Retracted: A School-Based,Peer-Led,Social Marketing Intervention To Engage Spanish Adolescents in a Healthy Lifestyle (“We Are Cool”—Som la Pera Study): A Parallel-Cluster Randomized Controlled Study

Abstract

Childhood Obesity

is officially retracting the article entitled, ‘‘A School-Based, Peer-Led, Social Marketing Intervention to Engage Spanish Adolescents in a Healthy Lifestyle (‘‘We Are Cool’’—Som la Pera Study): A Parallel Cluster Randomized Controlled Study,’’ by Aceves-Martins M, Llauradó E, Tarro L, et al. [Child Obes 2017;13:300–313; doi: 10.1089/chi.2016.0216], due to discovered inaccuracies in the p values, which lead to the determination that the results were irreproducible.

Almost three years after the publication of the original article by Aceves-Martins M, et al. the Editor of Childhood Obesity received and published a Commentary from Golzarri-Aorryo et al.,¹ (Indiana University, Bloomington, IN; USA) along with a response² from the authors of the original paper.

The commentary by Golzarri-Aorryo et al., raised concerns about an ‘‘unexplained deviation from the prespecified analytic plan,’’ and went on to say that ‘‘the authors do not specify whether (and, if so, how) clustering and nesting were taken into account in any of these analyses.’’

Aceves-Martins et al., responded, in part, saying ‘‘…other alternative approaches might have been used, like multilevel analysis…but since the [intracluster correlation coefficient] was negligible, and given the scope of this study, such approaches were not considered.’’

Voluminous correspondence took place between both parties through the Editor of Childhood Obesity which ultimately led to Aceves-Martins et al., to conclude, ‘‘We are concerned that the outcome for change from baseline to end could be coded incorrectly for how it is interpreted. And we are therefore unable to perform the appropriate re-analysis on the data adjusted for cluster when we cannot first match the sample sizes (n)…’’

At the conclusion of this protracted process, the Aceves-Martins, et al., team agreed with the Editor of Childhood Obesity that the article should be officially retracted. It is important to note that the Editor of Childhood Obesity has invited the Aceves-Martin team to submit their updated work on this study to be submitted to the journal as a new manuscript for peer review.

The two published commentaries will remain in the literature but will contain links to the official retraction notice.

Childhood Obesity

is committed to upholding the scientific record and the community it serves.

References

1. Golzarri-Arroyo L, Oakes JM, Brown AW, Allison DB. Incorrect analyses of cluster-randomized trials that do not take clustering and nesting into account likely lead to p-values that are too small. Child Obes 2020;16:65–66.

2. Aceves-Martins M, Llauradó E, Tarro L, et al. Response to: Comment about statistical analysis of a cluster-randomized trial about clustering and nesting. Child Obes 2020;16:67–69.

Background

Adolescent obesity is a public health concern, particularly in Europe, where one in three 11-year-old children is overweight or obese.¹ In Spain, up to 26% of 13-year-old males and 18% of 13-year-old females were overweight or obese in 2014.² This problem needs compelling solutions considering that adolescent obesity is a strong predictor of adult obesity, which has many well-known short- and long-term health and economic consequences, both for the individual and society as a whole.³

Adolescents are considered vulnerable to their neighborhood environments, with numerous studies of American populations finding that adolescents from high-income countries living in low-income neighborhoods are at a higher risk of obesity.^3–6 Moreover, obesity persistence is strongly associated with the transition to adulthood across socioeconomic status (SES) categories.⁷ Some environmental factors and behaviors may explain this association. For instance, in recent decades, European adolescents categorized with a low SES have shown decreased physical activity (PA), increased time spent on video gaming, increased unhealthy dietary lifestyles, and decreased breakfast consumption.⁸ These lifestyle factors are key components of weight gain in adolescence.^9,10 Understanding youth obesity and its modifiable risk factors is key to addressing its occurrence, particularly in adolescents living in disadvantaged neighborhoods. For this reason, obesity prevention should target modifiable factors, with particular attention to adolescents from low-income families and/or disadvantaged neighborhoods.¹¹

Adolescence represents an opportunity to offer educational programs that encourage healthy behaviors. However, motivating adolescents to make healthy food choices, engage in PA, and avoid sedentary behaviors to prevent obesity and chronic diseases remains a challenge.^12,13 As adolescents undergo an identity-reshaping process of establishing relationships with friends, family, and society,^14,15 they are less subject to parental advice and more subject to peer and media influences,^16,17 while simultaneously being an influence over their peers' healthy choices and behaviors.^12,13,18 Thus, the influence of peers can be used in peer-led education, which is defined as “a strategy that involves teaching or sharing health information, values and behaviors among individuals as part of normal communication within similar social groups.”¹⁹ Peer-led strategies applied in interventions have been shown to be effective in preventing tobacco, alcohol, and possibly cannabis use among adolescents.²⁰ However, few interventions have aimed to measure the effectiveness of peer-led education as an obesity prevention strategy in an adolescent group.¹⁸

In addition, social marketing (SM) is a social change strategy that applies commercial marketing principles in health promotion programs to influence voluntary behavior toward systematically making healthy choices.²¹ This strategy aims to improve the personal welfare of individuals in a target group and their society by providing a framework for innovative solutions to social problems and needs, which can range from improving health to preventing, detecting, and treating diseases.^21,22 SM can increase the quality and effectiveness of school-based interventions aimed at improving healthy habits, ultimately resulting in positive changes in obesity-related outcomes among young people. However, more scientific evidence is needed because few interventions have expressly used SM as a methodological strategy in youth obesity prevention.²³

Progress in tackling youth obesity has been slow and inconsistent, representing a gap in the literature.^3,4 Thus, to address this gap and build upon existing interventions, the present study aimed to provide new strategies to prevent and reduce youth obesity, particularly in low-income adolescents, who are more vulnerable to obesity.

The European Youth Tackling Obesity (EYTO) project was developed as a multicenter, peer-led, SM intervention aimed at improving adolescent lifestyles by encouraging healthy choices, such as making healthy dietary choices and increasing PA, with the long-term goal of preventing obesity in adolescents from socioeconomically disadvantaged neighborhoods in the United Kingdom, Spain, Portugal, and the Czech Republic.^2–4 This project recruited and engaged five adolescents per country to work as adolescent challenge creators (ACCs), who then designed and implemented a peer-led intervention for their classmates using SM benchmark criteria (SMBC) as the methodological basis. The SMBC help strengthen the use of effective SM strategies and include the following eight domains: customer or participant orientation, behavior, theory, insight, exchange, competition, segmentation, and the methods mix.^23,24 The teams in each country acted autonomously, and in Spain, the project consisted of a school-based intervention called Som la Pera (“We are Cool”).²⁵

The main aim of the present study is to assess the effectiveness of the Som la Pera intervention, a school-based, SM, and peer-led methodology focused on increasing fruit and vegetable consumption and PA while reducing screen time. The secondary aims are to evaluate the change in adolescents' breakfast consumption and the engagement of local organizations and stakeholders in reducing the obesity prevalence.

Methods

The original protocol was published in BioMed Central Public Health.²⁵ This study was approved by the Ethics Committee of the Hospital Universitari Sant Joan de Reus (ref: 14–04–24/4proj2) and was registered at clinicaltrials.gov (NCT02157402). The protocol followed the principles of the Declaration of Helsinki and the Good Clinical Practice Guidelines of the International Conference on Harmonization (ICH GCP). It was conducted in accordance with the CONSORT 2010 extension to cluster randomized trials (Supplementary Data; Supplementary Data are available online at www.liebertpub.com/chi).²⁶

Study Design

The Som la Pera intervention was a parallel cluster-randomized controlled study in Reus, Catalonia, Spain. Adolescents were the unit of analysis, and to minimize contamination between research conditions, high schools were the unit of randomization, with an allocation ratio of 1:1.²⁵ Local authorities identified nine public high schools serving socioeconomically disadvantaged neighborhoods. The randomization code was computer generated, and the high schools were assigned to either the control or the intervention arm using PROC PLAN in SAS 9.2 (SAS Institute, Inc., Cary, NC) software. Although the program was offered to all of the high schools identified, only four of these high schools were randomly selected, as previously mentioned, due to the sample size required for the study (only four high schools were needed to obtain the required sample size). The participant recruitment process was initiated on May 30, 2014, and finalized on June 27, 2014.

Sample Size

To detect a difference of 0.5 portions of fruit and vegetables between the intervention and control groups, a power of 90% was used, with a two-tailed 5% significance level. We anticipated a loss to follow-up rate of 30%. Thus, the required sample size was estimated to be 121 adolescents per group.

Inclusion Criteria

First, adolescents born between 1998 and 2002 (13- to 16-year-olds) who attended one of the four randomly selected high schools were invited to participate in the study.²⁵ Second, from this sample, adolescents who provided informed consent (forms signed by their parents/legal guardians and by the adolescent) were included in the study. Adolescents born before 1998 or after 2002, as well as those who did not provide signed consent forms, were excluded. Consequently, of the potential high school participants, only students in the second and third grades (in the Spanish education system, these grades include adolescents approximately 13- to 16-year-olds) were invited to participate in the study.

Intervention

The intervention included the following components: (a) ACC training and (b) design and implementation of 10 activities presented as challenges (hereafter, activities) over 12 months (Table 1) from June 30, 2014, to May 29, 2015, spanning two academic years (2013–2014 and 2014–2015).²⁵

(a) ACC training: A total of five ACCs from the two intervention high schools were selected by high school teachers based on their knowledge of the students' leadership characteristics and English language skills (to facilitate communication with EYTO partners). These five ACCs received a 4-hour initial training session on SM principles and healthy lifestyle theory led by a university specialist in health and communication.²⁵

(b) Design and implementation of the activities: The five ACCs designed and implemented activities to engage their school peers in the intervention and achieve its objectives. ACCs attended activity design sessions (1.30 hours/week, 24 weeks) every week, which was conducted by health promotion and communication specialists. Teachers supported the ACCs by providing adequate space or just being around in case someone needed something during the activities. The themes of the activities were based on the main and secondary objectives of the study. The ACCs selected themes based on the study objectives, which would stimulate the interest of their peers and designed the activities to be attractive, thereby effectively obtaining peer concern.

Table 1.

Activities Presented as Challenges Designed by the Adolescent Challenge Creators

Challenges designed and implemented in the 1st academic year		Challenges designed and implemented in the 2nd academic year
Challenges	Response rate (%; n)	Challenges	Response rate (%; n)
Challenge No. 1: Sports selfies: The five ACCs challenged their peers to post photos of themselves practicing their preferred sport to the Som la Pera Facebook^® page.	(<50%;73/170)	Challenge No. 6: Som la Pera exhibition: Campaign information, objectives, photographs, and healthy lifestyle recommendations were exhibited in a university hall and in a local theater, which ACCs invited their schoolmates to visit.	(>95%; 166/170)
Stakeholders participation: public high schools (print and share the best pictures of the contest in the hall of the high schools)		Stakeholders participation: cultural association—Centre de Lectura (allow to exhibit the pictures of the intervention in their hall), local TV channel and newspaper (interview the participants and published the exhibition)
Challenge No. 2: Healthy food photos: The five ACCs challenged their peers to post photos of an original plate composed of vegetables, fruits, and cereals to the Som la Pera Facebook page.	(<25%; 40/170)	Challenge No. 7: Sugar-sweetened beverages: The five ACCs designed a classroom activity focused on sugar-sweetened beverages and healthy beverage alternatives.	(>95%; 168/170)
Stakeholders participation: public high schools (print and share the best pictures of the contest in the hall of the high schools)		Stakeholders participation: public high schools (allow to use their classrooms)
Challenge No. 3: Gymkhana: The five ACCs designed five activities for their high school mates on the school playgrounds. The activities involved tasting different fruits and vegetables, performing various PA, and using their creativity to compose songs about healthy habits.	(>95%; 162/170)	Challenge No. 8: Balanced PA and food choices: The five ACCs designed a playground activity focused on energy balance in which adolescents selected food options and identified the amount of PA that offset its energy content.	(>95%; 169/170)
Stakeholders participation: public high schools (allow to use their playground and PA materials)		Stakeholders participation: Central Mercat of Reus (provided all the fresh food) and public high schools (allow to use their playground and PA materials)
Challenge No. 4: PeraXef Contest: Inspired by the MasterChef^® TV show, the five ACCs designed a contest in which groups of adolescents prepared two healthy and creative plates (salad and dessert).	(<50%; 80/170) Social media participation (70%; 117/170)	Challenge No. 9: PeraXef Contest 2: Inspired by the MasterChef TV show and the success of the other PeraXef contests, the five ACCs designed a contest in which groups of adolescents had to prepare two plates (healthy and creative summer recipes) integrating parents, relatives, and friends.	(<50%; 85/170) Social media participation (70%; 130/170)
Stakeholders participation: Central Mercat of Reus (provided all the fresh food), Municipality of Reus (allow to use local a hall to develop the contest) and local TV channel and newspaper (interview the participants)		Stakeholders participation: Central Mercat of Reus (provided all the fresh food), and local and national TV channel and newspaper (interview the participants)
Challenge No. 5: Christmas PeraXef: Inspired by the MasterChef TV show, the five ACCs designed a contest in which groups of adolescents had to prepare one healthy plate (Christmas starter or dessert), and share a video on the Facebook page to show the recipe to their peers so that they could vote to the best one.	(<25%; 20/170) Social media participation (70%; 125/170)	Challenge No. 10: Nutrition and Health Myths Contest: Inspired by the Buzz!™ Quiz World PlayStation^® game, the five ACCs designed a contest examining nutritional myths and concepts related to the Som la Pera intervention.	(>95%; 168/170)
Stakeholders participation: Central Mercat of Reus (provided all the fresh food), and local university (URV; allow to use the kitchens to develop the contest)		Stakeholders' participation: public high schools (allow to use their classrooms)

The percentage of response rate was calculated according to the type of adolescent's participation, face-to-face or social media usage.

ACC, adolescent challenge creator; PA, physical activity; URV, Universitat Rovira I Virgili.

The ACCs presented the Som la Pera intervention in 11 participating classrooms (second and third Spanish school grades classification) at the two intervention high schools, in which they explained the study, provided social media information, and invited their peers to provide suggestions for activities. The ACCs disseminated the activities using social media platforms as well as direct and indirect (posters and flyers) promotion at the two intervention high schools. In addition, information, photographs, and videos pertaining to each activity were uploaded to the campaign's social media platforms, including Facebook^® (www.facebook.com/somlapera), YouTube,^® and Instagram^® (https://instagram.com/somlapera/) (Table 1).

Social media use was measured using a Facebook analytics option, and the participating adolescents were asked about their involvement to determine how many had social media accounts.

Outcomes

The primary outcomes of the study were as follows: consuming ≥1 portion/day of fruits and ≥1 portion/day vegetables in accordance with international recommendations of a minimum of 400 g of fruit and vegetables per day²⁷; engaging in ≥6 hours/week of moderate to vigorous intensity PA (>4 hours/week was reported by adolescents in the study evaluation survey in addition to the 2 hours/week spent in compulsory physical education classes) based on international recommendations of a minimum of 1 hour of PA/day²⁸; and ≤2 hours/day of sedentary behavior (screen time), reported as hours spent watching television, using a computer, or playing video games, following international recommendations of a maximum of 2 hours of sedentary behavior/day (assessed as screen time).²⁹

The secondary outcomes included increased breakfast consumption (daily breakfast consisting of more than a glass of milk or juice), reduced obesity prevalence (based on self-reported data), and engagement of local organizations as stakeholders.

These outcomes were assessed using the self-reported Health Behavior in School-aged Children (HBSC) survey from 2009 to 2010,³⁰ using an online platform that the adolescents accessed from the computer laboratory at their high schools. Four questions regarding the main outcomes were mandatory:

(1) Fruit consumption: number of times per week adolescents ate portions of fruits³¹

(2) Vegetable consumption: number of times per week adolescents ate portions of vegetables³¹

(3) PA: hours per week adolescents exercised in their free time to the extent that they were out of breath or sweaty³²

(4) Sedentary behavior (in terms of screen time): television, game console, and computer usage in separate items to capture the number of hours per day adolescents spent watching TV, playing video games, or using a computer in their free time on weekends and weekdays.³³

Questions concerning secondary outcomes were not mandatory:

(5) Breakfast consumption: number of times per week adolescents ate breakfast (more than a glass of milk or juice)

(6) Self-reported weight and height: the prevalence of obesity was assessed using self-reported weight and height, which were used to calculate BMI values in accordance with the International Obesity Task Force (IOTF)³⁴ and World Health Organization (WHO) cut-offs.³⁵ The classification of BMI by WHO was performed using BMI z-scores analyzed according to the WHO Global InfoBase³⁵ that defines children with BMI z-scores >1 standard deviation (SD) as overweight and >2 SD as obese.³⁶

(7) Engagement of local organizations and stakeholders: evaluated qualitatively by their participation in and contributions to each activity. As part of the EYTO project, stakeholders' evaluations by a qualitative analysis were conducted in each of the four participating countries. Such analyses included questions about personal views and understanding of obesity in adolescents; for instance, in the Som la Pera intervention, participants were asked about their views on the success and challenges of the intervention; social media usage in this type of intervention, the impact of the intervention on the ACCs, adolescents who received the challenges, and policy makers and practitioners; and the future (changes needed to implement the intervention in the community over the long term).

Moreover, additional outcomes were measured. Although the randomized high schools were located in low-income neighborhoods, individual SES was assessed to evaluate socioeconomic factors that could affect the results. The Family Affluence Scale II (FAS II), a proxy for SES in youth, was used to measure the participants' familial material wealth.³⁷ This scale aimed to describe and explain socioeconomic inequalities using a wide range of health indicators. The FAS II scale included questions such as the number of cars that their family owned, whether they had their own bedroom, the number of vacations that their family went on each year, and the number of family-owned computers.³⁸ Each item was scored on a scale ranging from zero to nine points, classifying the participants as having low (0–2), middle (3–5), or high (6–9) family affluence.³⁹

The adolescents in the intervention and control groups completed the HBSC survey twice, at baseline (May 2014) and at the end of the intervention (May 2015). The retention rate was defined by the number of adolescents who answered the four questions regarding the main outcomes.

Statistical Analyses

Continuous variables were represented as the mean and 95% confidence intervals (95% CIs), and categorical variables were represented as percentages. Generalized linear models (GLMs) were used to analyze differences from the baseline to the end of the study in the primary outcomes of the intervention and control groups. Repeated-measure GLMs were used to analyze the trends in BMI between the baseline and end-of-study values. McNemar tests were performed to analyze the changes in the primary outcomes in the intervention and control groups over time. The main analysis was based on the intention-to-treat (ITT) population, and a sensitivity analysis based on multiple imputations⁴⁰ was conducted for all variables in Tables 3 and 4. For each variable with missing values, 100 datasets were generated using the package mice⁴¹ in software R,⁴² version 3.1.1, with the appropriate approach depending on the nature of the variable.

The intervention was clustered by high school because it was not feasible to cluster the results by classroom, taking into account that not all activities were held during school time and the distribution of the students in the classrooms participating in the intervention changed during the academic year.

To allow comparability between the results of the present study and the intervention effects by gender shown in previous studies,⁴³ the main analyses were also stratified by gender.

To evaluate the risk of obesity according to the FAS II, logistic regression analyses [odds ratios (ORs) and 95% CIs] were performed at baseline, with no distinction between the intervention and control groups.

The significance level was set at bilateral 5% and model estimations were also reported as a coefficient and 95% CI. The analyses provided in Table 2 were performed using SPSS version 22 (SPSS, Inc., IBM, Armonk, NY).

Table 2.

Baseline Characteristics of the Adolescents in the Intervention and Control Groups

	Intervention group (n = 170)			Control group (n = 223)
	Males	Females	Total	Males	Females	Total
Participants, % (n)	50.6 (86)	49.4 (84)	100 (170)	47.5 (106)	52.5 (117)	100 (223)
Age (mean ± SD)	14.72 ± 0.62	14.67 ± 0.87	14.69 ± 0.75	14.60 ± 0.89	14.65 ± 0.67	14.63 ± 0.78
Weight in kg (mean ± SD)	58.75 ± 10.54	51.70 ± 7.48	55.31 ± 9.81	57.46 ± 10.85	55.67 ± 11.52	56.53 ± 11.21
Height in cm (mean ± SD)	170.5 ± 10.10	162.3 ± 6.07	166.4 ± 9.28	168.3 ± 9.82	159.8 ± 8.21	164.8 ± 9.94
High SES,^a % (n)	67.5 (56)	54.9 (45)	61.2 (101)	52.0 (52)	44.3 (51)	47.9 (103)
Middle SES,^a % (n)	27.7 (23)	39.0 (32)	33.3 (55)	46.0 (46)	47.0 (54)	46.5 (100)
Low SES,^a % (n)	4.8 (4)	6.1 (5)	5.6 (12)	2.0 (2)	8.7 (10)	5.6 (12)

SES was evaluated using the Family Affluence Scale using the 2009–2010 HBSC self-reported survey.

The questions used to calculate SES were not mandatory, and as a consequence there are some losses.

HBSC, Health Behavior in School-aged Children; SD, standard deviation; SES, socioeconomic status.

Results

Enrollment

Figure 1 shows the flow diagram of the adolescents' recruitment in both the intervention and control groups. Overall, the acceptance rate was 75.4%. A total of 393 adolescents were recruited for this study. The average retention rate was 76.5% (ranging from 63% to 88.8%) in the intervention group and 89.2% (ranging from 89.2% to 89.3%) in the control group. Specifically, in the four high schools (two in the intervention group and two in the control group), the retention rates were 88.8% in intervention high school 1 (n = 79/89), 63% in intervention high school 2 (n = 51/81), 89.2% in control high school 1 (n = 107/120), and 89.3% in control high school 2 (n = 92/103). To increase the retention rate, the researchers returned to the high schools to remind the students to answer the HBSC online survey as well as inform the high school teachers about which adolescents had not yet answered the HBSC survey.

Figure 1.

Flow diagram of participants through the Som la Pera study.

The intervention and control group participants were 50.6% (n = 86) and 47.5% (n = 106) male, respectively. The mean age (mean ± SD) at baseline was 14.66 ± 0.77 years old for both groups, 14.69 ± 0.75 years old for the intervention group, and 14.63 ± 0.78 years old for the control group. The mean age did not significantly differ by gender or intervention status (Table 2).

Primary Outcomes

At the end of the 12-month study period, the percentage of adolescents in the intervention group who consumed ≥1 portion of fruit/day increased by 23.5% (p < 0.01), compared with nonsignificant changes in the control group, resulting in a difference pre- to postintervention between the groups of 28.9% (p < 0.01). Consequently, 51.2% of adolescents in the intervention group consumed ≥1 portion of fruit/day (a minimum of one-third of the internationally recommended amount of daily fruit consumption) compared with only 27.4% of those in the control group (Table 3).

Table 3.

Lifestyle Factors of the Intervention and Control Group

		Intervention group (n = 170)			Control group (n = 223)
Lifestyle factors	Gender	Baseline, % (n)	End of intervention, % (n)	p ^*	Baseline, % (n)	End of intervention, % (n)	p ^*	Intervention vs. control p-value^**
Primary outcomes
Fruit consumption ≥1 portion/day	Males	26.7 (23)	51.2 (44)	<0.01	33.0 (35)	23.6 (25)	0.08	<0.01
	Females	28.6 (24)	51.2 (43)	<0.01	32.5 (38)	30.8 (36)	0.86	0.03
	Total	27.6 (47)	51.2 (87)	<0.01	33.7 (73)	27.4 (61)	0.14	<0.01
Vegetable consumption ≥1 portion/day	Males	12.8 (11)	40.7 (35)	<0.01	16.0 (17)	15.1 (16)	1	<0.01
	Females	14.3 (12)	33.3 (28)	<0.01	12.8 (15)	20.5 (24)	0.07	0.10
	Total	13.5 (23)	37.1 (63)	<0.01	14.3 (32)	17.9 (40)	0.23	<0.01
Physical activity ≥6 hours/week	Males	40.7 (35)	70.9 (61)	<0.01	27.4 (29)	28.3 (30)	1	0.01
	Females	16.9 (14)	28.6 (24)	0.07	15.4 (18)	19.7 (23)	0.38	0.04
	Total	29.0 (49)	50.0 (85)	<0.01	21.1 (47)	23.8 (53)	0.51	<0.01
Screen time ≤2 hours/day on weekdays	Males	19.8 (17)	51.2 (44)	<0.01	17 (18)	29.2 (31)	0.03	0.01
	Females	28.6 (24)	38.1 (32)	0.19	17.1 (20)	26.5 (31)	0.07	0.60
	Total	24.1 (41)	44.7 (76)	<0.01	17.0 (38)	27.8 (62)	<0.01	0.03
Screen time ≤2 hours/day on weekends	Males	9.3 (8)	34.9 (30)	<0.01	5.7 (6)	14.2 (15)	0.07	0.01
	Females	6 (5)	21.4 (18)	0.01	9.4 (11)	17.9 (21)	0.07	0.76
	Total	7.6 (13)	28.2 (48)	<0.01	7.6 (17)	16.1 (36)	0.01	0.05
Screen time ≤2 hours/day total	Males	11.6 (10)	39.5 (34)	<0.01	5.7 (6)	17.9 (19)	0.01	<0.01
	Females	11.9 (10)	28.6 (24)	0.01	10.3 (12)	20.5 (24)	0.02	0.31
	Total	11.8 (20)	34.1 (58)	<0.01	8.1 (18)	19.3 (43)	<0.01	0.01
Secondary outcome
Breakfast consumption daily	Males	46.5 (40)	74.4 (64)	<0.01	48.1 (51)	51.9 (55)	0.62	0.35
	Females	39.3 (33)	52.4 (44)	0.05	41.9 (49)	39.3 (46)	0.71	0.61
	Total	42.9 (73)	63.5 (108)	<0.01	44.8 (100)	45.3 (101)	1	0.35

Screen time include hours watching television, playing video game, and using a computer.

p-Value: McNemar tests (changes within each group).

p-Value: GLM (differences in the changes from baseline to end of study between groups).

GLM, generalized linear model.

However, the vegetable consumption differed only in males. The percentage of males consuming ≥1 portion of vegetables/day increased by 27.9% (p < 0.01) in the intervention group, but showed a nonsignificant change in the control group, resulting in a difference pre- to postintervention between the groups of 28.8% (p < 0.01). Therefore, 40.7% of males in the intervention group consumed ≥1 portion of vegetables/day (a minimum of half of the internationally recommended amount of daily vegetable consumption) compared with only 15.1% of males in the control group (Table 3).

At the end of the study, the percentage of adolescents in the intervention group who engaged in ≥6 hours of PA/week participation increased by 21.2% (p < 0.01), compared with nonsignificant changes in the control group, resulting in a pre- to postintervention difference between the groups of 18.5% (p < 0.01). Accordingly, 50% of the adolescents in the intervention group engaged in ≥6 hours of PA/week participation (the amount of weekly PA in international recommendations), compared with 23.8% of the control group (Table 3).

Additionally, the percentage of male adolescents who engaged in ≤2 hours of screen time/week increased by 27.9% (p < 0.01) in the intervention group and 12.3% in the control group (p = 0.01), resulting in a pre- to postintervention difference between the groups of 15.6% (p = 0.01). Consequently, 39.5% of the males in the intervention group engaged in ≤2 hours/week of screen time (the internationally recommended amount of sedentary behavior in terms of screen time), compared with 17.9% of the control group (Table 3).

Secondary Outcomes

The response rate for secondary outcomes, such as breakfast consumption, was 85.9% (130 respondents of 170 participants) in the intervention group and 89.2% (189 respondents of 223 participants) in the control group. The percentage of adolescents who consumed breakfast daily (i.e., more than a glass of milk or juice) only increased significantly in the intervention group, by 20.6% (p < 0.01), a 63.5% prevalence at the end of the study (Table 3); however, the difference between the groups was not significant (p = 0.35). For weight and height measurements, the response rate was 63.5% (108 respondents of 170 participants) in the intervention group and 74.9% (167 respondents of 223 participants) in the control group. The percentages of overweight and obesity (from self-reported weight and height) in the adolescents were similar across the intervention and control groups at the end of the study based on the IOTF and WHO classifications (Table 4).

Table 4.

BMI Adolescent's Classification According to International Obesity Task Force and World Health Organization Cut-Off Points (Intervention and Control Group)

		Intervention group			Control group
BMI classification	Gender	Baseline, % (n)	End of intervention, % (n)	p ^*	Baseline, % (n)	End of intervention, % (n)	p ^*	Intervention vs. control p-value^**
IOTF criteria overweight	Males	10.9 (6)	9.6 (5)	0.70	15.7 (14)	15.3 (13)	0.74	0.52
	Females	7.5 (5)	7.8 (5)	1	13.9 (14)	14.1 (14)	1	0.31
	Total	9.0 (11)	8.6 (10)	0.74	14.7 (28)	14.7 (27)	0.83	0.24
IOTF criteria obesity	Males	1.8 (1)	0 (0)	0.32	3.4 (3)	3.5 (3)	1	0.17
	Females	0 (0)	3.1 (2)	0.21	5.0 (5)	5.1 (5)	1	0.26
	Total	0.8 (1)	1.7 (2)	1	4.2 (8)	4.3 (8)	1	0.08
WHO criteria overweight	Males	10.9 (6)	13.7 (7)	1	22.5 (20)	18.6 (16)	0.23	0.44
	Females	10.4 (7)	8.2 (5)	0.66	15.8 (16)	15.7 (14)	0.57	0.33
	Total	10.7 (13)	10.7 (12)	0.74	18.9 (36)	17.1 (30)	0.20	0.21
WHO criteria obesity	Males	1.8 (1)	2.0 (1)	1	5.6 (5)	4.7 (4)	0.66	0.41
	Females	0 (0)	3.3 (2)	0.32	5.9 (6)	5.6 (5)	0.66	0.23
	Total	0.8 (1)	2.7 (3)	0.32	5.8 (11)	5.1 (9)	1	0.15

p-Value: McNemar tests (changes within each group).

p-Value: GLM (differences in the changes from baseline to end of study) between groups.

IOTF, International Obesity Task Force; WHO, World Health Organization.

According to the SES of the adolescents, which was based on the FAS II evaluation, 204 adolescents (53.7%) were categorized as high FAS, 155 (40.8%) as middle FAS, and 21 (5.5%) as low FAS. As shown in Table 5, a low FAS II score was a risk factor for obesity (OR 5.81; 97.5% CI 1.15–24.05; p = 0.02) according to the WHO obesity criteria and (OR 4.42; 97.5% CI 0.61–22.09; p = 0.09) according to IOTF obesity criteria.

Table 5.

Obesity Risk Factors and Family Affluence, Proxy of Socioeconomic Status

	WHO criteria			IOTF criteria
SES	OR	CI 97.5%	p	OR	CI 97.5%	p
Low	5.81	1.15; 24.05	0.02	4.42	0.61; 22.09	0.09
Medium	2.12	0.75; 6.44	0.16	1.38	0.38; 5.05	0.61
High	1	1	NA	1	1	NA

The prevalence of obesity was obtained using self-reported weight and height from the HBSC survey and BMI classifications from the WHO and IOTF. The Family Affluence Scale II (FAS II), a proxy for SES in youth, was used to measure the participants' familial material wealth.

CI, confidence interval; OR, odds ratio; IOTF, International Obesity Task Force; WHO, World Health Organization.

Social media usage

The Facebook page created by the ACCs received 496 likes. Of the 170 participants in the study, 113 (67%) followed the Facebook page, 39 (21.5%) did not follow the page, and 18 (11.5%) did not have a Facebook account or used a different nickname on their social media account. These numbers indicated only followers of the Facebook page, whereas several interactions among adolescents who did not follow the page were found throughout the study during the Facebook activities, such as using the information posted to the classroom wall or schoolmates internal chats. In addition, none of the students in the control group followed the Som la Pera Facebook page. However, it could be possible that some of them had consulted the Facebook page without following it because the page was not private.

Stakeholders' engagement

Local organizations, such as the central marketplace, public high schools, city council, and local university, supported the Som la Pera intervention as keystone stakeholders by providing fresh food and beverages and hosting specific activities. Moreover, national and international organizations supported the EYTO project by disseminating information in local, national, and international media. The participation of different stakeholders was qualitatively evaluated, revealing that relevant and accessible information can be provided using a youth-led approach, accessible choices are required for young people to make healthy choices, and that collaborative and holistic approaches are necessary to address obesity in adolescent populations.⁴⁴ A final report of the results of the qualitative analysis of the EYTO project was published.⁴⁵ For each challenge, the involvement of at least one stakeholder was essential (Table 1).

Discussion

Som la Pera, a school-based, peer-led SM intervention designed to encourage adolescents from disadvantaged neighborhoods to make healthy choices by implementing 10 activities over 12 months, improved the daily fruit consumption and weekly PA participation of male and female adolescents in the intervention group. However, daily vegetable consumption and engagement in less sedentary behavior (as assessed using screen time) improved only in the male adolescents in the intervention group.

The present study provided evidence, through a peer-led intervention that ACCs may have credibility among young peers. Consequently, adolescents may serve as positive role models, and thus, ACCs could influence their peers' specific health-related lifestyles.⁴⁶ The results of the adolescent peer-led interventions suggest that these interventions may generate more favorable results than adult-led interventions that target adolescents⁴⁷; however, this hypothesis should be tested by administering the same Som la Pera interventions to adolescents, but led by adults.

Two examples of peer-led interventions implemented in a school setting to improve healthy lifestyles were previously conducted.^48,49 One was the TEENS study,⁴⁸ a 2-year intervention implemented by youth to their classroom peers to promote healthy eating. However, although the intervention in the TEENS study was widely accepted by the youth in the study, no improvement in healthy eating was observed. Another program was the Healthy Buddies study,⁴⁹ a 10-month intervention to promote healthy lifestyles that was implemented by older adolescents (fourth school grade in the US Education System) to younger (kindergarten) school children, which improved the health knowledge, attitudes, and behaviors in both populations. Thus, the results reinforced the effectiveness of peer-led studies. Notably, the Som la Pera study is the first study incorporating a peer-led intervention with an SM methodology to encourage a healthy lifestyle in adolescents. SM was a useful methodological base that helped the ACCs connect and disseminate health information directly to their own networks and peers. The results of the Som la Pera intervention may be attributed to the use of SM and peer-led education as a novel joint approach, as well as the empowerment of the young people in the design and implementation of a lifestyle improvement intervention.

The Som la Pera study achieved interesting advances in the approaches to a healthy lifestyle in an adolescent population. The WHO estimates that half of the European population does not consume the recommended daily amount of fruits and vegetables (400 g).²⁷ According to the HELENA Study, European adolescents consume ∼200 g/day of fruits and vegetables, which is one-half the amount recommended by the WHO.⁵⁰ After this intervention, 51.2% of the intervention group consumed at least one portion of fruit per day. In Spain, one portion of fruit is approximately 150–200 g,⁵¹ which is equivalent to approximately one-half of the recommended amount (400 g).²⁷ These results showed that adolescents progressed toward achieving the WHO recommendation. Additionally, 50% of the adolescents in the intervention group of the present study consumed the recommended amount of fruit, which is higher than the 30% previously observed in 15-year-old Spanish adolescents in the 2013/2014 HBSC International Report.²

The daily recommended amount of fruits and vegetables was associated with a lower risk of mortality, specifically from cardiovascular disease.⁵² According to the European Heart Network (EHN),⁵³ each piece of fruit or vegetable (106-g portion) consumed daily decreases cardiovascular risk, the leading cause of mortality worldwide, by 4%. Accordingly, consumption of greater than five portions of fruits and vegetables per day in adults leads to a 17% reduction of cardiovascular risk.

In the Som la Pera intervention, fruit consumption was improved in the participating adolescents, representing prevention at an earlier age, with possible long-term benefits that should be confirmed.

Regarding PA, 50% of the adolescents in the intervention group and 23.8% of those in the control group reached or were close to the weekly recommended level (at least 60 minutes of moderate-to-vigorous PA per day²⁹). Specifically, 70.9% of the males in the intervention group achieved at least 60 minutes of moderate-to-vigorous PA per day²⁹ at the end of the study; this prevalence was more than two times higher than the females (28.6%) in the intervention group. These data indicated that the adolescents in the Som la Pera intervention group exhibited higher PA participation than that of the 15-year-old female (12%) and male (28%) Spanish adolescents described in the 2013/2014 HBSC International Report.² The higher PA participation following the Som la Pera intervention could, based on evidence from previous studies of young people (5–17 years old), translate to more favorable health parameters (e.g., cardiorespiratory fitness, muscular strength, reduced body fat, favorable cardiovascular and metabolic disease risk profiles, enhanced bone health, and reduced symptoms of depression).^28,54–56 Furthermore, maintaining the internationally recommended amount of PA (hours and intensity) from youth into adulthood can enable the long-term maintenance of lower rates of cardiovascular disease morbidity and mortality.²⁸ Increased fruit consumption and PA activity in adolescents, representing small daily changes, may yield long-lasting health benefits and a significant reduction in chronic diseases in adulthood.

Despite all the results obtained using Som la Pera intervention, we should consider that a healthy lifestyle in youth could influence by gender, which is one of the strongest determinants of adolescent lifestyles.⁴³ Gender differences in the results of Som la Pera intervention were consistent with the findings of previous studies showing higher levels of PA in males⁸; however, the higher vegetable consumption in the males in the intervention group was in contrast with the current scientific literature,⁴³ demonstrating that it is possible to override school-based evidence on lifestyle improvements by gender using the present innovative approach. In the Som la Pera intervention, females showed more interest than males in participating in the activities created by the ACCs when they involved food or cooking activities, whereas males showed more interest than females in the PA-promoting activities. The gender differences in lifestyle improvement may be the result of differences in preferences, attitudes, social desirability, or dieting status.⁵⁷ Additionally, learning strategies could function differently between genders; females respond more enthusiastically to traditional classroom and theoretical environments, and males may be more involved when experiential learning is used as a strategy to improve lifestyles.

Regarding the lasting sedentary behaviors, screen time was specifically reduced on weekdays and weekends in both the intervention group and the control group. To achieve a greater reduction in sedentary behavior (as assessed using screen time), some previous studies have suggested that the involvement of family members and the home environment as a part of the intervention could be a suitable option for addressing sedentary behavior.⁵⁸ This suggestion can also be extended to vegetable and breakfast consumption since it is easier to manage these dietary behaviors at home. However, changes in dietary behaviors at home require the involvement of the parents for the intervention to be successful, with the parents adopting the same healthy lifestyle aims as their children. However, the parents should pursue these healthy lifestyle aims separately from the adolescent population to protect adolescent freedom.

In terms of the secondary outcomes, the Som la Pera resulted in no significant improvements in breakfast consumption or the prevalence of obesity after the intervention, as assessed from baseline to the end of the study. The maintenance of the obesity prevalence could be attributed to insufficient time to detect a change in youth BMI due to the fact that healthy adolescents, and not only overweight or obesity adolescents, participated in the study.

Our study indicated an association between FAS (as SES indicator) and obesity. Specifically, the adolescents with a low FAS living in low-income neighborhoods were found to be at a higher risk of obesity; thus, this finding is in agreement with the scientific literature concerning the relationship between SES and obesity.⁵⁹

The present study has certain limitations. First, although surveys are the most commonly used tools to assess health behaviors, they are limited when analyzing the success of an intervention using self-reported information. The quantification of some of the variables could have been more precise (i.e., body weight and height were self-reported, not objectively measured; PA was assessed using a questionnaire, whereas PA is more precisely measured using an accelerometer). However, the priority of the study was to achieve a high response rate for the lifestyle questionnaires among adolescents. Additionally, self-reported data were used to avoid the difficulties of persuading adolescents to participate in weight measurements.⁶⁰ In addition, related to the HBSC survey, the assessment of sedentary behavior only accounted for screen time and not sedentary behavior as a whole, which is a limitation of the study. Second, although certain items in the FAS evaluation from the HBSC survey might be sensitive, depending on family demographics, urban/rural location, and/or living situations, its validity has been previously confirmed.³⁹

Another limitation was the higher retention rate in the control group than in the intervention group. Although all eligible students in the intervention group participated in the activities designed by the ACCs (except for those without signed consent), the retention rate was calculated relative to the HBSC survey because the participants answered the surveys at baseline and at the end of the intervention. Specifically, high school 2, one of the intervention high schools, had a lower retention rate due to a lack of encouragement of the adolescents to answer the questionnaires, such as the provision of school time, computer laboratories, and reminders. Finally, in the present study, only short-term behavioral changes were measured; however, it is necessary to assess the maintenance of these behaviors over longer periods of time.

Nevertheless, the main strength of this study was that the Som la Pera intervention was created by adolescents for adolescents. The ACCs were a major source of information collection and problem identification. They designed attractive activities with a meaningful message using the SM and peer-led education as the methodological basis, and empowering young people in the design and implementation of the intervention was crucial for the study's success.

Moreover, the inclusion of teachers, local organizations, and policy makers as stakeholders may have also influenced the success of this intervention because these groups actively contributed to the adolescent's environment. In addition, the adolescents in the study were likely motivated by knowing that their peers were participating in similar interventions across Europe, allowing them to share and apply their ideas.

The results of our study could be generalized to high schools located in low socioeconomic neighborhoods in Spain. However, the low socioeconomic context of the neighborhood may not be synonymous with adolescent's SES. In this study, although the high school was situated in a low socioeconomic area, the students attending the schools could come from other city districts, and it could be difficult to identify students' SES. For this reason, we considered it a priority in this setting to evaluate not only the socioeconomic level of the neighborhood, but also the FAS of the students in each participating high school before implementing the educational program. Moreover, the SM and peer-led methodologies could be useful for generalizing this intervention because when both methodologies were used, the intervention could be adapted directly to the specific SES and motivations of the study population. The SM and peer-led methodologies ensured that relevant content was created for adolescents living or attending high schools in low-income neighborhoods.

Conclusions

A school-based, peer-led, SM intervention developed by adolescents attending high schools in low-income neighborhoods effectively improved the healthy choices of their school-aged peers, leading to increased fruit consumption and PA in males and females. Furthermore, adolescent males were more sensitive to improvements in healthy choices, showing increased vegetable consumption and decreased sedentary behavior.

Footnotes

Acknowledgments

This project benefited from valuable collaborations with the National Children's Bureau (the United Kingdom), Companhia de Ideias (Portugal), and Komunikujeme (Czech Republic). The Spanish research project was supported by the Central Market of Reus, Spain (Mercat Central de Reus), which provided fresh food for the intervention, and the Municipality of Reus, Spain (Ajuntament de Reus, Spain). The authors thank the teachers, parents, and students of the Reus high schools for their enthusiastic participation in this study. This research project was funded by the European Commission (European Directorate General HEALTH—December 19, 2012). This funder did not play a role in the Spanish study design, data collection, study management, data analysis, data interpretation, article writing, or decision to submit the report for publication. D.M. was partially supported by grants from the Instituto de Salud Carlos III-ISCIII (Spanish Government) cofounded by FEDER funds/European Regional Development Fund (ERDF)—a way to build Europe (References: RD12/0036/0056, PI11/02090) and from the Agència de Gestió d'Ajuts Universitaris i de Recerca (2014SGR 756) and RecerCaixa 2015 (MD088652).

The study participants provided informed consent (a form signed by the participants and by their parents/legal guardians).

Author Disclosure Statement

No competing financial interests exist.

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