Serious games as an educational strategy to control childhood obesity: a systematic literature review 1

ABSTRACT Objectives: to identify in the literature the efficacy of serious games to improve knowledge for and/or behavioral changes among overweight or obese children. Method: Systematic Literature Review. The Cochrane Systematic Reviews Handbook was used. The studies were collected from the following databases: Public Medline; Web Of Science; Science Direct; Latin American and Caribbean Health Sciences Literature; and the Health Game Research and Cumulative Index to Nursing & Allied Health Literature. The descriptors were video games and obesity, while the key word was serious games. Inclusion criteria were: studies classified as Randomized Clinical Trials written in English, Spanish or Portuguese and in which children were the subjects of the study. Results: 2,722 studies were identified in the initial search and six studies remained in the final sample. The papers focused on encouraging behavioral changes in players, including physical exercise and improved eating habits. The studies report that serious games are a potential strategy to encourage positive coping with childhood obesity. Conclusion: research in this field is an expanding and promising strategy and serious games represent an alternative means to provide health education to children.


Introduction
Childhood obesity is a complex condition that is related to genetic factors, nutritional intake, levels of physical activity, and environmental factors. According to the literature, being overweight is defined as Body Mass Index (BMI) between the 85 th and 97 th percentiles, while obesity is when BMI is equal to or above the 97 th percentile (1) .
Being overweight and obesity are social and epidemiological phenomena. Studies report that 42 million children under the age of five are already considered obese or overweight (2) and this number is expected to increase to 70 million in 2025 (3) .
Many intervention studies have addressed the problem of obesity and being overweight among children, which is already considered a public health problem (4)(5) . Due to the intensive use of technology among the children of this generation, there are opportunities to promote health through technological devices, as these enable access to tools children are already familiar with (6) . In the last decade, various interventions have used technology to prevent obesity in school environments and in clinical practice, aiming to provide health education to children (7)(8) .
Health education is seen as a strategy to improve the understanding of patients regarding a disease, enabling them to improve their general condition and decrease the use of health resources (9) . Individualized educational programs are efficacious but expensive (10) , while more traditional methods to provide education to patients, such as lectures or printed pamphlets, are more accessible but do not substantially improve clinical results (11) .
For this reason, innovative new systems of educational interventions that are friendlier to the target population have been created. These evidence-based interventions are intended to provide health education in a way that is more accessible to the public. One of the approaches is based on the use of games as a strategy to improve knowledge concerning health and a tool to complement medical treatment, therapies or disease management (12) .
With the increased popularity of video games over the last 30 years, researchers started exploring their potential for serious purposes (13) , the so-called "serious games". These are defined as games implemented within an educational context, with specific learning objectives, which gamers are expected to achieve during game play (14) .
Digital game-based learning has the potential to spark interest among gamers, motivating them to engage in a task regularly over a long period of time, which is difficult to achieve with traditional learning material and approaches and, therefore, may make a difference in terms of educational efficacy (15)(16) .
According to the literature, serious games in the health field can be innovative and potentially efficacious methods to improve knowledge, transmit a persuasive message, support behavioral change, and influence the results of health programs (17) .
Therefore, this study's objective was to identify in the literature the efficacy of serious games in improving the knowledge and/or behavioral change of overweight or obese children.

Method
A systematic literature review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (18) , addressing serious games as an educational intervention to cope with childhood obesity.
A systematic review is intended to gather evidence available according to pre-specified eligibility criteria, with the goal to answer a specific question. Thus, a systematic method able to provide more reliable results is used, which leads to conclusions and supports decision-making (19) .
This systematic review was submitted to and approved by the international prospective register of systematic reviews -PROSPERO under No.

CRD42016042272.
The Cochrane Systematic Review method (19) was adopted and the stages proposed in the literature (20) were followed, namely: establishment of a protocol; establishment of a research question; search for studies; selection of studies; critical assessment; data collection; and synthesis of data.
The PICO strategy, in which PICO stands for "Patient population/disease, Intervention or issue of interest, Comparison intervention or issue of interest, and Outcome" (21) was used to establish the research question. Figure 1 presents  After recording information with the analysis instrument, the data were organized in a Microsoft Excel worksheet. The papers were analyzed, after reading the full texts, to describe and classify the results and report the knowledge produced.
A total of 2,746 studies were identified in the initial search. All titles and abstracts were read and, after applying the inclusion criteria, six studies were selected.
A synthesis of the studies selection process following the PRISMA model is presented in Figure 2.

Results
To better identify each study, the studies were organized in a sequence of letters and numbers, from A1 to A6 ( Figure 3).   Coping, Both and None. A goal was established for fruits and vegetable intake for the Action group and an action plan specifying how they would achieve this goal was also established. A goal was also established for the Coping group to eat more fruits and vegetables together with a coping plan, which identified potential barriers that could prevent them from achieving the goal. The Both group followed both plans of action and the last group, None, did not follow a plan at all. The children considered the serious games platform to be a useful means to improve their nutritional knowledge.
At the end of the study, the authors state that the online serious games can be an efficacious method to improve knowledge to prevent and treat diseases as information is presented in a different way to children (28) .
The fifth study (29) assessed the results of two serious games "Escape from Diab" and "Nano Swarm The sixth and last study (30) reports the application

Discussion
Based on the studies selected and analyzed in this review, the conclusion is that serious games used as a strategy to cope with obesity is an expanding field and its application has promising results that should not be ignored. It is, however, an incipient field and the limited number of randomized clinical trials that met this review's inclusion criteria do not allow the efficacy of these games as an intervention to be determined. can support education, as well as encourage more active learning (31)(32) .
The introduction of serious games as an additional component in programs intended to enable patients to cope with disease can increase motivation and conformity to a program, improving the results of interventions (33) .
There is evidence in the literature that corroborates these findings. A meta-analysis identified 64 serious games that promote healthy life styles, revealing that the games had a statistically significant effect on behavior (34) . Other authors performed a systematic review with 19 studies addressing changes in health or safety behaviors among young individuals and verified that 17 of these papers reported at least one statistically significant effect concerning behavior (35) .
A systematic review analyzed 28 games intended to prevent childhood obesity utilized between 2005 and 2013 and reports that 40% of the studies obtained the desired effect on a variable related to adiposity (7) .
Hence, substantial evidence supports the efficacy of serious games in improving knowledge and encouraging behavioral changes or even better health results.
Another point raised by this study's review was the fact that the attention of a child is naturally captured by video games and the time children already spent playing can be used to promote health education (31) . It is interesting to develop games directed to decreasing obesity, for this generation of children is already accustomed to these technologies as entertainment.
Such games can include educational content intended to increase their knowledge and self-care.
Additionally, even though the games identified in this review are inactive and sedentary in their natures, as they are played on tablets or computers, children can make better use of their time playing games available online using mobile devices in their daily routine.
Few systematic reviews identified in the literature examine the impact of technology-based interventions to fight childhood obesity. Some authors explored the effect of technological interventions, while others focused on the use of video games designed to prevent childhood obesity (7,36) . This review focuses on serious games, a more specific category of video games.
New studies are needed to include family members and the children's responsible adults, something only one study addressed in this review did (25) . The parents are important for the adherence of children to interventions and the results they achieve, considering that parents are the role models for good eating habits, nutrition, and exercise, as well as controlling the environment and experiences of children (37) . Using digital games as a tool to direct or involve parents can also have a good cost-benefit relationship. Parents can be the targetpopulation giving them access to games and tasks they are supposed to do by themselves, together with their children, or parallel with them.
Additionally, health education linked to schools is also a good alternative. Schools would benefit from incorporating serious games into their curricula, making it more attractive to students and approximating children to technology on their daily routine (38) .
To achieve such results, however, more studies addressing the theme need to be analyzed in order to acquire greater understanding and determine the most appropriate and effective application of serious games in prevention and treatment programs directed to childhood obesity.