The data in each article selected were analysed to obtain the study design, total sample size, sex, age and origin of the individuals in the sample, instruments used and principal results.
RESULTS
We identified 1,412 publications with the key word combinations in all the databases selected, with 40 duplicated articles. After reading the title and abstract, studies which did not meet the inclusion criteria were excluded. The full texts of the remaining articles were read, and 17 were selected for qualitative analysis (Figure 1). The characteristics of the studies selected are provided in table 1.
Table 1 Characteristics of the studies included. NI= no information, F= females, M= males, PA= Physical Activity.
| Author | Design | Total n | Sex | Population | Percentage of subjects by BMI | Instruments | Primary results |
|---|---|---|---|---|---|---|---|
| Farajian et al.30 | Cross-sectional | 4786 | F: 50.7% M: 49.3% |
Greek pupils aged 10 to 12 years. | Underweight 4.2% (girls:5.0%; boys: 3.3%) Overweight 29.5% (girls: 29.2%; boys: 20.9%) Obese 11.7% (girls: 10.6%; boys: 12.9%) | Children with healthier eating habits, based on a Mediterranean diet, are more physically active | |
| Iannotti and Wang25 | Cross-sectional | 2001-2002 14,607 2005-2006 9,150 2009-2010 10,848 | 2001-2002 F:7630 M:6977 2005-2006 F:4719 M:4431 2009-2010 F:5261 M: 5587 |
US adolescents aged 11 to 16 | Underweight 4.7%/ 3.7%/ 4.2% Normal weight 70.1%/ 66.6%/ 66.5% Overweight 14.9%/ 17.0%/ 16.6% Obese 10.3%/ 12.7%/ 12.7% |
Adolescents present a high frequency of obesogenic habits; the majority do not carry out the recommended minimum of 60 minutes PA per day and do not consume more than 5 portions of fruit and vegetables per day. | |
| Kruger et al.14 | Cross-sectional | 1257 | F:649 M: 608 |
10- to 15-year old school children in the North West Province of South Africa. | Normal weight 92.1% Overweight/obese 7.8% |
–. The frequency of over- weight/obese chidren was lower in children aged 11 years (6.7%) and higher in children aged 10 years (9.1%) and 15 years (9.1%). The greatest prevalence of overweight/ obesity was found in female, white-skinned children. –. Smaller households, sedentarism and increasing age in girls were determiners of increased weight. –. Prevention programmes should focus on increasing the practice of physical activity by children to improve their current and future weight. |
|
| Liberona et al.17 | Cross-sectional | 1732 | F: 838 M: 894 |
9- to 12-year olds in primary schools in the Metropolitan Region of Santiago, Chile. | Normal weight 59% Overweight 22% Obese 17% Underweight 2% |
The high indices of overweight and obesity in Chilean schoolchildren are due to the combination of low PA and poor diet. Obesity was most prevalent in children from the lowest socio-economic level, probably due to higher consumption of carbohydrate-rich foods. | |
| Manios et al.20 | Cross-sectional | 2492 | F: 1251 M: 1241 |
Schoolchildren aged 9–13 years from Attica, Thessaloniki and Heraklion. | Normal weight 57.6% Overweight 30.9% | Obesity was the only factor which significantly increased the probability of anaemia in boys and girls. Obesity was related with low step inces. | |
| Moschonis et al.22 | Cross-sectional | 2043 | F: 1025 M: 1018 |
Greek children and adolescents aged 9 to 13 years. | Normal weight 59.0% Overweight 29.7% Obese 11.3% |
Eating behaviour with more than 5 meals and 45 minutes of moderate to vigorous physical activity is related with a reduction in dyslipidaemia in schoolchildren aged 9-13 years. | |
| Moschonis et al.18 | Cross-sectional | 2073 | F: 1041 M: 1032 |
Primary schools from four regions in Greece in schoolchildren aged 9–13 years. | Underweight 2.9% Normal weight 56.0% Overweight 29.9% Obese 11.2% |
Increased consumption of dairy products and high-fibre food, having a proper breakfast and spending more time on moderate to vigorous physical activity are factors which diminish the probability of obesity and/or increased levels of fat mass. | |
| Muros et al.21 | Cross-s ectional | 456 | F: 235 M: 221 |
Spanish Adolescents aged between 11 and 14 years |
Normal weight 77.3% Overweight 17.1% Obese 5.6% |
PA had a greater influence on BMI than eating habits (Mediterranean diet), therefore the focus of interventions to improve health and thus the quality of life of adolescents should be PA. | |
| Sabiston and Crocker24 | Cross-sectional | 532 | F: 326 M: 206 |
Caucasian, Asian, South Asian, South East Asian, Hispanic, Aboriginal West Asian/Middle East and Black Adolescents aged 15 to 18 years in Vancouver, British Columbia, Canada | Underweight 15.4% Healthy weight 72.4% Overweight 9.8% Obese 2.4% |
Adolescents presenting obesity expressed the intention of consuming healthier foods. Males are more active while females seek to eat a healthier diet. | |
| Saucedo-Molina et al.28 | Cross-sectional | 1028 | F: 605 M:423 |
Mexican adolescents (15-19 years) | Underweight F: 1.3% M: 2.6% Low weight F: 2.5% M: 6.9% Normal weight F:66.3% M: 61.2% Overweight F:22.1% M: 15.5% Obesity F:7.1% M:13.8% |
The lowest BMI was related with greater frequency of meals and more physical activity. Subjects with low weight or underweight practised vigorous/intense physical activity for a longer mean period in minutes, with boys more active than girls. | |
| San Mauro et al.35 | Cross-sectional | 189 | F: 95 M: 94 |
School children between 6 and 16 years old, from an elementary school and a high school in the Community of Madrid, Spain | Overweight 27.6% F: 12.4% M:15.3% |
Obese boys spent more time in sedentary leisure activities | |
| Stevens et al.36 | Randomized Clinical Trial | 1455 | F:692 M: 755 |
American Indian Children, 3rd, 4th and 5th series | NI | Attempts to use diet and weight-loss programmes were negative in the control group and the intervention group at the start of the study. They increased as the assessments progressed, however these changes were not significant, indicating that the intervention had no positive effect. The intervention was based on physical activity, and the intervention group was found to be more active in all the assessments, but this level of activity tended to diminish with time. | |
| Story et al.16 | Cross-sectional | 1441 | F: 693 M: 748 s |
American Indian Children, average age 8.6 years | 2.3% lean, 55.5% normal weight, 17.9% overweight, 24.3% obese | The results of this study show that the children were very concerned about their weight and that efforts to alter their weight were common among overweight children. | |
| Suñé et al.29 | Cross-sectional | 719 | F: 361 M: 358 |
School children aged 11-13 years in Capão da Canoa, Rio Grande do Sul State, Brazil | Normal weight 75.2% Overweight 21.3% Obesity 3.5% |
Carrying out sedentary activities for long periods and consuming foods with a high energy a high energy content are determiners for increased bodyweight | |
| Utter et al.26 | Cross-sectional | 4746 | F: 2263 M: 2483 |
White, Black, Asian, Hispanic, Native American, Mixed/other Average age 14.9 years |
NI | Boys and girls with more sedentary behaviour were also associated with higher fat consumption. However sedentary adolescents who spent more time reading and studying consumed fewer fat- based energy foods. | |
| Vilchis-Gil et al.27 | Case-control | 402 | F: 44.8% M: 55.2% |
Children 6-12 years old in Mexico City. | Obese (case) 50.2%, normal weight (control) 49.8% Questionnaire (FFQ) 3. Physical activity |
Poorer eating habits, skipping breakfast, fewer hours of sleep and lower frequency of physical activity were factors associated with obesity. | |
| Zanirati et al.19 | Cross-sectional | 294 | F:48.9% M: 51.1% |
Pupils aged 7 to 11 years in a municipal school in Belo Horizonte, Minas Gerais, Brazil | Underweight 3.6% Normal weight 80.2% Overweight 10.8% Obese 3.9% Severe obesity 1.2% |
In children from a low socio-economic level the full-time school environment encouraged healthier habits such as the practice of physical activity and a healthier diet |
The total number of children and adolescents was 60,250, of both sexes, between 6 and 19 years of age, including whites, blacks, Hispanics, Mexicans, Asians, American Indians, Latin Americans, Greeks, Europeans and South Africans. Between 55.5%16 and 92.1%14 of the children and adolescents presented normal weight. The proportion of underweight children was between 2%17 and 4.7%18. The proportion of overweight children varied between 10.8%19 and 30.9%20, and the proportion of obese children between 3.9%19 and 24.3%16.
Three studies reported an association between sedentary behaviour and incorrect dietary behaviour. A relationship between sedentarism and overweight was observed in 9 studies (56.3%), and an association between incorrect dietary behaviour and overweight was observed in 5 studies (31.25%).
DISCUSSION
Obesity has a serious effect on adolescents, reducing their quality of life due to the stigma and the social discrimination21 triggered by not having an ‘acceptable’ body. Apart from the psychological effects, obesity is also associated with dyslipidaemia22, iron deficiency and iron deficiency with anaemia20, as well as cardiovascular disease, diabetes and metabolic syndrome23.
Story et al.16, observed in their study that overweight subjects had strong intentions of choosing a healthier diet; the same was reported by Sabiston & Crocker24, possibly because normal weight schoolchildren have no need to change their dietary behaviour to achieve changes in their bodies13. Iannotti & Wang25 say that young whites present many obesogenic behaviours, with excess weight of up to 29.7%. South Africans presented the highest indices of children/adolescents with normal weight (92.1%); overweight/ obesity was observed to be related with sedentarism and higher age in girls14. The highest percentages of overweight were found in Greek schoolchildren, at 30.9%20, and the highest percentage of obesity (24.3%) in American Indian Children16.
Adolescents with normal weight carry out more PA, prefer healthier foods and spend less time in front of screens; these behaviours reflect a healthy lifestyle and are good predictors of quality of life in this population21. In their study, Utter, Neumark-Sztainer, Jeffery & Story26 observed that boys and girls with healthier dietary behaviour spent less time in front of the television, or reported inactivity associated with other habits, such as reading. Children and adolescents who sleep less, spend more time in front of the screen or playing video games, and consume more high-sugar soft drinks present a higher probability of developing obesity27, as well as presenting alterations in their lipid profile and a higher prevalence of dyslipidaemia22. It is remarkable that older adolescents tend to carry out less PA14,25 and more sedentary activities, as well as presenting a higher consumption of sweets and soft drinks and a lower intake of fruit and vegetables25. Obesogenic behaviour increases with age, and this increase is consistent with the increase in obesity in the population up to adulthood14,25. Overweight and obese children live in more obesogenic and sedentary environments, closer to fast-food outlets and other sources of very dense, high-energy foods, and where outdoor physical activity is not encouraged due to the availability of indoor entertainment and vehicle travel14. Eating a proper breakfast and/or not skipping breakfast, together with higher consumption of dairy products, were related with a healthier diet and lower BMI; consumption of fibre-rich foods (fruit, vegetables and whole-grain products) was related with lower thickness of cutaneous folds13,18; this was corroborated by Vilchis-Gil et al.27, who found that higher intake of fruit is associated with lower BMI. Furthermore, higher consumption of carbohydrates (traditional foods with added fat), soft drinks and natural fruit juice were associated with a risk of greater obesity27. Children are strongly attracted by high-sugar soft drinks due to a combination of factors, including the flavour and the image of an effervescent drink. Consumption of these drinks is very worrying, since in most houses they are readily available and there are no rules on their consumption13, constituting an ‘invitation’ to unhealthy habits in the home. In a study of children and adolescents in the Metropolitan Region of Chile, Liberona et al.17 observed that more than half of the schoolchildren were sedentary (65.4%) and only 0.7% had good levels of PA. In a comparison of PA between the sexes, Kruger et al.14 observed that boys practice more PA than girls, and this finding was corroborated by Sabiston & Croker24 and Saucedo-Molina et al.28 Iannotti and Wang25 also found that boys engage in more PA, but say that they also spend more time in sedentary activities, while girls consume more fruit and vegetables, but also more sweets; there was no uniform pattern of greater obesogenic behaviours in one sex or the other, corroborating earlier studies24. Female sex and post-menarche development were identified as determining factors for higher body fat content in adolescents14, although other authors found that the male sex was more affected by overweight17,18,22,28,29. Kruger et al.14 reported that the obesity and overweight indices were lower in children aged 11 years and significantly higher in children aged 10 years and adolescents aged 15 years. The percentage of overweight and obese children has been increasing in recent years; it is therefore important to create healthy lifestyle habits from childhood. The family environment is responsible for encouraging healthy dietary habits, but furthermore the parents play a fundamental role in instilling in their children the habit of practising sports, by being more active themselves, setting an example and carrying out PA with their children30.
Higher levels of overweight/obesity may be found in smaller households, since families with fewer than 5 members have a higher incomes and more food available per person14. Socio-economic level, related with the occupations and incomes of the parents, influences the food intake and PA patterns in the home14. Liberona et al.17 and Muros et al.21 report that adolescents from a lower socio-economic level have less access to healthier foods, such as fruit, vegetables, fish and olive oil. Lower-income families consume a smaller proportion of foods rich in protein and fat, which are more expensive, and instead consume more carbohydrate-rich foods17. Suñé et al.29 analysed the prevalence of obesity and overweight in schoolchildren aged 11 to 13 years in southern Brazil. They observed that children in private schools had higher levels of obesity and overweight than children in state schools. Furthermore, children in private schools presented a 53% higher risk of becoming overweight or obese29. In Brazil, primary and secondary school children matriculated in state schools tend to come from families with lower incomes than children in private schools, so it is surprising that adolescents from families with better resources and therefore greater access to food of better nutritional quality should present higher rates of overweight and obesity than children with fewer economic resources. Kruger et al.14 found similar results, observing that higher-income homes present a higher index of overweight/obese children due to their access to fast foods with a higher fat content. Liberona et al.17 observed that obesity was more prevalent in pupils from a lower socio-economic level, while overweight was more prevalent in the medium-high socio-economic group and normal weight was most prevalent in pupils from a high socio-economic level. These results suggest that socio-economic level alone is not the determining factor for better (healthier) nutrition, but that the nutritional behaviours and sports habits established by the parents in each home are much more important. Kruger et al.14 say that the fact of living in an urban area may be an obesogenic factor, since in such environments there are more sales outlets for fast food and street sellers offering children foods with higher contents of refined carbohydrates and fats. Furthermore, the fear of violence in large metropolitan areas reduces recreational activities in public spaces, and people are more inclined to use their cars even for short journeys.
The regular practice of physical activity, adherence to healthy nutritional habits and proper body composition are agreed to be related with the promotion and/or maintenance of the quality of life in children, adolescents and adults21. Diet does not appear to be the principal cause of weight gain, while low levels of PA do appear to be the most important determinant of obesity14,21. Moschonis et al.18 say that the practice of moderate physical activity for 45 minutes per day is able to diminish significantly the blood concentration of fats in children and adolescents. Vilchis-Gil et al.27 state that carrying out at least 1h/week of PA in school is sufficient to reduce the probability of becoming obese. Sedentary adolescents have a four times higher risk of presenting overweight or obesity28. Some studies say that combining continuous practice of physical activity with proper eating behaviour minimises the prevalence of overweight and/or obesity, and increases the likelihood of behaviour patterns established in children being maintained when they become adults27,31.
Policies to encourage healthy eating habits in school are considered to be a high priority as a means of prevention and intervention in pursuit of better health32,33. We need to identify the social and environmental conditions which influence the obesogenic behaviours of young people and the need for intervention in children and adolescents25. Prevention programmes should be aimed at increasing PA in children in order to improve their current and future weight status14.
CONCLUSIONS
In most of the studies analyzed, schoolchildren presented normal weight, with a tendency for their BMI to increase over time. Overweight and obesity are related with incorrect dietary habits (skipping breakfast, consumption of foods with high fat contents and high-sugar drinks), low levels of PA and long hours devoted to sedentary activities (playing video games or watching TV). Girls pay greater attention to eating a healthy diet, while boys present better levels of PA, however there is no sex-related pattern of healthy behaviour. Children and adolescents are exposed to social conditions which tend not to support healthy behaviour; these environments favour the development of poor eating and sports habits.
