Overweight and obesity in Brazilian adolescents

Abstract

OBJECTIVE: This study aimed to describe the prevalence of overweight and obesity (OW+O) among Brazilian adolescents and to identify risks for subpopulations defined according to the five country macro-regions and situation (urban–rural) of the domiciles, income, years of school attendance, age and sex.

DESIGN: A nationwide home-based survey representative of the Brazilian civilian noninstitutionalized population, performed in 1989.

METHODS: The sampling plans followed a stratified, multistage, probability cluster design in The National Research of Health and Nutrition sample, which collected anthropometric data of 14,455 domiciles. In all, 13,715 adolescents ranging from 10 to 19 y of age were studied. The OW+O was defined from a body mass index (BMI) equal or superior to the 85th percentile of the reference population of the NCHS. The prevalences in the different studied groups were compared using the adjusted odds ratio in logistic regression models.

RESULTS: The prevalence of OW+O was of 7.7%, reaching 10.6% within the female group and 4.8% within the male group. A direct relation could be established between the socioeconomic level and OW+O. Adolescents of the most industrialized region of the country presented a risk of OW+O 1.86 (95% CI 1.51–2.30) times higher than that found in the least developed region. Male youngsters who lived in urban areas were more liable (OR=1.71, 95% CI 1.30–2.25) to overweight than their counterparts of rural areas. The occurrence of menarche increased two and a half times (OR=2.58, 95% CI 2.11–3.15) the risk of OW+O within the female group of adolescents.

CONCLUSIONS: The results demonstrate a low prevalence of OW+O among Brazilian adolescents when compared with adolescents of more industrialized regions. The OW+O is twice as high within the female group, which represents a much greater difference than the one encountered in industrialized countries, probably owing to the muscular work carried out preponderantly by male adolescents of lower socioeconomic levels. Higher prevalences in subpopulations of higher socioeconomic level and of more industrialized regions show the great need for differentiated actions to control overweight and obesity in the country.

Introduction

Adolescents, defined by the World Health Organization1 as people ranging from 10 to 19 y of age, represent 20% of the global population. About 84% of the adolescents are encountered in developing countries, and their percentage in relation to other groups has increased. However, little attention has been given to the nutrition of this group.2 The emergence of obesity and its consequences has renewed the interest in the nutritional assessment of adolescents and in the identification of risk factors aiming to control obesity among adults.3

Throughout developed and developing countries, obesity has increased alarmingly.4 From 1988 to 1991, the prevalence of overweight in North American adolescents aged 12–19 rose by 6%.11 In a period of 15 y (1974–1989), the Brazilian population of obese adults almost doubled.10 As soon as the industrialization of the economies takes place in developing regions, the prevalence of chronic-degenerative diseases increases mainly due to the adoption of occidentalized lifestyles characterized by higher indices of sedentariness as well as the adoption of high-fat and low-fiber diets.5

Obesity in adolescence is associated with several problems, from which the most prevalent are the psychosocial consequences in youth and persistence of obesity in adult life. Obesity at an early age may affect the risk factors for cardiovascular diseases more drastically than in a later phase in life.4,6 In addition, some studies have reported important social and economic consequences of overweight in adolescence. In a study developed by GORTMAKER,7 it was revealed that women who had been obese adolescents had completed fewer grades at school, were less frequently married and had lower per capita incomes in adult life.

However, until now there has been limited availability of data with national representativeness, especially for adolescents, allowing a global evaluation of the prevalences of overweight and obesity. Therefore, there has been an urgent need for the evaluation of available data sources about adolescents in the world based upon an obesity-standardized classification system.4

Thus, this study is proposed to contribute to the discussion on the nutritional assessment of the age group from 10 to 19 y through the description of the prevalence of overweight (and its risk factors) among Brazilian adolescents, also expecting that these data may be used in populational studies for follow-up of trends and comparisons with other countries. To allow further comparisons the most accepted and diffused methods of population diagnosis of obesity were adopted.3

Material and methods

The present study comprises a subdivision of the sample of the National Research of Health and Nutrition (Pesquisa Nacional sobre Saúde e Nutrição—PNSN), which was an anthropometric inquiry conducted on a national basis, and had as its main goal the evaluation of the nutritional status of the Brazilian population through the collection of anthropometric data. It was a nationwide home-based survey performed from June to September of 1989.8

The PNSN sampling plans followed a stratified, multistage, probability design to provide representative estimates of the Brazilian population resident in private and collective homes, with the exception of people living in military headquarters, hospitals, homes for old people, hotels and Indian settlements. Weight factors for the original samples were provided in the original data sets for different kind of collected information. For all analysis we utilized the weights provided to correct anthropometric estimations.9

In addition to the determination of the anthropometric measures of weight and height, which was the major focus of the PNSN, standardized inquiries enabled the collection of data regarding basic demographic characteristics (housing conditions, scholarship degree, income, occupation, etc) and information on health and nutrition (menarche, signs and symptoms of diseases, food supplementation, access to health care, etc).8

The anthropometric measures of weight and height were determined in the subjects’ domiciles by two trained interviewers (anthropometrist and annotator). The subjects were barefoot and wearing indoor clothing for the measures to be taken. A portable microelectronic scale (Filizola) with capacity for 150 kg and precision of 100 g was adopted for the determination of weight. Height measures were determined by a non-stretch tape with a precision of 0.1 cm affixed to a flat and vertical surface of the subjects’ domiciles. The height was registered in cm and one decimal unit.10 Further details concerning data collection, transcription and the creation of indicators are duly described in specific documentation of the PNSN.8,10

The present study selected from the file ‘adolescents’ of the original research database those adolescents ranging from 10 to 19 y of age, totaling 13,992 individuals. From these records, 111 were excluded for not presenting complete anthropometric data. Adolescents who were pregnant while the inquiry was in progress were also disregarded. Thus, the final sample included 13,715 adolescents, representing 98% of the original sample.

The OW+O was defined taking into account the body mass index (BMI), which is the weight (in kg) divided by the height square (in m). The adolescents regarded as part of the overweight group were the ones who revealed a BMI equal to or above the 85th percentile of the North American reference population.3

In the analysis of the prevalence of OW+O, the following variables were considered: sex, color of the skin (White or not), age (in complete years), scholarship degree (defined by the adequacy of the chronological age to the total of school grades attended by the adolescent), domicile region (according to the five Brazilian macro-regions), domicile situation (urban or rural), sexual maturation (occurrence of menarche), domiciliary monthly per capita income in dollars (distributed in three categories: upto US$34.49 (‘line of poverty’), US$34.50–150.00, and over US$150.00). Complete data were available for all the adolescents included in the sample for all the variables considered, with the exception of the information on menarche, which was not available for 41 adolescents (0.6%).

The uni- and bivariate analyses were performed with the program Epi-Info 6.0, using as risk estimate the odds ratio and its 95% confidence intervals. For multivariate analysis, logistic regression models were adjusted using the program SPSS/PC+. Explanatory variables with P values ≤0.10 in the univariate analysis were included in the initial models. Odds ratios and their 95% intervals were calculated for two-tailed tests of statistical significance. Model fitness was assessed through the likelihood ratio test. A special treatment was given to the variable sex once a differentiated behavior of overweight and obesity could be verified between male and female populations. The multivariate analysis considered three models: one referring to both sexes and then one for each sex.11

Results

The prevalence of overweight in the population studied was 7.7%. The sample comprised 1052 overweight adolescents, who, once expanded to the Brazilian population, corresponded to 2.5 million adolescents. Within this percentage, 200 (1.5%) adolescents had their BMI above the 95th percentile (effectively obese), which included 116 (1.7%) of the female group and 84 (1.2%) of the male group.

In Figure 1, the prevalences of OW+O in adolescents according to age are presented. The prevalences for both sexes are significantly different, rising among the girls and falling among the boys after the growth spurt.

Figure 1
figure1

Prevalence (%) of overweight and obesity (OW+O) according to age and sex. PNSN, Brazil, 1989.

Table 1 reveals that the prevalence of OW+O is (at least) twice as high in the female group than in the male group. A direct relation can also be observed between the socioeconomic level and OW+O, ie the prevalence of OW+O is always higher in adolescents with higher levels of scholarship and domiciliary income. Moreover, as regards domicile region, the risk of OW+O for adolescents living within major industrialized regions (South and South east) doubles (OR=2.13, 95% CI 1.73–2.63) when compared with the least developed region (North east). Similarly, the domicile situation presented a direct connection with overweight, and adolescents who lived in urban areas were more liable (OR=1.23, 95% CI 1.06–1.43) to overweight than their counterparts in rural areas.

Table 1 Prevalence and odds ratio (OR) with 95% confidence intervals (CI) of overweight and obesity (OW+O) by demographic, socioeconomic and biological variables for both sexes (n=13,715)

Tables 2 and 3 present the results of the uni- and multivariate analyses for female and male groups separately. It is clear that even after the adjustment for the other variables, domiciliary income and region remain as significant risk factors for OW+O. In accordance with the data encountered in the crude analysis, the multivariate model also revealed the Southern region as the one presenting the highest risks for male and female adolescents. Male adolescents of the high-income group were three times (OR=3.27, 95% CI 2.27–4.56) more liable to overweight when compared with the low-income group, while among female adolescents, the risk in the high-income group was twice as high (OR=2.12, 95% CI 1.64–2.75). The variables scholarship and housing situation were not established as risk factors for OW+O in the female group, whereas they could be considered as minor risk factors for the male group. Furthermore, the advance in age acts as a protection factor for OW+O in the male group (OR=0.67, 95% CI 0.52–0.87), yet it represents a non-significant risk factor for the female group (OR=1.16, 95% CI 0.98–1.37). Girls who had already undergone menarche were two and a half times more subject to developing OW+O than those who had not yet experienced it.

Table 2 Prevalences and odds ratio (OR) with 95% confidence intervals (CI) of overweight and obesity (OW+O) by demographic, socioeconomic and biological variables among female adolescents (n=6780)
Table 3 Prevalences and odds ratio (OR) with 95% confidence intervals (CI) of overweight and obesity (OW+O) by demographic, socioeconomic and biological variables among male adolescents (n=6935)

Discussion

The prevalences of OW+O encountered among Brazilian adolescents (7.7%) are lower than those reported in national inquiries of other countries.12,13,14 They are approximately three times lower than the prevalences found in the USA and Saudi Arabia.12,14

It is worth registering the strong effect of the variable sex on the determination of overweight. Although other surveys12,14,15 had encountered significant differences of OW+O between the sexes, no other study had verified a risk twice as great among girls in relation to the boys, as detected in the present study. This fact could be partially explained by the gradual increase of body fat storage at the end of childhood and beginning of adolescence.16

During puberty, the girls still undergo fat storage even during the growth spurt in height. The boys probably lose fat during the fast puberal growth.16,17 Among women, the spurt of thin-mass deposition is short and the fat deposition predominates throughout puberty.18

Differences regarding physical activities may also explain the variation in the prevalence of overweight between the sexes. Longitudinal studies in Europe demonstrated that behavioral changes following puberty affect the physical shape, ie physical activities drop by 50% between the ages of 12 and 18, when the boys are consistently more active than the girls.18 A similar decrease occurred in the prevalence of regular, vigorous activity among American adolescents. The National Children and Youth Fitness Study conducted in 1984 showed that 61.7% of students in grades 10–12 participated in vigorous physical activity for 20 or more minutes three or more days per week; in 1990, data from Youth Risk Behavior Surveillance System showed that only 36.1% of students in grades 10–12 reported doing so.19

The reduction of the energetic expenditure observed with modernization and other social changes are associated with a more sedentary lifestyle, in which motorized transportation, mechanized equipment and labour-saving strategies (at home and work) have substituted for heavy tasks. In the UK, for instance, the average distance walked by a 14-y-old adolescent dropped by 20% between 1985 and 1992 and the average distance cycled decreased about 26%, whereas the average distance covered by car increased by 40%.20

A plausible hypothesis is that the Brazilian girls have been more affected by this modernization than the boys. Therefore, this hypothesis suggests that muscular work would be exerted preponderantly by male adolescents of lower socioeconomic levels. In developing countries like Brazil, most available positions for poor unskilled male adolescents depend on heavy muscular work, which is not as intensive for female occupations. On the other hand, the most diffused and traditional sport activity in the country, soccer, is practised by the majority of low-income male adolescents but is not considered appropriate for females. Follow-up studies among specific adolescent populations are necessary to assess the reliability of such a hypothesis.

The analysis of the prevalence of OW+O according to income revealed that, in Brazil, a higher acquisitive power is concurrent with an increased frequency of overweight. In accordance with our results, several studies have repeatedly demonstrated that, although the socioeconomic level is negatively correlated with obesity in developed countries, particularly among women; it is positively correlated with obesity in developing countries.21

On reaching a certain development level, better economic conditions give rise to improved aspects of health and nutrition and, conversely, to the opportunity to develop obesity as well. Above this level, the social unacceptability of obesity favors the development of a relatively thinner population.17 Maybe this fact has already taken place among Brazilian girls, where an adequate scholarship degree within girls seems to have conferred protection against the disease.

However, it is worth emphasizing that this picture is dynamic. Although the prevalence of overweight among Brazilian adolescents has not been as high as the levels found in developed countries and it has still been higher in the population with higher socioeconomic resources, Brazil is now undergoing the so-called nutritional transition, where, in parallel to nutritional deficits, nutritional excess problems (overweight and obesity) increase significantly.22 Changes in obesity prevalences among adolescents would depend on two main modifications on food intake and physical activity. The first change contributes to the increase in obesity prevalence and is caused by increased access to high fat and low fiber foods associated with the decrease in muscular work due to mechanization of most activities. The second change contributes to the decrease in obesity prevalences and is related to the capacity of youngsters to control their food and physical habits to the industrialized environment, choosing less caloric foods and developing some physical activity for leisure, aesthetic or health purposes.

In the few studies conducted with adolescents in developing countries,23,24 a similar trend has been observed: a higher prevalence among the so-called dominant classes. It is possible that, in the process of nutritional transition, the minorities of the industrialized countries and the dominant classes of countries under industrialization occupy a similar stage, which is characterized by higher risks to the health. The alarming fact of this hypothesis is that, if these tendencies are sustained, obesity will grow in the world's largest populational contingent represented by low-income populations of developing countries. Patterns of dietary intake and physical activities of privileged groups of the Third World have progressively been adopted by lower socioeconomic groups in the process of nutritional transition following the crescent urbanization and industrialization in these countries.25

As concerns geographical location, it was observed that, similarly to obesity tendencies found in Brazilian adults10 and children,26 overweight among adolescents varied significantly according to the region of the country and urbanization. The prevalence of overweight was positively associated with the urbanization and a higher development of the geographical regions of Brazil.

The remarkable variations in the BMI in function of the income, urbanization and region indicate that environmental factors represent important determinant factors of overweight and obesity. The North east, North, Middle-west, South east and South regions present different levels of development, which can be visualized by their Human Development Indexes (HDI)* of 0.517, 0.617, 0.757, 0.775 and 0.777, respectively. To demonstrate the diversity of Brazilian regions, we can draw a parallel between their HDI and the same scores presented by better known geopolitical units. The Brazilian North east has the same HDI as Kenya, the Brazilian North is similar to Egypt, the Middle-West assimilates Thailand, the South east compares with Mexico and the Brazilian South presents the same HDI of Grenada.27

Considering the menarche as an indicator of the puberal stage within girls, it was found that girls who had already experienced menstruation had a higher risk of OW+O than those who had not undergone menarche. These findings are in agreement with the studies of Knishkowy,28 who followed up the adiposity change in 587 Jerusalem schoolchildren aged 6–14 in 1989 and concluded that girls who had already menstruated were taller, heavier and presented higher overweight rates than the girls who had not experienced menstruation. Similarly, MILLER29 reported that early-maturing girls in the UK were taller and heavier at the ages of 9–13 than those who maturated later. The hypothesis of Frisch and Revelle30 that a critical weight is necessary to initiate the growth spurt in height and the puberal alterations may partially explain this phenomenon.

Although the consequences of overweight and obesity are rare during adolescence, their persistence in adult life is associated with higher morbidity and mortality rates. Studies have demonstrated that the presence of obesity in adolescence persists until adult life in 80% of the cases.31 In a study developed by Di Pietro et al it was revealed that subjects who died by the 40th year of follow-up and those reporting cardiovascular disease were significantly heavier at puberty and in adulthood than were healthier subjects. There was a marked increase in the BMI between postpuberty and age 25 among those who subsequently died, those who developed cardiovascular disease, and particularly among those who developed diabetes. The authors concluded that overweight in adolescence may continue into adulthood and may be associated with subsequent adverse health outcomes.32 Moreover, overweight adults who had been obese adolescents tended to be more severely obese than adults who became obese during adult life.33

This persistence of obesity from adolescence to adult life probably occurs among Brazilian adolescents as well, yet cohort studies are necessary to establish these patterns. Educational programs of intervention aimed at adolescents should encourage physical activities and adequate dietary habits. In addition, there is a need for a systematic surveillance of growth indices in order to identify and treat adolescents with OW+O, thus avoiding precocious deaths and promoting lower rates of chronic-degenerative diseases.

*The HDI measures the overall achievements in a country in three basic dimensions of human development—longevity, knowledge and a decent standard of living. It is measured by life expectancy, educational attainment and adjusted income.

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Neutzling, M., Taddei, J., Rodrigues, E. et al. Overweight and obesity in Brazilian adolescents. Int J Obes 24, 869–874 (2000). https://doi.org/10.1038/sj.ijo.0801245

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Keywords

  • obesity
  • overweight
  • body mass index
  • prevalence
  • epidemiology
  • adolescents

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