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. 2021 Sep 28;16(9):e0257755. doi: 10.1371/journal.pone.0257755

Time-trend in excess weight in Brazilian adults: A systematic review and meta-analysis

Katia Kodaira 1,#, Flavia Casale Abe 1, Tais Freire Galvão 2, Marcus Tolentino Silva 1,*,#
Editor: Cesario Bianchi3
PMCID: PMC8478247  PMID: 34582470

Abstract

Background

This review aimed to estimate the time-trend prevalence of excess weight, overweight and obesity in the Brazilian adult population, from the 1970s–2020, through systematic review and meta-analysis (Protocol: CRD42018091002).

Methods

A search for articles was conducted in the databases MEDLINE, EMBASE, Scopus, and LILACS up to June 2021. Studies that assessed excess weight, overweight and obesity in the adult population were eligible. Two authors selected studies, collected data and assessed the methodological quality of the studies. The primary outcomes were the prevalence of excess weight, overweight, and obesity by sex and period of years. Pooled prevalence and 95% confidence intervals (CIs) were calculated in the meta-analysis of the random effects model. Heterogeneity (I2) was investigated by meta-regression and publication bias was investigated by Egger’s test.

Results

A total of 7,938 references were identified in the search strategies, of which eighty-nine studies and nine national surveys, conducted from 1974–2020, were included in the meta-analysis. The pooled prevalence of excess weight in Brazilian adults increased from 33.5% (95% CI: 25.0; 42.6%) in 1974–1990 to 52.5% (95% CI: 47.6; 57.3%) in 2011–2020. The pooled prevalence of overweight in Brazilian adults was 24.6% (95% CI: 18.8; 31.0%) from 1974–1990 and 40.5% (95% CI: 37.0; 43.9%) from 2011–2020. The pooled prevalence of obesity in Brazilian adults increased by 15.0% from 1974–1990 to 2011–2020. The increases were observed for both men and women in almost all periods. The prevalence of excess weight and obesity remained higher among women in all periods.

Conclusions

A continuous increase in the prevalence of excess weight, overweight and obesity were observed over the years. The prevalence of excess weight affected half of Brazilian adults in the period from 2011–2020 and both sexes.

Introduction

Obesity is a consequence of excessive fat accumulation in adipose tissue, and it is harmful to an individual’s health [1]. The prevalence of this condition is on the rise and has become a global risk factor, affecting almost all countries, populations, and social classes [2]. Its evolution involves multiple factors, such as changes in lifestyle and food consumption, as well as socioenvironmental influences [3].

Obesity is also an important risk factor for major chronic noncommunicable diseases, such as diabetes, high blood pressure, cardiovascular diseases, cancer, and osteoarthritis [4–6]. The consequences of being overweight affect the quality of life and, development of psychosocial disorders and decrease life expectancy [7].

Brazil is one of the few middle-income countries that conducts frequent national cross-sectional, population-based surveys, either by the Brazilian Institute of Geography and Statistics or by educational research institutions. Comparative results of some national surveys have shown an increase in the prevalence of excess weight in adults, an important process in the nutritional and socioeconomic transition [8,9].

The first national survey in Brazil with information on the population’s weight and height was the National Survey on Household Expenses, carried out in 1974, and the prevalence of excess weight was 21.4% in the adult population [10,11]. According to a national telephone survey carried out in Brazilian state capitals in 2019, the prevalence of excess weight was 75.7% [12]. The problem of excess weight is not exclusive to the adult population, as the prevalence in children and adolescents is also increasing [13,14].

Despite numerous national surveys and local studies, carried out in different Brazilian cities and regions, studies on the prevalence of excess weight, overweight and obesity in Brazilian adults are still fragmented. Previous analyses included nationally representative studies, telephone surveys or few regional studies, and to the best of our knowledge, there are no previous systematic reviews that synthesized available data [11,15–17]. Thus, we observed a need to group studies on the prevalence of excess weight and to assess the influence of study year on the estimates. This review aimed to estimate the time-trend prevalence of excess weight, overweight and obesity in the Brazilian adult population, from the 1970s–2020.

Materials and methods

Protocol and registration

A systematic review and a meta-analysis of cross-sectional studies were carried out. The study protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO) (Protocol: CRD42018091002).

Eligibility criteria

Studies were considered eligible if they met the following criteria: a) cross-sectional, population-based studies with random sampling carried out in Brazil (city, regional or national), which assessed the prevalence of excess weight, overweight, and/or obesity; b) studies including adults aged ≥18 (according to the age of majority criterion in Brazil) [18], of both sexes; c) studies regardless of the presence of comorbidities; d) longitudinal population-based studies that described the baseline of the study and not the segment; and e) studies without restrictions on year, publication status, or language. Studies carried out in groups of specific populations, such as indigenous people, pregnant women, institutionalized persons, and children were excluded.

Search strategy

The search for articles was carried out in the databases MEDLINE (via PubMed), EMBASE, Scopus, and LILACS. As a strategy to identify potentially eligible studies not indexed in databases, we screened the references of relevant publications. Also, other sources like letters, personal opinions, books, or conference abstracts were considered as a strategy to identify other possible additional studies. The search strategy is available in Supporting information S1 Table. Searches were held in March 2018 and updated in June 2021.

Study selection and data collection

Study selection was performed using Covidence platform (www.covidence.org) [19]. This Platform allows to remove duplications and the independent selection of titles, abstracts, and full texts, as well as their extraction. After removing duplicate articles, two independent authors (KK, FCA) selected the articles by title and abstract, according to the eligibility criteria. Any mention of excess weight, overweight or obesity was taken in consideration to include the study in the full text review.

Relevant articles were retrieved for full text review. Studies that used data from a same research with similar results were assessed, and the publication that included the data and results in a more complete and detailed way was included, and the others were excluded. Selected articles that referred to national surveys were replaced by the original microdata, when available. Disagreements at all stages were solved by consensus or decided by a third author (MTS).

The following data were extracted by two authors from the selected studies, using standardized spreadsheet: author; year; place (city or state); macro-region of the country; total sample size; women sample size; prevalence of excess weight, overweight, and obesity by sex; overall prevalence of excess weight, overweight, and obesity; age group; self-reported or measured data; body mass index (BMI) classification. The BMI categories considered were excess weight (BMI ≥ 25kg/m2), overweight (25kg/m2 ≤ BMI < 30 kg/m2), and obesity (BMI ≥ 30kg/m2). These categories were defined according to World Health Organization (WHO) guidelines on BMI classification [20]. Studies that considered other BMI classifications were classified into the WHO classification.

Quality assessment of included studies

Two authors (KK, FCA) independently assessed the methodological quality of the studies using a standardized tool [21], consisting of nine items: i) was the sample frame appropriate to address the target population?, ii) were study participants sampled in an appropriate way?, iii) was the sample size adequate?, iv) were the study subjects and the setting described in detail?, v) was the data analysis conducted with sufficient coverage of the identified sample?, vi) were valid methods used for the identification of the condition?, vii) was the condition measured in a standard, reliable way for all participants?, viii) was there appropriate statistical analysis?, and ix) was the response rate adequate, and if not, was the low response rate managed appropriately?.

Disagreements were resolved by the third author (MTS). For each study, the value 0 corresponded to a limitation in the respective item and the value 1, corresponded to a met expected criterion. The total score could range from zero (low quality) to nine (high quality).

Data synthesis and statistical analyses

Data analyses were performed using Stata® version 14.2 (Stata Corp, College Station, Tx, United States). The primary outcomes were the prevalence of excess weight, overweight, and obesity with a 95% confidence interval (CI) by sex and year of study. The years considered were: 1974–1990 (due to few studies in the period), 1991–2000, 2001–2010, and 2011–2020.

The results were pooled by meta-analysis using the random effects model described by DerSimonian and Laird and the double-arcsine transformation for variance stabilization as proposed by Freeman-Tukey [22]. Heterogeneity was assessed by the chi-square test with a significance of p < 0.10, and its magnitude was determined by the I-square (I2) [23]. To identify the possible causes of heterogeneity, a meta-regression was performed using the Knapp-Hartung method [24]. The effects of the prevalence of excess weight, overweight, and obesity; year of data collection; and methodological quality of the studies were evaluated. Potential publication bias was assessed using a funnel plot and Egger’s test [25].

Results

The literature search yielded a total of 7,938 potentially eligible articles (Fig 1). Based on titles and abstracts, we selected 236 articles for full text review. Eighty-nine studies carried out between 1974 and 2020 met the eligibility criteria and were included in the research. No new studies were identified by searching the references of the included articles. Microdata from nine national surveys were included. The references of all 85 reports from 89 included studies are listed in Supporting Information S2 Table.

Fig 1. PRISMA flow chart showing the selection of studies included in systematic review.

Fig 1

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Some studies used self-reported data to calculate BMI. Most studies scored between 7 and 9 in the evaluation of methodological quality. No study was excluded because of its low methodological quality (S2 Table).

The pooled prevalence of excess weight in Brazilian adults increased from 33.5% (95% CI: 25.0; 42.6%) in the 1974–990 to 52.5% (95% CI: 47.6; 57.3%) in the 2011–2020 period (Table 1). In both sexes, the prevalence of excess weight increased in all periods and the prevalence remained higher among women.

Table 1. Meta-analysis of excess weight, overweight and obesity in Brazilian adults, by sex and period of years, from 1974 until 2020.

Period 1974–1990 1991–2000 2001–2010 2011–2020
Prev. (%) (95% CI) I2(%) studies Sample size Prev. (%) (95% CI) I2(%) Studies Sample size Prev. (%) (95% CI) I2(%) Studies Sample size Prev. (%) (95% CI) I2(%) Studies Sample size
Excess weight 33.5 (25.0; 42.6) 99.9 4 164,425 40.0 (35.8; 44.3) 98.9 19 47,286 47.7 (45.1; 50.2) 99.5 50 331,003 52.5 (47.6; 57.3) 99.3 25 68,542
Men 37.5 (28.5; 46.9) 99.7 4 80,851 33.7 (25.3; 42.7) 98.8 11 11,459 44.5 (40.6; 48.5) 99.3 28 128,078 49.1 (43.4; 54.8) 98.1 12 22,994
Women 28.5 (20.5; 37.3) 99.7 4 83,574 41.8 (37.0; 46.6) 98.0 14 24,843 45.2 (42.4; 48.0) 99.1 33 169,756 62.9 (61.2; 64.5) 98.9 14 31,175
Overweight 24.6 (18.8; 31.0) 99.7 4 164,425 31.8 (28.8; 35.0) 97.6 14 41,384 33.8 (32.1; 35.4) 98.6 41 299,300 40.5 (37.0; 43.9) 98.1 14 57,216
Men 22.8 (16.7; 29.6) 99.5 4 80,851 33.0 (27.8; 38.3) 95.6 7 9,258 37.2 (34.7; 39.6) 97.7 20 115,426 43.7 (39.8; 47.6) 95.7 9 22,260
Women 26.0 (20.4; 32.0) 99.4 4 83,574 29.7 (27.4; 32.2) 90.8 9 21,142 33.9 (31.7; 36.1) 98.3 24 151,765 42.6 (37.7; 47.5) 98.0 10 29,312
Obesity 8.6 (5.7; 11.9) 99.6 4 164,425 16.9 (14.0; 20.2) 98.5 16 42,141 17.2 (15.6; 19.0) 99.2 39 297,634 23.9 (21.8; 26.0) 96.6 17 60,675
Men 5.3 (3.3; 7.8) 98.9 4 80,851 12.7 (8.8; 17.0) 97.4 11 11,459 14.6 (12.3; 17.1) 98.8 20 115,256 20.4 (18.4; 22.4) 87.4 8 21,788
Women 11.2 (7.7; 15.3) 99.3 4 83,574 20.9 (16.4; 25.8) 98.6 13 24,041 19.3 (17.3; 21.4) 98.7 24 151,712 29.7 (26.3; 33.2) 96.5 10 29,726
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Prev.(%), prevalence. 95%CI, 95% confidence interval. I2, heterogeneity.

The pooled prevalence of overweight in Brazilian adults was 24.6% (95% CI: 18.8; 31.0%) in the 1974–1990, and it has increased over the years. In the last decade, the prevalence of overweight was 40.5% (95% CI: 37.0; 43.9%). In almost all periods, there was a predominance of overweight men compared to women, except for the period from 1974–1990, in which the prevalence of overweight was 26.0% (95% CI: 20.4; 32.0%) for women and 22.8% (95% CI: 16.7; 29.6%) for men (Table 1).

The pooled prevalence of obesity in Brazilian adults increased by 15.0% from 1974–1990 to 2011–2020. Increases were observed for both men and women, although the increase in the prevalence of obesity was greater among women than men over the past three and a half decades analyzed in this study.

Trends in the prevalence of excess weight, overweight and obesity in Brazilian adults have increased over the years, both for men and women (Fig 2). All trends were statistically significant (p<0.001).

Fig 2. Tendency of excess weight, overweight and obesity in Brazilian adults, by sex and year, from 1974 to 2020.

Fig 2

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All estimates were heterogeneous. Subgroup analysis did not identify causes of heterogeneity. The excess weight prevalence funnel plot showed high asymmetry (S1 Fig). and potential publication bias, which was confirmed by the presence of the effect of small studies (p = 0.001). This behavior was also observed for the overweight and obesity outcomes (S2 and S3 Figs).

Discussion

Summary of results

The prevalence of excess weight, overweight and obesity in Brazilian adults has been increasing since the mid-1970s. This increase is reflected in both sexes and in all periods of years analyzed in the review (1974–2020).

Research validity and limitations

The included studies adopted probabilistic sampling with different strategies, ensuring greater representativeness of the sampled population. The research covered a wide period, between the mid-1970s and 2020. The data presented were collected during different phases of an increasing trend in the prevalence of overweight and obesity, ensuring the temporality of results. The amplitude of the periods covered by the review made it possible to assess the growing trend.

Studies were not grouped by sample size, urban or rural location, age group, or socioeconomic status, which are factors that can affect the prevalence of excess weight and heterogeneity [26–28]. We also observed a trend to publish results with high prevalence. Our hypothesis is that studies with low prevalence were omitted because of a lack of interest in the scientific environment or even by the author’s decision not to publish the work, which fails to reflect reality [29].

Most studies used the WHO [20] as a reference to classify overweight and obesity. Some studies involving the elderly population adopted the Lipschitz [30] or the Pan American Health Organization [31] classifications, which consider the physical changes in weight and height during the aging process. Ideally, the adoption of the same cutoff point to define the outcome would bring greater validity [1]. The use of self-reported data in certain publications may also affect the results found. The variability in self-reported weight and height values induces changes in BMI and, therefore, in the prevalence of excess weight [32,33]. Anthropometric measures in studies based on self-reported data have shown a trend to underestimate weight and overestimate height [34,35]. Women tend to report lower weight values and men tend to report higher height values [32].

The prevalence of excess weight may also be influenced by survival bias. The mortality rate of individuals with moderate obesity (BMI from 30.0–39.9 kg/m2) can reduce life expectancy by up to four years, and in cases of severe obesity (above 40 kg/m2), the decrease can reach ten years [36]. It is possible that obese people are missed by random sampling at the time of population surveys. Survival bias changes the lifetime prevalence, but it does not change the prevalence that we estimate.

Comparison with the relevant literature and interpretation of the findings

The prevalence of excess weight has been increasing in Brazil. Similar results from other global studies show the trend of increasing prevalence of excess weight and obesity, both in high income, low-middle and low- income countries [4,17,37].

This review has found a progressive growth of excess weight in Brazil over the years. The United States, a country with one of the highest rates of obesity in the world, presented a prevalence of obesity of 14.6% in the 1970s, with an increase to 38.7% in 2016 [38,39]. In a study that evaluated different countries in Europe in 2014, the prevalence of overall excess weight was 53.1%, close to the Brazilian reality [40]. A Chinese study also observed increasing trends of overweight and obesity even considering different BMI cutoff points for Asian countries [41], as recommended by the WHO. The prevalence of overall obesity was 2.2% in 1989 and 14.0% in 2011.

We found a higher prevalence of excess weight and obesity in women than in men in this review. A worldwide study showed an increasing prevalence of obesity among women of all age groups, regardless of the country’s economic development [4]. Another review covering women from developing countries found an increase in obesity, mainly in Latin America and the Caribbean, the Middle East, North Africa, and Central Europe [42]. A Chinese study assessed the prevalence of excess weight among women and men between 1991 and 2000 [43]. The prevalence of excess weight was 14.5% for women and 9.6% for men in 1991. In 2000, there was an increase for both sexes but mainly among women, in which the prevalence was 26.5%, with 20.0% for men. Compared with our results, the prevalence of excess weight in Chinese population was lower than that found for both women and men within the same period (1991–2000).

An Ethiopian study investigated trends in excess weight in women from 2000–2016. The observed prevalence of excess weight was much lower for Ethiopian women than that for women in Brazil. The prevalence of excess weight in Ethiopian women was 10.9% in 2000, 14.9% in 2011, and 21.4% in 2016 [44].

Conclusion

The prevalence of excess weight in Brazil is rising. An alert must be raised to the problem and the urgent need for initiatives aimed at controlling overweight and obesity, since excess weight affected half of Brazilian population. Policy-makers and health managers should reassess current interventions and policies to prevent a serious obesity epidemic and initiate effective preventive measures to reduce excess weight in the country.

Supporting information

S1 Fig. Funnel plot of excess weight prevalence in Brazilian adults, from 1974 until 2020.

(DOCX)

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S2 Fig. Funnel plot of overweight prevalence in Brazilian adults, from 1974 until 2020.

(DOCX)

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S3 Fig. Funnel plot of obesity prevalence in Brazil, from 1974 until 2020.

(DOCX)

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S1 Table. Electronic search strategy.

(DOCX)

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S2 Table. Main characteristics and quality assessment of included studies in meta-analysis.

This is the S2 Table legend. M, measured. SR, self-reported. BMI, body mass index. BR, Brazil. WHO, World Health Organization. PAHO, Pan American Health Organization. ENDEF, Estudo Nacional de Despesa Familiar (National Survey on Household Expenses). PNSN, Pesquisa Nacional de Saúde e Nutrição (National Survey on Health and Nutrition). PNDS, Pesquisa Nacional de Demografia e Saúde (National Demography and Health Survey). PPV, Pesquisa sobre Padrões de Vida (Living Standards Survey). POF, Pesquisa de Orçamentos Familiares (Household Budget Survey). PDSD, Pesquisa Dimensões Sociais das Desigualdades (Social Dimensions of Inequalilies Survey). PNS, Pesquisa Nacional de Saúde (National Health Survey). ELSI, Estudo Longitudinal da Saúde dos Idosos (Brazilian Longitudinal Study of Aging). aWHO–overweight:BMI ≥ 25 and <30 kg/m2, obesity:BMI ≥ 30kg/m2; Lipschitz–underweight: BMI less than 22kg/m2, overweight: BMI more than 27kg/m2; PAHO–underweight: BMI ≤ 23 kg/m2, overweight: BMI ≥ 28 kg/m2 and < 30 kg/m2, obesity: BMI ≥ 30 kg/m2. bCritical appraisal according to The Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data: 1. Was the sample frame appropriate to address the target population? 2. Were study participants sampled in an appropriate way? 3. Was the sample size adequate? 4. Were the study subjects and the setting described in detail? 5. Was the data analysis conducted with sufficient coverage of the identified sample? 6. Were valid methods used for the identification of the condition? 7. Was the condition measured in a standard, reliable way for all participants? 8. Was there appropriate statistical analysis? 9. Was the response rate adequate, and if not, was the low response rate managed appropriately?.

(DOCX)

Click here for additional data file. (101.9KB, docx)

Data Availability

All relevant data are within the manuscript and its Supporting information files.

Funding Statement

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Cesario Bianchi

13 May 2021

PONE-D-20-38212

Time-trend of excess weight in Brazil: a systematic review and meta-analysis

PLOS ONE

Dear Dr. Silva,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Many suggestions were made and some important issues need to be addressed that include originality of the work, the classification of participants as being adolescents, justifying the methodology employed, discrepancies in the data between results and figures. I addition present the data yearly instead of an average and separated meta-analyses. Additional references are needed to substantiate some statements and a more comprehensive PubMed search for similar studies.

Please address all recommendations and questions raised by the 3 reviewers and answer them completely. We look forward to the revised manuscript.

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We look forward to receiving your revised manuscript.

Kind regards,

Cesario Bianchi

Academic Editor

PLOS ONE

Additional Editor Comments:

Dear Dr. Silva:

Thank you for submitting your interesting manuscript that was reviewed by 3 experts.

Many suggestions were made and some important issues need to be addressed that include originality of the work, the classification of participants as being adolescents, justifying the methodology employed, discrepancies in the data between results and figures. I addition present the data yearly instead of an average and separated meta-analyses. Additional references are needed to substantiate some statements and a more comprehensive PubMed search for similar studies.

Please address all recommendations and questions raised by the 3 reviewers and answer them completely. We look forward to the revised manuscript.

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Reviewers' comments:

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Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: I Don't Know

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I appreciate the opportunity to review this manuscript. The manuscript "Time-trend of excess weight in Brazil: a systematic review and meta-analysis" summarizes studies of prevalence of the excess of weight and assesses the temporal tendency of this indicator in the adult Brazilian population. This is an important area of research and strengthens the formulation of public policies, plans and actions to reduce, prevent and treat the excess of weight in Brazil. The authors provided all the data extracted from the studies included in the systematic review and meta-analysis and the PRISMA-P checklist. The manuscript brings interesting results, however, there are details that need to be clarified or explained more specifically for the final publication (see the specific comments below).

Title:

• I suggest including the studied population in the title.

Introduction:

• I suggest bringing evidence-based studies which prove that there is no previous systematic review about the topic addressed. This information cannot be empirical;

• Including epidemiological data about the excess of weight in Brazil;

• Evaluating the possibility of including in the “study objective” the period of time in which the temporal tendency was assessed.

Methodology

• Were the researchers who assessed the eligibility criteria blindfolded? It is important to describe this;

• Why was the adult population aged 18 or older considered? According to WHO criteria, for the assessment of nutritional status/growth curves, people aged between 10 and 19 years old are considered adolescents. I recommend justifying this choice of the methodology;

• The article is registered in PROSPERO, but it is not up to date. I recommend reviewing it.

Reviewer #2: Manuscript Review

PONE D-20-38212-R1

April 17, 2021.

Title: “Time-trend of excess weight in Brazil: a systematic review and meta-analysis.”

Summary

The authors conducted a systematic review and meta-analysis involving the adult Brazilian population up to December 2020. They investigated the time trend in excess weight in Brazil and found an overall prevalence of 46.7%, with a 12% increase between 2005 and 2016.

According to the authors, excess weight affected half of the adult Brazilian population of both sexes and in all regions of Brazil.

Study strengths

• Meta-analysis.

• The wide period investigated.

Main study limitations

• The authors did not consider other important keywords in the search strategy, such as “excess weight” and “excess body weight”, a major limitation.

Points that need clarification

Study overview

The field of the study is important and relevant since excess weight is a serious public health problem worldwide. However, the study has several methodological problems mainly in the Methods and Results sections. The justification for the study needs to be included in the introduction

Title:

1. The title should state that the study was carried out in adults: “Time trend in excess weight in Brazilian adults: a systematic review and meta-analysis.”

Abstract:

2. At the end of the conclusion, the authors state: “Excess weight affected half of the adult Brazilian population, both sexes and in all regions of Brazil.”. However, they do not report the most prevalent sex and region in the Results section.

3. The authors reported that 86 studies and 8 national surveys were included in the study. However, the results are different from in Figure 1 “…(n = 91), that refers to 94 studies”?

Introduction:

4. Page 3, line 59: Please add references.

5. Page 3, lines 64-65: “This review aimed to estimate the time-trend prevalence of excess weight in the Brazilian adult population.”. Please include the period investigated.

6. I was unable to locate the justification for the study. Why did the authors decide to do a systematic review on excess weight involving Brazilian adults?

Methods:

7. The Methods section is poorly described. The authors should follow the PRISMA checklist to better describe the methods of the study.

8. Page 4, line 71-73: Did the authors include a grey literature search? The grey literature refers to unpublished research or published in non-commercial form and allows a more comprehensive search strategy.

9. Page 4, line 75: Did the authors consider longitudinal studies in the eligibility criteria? If so, it is important to mention. Otherwise justify. Also, were letters, personal opinions, book chapters or conference abstracts considered?

10. Page 4, line 78: Were studies involving people with other comorbidities (diabetes, cardiovascular diseases, …) also excluded? This must be mentioned.

11. Page 4, line 80: “…and children (< 18 years old)…” repeated from “b”, line 77.

12. Page 5, line 95: Include checklist reference. I suggest inserting the checklist as complementary material.

13. Page 5, lines 99-101: “The total score obtained could range from zero (low quality) to nine (high quality). Surveys were considered adequate when they scored ≥ 6.” Please justify or include a reference explaining why the authors chose scored ≥ 6 as adequate.

14. S1 Table. Electronic search strategy: It is difficult to understand why the authors did not use other important key words in the search strategy, such as “excess weight” and “excess body weight”. In fact, the keyword “excess weight” appears in the title of this review! In a quick search using the terms “(excess weight OR excess body weight) AND (brazil OR brasil) AND (prevalence OR prevalences)”, I found 642 articles!

15. Still regarding the search strategy, many studies report the prevalence of overweight/obesity/excess weight throughout the article and not in the title or abstract because it is not the main objective of the article. Did the authors consider this fact in the search?

Results:

16. The authors should follow the PRISMA checklist to better describe the results of the study.

17. Fig 1: What do the authors mean by “Additional records through other sources”? This explanation was not mentioned in the Methods section.

18. Page 6, line 124, S2 Table: I suggest including S2 Table as Table 1 in the Results section. Change the current Table 1 to Table 2. Qualitative data must be shown before meta-analysis data.

19. Page 6, line 129: “The prevalence …” of what? Excess weight? Overweigh? Please, define. The same inconsistency in line 131.

20. Page 6, lines 125, 127, 131-32, Table 1, and Fig 2: Which means, “excess weight”? The authors did not define this term before and did not consider it in the search strategy.

21. Page 6, lines 132-34: “Between 1974 and 2004, the prevalence of excess weight was 40.2% (95% CI: 36.8; 43.7%) and from 2005 onwards, it has been 51.7% (95% CI: 134 48.8; 54.6%).” Does the prevalence reported by the authors refer to an increase? Was there an increase of 40.2% and 51.7% over the periods mentioned?

22. Table 1: Please include “n” for each category.

23. Figure 1, title: Again, update the word “excess weight”.

24. S1 Figure was not cited in the Results section. Also, include the definition of “ES” in the S1, S2 and S3 Figures.

25. Page 6, line 144: Use only one type of denomination (sex: male/female or gender: men/women) throughout the manuscript, including tables and figures.

26. Page 8, lines 143-46: “In almost all regions and in national surveys, except in North region, there was a predominance of male overweight compared to female”. This information is from Table 1, not S2 Fig. Add Table 1 at the end of the paragraph.

Discussion:

27. Page 9, line 172: “We also observed a trend to publish results with high prevalence”. I wouldn’t say that! Is that a phenomenon that occurs only in Brazil? However, the authors need to better support this statement with more studies conducted in Brazil and in other countries.

28. Page 9, line 185: “The results…”. Which results?

29. Page 10, line 191: “The prevalence of excess weight has been increasing.” In Brazil? Worldwide? Please mention!

30. Page 10, line 192: “…trend of increasing prevalence, …”. Which prevalence? Excess weight? Overweight? Obesity?

31. Page 10, line 197: “…in 2016; high values …” high or higher values?

32. Page 10, lines 197-98: “…In a study that evaluated different countries in Europe, the prevalence of overall excess weight was 53.1% and obesity, 15.9%, close to the Brazilian reality”. Were these studies carried out over the same period?

Reviewer #3: Reviewer Feedback on PONE-D-20-38212

This is a well-written and well-conducted systematic review on an important topic, and I recommend it for publication. There are, however, a number of issues which should be addressed beforehand.

Of note, I’m not a statistician or a mathematician. While the statistical analyses done in the study seem sound to me, their validity should also be assessed by a meta-analysis specialist.

General issues

You seem to have lumped all data from 1974 to 2016 together into one meta-analysis, which yielded average prevalence data for this time period. I’m not sure how meaningfull it is to combine data from such a long time period, in particular given the enormous changes Brazil has undergone during this time period. For decicion-makers in policy and practice and researchers it would be more useful to know how high the prevalence was in 1974, and how high it was in 2016, rather than having an average figure for the whole time period. Please explain, and consider doing separate meta-analyses for different time periods or points of time.

Minor issues

Abstract, line 34-35 (“The overall prevalence of excess weight in Brazilian adult population was 46.7% (95% CI: 43.6; 49.7%).”): Please specify to which time point or time period this refers.

Introduction, line 51-52 (“The consequences of being overweight… decrease life expectancy (7) due to an increased risk of premature death (1,8).“): Isn’t a decrease in life expectancy just another way of saying that the risk of premature death is increased? I find it somewhat strange to say that one is the consequence of the other.

Introduction, line 53-54 (“Brazil is one of the few developing countries that conducts frequent national cross-sectional, population-based surveys..“): Wouldn’t it be more appropriate to describe Brazil as a middle-income country?

Introduction, line 55-57 („Comparative results of some national surveys have shown an increase in the prevalence of excess weight in adults, an important event in the

process of nutritional and socioeconomic transition“): I would frame the increase in the prevalence of excess weight as a development or process rather than an event.

Introduction, line 57-59 (“This is not exclusive to the adult population, since there is a higher prevalence in children and adolescents, suggesting that the problem becomes even more serious over the years.“): Please provide a reference for the statement that the prevalence of obesity is hight among children and adolescents than among adults in Brazil (in most countries I am aware of it’s the other way round).

Introduction, line 60-62 („Despite the numerous national surveys carried out, studies on prevalence of excess weight, overweight and obesity with Brazilian adults still so far fragmented and to the best of our knowledge, there are no previous systematic review that synthesized available data.): The NCDRisC Risk Factor Collaboration has published multiple pooled analyses of body weight trajectories, which include Brazil and which are based on reviews of existing surveys, see https://ncdrisc.org/publications.html.

Methods, line 67-70 (Protocol and registration): Please state if this was an a priori protocol, i.e. a protocol developed before the study began, and if there were any deviations from the protocol (i.e. anything you ended up doing differently than envisioned in the protocol – which is fine as long as it is stated transparently and reasonably justified).

Methods, line 71-73: I would propose to insert a separate sub-heading for the section on search methods (line 71-73).

Eligibility criteria, line 76-77 („cross-sectional, population-based studies and random sampling, carried out in Brazil“): Please specify if studies had to be conducted on a national basis, i.e. if it was an eligibility criteria that they were representative for the whole of Brazil, or if you also included studies from specific regions within Brazil.

Eligibility criteria, line 76-77 („cross-sectional, population-based studies and random sampling, carried out in Brazil“): Please specify if you also included cohort studies.

Methods, line 95-97 (“The methodological quality of included studies was assessed using standardized tool The Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data)“). As not all readers may be familiar with this tool, please consider providing a concise summary of it (2-3 sentences, and a table with the criteria used by the checklist).

Results, line 116-117 („No new studies were identified by searching references of the included articles.“): Searchign the reference lists of included studies is indeed recommended, and should also be mentioned in the methods section under the sub-heading „Search methods“.

Results, line 125 („The overall prevalence of excess weight was 46.7%“). Please specify to which year this statement refers. This also applies to all similar statements in the subsequent sections of the manuscript.

Results, line 131-13 („Trends on prevalence of excess weight has been increasing over the years (Fig 2).“): Figure 2 seems to show that the level of prevalence of obesity is increasing, which is not the same like saying that the trend on the prevalence of obesity is increasing (the latter seems to imply that the rate of chenge ist increasing.

Results, line 132-134 („Between 1974 and 2004, the prevalence of excess weight was 40.2% (95% CI: 36.8; 43.7%) and from 2005 onwards, it has been 51.7% (95% CI: 48.8; 54.6%).“): To me, it seems a bit strange to lump such a long time period (1974-2004) together, and to say that from 2005 onwards, the prevalence has been exactly 51.7%. In reality, the prevalence seems to have been constantly rising. Besides, why have you chosen this specific cut-off (i.e. the year 2004/2005)?

Table 1, as well as several instances throughout the manuscript: It seems as if you used the term „excess weight“ as summary category for both simple overweight (i.e. overweight without obesity) and obesity. Besides, you seem to use the category „overweight“ for simple overweight only (i.e. a BMI from 25 to 30), not including those with obesity. This should be made explicit somewhere.

Results, line 141 („The overall prevalence of overweight in Brazil was 34.3%“): Please specify to which time period this refers. The same applies to similar statements in the following sections. Whenever a prevalence rate is given, the time frame should be stated explicitly.

Results, line 154-156 (“The excess weight prevalence funnel plot showed a high asymmetry (S4 Fig.). and a potential publication bias, which was confirmed by the presence of the effect of small studies (p = 0.001).“): Please state in which direction the data is likely to be biased (i.e. did small studies find, on average, higher prevalence rates than bigger studies, or was it the other way round?).

Discussion, line 159 (“The prevalence of excess weight has been increasing since the mid-1970s.“): While it may be obvious, it may still be worthwhile stating that this sentence refers to Brazil.

Discussion, line 185-188 („The results may also be influenced by survival bias. (…)“). Survival bias implies that the lifetime prevalence of obesity may be higher than the estimates for the point prevalence of obesity which you derived. However, in my understanding it does not impact the validity of the the latter – it just implies that they are lower than the lifetime prevalence. Please consider making this clearer in the discussion.

Further issues: The PubMed search syntax which you used was rather simple, and may have missed relevant studies. Besides, you seem not to have done a citing-studies search (also known as forward-citation search), i.e. a search for studies that cited the studies included in your review (such searches can be done in databases such as Scopus). Please consider mentioning this in the limitations section.

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Reviewer #1: Yes: Mariana Balestrin

Reviewer #2: No

Reviewer #3: Yes: Peter von Philipsborn

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Decision Letter 1

Cesario Bianchi

10 Sep 2021

Time-trend in excess weight in Brazilian adults: a systematic review and meta-analysis

PONE-D-20-38212R1

Dear Dr. Silva,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Cesario Bianchi

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Dear Dr. Silva;

Thank you for submitting the revised version of your interesting work. I am glad to accept the manuscript at this time.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: Although the presentation of this version has been relatively confused displaying all the suggested changes, the authors have adequately addressed my comments and significantly improved the manuscript.

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Reviewer #1: Yes: Mariana Balestrin

Reviewer #2: No

Acceptance letter

Cesario Bianchi

16 Sep 2021

PONE-D-20-38212R1

Time-trend in excess weight in Brazilian adults: a systematic review and meta-analysis

Dear Dr. Silva:

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Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Fig. Funnel plot of excess weight prevalence in Brazilian adults, from 1974 until 2020.

    (DOCX)

    Click here for additional data file. (3.5MB, docx)
    S2 Fig. Funnel plot of overweight prevalence in Brazilian adults, from 1974 until 2020.

    (DOCX)

    Click here for additional data file. (2.1MB, docx)
    S3 Fig. Funnel plot of obesity prevalence in Brazil, from 1974 until 2020.

    (DOCX)

    Click here for additional data file. (3.4MB, docx)
    S1 Table. Electronic search strategy.

    (DOCX)

    Click here for additional data file. (15.3KB, docx)
    S2 Table. Main characteristics and quality assessment of included studies in meta-analysis.

    This is the S2 Table legend. M, measured. SR, self-reported. BMI, body mass index. BR, Brazil. WHO, World Health Organization. PAHO, Pan American Health Organization. ENDEF, Estudo Nacional de Despesa Familiar (National Survey on Household Expenses). PNSN, Pesquisa Nacional de Saúde e Nutrição (National Survey on Health and Nutrition). PNDS, Pesquisa Nacional de Demografia e Saúde (National Demography and Health Survey). PPV, Pesquisa sobre Padrões de Vida (Living Standards Survey). POF, Pesquisa de Orçamentos Familiares (Household Budget Survey). PDSD, Pesquisa Dimensões Sociais das Desigualdades (Social Dimensions of Inequalilies Survey). PNS, Pesquisa Nacional de Saúde (National Health Survey). ELSI, Estudo Longitudinal da Saúde dos Idosos (Brazilian Longitudinal Study of Aging). aWHO–overweight:BMI ≥ 25 and <30 kg/m2, obesity:BMI ≥ 30kg/m2; Lipschitz–underweight: BMI less than 22kg/m2, overweight: BMI more than 27kg/m2; PAHO–underweight: BMI ≤ 23 kg/m2, overweight: BMI ≥ 28 kg/m2 and < 30 kg/m2, obesity: BMI ≥ 30 kg/m2. bCritical appraisal according to The Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data: 1. Was the sample frame appropriate to address the target population? 2. Were study participants sampled in an appropriate way? 3. Was the sample size adequate? 4. Were the study subjects and the setting described in detail? 5. Was the data analysis conducted with sufficient coverage of the identified sample? 6. Were valid methods used for the identification of the condition? 7. Was the condition measured in a standard, reliable way for all participants? 8. Was there appropriate statistical analysis? 9. Was the response rate adequate, and if not, was the low response rate managed appropriately?.

    (DOCX)

    Click here for additional data file. (101.9KB, docx)
    Attachment

    Submitted filename: Response_to_reviewers_2021_06.docx

    Click here for additional data file. (40.2KB, docx)

    Data Availability Statement

    All relevant data are within the manuscript and its Supporting information files.

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