Consumption of ultra-processed foods and metabolic syndrome in adolescents: a systematic review protocol

Objective : This protocol will describe the methods of a systematic review that examined studies on the relationship between consumption of ultra-processed foods and metabolic syndrome in adolescents. Methods : The searches will be carried out in the MEDLINE (via PubMed), EMBASE (via ScienceDirect), LILACS (via VHL), and Cochrane databases until March 2022. Observational (cohort, case-control and cross-sectional) and experimental (clinical trials) studies will be included, two researchers’ independents will use the Rayyan QCRI software for retrieval of the articles, in addition, the Mendeley software Reference Manager will be used for reference management. After reading them in full, the articles will be selected according to the eligibility criteria. Results : The synthesis of evidence data will be approached from the relationship of consumption of ultra-processed foods and metabolic syndrome in adolescents. Conclusion : Therefore, the importance of this review protocol is highlighted to compose the current evidence on the relationship between consumption of ultra-processed foods and the metabolic syndrome.


Introduction
Metabolic syndrome (MS) is characterized by a set of metabolic disorders that include high levels of blood pressure, blood glucose, dyslipidemia and abdominal obesity and has been associated with increased risks of morbidity and mortality (O'Neill & O'Driscoll, 2015). It is estimated that around 20 to 25% of the global population has developed the metabolic syndrome (MS), and its prevalence continues to grow, especially in developing countries (O'Neill & O'Driscoll, 2015). In Brazil, data from 2013 (De Carvalho Vidigal et al., 2013)indicate a prevalence of MS in adults of approximately 29%, but we believe that these values are currently higher. Among adolescents aged between 15 and 17 years, according to data from the Study of Cardiovascular Risks in Adolescents (ERICA) in 2014 (Kuschnir et al., 2016), they indicated that the prevalence of MS was 2.6%. This prevalence showed a significant association between MS conditions and behavioral risk factors, physical inactivity and abdominal obesity.   reported that the dietary intake of ultra-processed foods (UPF) was classified from 10.2% to 50.7% of the total energy value and their consumption was positively correlated with the prevalence of obesity in adults. In Brazilian adolescents, UPF consumption was associated with MS and was a predictor factor related to an increase in total cholesterol and LDL cholesterol from preschool to school age (Rauber et al., 2015;Tavares et al., 2012) . This type of food has essentially industrial ingredients in its formulation, normally containing little or no complete food  . UPAs are also characterized by the presence of fast-absorbing carbohydrates, with high lipid content and low in fiber (Damiani et al., 2011) . These eating and nutritional behaviors have been identified as a fundamental factor both in the development and in the subsequent course of MS (Damiani et al., 2011;Grundy et al., 2005) .
UPF consumption has grown significantly in recent decades and currently 75% of all world food sales are UPF (Alexander et al., 2011). These foods already account for more than half of the total dietary energy consumed in high-income countries such as the US, Canada and the UK and between 20-30% of total dietary energy in middle-income countries such as Brazil, Mexico. and Chile (Baraldi et al., 2018;Louzada et al., 2018;Marrón-Ponce et al., 2018;Monteiro et al., 2019;J. C. Research, Society and Development, v. 11, n. 16, e159111629059, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i16.29059 Moubarac et al., 2017;Rauber et al., 2018). Despite this increase in consumption occurring at all social levels, the greatest trends occur especially in the lower social classes  . The health effects caused by UPAs still remain uncertain, especially in adolescents, since not enough epidemiological and intervention studies were carried out for this purpose (Juul;Hemmingsson, 2015). However, some evidence shows that UPF like sugary drinks are one of the main contributors to lipid alterations, weight gain, obesity and type 2 diabetes (Shin et al., 2018). In addition, trans fats present in UPF can negatively affect cardiovascular health; processed meats may be associated with an increased risk of mortality from cardiovascular diseases and cancer (Ambrosini et al., 2013) . In recent years, changes in the dietary profile have occurred in all age groups, especially among children and adolescents. However, despite some studies indicating a relationship between excess weight and metabolic alterations with high UPA intake  , to the best of our knowledge, we did not find in the literature studies that had synthesized evidence on the relationship between alcohol consumption. AUP and MS in adolescents. In this sense, the objective of the study will be to describe the protocol methods that we will use for the development of a systematic review involving UPF consumption and MS in adolescents.

Methodology
This study is a protocol systematic review. The protocol was submitted to the International Prospective Register of Systematic Reviews (PROSPERO) registered under number CRD42021227770 (http://www.crd.york.ac.uk/PROSPERO). This systematic review protocol followed the guidelines indicated in Preferred Reported Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) (Moher et al., 2016). The systematic review will include studies that meet the following eligibility criteria based on the Population, Exposure, Control, Outcome (PECO acronym) design framework. The acronym PECO (Ministério da Saúde, 2014) was used to describe all components related to the problem identified and to structure the research question: "Adolescents with high consumption of UPF are more likely to develop MS than adolescents with low UPF consumption?".
Observational (cohort, case-control and cross-sectional) and experimental (clinical trial) studies carried out in adolescents aged 10 to 18 years will be included, with no limits on ethnicity, gender and nationality and that address the consumption of AUP, without language or date restriction. of publication. For attribution of consumption of ultra-processed foods, studies will be selected with registered food items with a high degree of industrial processing, or that have more than 5 ingredients added to their formulation or articles that used a food classification system that considers industrial processing and different techniques of processing as a definition for ultra-processed foods.
The comparator group will include adolescents who have a low AUP consumption and who did not participate in any type of intervention or guidance during the period in which the study was developed. The primary outcome will include metabolic syndrome. Secondaries will include at least one of the components of the metabolic syndrome (abdominal obesity, dyslipidemia, hypertension, hyperglycemia, insulin resistance). The research development process will be carried out according to the PRISMA flowchart as presented in Figure 1.

The searches will be carried out in the MEDLINE (via PubMed), EMBASE (via ScienceDirect), LILACS (via VHL),
and Cochrane databases. For searches, publications up to march 2022 will be considered. The descriptors will be combined with the medical subject headings (MeSH), (Emtree) and (DeCS): "The chosen descriptors will be identified by "quotes" and properly separated by the Boolean terms AND and OR. Combinations of free words and subject terms will be used for the search, which will not be limited by language. Likewise, cross-searching will be carried out across all databases to ensure that all relevant articles are identified.
A software (Mendeley Reference Manager) will be used for reference management and duplicate removal.
Subsequently, the data will be imported into the Rayyan software (Ouzzani et al., 2016), so that the screening process can be carried out. The selection process will be presented as follows: After searching the databases, all references will be transferred to a single Mendeley library for subsequent removal of duplicates. A manual check of all references will be performed to ensure that all duplicates have been removed. Subsequently, all references will be transferred to Rayyan Software QCRI 27 with the intention of allowing independent selection by two experienced reviewers (LL and CL), meeting all eligibility criteria to be included in the present study, reasons for excluding materials not selected will be logged. In case of doubts or disagreements between reviewers, the inclusion or exclusion of the study will be decided by discussion and a third researcher (RL) will help in the evaluation in cases of disagreement. Research, Society andDevelopment, v. 11, n. 16, e159111629059, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i16.29059 5 Data in these articles will be independently extracted by LL and CL and reviewed by RL. If data extraction from a selected study cannot be performed due to lack of information or information inadequately described in the full-text article, LL will contact the corresponding author of the publication via email to request the data.
The extracted data will include descriptive information about the study (authors, year of publication, study collection period, study design, country in which the study was carried out, number of participants, sex, age group), intervention/exposure (food consumed), instruments used to collect food consumption, Food Frequency Questionnaire (FFQ) and 24-hour recall (R24h), result information, information on secondary results.
The quality assessment of the articles included will be carried out by two reviewers (LL and CL), using the Joana Briggs Institute tools JBI Critical appraisal for clinical trials and for cohort, case-control and cross-sectional studies, in order to assess the risk of bias. The level of certainty of evidence for the relationship between AUP consumption and outcome will be conducted using the Grading system. of Recommendations Assessment, Development and Evaluation (GRADE). In case of divergence, the third reviewer (RL) will make the final decision.
RevMan software (v.5.3) will be used to calculate the relative risk (RR) in dichotomous data and the mean difference (MD) for variables with continuous data. The estimated value and 95% CI of each effect will be calculated. The magnitude of heterogeneity will be evaluated by the Q test and I 2 statistics with RevMan 5.4, which ranges from 0 to 100%. I² index percentages of approximately 25% (I 2 ≤25), 50% (25<I 2 <75) and 75% (I 2 ≥75) will be considered, respectively, low, medium and high heterogeneity. Random effects models can be used, depending on the number of studies selected and if the studies are significantly different (I 2 > 50%). The forest-plot type plot will be used to summarize the estimates.
Results that presented a significance level ≤0.05 will be considered statistically significant associations.

Results and Discussion
The synthesis of evidence data will be approached from the relationship of consumption of ultra-processed foods and metabolic syndrome in adolescents. Data will be presented in a narrative format using tables. This process will be carried out through consensus between two reviewers. Any discrepancies will be resolved using a third reviewer.
We understand that this systematic review protocol is the first that proposes to synthesize evidence on the relationship between UPF consumption and MS in adolescents. Diets with the highest UPA intake, therefore, with lower nutritional quality, are strongly associated with increased prevalence of cardiovascular diseases, dyslipidemia, obesity and metabolic syndrome in adults (Batal et al., 2018).
However, when the same situation is observed in adolescents, the same association has not been evidenced. According to research involving adolescents, there was no significant association between AUP ( fast foods and snacks) with obesity and hypertension (Payab et al., 2015).
Previous studies have shown that higher UPA consumption is related to lower consumption of vitamins, proteins and fiber, as well as higher consumption of saturated fats, free sugars, carbohydrates, sodium and overall energy intake. The results of studies corroborate the literature indicating that UPF contribute negatively to the nutritional quality of the diet (Cornwell et al., 2018).
It is possible to affirm that the significant increase in the prevalence of obesity in adolescents has become irrefutable, pointing to the need for preventive measures, since this group is directly exposed to favorable environments and habits (Nascimento et al., 2020).
UPA intake is a marker of an unhealthy diet, however, experimental studies aimed at displacing energy foods by increasing vegetable and fruit consumption have not been successful and some studies have not confirmed that fruit intake is an adequate intervention for prevention. of obesity. These findings suggest that obesity is much more a problem of quantity than quality of food consumption (Bayer et al., 2014;Kaiser et al., 2014).

Partial Final Considerations
Note the importance of a survey on food consumption and metabolic parameters of adolescents and their associations with the increase in UPF intake. Thus, it is essential that more robustness in relation to the amount of evidence on this theme occur, a fact that highlights the importance of this review.
The review is expected to systematically map evidence available in the literature on the consumption of ultraprocessed foods and the relationship with the metabolic syndrome in adolescents.