Global Trends in Scientific Research on Pediatric Obesity

(1) Introduction: The aim of this study was to analyze scientific production, collaboration among countries, and research topics focusing on pediatric obesity. (2) Methods: The papers that were included in the study were retrieved from the Web of Science Core Collection from Clarivate Analytics. A bibliometric analysis of several focuses, including journals of publication, subject categories, most frequent author keywords, and journal impact factors, was conducted. Social network analysis was used to recognize collaboration groups between countries and the co-occurrences of author keywords. (3) Results: A total of 12,171 research articles were published in 2036 journals classified under a variety of subject areas, with pediatrics (27.7%), nutrition and dietetics (18.5%), and public environmental and occupational health (18.4%) accounting for the most frequent study areas, and Pediatric Obesity (309), the International Journal of Obesity (299), and BMC Public Health being the most productive journals. The main challenges identified for pediatric obesity include general topics such as physical activity, nutrition, diet, and prevention as well as other more specific challenges such as metabolic syndrome, insulin resistance, eating behavior, and cardiovascular diseases. (4) Conclusions: We observed a growth rate in the number of published articles of 59.8%, which serves as evidence of the importance of the topic. The number of funded papers also doubled from 2010 to 2019. There has been significant global collaboration on the topic, with countries across five continents being involved. The results of the thematic analysis reveal the importance of exercise and nutrition-related topics along with specialized health terms and terms related to public health.


Introduction
Childhood obesity is a global problem that has grown considerably more prevalent in recent years, becoming a serious public health problem and a major challenge for the scientific community. Since 1980, the prevalence of obesity has doubled in more than 70 countries. In the United States, its prevalence doubled from 6% to 12%, and in Spain, morbid obesity increased by over 200% over the course of 13 years [1][2][3]. This growing trend also applies to childhood obesity [4]. If this pattern is maintained, by 2030, approximately 38% of the world's adult population will be overweight, and another 20% will be obese [5].
Obesity is defined by the World Health Organization as an abnormal or excessive accumulation of fat that poses a health risk [6]. It is a chronic disease of multifactorial origin in which environmental, genetic, behavioral, and endocrine factors are involved [7,8]. The evaluation of these factors is vital to taking preventive and treatment measures, but in each particular case, it is difficult to assess the relative importance of each [9]. of publication and collaboration among countries; and (d) discusses trending research topics through a review of the most frequently used keywords and a co-word analysis.

Materials and Methods
The papers that were included in the study were retrieved from the Web of Science Core Collection (WOS) from Clarivate Analytics. The following search terms were used: TI = ((Obesity OR Overweight OR "exces* weight*" OR adiposit*) AND (school* OR scholar* OR Child* OR Adolescen* OR Infant* OR Pediatr* OR paediatr* OR infanc* OR teenage* OR kindergarten OR preschool* OR "teen* year*" OR childhood)) OR TI = (Obesity OR Overweight OR "exces* weight*" OR adiposit*) AND WC = PEDIATRICS.
The search was performed in December of 2020. To achieve greater precision in the results, the search was conducted in the "Title field." Papers including terms derived from the same linguistic root were obtained using an asterisk to truncate the words (e.g., "Adolescen*" allows for the recovery of items containing the terms "Adolescency", "Adolescent", and "Adolescents"). Only original articles and reviews were downloaded, and proceeding papers, letters, and editorial material were excluded. The search was performed in December of 2020. The search was limited to the 2010-2019 period.
A standardization of the keywords was carried out to group variations in the spelling and synonyms of the same concept: singulars and plurals (e.g., "scholar" and "scholars"), acronyms (e.g., "autism spectrum disorder" and "ASD"), hyphenated words (e.g., "parent-adolescent reciprocity" and "parent adolescent reciprocity"), and synonyms (e.g., "infancy" and "childhood"). The words "physical activity" and "physical exercise" were not considered synonymous, since "physical activity" involves any movement carried out by the muscles, while "physical exercise" involves planned, structured, repetitive, and intentional movement.
Trends in scientific research on pediatric obesity were analyzed through a bibliometric analysis of several topics: annual evolution and growth rates, journal of publication, subject categories in which a journal is classified according to the WOS database, most frequently used author keywords, and journal impact factors. Information about funded papers was also analyzed. Social network analysis (SNA) was used to identify collaborations between countries and cooccurrences of author keywords in the collection of papers. A co-word network is a useful tool that is able to generate a comprehensive overview of the keywords that define articles, allowing us to measure the significance of some topics to the published papers and their relationships to other concepts. The Pajek software program was used to represent the co-word network [21]. A density map of the keywords was created with VOSViewer software. In the author keyword networks, the size of the spheres is proportional to the number of co-occurrences that each keyword has with the others, and the size of the line connecting two keywords is also proportional to the number of cooccurrences of these two keywords. A threshold of at least 15 co-occurrences in common was applied for representation. The impact factors of the journals were obtained from the 2019 edition of Journal Citation Reports.

Annual Evolution
A total of 12,088 published articles were retrieved from the WOS database. The annual number of articles increased steadily from 919 (7.6%) in 2010 to 1468 in 2019 (12.1%) ( Table 1).
The number of funded papers increased throughout the decade and doubled between 2010 (n = 485) and 2019 (n = 956) ( Figure 1). In percentages, the number of funded papers increased from 52.8% of the total number of articles published in 2010 to 65.8% of the total number of articles published in 2019. Funded papers accounted for 76.23% of the total citations received. total citations received.   Table 2 presents the 10 journals that published the most articles, rece citations, and had the highest impact factors and percentages of funded p were published in 2036 journals. Two journals, the International Journal of Ob Pediatric Obesity (295), included close to 300 published papers, and another more than 200 articles: BMC Public Health, PLoS One, Obesity, and Childhoo ratio of citations per paper is greater from Pediatrics (53.59), which is follo from Obesity Reviews (43.67) and the International Journal of Obesity (34.92). T of funded papers is close to 90% for seven of the 10 journals, with BMC Publi ing out with almost 92%. For the 5-year impact factor values, Obesity Reviews out, followed by Pediatrics (6.45) and the International Journal of Obesity ( these journals are in the first quartile in their JCR subject categories, and the in their second quartile. Regarding countries of origin, among all of the jou has published the most articles; the United Kingdom is the second most pro try with six articles, and other leading countries include China, Australia Spain. A total of five of the 10 journals focus on pediatrics, and four focus  Table 2 presents the 10 journals that published the most articles, received the most citations, and had the highest impact factors and percentages of funded papers. Articles were published in 2036 journals. Two journals, the International Journal of Obesity (299) and Pediatric Obesity (295), included close to 300 published papers, and another four included more than 200 articles: BMC Public Health, PLoS One, Obesity, and Childhood Obesity. The ratio of citations per paper is greater from Pediatrics (53.59), which is followed by those from Obesity Reviews (43.67) and the International Journal of Obesity (34.92). The percentage of funded papers is close to 90% for seven of the 10 journals, with BMC Public Health standing out with almost 92%. For the 5-year impact factor values, Obesity Reviews (9.768) stands out, followed by Pediatrics (6.45) and the International Journal of Obesity (5.336). Half of these journals are in the first quartile in their JCR subject categories, and the other half are in their second quartile. Regarding countries of origin, among all of the journals, the USA has published the most articles; the United Kingdom is the second most productive country with six articles, and other leading countries include China, Australia, Canada, and Spain. A total of five of the 10 journals focus on pediatrics, and four focus on endocrinology and metabolism.

Subject Categories
The WOS subject categories with the highest number of published papers, most frequently used keywords, and journals with the most articles in each subject category are listed in Table 3. The subject category of pediatrics covers a number of published papers (2737; 22.6%), followed by public, environmental, and occupational health (1887; 15.6%); nutrition and dietetics (1797; 14.9%); and endocrinology and metabolism (1614; 13.4%). In terms of citations, pediatrics (21.5%) is followed by endocrinology and metabolism (17.7%); nutrition and dietetics (17.4%); and public, environmental, and occupational health (13%). The percentage of funded papers is high for multidisciplinary sciences (86.7%), nutrition and dietetics (76%), and endocrinology and metabolism (75.2%). The most productive journals vary by area, except for in the case of nutrition and dietetics and endocrinology and metabolism, which tend to share the same journals, and public, environmental, and occupational health, which shares some journals with medicine: general and internal.
Collaboration between countries is illustrated in the global map in Figure 3, where intense collaboration is shown between the United States and many EU countries, such as the United Kingdom (n = 166 papers in collaboration), Spain (n = 76), and Germany (n = 73), as well as between the United States and China (n = 199), Canada (n = 153), and Australia (n = 119). For Central and South American countries, the following stand out in terms of collaboration: Mexico, Colombia, Brazil, and Chile. Among African countries,

Keyword Analysis
The most frequently used keywords, which were found in 300 papers or more, were "body mass index" (n = 1447), "physical activity" (n = 802), "physical exercise" (n = 379), "nutrition" (n = 362), "diet" (n = 339), "prevention" (n = 337), and "metabolic syndrome" (n = 300) ( Table 5). We excluded keywords used in the search profile. When we analyzed the distribution of the main keywords by continent, "body mass index" and "physical activity" (n = 802) were the two most frequently used keywords, but the third most frequently used word varied by continent and was determined to be "nutrition" for North America, "prevention" for Europe, "physical exercise" for South America, "intervention" for Oceania, and "prevalence" for Asia and Africa. Figure 4 shows the word cloud for each continent. The co-word network shown in Figure 5 highlights the greatest centrality value for two keywords: that for "body mass index" and "physical activity" and its relation to other words. "Body mass index" was shown to mainly be related to "waist circumference" (n = 98), "body fat" (n = 51), "prevalence" (n = 47), "socioeconomic status" (n = 35), "blood pressure" (n = 34), and "pregnancy" (n = 34). The most frequently used relationships for "physical activity" were with "nutrition" (n = 86), "diet" (n = 85), "sedentary behavior" (n = 50), and "intervention" (n = 46)".

Discussion
Pediatric obesity is a complex public health problem that has stimulated international research to identify its causes and possible solutions. The results of this study help to better elucidate the current state of research in this field and its complexity, as it identifies numerous variables related to its diffusion and impact worldwide. The present study allowed us to measure the influence or impact of research articles on pediatric obesity, such as the growth in the number of articles published, funding, impact according to the num-

Discussion
Pediatric obesity is a complex public health problem that has stimulated international research to identify its causes and possible solutions. The results of this study help to better elucidate the current state of research in this field and its complexity, as it identifies numerous variables related to its diffusion and impact worldwide. The present study allowed us to measure the influence or impact of research articles on pediatric obesity, such as the growth in the number of articles published, funding, impact according to the number of citations these articles receive, the interdisciplinarity of the problem, existing collaboration in the area, and the main research topics, among others. The present research helps address what the World Health Organization calls "one of the most serious public health challenges of the 21st century" [22]. Through this study, we analyzed production levels (which refers to the number of publications that normally has an increasing trend over the years), scientific impact levels, funding levels, most frequently studied topics, and patterns of distribution across countries and continents for papers on pediatric obesity published in the most relevant journals worldwide. Searches of bibliographic databases improved our ability to gather objective data on research in this field, including data on aspects such as funding and international collaboration.
The number of published papers has progressively increased over the last decade, with a growth rate of 59.8% measured for 2010 to 2019. It could be argued that an increase in publications in recent times has occurred in most scientific areas and is due to the increase in the number of journals indexed in databases. However, to determine whether this growth is greater than the number of records added to bibliographic databases, we calculated the same indicator listed by the WoS and PubMed for the same period and obtained growth rates of 43.4% and 48%, respectively. Therefore, it can be concluded that the growth of publications on pediatric obesity is 16.4 points higher than the growth of publications listed by the WoS and that it was 11.5 points higher than the growth of publications listed in PubMed. This fact clearly demonstrates international interest in pediatric obesity research. This growth has also been observed in other pediatric areas, such as in preterm births, where the annual number of publications increased significantly, by 443%, in 2016 compared to in 1997 [23]. In maternal mortality, the annual number of studies related to this topic increased from 87 in 1994 to 397 in 2013 [24], and a similar tendency has been observed in childhood epilepsy [25].
Regarding research funding, it should be noted that the number of funded papers doubled from the beginning to the end of the decade under review. Despite this, some studies indicate that research in this field is limited and that research focusing on health promotion, i.e., strategies, interventions, and policies to prevent obesity, is even more limited [26]. Some authors have even found relationships between obesity research outcomes and funding sources. A study by Wilde et al. [27] indicated that industry funding sources are more likely to fund research on certain issues, such as studies on the positive effects consuming certain products on weight loss [28]. On the other hand, pediatric urologists with federally funded grants have higher publication rates [29] One of the ways in which the impact of research can be measured is through the number of citations that a paper receives. In our case, funded papers accounted for 76.23% of all citations received by the articles that were studied. According to some studies, this is not a general phenomenon but rather a reflection of the fact that some countries obtain a better return on research funding than others in terms of funded study citations [30,31].
Our analysis of the studied journals and their impact shows that the most productive journals are in the upper quartiles of the JCR rankings, with high citation per paper ratios. The journals with the highest impact factors and citation per paper indexes were identified as Pediatrics and Obesity Reviews. Pediatrics ranked first in the pediatrics area (positions 2 to 5 over the last decade). Obesity Reviews, on the other hand, was ranked in positions 7 to 12 during the same period. However, it should be kept in mind that it is problematic to use impact factors as the sole indicator to assess whether the academic achievements of a given journal, area, or disease are important and worthy of academic consideration, and it is necessary to use an integrated combination of several indicators and to place them in context [32].
Our analysis by journal subject area illustrates the importance of pediatric obesity in many medical specialties and the cross-cutting nature of the problem. Since pediatric obesity is a nutritional and endocrinological problem that affects children, numerous articles have been published in pediatrics and in nutrition and dietetics and endocrinology and metabolism, as expected. However, pediatric obesity is also a public health concern [33][34][35][36] and a focus of general and internal medicine [37,38], nursing [39], developmental psychology [40,41], psychiatry [42,43], and even sport sciences [44].
As noted above, there is significant global collaboration in pediatric obesity research. Scientific collaboration is common between the United States and Europe, especially between the United States and the United Kingdom, but increasing collaboration with China and South American countries should be highlighted. The development of collaborative networks is very important, as many studies and prevention programs are implemented in isolation, resulting in a fragmented response to pediatric obesity [45]. Collaborative networking the enables mutual learning and sharing of strategies and methods and helps to identify common problems and to share strategies and lessons learned on the effectiveness of childhood obesity prevention interventions. One example is INFORMAS (International Network for Food and Obesity/noncommunicable diseases Research, Monitoring and Action Support) [46], which is a global network of public interest organizations and researchers that aims to monitor, compare, and support public and private sector actions to create healthy food environments and to reduce obesity rates [46].
The analysis of the keywords made it possible to identify the most relevant topics in pediatric obesity as well as their intensity through the co-occurrence of words or cowords. This is based on the principle that when two or more professional keywords that represent a special research topic appeared in the same article, then they represent essential relationships, and the more co-occurrence there is between two keywords, meaning that the relationship is closer. On the other hand, word clouds have made it feasible to observe the greater or lesser intensity of the words that occur. Therefore, they play an important role in the conceptual identification of pediatric obesity. It is not surprising that the most frequent keywords after "body mass index" are "physical activity", "physical exercise", "nutrition", "diet", and "dietary", as these words are considered the key determinants in the development of obesity [45]. Numerous initiatives worldwide have a common focus on encouraging healthy eating and physical activity through education and skill building [47]. Additionally, there are several keywords and epidemiological terms that are relevant to the public health problem of pediatric obesity, such as "prevalence", "prevention", and "intervention". The National Centre for Health Statistics in the United States estimates that 16.9% of children and adolescents aged 2-19 years are obese, and similar prevalence rates have been observed in other countries [48,49]. More than one-third of all children in the U.S. are overweight or obese, with substantial disparities present according to race and ethnicity, income, education, and geographic location. Furthermore, the rate of overweight and obesity has increased rapidly over the past 30 years, even in preschool-aged children. Moreover, early childhood offers a unique opportunity to influence behavior, as it is a developmental stage during which parents still have control over their children's diet and can promote physical exercise in their children [50]. Finally, some related or consequential diseases stand out, including "metabolic syndrome", "insulin resistance", "cardiovascular diseases", and "hypertension." The economic impact of childhood obesity as well as a cost-benefit analysis of obesity interventions is of great interest. The estimated economic impact of childhood obesity is USD 2 trillion, or 2.8% of the global GDP. In the United States, the excess direct medical costs required to care for an obese child throughout his/her lifetime are currently approximately USD 13,000, and the indirect costs of childhood and adult obesity must be added into this cost, which include educational underachievement, disability and absenteeism from work, and lost human productivity. In other developed countries such as Australia, such numbers are also observed, where the additional annual medical cost due to overweight and obesity among children aged 6 to 13 years old is about USD 43 million. This is why we highlighted the importance of the economic impact of childhood obesity: to make the continuous need for updated research on this topic in order to identify effective, feasible, and locally relevant interventions evident. However, in our bibliometric analysis, we focused on studying the indicators that refer to the quality of scientific production on the strategies that have been implemented for childhood obesity to date, without assessing their economic profile.
As previously discussed, behavioral economics is a strategy that is currently in vogue and that has great potential to be employed in public health, offering a very interesting perspective that combines psychological and economic principles to promote changes in lifestyle habits and risk factors with small "nudges" that help individuals to make better decisions about their health. In our analysis, behavioral economics was not evaluated as a keyword, since the Web of Science had few articles on the subject; however, it was studied indirectly by evaluating strategies based on its application model.
To increase collaboration between researchers, it is necessary to facilitate the exchange of raw research data, which is an aspect not addressed in our study. However, to enable the use and exchange of data, it is necessary to develop infrastructures to facilitate this process, such as data repositories, as well as legal regulations that ensure data security and the confidentiality of sensitive data [51]. Data sharing increases the power of clinical trials conducted with small sample sizes, which is an aspect that is sometimes common in research on certain pediatric diseases for which large populations of pediatric patients are difficult to obtain [52]. Pediatrics journals play a significant role in the promotion of data sharing and its implementation, as they are currently the main vehicle used to disseminate research. Most pediatric journals accept additional material and allow authors to store data in specific or institutional repositories [52][53][54].
This study has some limitations that must be discussed. First, it analyzes articles published in the WoS, and other databases, such as Scopus or PubMed, could have been taken into consideration. However, the WoS includes journals that are considered to have the greatest impact and measure indicators that are not provided by other databases, such as the number of citations, journal impact factors, quartiles, and classifications of subject categories. Another limitation is related to possible flaws in our keyword analysis, as errors may have been made in their normalization or they may not fully reflect the content of the articles reviewed.
Future work could follow the evolution of research topics explored in this field in successive years as well as their comparison to health, social, and economic indicators. It would also be interesting to analyze the cost-benefit ratio between research funding and the reduction of the burden of disease due to overweight and obesity. It would be interesting to evaluate the bibliometric indicators on the different direct and indirect economic determinants, providing an analysis of the costs versus the benefits derived from the interventions, so that the actors who are outside the health sector are able to perceive why it is necessary for all sectors to be involved in coming up with solutions, establishing better priorities and using existing resources more efficiently. Other interesting work would include determining the state of the knowledge in this field through the use of the PRISMA protocol.

Conclusions
Among the conclusions drawn from this work, the identified 59.8% increase in the number of published articles from 2010 to 2019 should be noted, as this result serves as evidence of the importance of this research topic. The number of funded papers also doubled between the beginning and end of this period. Our analysis by research subject areas shows that pediatric obesity affects many medical specialties beyond those of pediatrics and nutrition and dietetics, including endocrinology and metabolism, public health, general and internal medicine, nursing, developmental psychology, psychiatry, and sport sciences. Significant global collaboration on the issue has involved countries from five continents. Our thematic analysis demonstrates the importance of exercise and nutrition-related topics and of specialized health terms and terms related to public health.

Conflicts of Interest:
The authors declare no conflict of interest.