INTRODUCTION

Ultra-processed foods are industrial formulations made largely from substances extracted from foods (oils, fats, sugar, starch, proteins), derived from food constituents (hydrogenated fats, modified starch) or synthesized in the laboratory based on organic materials such as petroleum and coal (dyes, flavorings, flavor enhancers and various types of additives used to provide products with attractive sensory properties) ¹ . The increased production and consumption of processed and ultra-processed foods is one of the main causes of the current global pandemic of obesity and non-communicable diseases and conditions ² .

The participation of ultra-processed foods in the Brazilian diet is still much lower than that found in developed countries or even in other developing countries, where the fast-food food culture already predominates over the traditional food culture ³ . In Brazil, the diet is composed of several influences and is currently strongly characterized by a combination of a so-called “traditional” diet (based on rice and beans) with ultra-processed foods, varying according to age groups ⁴ . Among adolescents, a diet with a higher consumption of ultra-processed foods and a lower consumption of beans, salads and vegetables in general is noted, which characterizes this age group as having the worst dietary profile among Brazilians ⁴ .

The growing interest of young individuals in ultra-processed foods has alerted government agencies to the need to recommend and monitor eating habits, since it is known that diet is one of the main determinants of energy balance and is directly related to the development of obesity ^5-7 . The World Health Organization (WHO) recommends reducing the consumption of foods with high energy and sodium content, saturated fats, trans fats and refined carbohydrates that are poor in nutrients ¹ . In Brazil, the new food guide for the Brazilian population warns about the type of processing to which foods are subjected before their acquisition, preparation and consumption ² .

Several observational studies have sought to investigate food consumption trends. International studies have observed an increase in the consumption of snacks, savory snacks, fast food and soft drinks ^8-11. In Brazil, the Household Budget Survey (POF) has verified, at each stage of the survey, a significant increase in the consumption of ultra-processed products. Another study, with adolescents from public schools, evaluated changes in the profile of beverage consumption and found a reduction in milk consumption and an increase in the consumption of processed beverages ¹² .

Despite this evidence, there are few studies that specifically examine the consumption of soft drinks, sweets and snacks, especially focusing on changes in their consumption. Thus, the objective of the study was to evaluate changes in the consumption of these foods among adolescents in southern Brazil from 2001 to 2011. Our hypothesis is that there may be changes in the prevalence of consumption of soft drinks, sweets and snacks over a decade.

METHODS

This was a cross-sectional study that originated from a larger study entitled “Lifestyle and risk behaviors of young people from Santa Catarina (COMPAC)”, carried out in 2001 and 2011 with high school students aged 15 to 19 years enrolled in public schools in the state of Santa Catarina, Brazil. Participants received a letter of informed consent, or their guardians if they were under 18 years of age, and could only participate in the research with authorization from their guardians. This study was approved by the Research Ethics Committee of the Federal University of Santa Catarina, under processes no. 064/2000 and 1029/2010.

According to the 2000 and 2010 school censuses, a total of 205,543 and 205,572 young people enrolled in public schools, respectively, were identified, and these data were used to calculate the sample size. The following statistical parameters were also used to estimate the sample size: unknown prevalence, with an estimate of 50%, due to the numerous existing variables; 95% confidence interval, with a maximum error of two percentage points, resulting in a minimum sample of 2,373 students. The sample was by cluster, and the total value was multiplied by two, totaling a sample of 4,746 students, of which 25% were added in case of losses or refusals during the collection. Thus, the final sample size was 5,932 participants. The sampling calculation was the same for both surveys.

The sampling strata considered the six geographic regions and their Regional Education Councils (26 in total). The sampling procedures were divided into two stages. In the first stage, schools were stratified by size (large: ≥ 500 students; medium: 200 to 499 students; and small: <200 students). In the second stage, classes were selected according to the study period and school year. In 2001, 216 schools were selected by systematic sampling, with five refusing to participate, totaling 211 schools. And in 2011, 90 schools were selected. All students from the selected classes who were present in the classroom were selected. More information can be obtained in a previous publication ¹³ .

The study variables were derived from questionnaires used in the 2001 and 2011 survey, which was based on other international questionnaires for the adolescent population ¹³ . This study used questions related to eating habits, gender, area of ​​residence and age. Table 1 contains more details about the study variables.

Initially, descriptive analyses were performed for all variables. Prevalence rates and respective confidence intervals (95%CI) were calculated, as well as the percentage delta to verify the difference in prevalence between years. Multinomial logistic regression was used to analyze the odds ratio of adolescents consuming sweets, snacks and soft drinks in the 2011 survey compared to the 2001 survey. The analyses were stratified and adjusted for gender, age group and area of ​​residence. The statistical program Stata 13.0 (Stata Corp., College Station, USA) was used.

RESULTS

In 2001, the majority of students were female (59.6%), aged between 17 and 19 years (53.0%) and living in urban areas (82.4%). In 2011, this prevalence continued, with the majority of students being female (57.8%), aged 15 to 16 years (60.7%), and living in urban areas (80.4%). Figure 1 provides information on trends in eating habits over a decade among adolescents in Santa Catarina. From 2001 to 2011, there was a reduction in daily consumption of soft drinks (from 19.7% to 10%), sweets (from 34.3% to 8%), and snacks (from 17.9% to 3.9%). On the other hand, the proportion of weekly consumers increased for all outcomes analyzed during this period.

Regarding changes in soft drink consumption from 2001 to 2011 (Table 1), the prevalence of daily consumers decreased by 50% for each subgroup. In the 2011 survey, boys (OR: 0.57; 95% CI: 0.43; 0.76), in both age groups (OR: 15-17 years: 0.57; 95% CI: 0.42; 0.78 and OR: 18-19 years: 0.70; 95% CI: 0.52; 0.92) and living in urban areas (OR: 0.60; 95% CI: 0.47; 0.76) were less likely to drink soft drinks every day than adolescents with the same characteristics in the 2001 survey. The prevalence of weekly soft drink consumers increased from 2001 to 2011 in all subgroups.

Regarding sweets consumption, the prevalence of daily consumption decreased in all subgroups studied between 2001 and 2011 (Table 2). The proportion of this decrease ranged from -75.5% (urban area) to -80.6% (rural area). Adolescents from all subgroups in 2011 were less likely to be daily sweets consumers than those in 2001, and the probability values ​​ranged from 0.15 (95% CI: 0.10; 0.20) to 0.24 (95% CI: 0.19; 0.32). The prevalence of weekly sweets consumers increased from 2001 to 2011 only among older adolescents (OR: 1.42; 95% CI: 1.09; 1.84).

The prevalence of daily consumption of snack foods decreased in all subgroups between 2001 and 2011, this reduction ranging from -77.2% (urban area) to -82.9% (rural urban area). In 2011, adolescents in all subgroups were less likely to consume snack foods every day when compared to 2001, and the odds ranged from 0.17 (95% CI: 0.09; 0.30) to 0.29 (95% CI: 0.21; 0.38). Weekly consumers increased from 2001 to 2011 in all subgroups, except those in rural areas (Table 3).

DISCUSSION

Our results suggest that there was a decrease in the daily proportion of consumption of these foods over a decade, with differences between subgroups. These findings are relevant, considering the need for more actions focused on food consumption among adolescents, as already highlighted by other authors ¹⁴ .

Monitoring trends in eating habits is essential for planning future intervention programs and formulating and evaluating national policies and nutritional guidelines ¹⁵ .

This study identified a decrease in the daily consumption of soft drinks, sweets, and snacks among Brazilian adolescents over a decade, corroborating data from the Health Behavior in School-Aged Children (HBSC) survey. This survey was conducted in the United States and in several European countries, focusing on the behaviors of children and adolescents. In their findings, the authors found a decrease from 2001/2002 to 2009/2010 in the proportion of daily consumers of sweets and soft drinks in the United States ¹⁰ , Finland, Norway and Sweden ^14-16 , and the Czech Republic ¹⁷ .

The authors hypothesize that these changes are the result of the success of current public policies implemented in their countries ¹⁰ at both the individual and population levels ¹⁴ . Examples of these initiatives include attempts to raise awareness about healthy eating habits and control the sale of unhealthy foods and drinks in schools ¹⁷ . In Santa Catarina, a law (State Law No. 12,061 of December 2001) was implemented determining that food and beverage services in schools should comply with nutritional quality criteria in order to preserve the health of adolescents. Thus, sweets, soft drinks and snacks were banned from school cafeterias. Furthermore, in 2004, the Ministry of Health launched a plan to promote healthy nutritional behavior in the school community, called “Ten steps to promote healthy diets in schools” ¹⁸ . It is possible that these initiatives contributed to the changes observed in the present study.

Although there was a decrease in the proportion of daily consumers, it was possible to observe an increase in weekly consumers of sweets (42.1%), soft drinks (16.1%) and snacks (23.4%). The National Food Guide recommends avoiding these food indicators since they are ultra-processed products and, therefore, are associated with high caloric intake and tend to replace healthy foods, which increase the risk of heart disease, diabetes and several types of cancer ². In this context, more approaches to reduce the consumption of these foods are needed. In addition to public policies focusing on the school community, broader actions should be outlined with an emphasis on the family and environments close to the school ⁷ .

Furthermore, actions should be directed to subgroups, since trends differ according to sex, age and region of residence. More research is needed to understand why some groups improve their diet while others do not. For example, it is important to understand why there was a large odds ratio in 2011 (vs. 2001) of being a weekly consumer of sweets among older adolescents, but not among younger ones, as well as being a weekly consumer of soft drinks in urban areas, but not in rural areas. These findings can help detect what really works, or does not work, for each group of adolescents. These issues are of great relevance and have been highlighted by other authors ^14,19,20 .

This study provides information on trends in the consumption of different food indicators among a representative sample of adolescents from public schools in Santa Catarina. In addition, these trends were analyzed according to sociodemographic characteristics in order to clarify some disparities that could be considered and prioritized in future actions for high-risk groups. Despite these strengths, it is also necessary to consider the limitations of this study, such as the fact that the questionnaire only allowed verification of the frequency and not the total consumption of each of the food indicators. Therefore, it was not possible to infer conclusions about the changes between 2001 and 2011 in relation to the total consumption of these foods. Finally, although the study design allows the identification of trends over a decade, more collections carried out between these years could allow for a more detailed trend analysis.

CONCLUSIONS

Daily consumption of sweets, soft drinks and snacks decreased among adolescents in Santa Catarina from 2001 to 2011. These results are encouraging, but more action is needed since the proportion of weekly consumers has increased, which means that a considerable proportion of adolescents still consume ultra-processed foods on some days of the week. Furthermore, initiatives that take into account healthy eating should consider the characteristics of adolescents, such as gender, age and area of ​​residence, since trends seem to be different according to these subgroups.

IMPLICATIONS FOR SCHOOL HEALTH

Actions aimed at reducing the consumption of soft drinks, sweets, and snacks are necessary to further reduce the consumption of ultra-processed foods. Thus, targeted initiatives should consider the characteristics of adolescents, such as gender, age, and area of ​​residence.

ACKNOWLEDGMENTS

This work was supported by the Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES) – Financing Code 001. The authors would also like to thank the National Council for Scientific and Technological Development (CNPq).