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Pediatric obesity continues to be a significant public health issue (Hedley et al., 2004, Ogden et al., 2008). Obesity during childhood is associated with increased disease risk and morbidities during young adulthood, and increased mortality later in life (Must and Strauss, 1999, Reilly et al., 2003). Dietary habits acquired in childhood track to adulthood (Kelder et al., 1994, Li and Wang, 2008, Lien et al., 2001), and changes in diet during childhood are significant predictors of diet quality in adults (Mikkila et al., 2004). Child dietary behavior is determined in part by individual factors (e.g. food preferences) (Capaldi, 1996), socio-cultural factors (e.g. peer norms, parent attitudes/beliefs) (Rozin, 1996) and environmental factors (e.g. availability of healthy food)(French et al., 2001). Parents are instrumental in influencing child diet by providing their child with the ability and opportunity to make healthy or unhealthy choices through the selective use of food parenting practices (i.e. behaviors that parents use to influence children on what and how much to eat)(Hoerr et al., 2009). Since food choices are related to energy intake and obesity risk, parent involvement in child dietary interventions seems crucial to mitigating risk (Rennie et al., 2005). The refractory nature of adult obesity suggests early establishment of healthy eating habits may be a key to prevention (Lobstein et al., 2004).
Reviews of childhood obesity prevention studies have largely focused on school-based programs, many of which did not include a parent component. (Baranowski et al., 2002, Brown and Summerbell, 2008, Sharma et al., 2004, Shaya et al., 2008, Summerbell et al., 2006, Thomas, 2006). A meta-analysis of pediatric obesity prevention programs that included an estimation of a “parent effect” found parental involvement (in 12 of the 46 studies) to be unrelated to larger effect sizes(Stice et al., 2006). A systematic review of studies that aimed to impact young children's weight status, physical activity, diet or sedentary behaviors (Campbell and Hesketh, 2007) concluded parents were “receptive to and capable of some behavioural changes that may promote healthy weight in their young children,” but due to the limited number of studies in this age group, the authors were unable to draw any conclusions as to the most effective strategies. As a result, we conducted a systematic review of randomized controlled intervention trials designed to prevent obesity, prevent disease, and/or promote health in children and adolescents through dietary behavior changes that involved parents. We summarized and evaluated the type of parent involvement that had been implemented in each study to answer two questions: 1) whether parent involvement enhanced program effectiveness, and 2) what type of parent involvement, if any, was most effective in achieving dietary change outcomes.
Following procedures for a systematic review (Lichtenstein et al., 2008), we searched Pub Med, Medline, Psych Info, and Cochrane Library electronic databases to identify individual and population-based obesity/disease prevention and health promotion programs designed to change child and adolescent dietary intake that involved parents. Key terms representing child and adolescent dietary behaviors that were associated with obesity in the literature were used in combination with key terms for parent/family involvement and intervention studies. The following search terms were used: (1) preschool child, preschooler, toddler, child, adolescent, teen; (2) fruit, vegetables, healthy eating, fat, salt; (3) obesity, weight, overweight, prevention, intervention; (4) family, parents, parent education, parenting practices; and (5) childhood obesity, prevention.
Study inclusion criteria for this review were i) randomized controlled trials of an obesity prevention, chronic disease prevention, or health promotion intervention that included child dietary intake as a behavior change target and as a measured primary or secondary outcome; ii) published in peer-reviewed, English language journals between January 1st, 1980 and December 31st, 2008; iii) recruited children (2-12 years), or adolescents (13-18 years); and iv) included a parent component. The parent component was defined as an intervention strategy that indirectly or directly engaged parents to support or assist children or adolescents to achieve changes in dietary intake. Exclusion criteria were: i) intervention programs designed solely to treat overweight or obese children (since these parents may have different and stronger motivations), ii) programs that enrolled children with a specific medical problem that could impact diet or weight; ii) studies for which statistics of outcome data were not reported; iii) studies without an intervention component; iv) literature reviews; v) studies with diet as a correlate and not an outcome; vi) qualitative studies; vii) pilot studies; and viii) non-randomized studies. For the current review, a previous definition of a randomized controlled trial (Rothman and Greenland, 1998) was adapted to child dietary interventions.
Publications with titles and abstracts that met initial screening criteria were retrieved and read by the primary author and a co-author to determine whether these met the inclusion criteria. Discrepancies in retrieved studies between primary author and co-author were resolved through discussions that included all co-authors and were guided by criteria established a priori.
Data from the studies were extracted using standardized forms developed by the authors for this purpose. For each publication that met criteria, the following were extracted when available: lead author, year published, geographic location of intervention, sample size (initial and ending), age, sex, ethnicity, and SES of participants, primary intervention location (e.g. school, home, etc), study design (including intervention arms), theoretical framework used to guide intervention design, primary and secondary outcomes, dietary measurement methods, adiposity measurement methods, description of intervention, intervention frequency and duration, main findings, methods of parental involvement in intervention activities, and any analysis that assessed whether subsequent changes in child or parent behavior could be attributed to this involvement. Recruitment methods and process evaluation measures as they related to parental involvement (e.g. program attendance) or subject participation when reported were also extracted. When studies cited additional published articles that further described their study (e.g. design, outcome evaluation, etc), the referenced article was also pulled and relevant information extracted (Haerens et al., 2006, Helitzer et al., 1998, Lytle et al., 2004, Nicklas et al., 1998). Thirteen studies included physical activity or physical fitness as an outcome, and while these data were also extracted and summarized (Appendix A, Supplementary Data), we did not assess the effect of parental involvement on child physical activity in this review. The extent to which parent involvement in physical activity interventions impacted child physical activity behavior has been summarized and reported elsewhere (O'Connor et al., 2009).
The Extended CONSORT checklist for non-pharmacologic randomized controlled trials (Boutron et al., 2008) was used to evaluate consistency and quality of methods and outcomes reporting for each of the twenty-four RCTs included in this review. CONSORT comprises a list of items that are recommended as discussion points in reports of RCTs to facilitate critical appraisal and interpretation of the trials(Altman et al., 2001). The extended checklist for reporting trials modified and elaborated on the original 22-item CONSORT checklist developed in 1996(Begg et al., 1996), and is appropriate for evaluating behavior interventions. Each RCT was scored on this 26-item checklist (1-4, 4A-C, 5-10, 11A, 11B, 12, 13, New Item, and 14-22) to determine if methodological characteristics may be associated with study outcomes. (Table 3)
The initial search yielded 1,774 citations. After screening the titles and abstracts of candidate studies, 100 papers were retrieved and the full article reviewed. Of these 100 articles, twenty-four studies met all our criteria and were included in this review.
Methods of parental involvement used in studies were summarized based on the type and intensity of parental involvement represented, broadly categorized as “indirect” or “direct” strategies. (Table 1) Three types of indirect strategies were identified: i) provision of information that did not require a parental response (e.g. newsletters, tip sheets with nutrition information sent to the home through mail, email, or with the child); ii) invitations to parents and children to participate in activities sponsored by the study (e.g. Family Fun Nights/Health Fairs with nutrition topics); and, iii) communications directed at child and/or parent meant to involve parents in intervention activities (e.g. “try this at home”). Two categories of direct strategies were identified: i) parents' presence requested at nutrition education sessions (e.g. didactic or workshop format); and ii) parents' attendance and participation requested for family behavior counseling or parent training sessions.
Of the twenty-four intervention studies included in this review, ten sought to improve diet as a primary objective (Baranowski et al., 2003b, Baranowski et al., 2000, Cullen et al., 1997, Haire-Joshu et al., 2008, Lytle et al., 2006, O'Neil and Nicklas, 2002, Perry et al., 1998, Perry et al., 1988, Reynolds et al., 2000, Vandongen et al., 1995); five studies focused on obesity prevention (Caballero et al., 2003, Fitzgibbon et al., 2006, Fitzgibbon et al., 2005, Foster et al., 2008, Haerens et al., 2006); two studies focused on reducing cardiovascular disease risk factors (Bush et al., 1989, Luepker et al., 1996) one on reducing diabetes risk factors(Trevino et al., 2004); and six studies focused on a combination of diet improvement and increased physical activity and/or fitness (Nader et al., 1989, Neumark-Sztainer et al., 2003, Patrick et al., 2006), or a combination of improved diet and obesity prevention (Epstein et al., 2001, Paineau et al., 2008, Stolley and Fitzgibbon, 1997).
The majority of interventions (n=16) were delivered in a school setting (Baranowski, et al., 2003b, Baranowski, et al., 2000, Bush, et al., 1989, Caballero, et al., 2003, Fitzgibbon, et al., 2005, Foster, et al., 2008, Haerens, et al., 2006, Luepker, et al., 1996, Lytle, et al., 2006, Nader, et al., 1989, Neumark-Sztainer, et al., 2003, O'Neil and Nicklas, 2002, Perry, et al., 1998, Perry, et al., 1988, Reynolds, et al., 2000, Trevino, et al., 2004, Vandongen, et al., 1995). The remaining eight studies were implemented in community settings, including Girl Scouts meetings (Cullen, et al., 1997), an after-school tutoring program (Stolley and Fitzgibbon, 1997), Head Start/preschool centers (Fitzgibbon, et al., 2006, Fitzgibbon, et al., 2005), clinics (Epstein, et al., 2001, Patrick, et al., 2006), or at the child's home (Haire-Joshu, et al., 2008, Paineau, et al., 2008). Three studies took place outside of the United States – in Australia (Vandongen, et al., 1995), Belgium (Haerens, et al., 2006), and France (Paineau, et al., 2008).
Sample sizes varied from thousands (Baranowski, et al., 2003b, Baranowski, et al., 2000, Bush, et al., 1989, Caballero, et al., 2003, Fitzgibbon, et al., 2005, Foster, et al., 2008, Haerens, et al., 2006, Haire-Joshu, et al., 2008, Luepker, et al., 1996, Lytle, et al., 2006, O'Neil and Nicklas, 2002, Paineau, et al., 2008, Perry, et al., 1998, Perry, et al., 1988, Reynolds, et al., 2000, Trevino, et al., 2004, Vandongen, et al., 1995) to fewer than one hundred participants (Cullen, et al., 1997, Epstein, et al., 2001, Nader, et al., 1989, Neumark-Sztainer, et al., 2003, Stolley and Fitzgibbon, 1997). Interventions recruited a wide range of ages, the most common being school age (6-11 years) (Baranowski, et al., 2003b, Baranowski, et al., 2000, Bush, et al., 1989, Caballero, et al., 2003, Cullen, et al., 1997, Epstein, et al., 2001, Foster, et al., 2008, Luepker, et al., 1996, Paineau, et al., 2008, Perry, et al., 1998, Perry, et al., 1988, Reynolds, et al., 2000, Stolley and Fitzgibbon, 1997, Trevino, et al., 2004, Vandongen, et al., 1995) followed by early adolescence (12-14 years) (Haerens, et al., 2006, Lytle, et al., 2006, Nader, et al., 1989, Patrick, et al., 2006), pre-school-age children(Fitzgibbon, et al., 2006, Fitzgibbon, et al., 2005, Haire-Joshu, et al., 2008) and mid- to late adolescence (15-18 years) (Neumark-Sztainer, et al., 2003, O'Neil and Nicklas, 2002).
Behavioral theories may inform the design of dietary interventions to provide a rationale for the strategies used to change behavior, thereby increasing the probability that they will be effective (Baranowski et al., 2003a). The most frequently reported behavioral theory was the Social Cognitive Theory (Baranowski, et al., 2003b, Baranowski, et al., 2000, Cullen, et al., 1997, Fitzgibbon, et al., 2006, Fitzgibbon, et al., 2005, Lytle, et al., 2006, Neumark-Sztainer, et al., 2003, Reynolds, et al., 2000) (n=8) followed by its predecessor, Social Learning Theory (n=5) (Bush, et al., 1989, Caballero, et al., 2003, Nader, et al., 1989, Perry, et al., 1998, Perry, et al., 1988). The remaining studies used a multi-theoretical approach (n=5) (Haerens, et al., 2006, Haire-Joshu, et al., 2008, O'Neil and Nicklas, 2002, Patrick, et al., 2006, Trevino, et al., 2004) or did not specify a theory (n=6) (Epstein, et al., 2001, Foster, et al., 2008, Luepker, et al., 1996, Paineau, et al., 2008, Stolley and Fitzgibbon, 1997, Vandongen, et al., 1995).
Methods to quantify dietary intake included 24-hour food recalls (11 studies, 46%) (Baranowski, et al., 2003b, Bush, et al., 1989, Fitzgibbon, et al., 2006, Fitzgibbon, et al., 2005, Luepker, et al., 1996, Lytle, et al., 2006, Patrick, et al., 2006, Perry, et al., 1998, Perry, et al., 1988, Reynolds, et al., 2000, Trevino, et al., 2004); food frequency questionnaires (8 studies, 33%) (Cullen, et al., 1997, Epstein, et al., 2001, Foster, et al., 2008, Haerens, et al., 2006, Haire-Joshu, et al., 2008, Neumark-Sztainer, et al., 2003, O'Neil and Nicklas, 2002, Stolley and Fitzgibbon, 1997); diet records (4 studies, 17%) (Baranowski, et al., 2000, Nader, et al., 1989, Paineau, et al., 2008, Vandongen, et al., 1995); and observation by research staff (2 studies) (Caballero, et al., 2003, Paineau, et al., 2008). In seventeen studies (71%), dietary intake was reported by the child participant (Baranowski, et al., 2003b, Baranowski, et al., 2000, Bush, et al., 1989, Cullen, et al., 1997, Foster, et al., 2008, Haerens, et al., 2006, Luepker, et al., 1996, Lytle, et al., 2006, Nader, et al., 1989, Neumark-Sztainer, et al., 2003, O'Neil and Nicklas, 2002, Patrick, et al., 2006, Perry, et al., 1998, Reynolds, et al., 2000, Stolley and Fitzgibbon, 1997, Trevino, et al., 2004, Vandongen, et al., 1995); parents reported for their children in four studies (Fitzgibbon, et al., 2006, Fitzgibbon, et al., 2005, Haire-Joshu, et al., 2008, Paineau, et al., 2008); parents assisted their child with reporting in two studies (Epstein, et al., 2001, Perry, et al., 1988); and in one study, dietary intake was observed and reported by research staff (Caballero, et al., 2003).
To determine whether parent involvement enhanced program effectiveness and what type of parent involvement was most effective, studies were categorized based on dietary outcomes (positive, mixed, no effect) and cross-tabulated with method of parental involvement. (Table 2) “Positive” indicated dietary changes that occurred in the desired or hypothesized direction; “mixed” indicated changes that occurred for some subgroups but not others (e.g. girls only), or for some but not all outcomes (e.g. fat intake decreased, but no change in fiber); and “no effect” meant that there were no reported changes in child diet. (Table 2) There were no negative findings reported (i.e. intervention had opposite, or detrimental effect on diet).
Four of twenty-four studies were designed to assess whether parent involvement enhanced the effectiveness of interventions that aimed to change child dietary intake (Haerens, et al., 2006, Luepker, et al., 1996, Perry, et al., 1988, Vandongen, et al., 1995). The effect of parent involvement was estimated by including “parent-only” and/or “parent-plus” comparison arms. Of those four studies, one achieved significant changes in the primary dietary outcome (reduced intake of total fat and increased intake of complex carbohydrates) for children enrolled in the home-based (parent) arm of the study compared to the control group (Perry, et al., 1988). Two other studies reported changes in dietary outcomes that differed by gender. A study conducted in Belgium demonstrated reduced fat intake and percent of energy from fat two years post-intervention in girls (but not boys) who were enrolled in the intervention condition plus parent support group compared to the control group (Haerens, et al., 2006). The same girls were also found to have significantly lower BMI and BMI z-scores compared to the control boys and girls and girls in the intervention without parent support (Haerens, et al., 2006). In a study conducted in Australia, girls in a home nutrition group, and girls in the school plus parent intervention group both reported significantly greater decreases in total fat intake compared to boys in the parent group and control girls (Vandongen, et al., 1995). In this same study, boys but not girls in the fitness, fitness plus school nutrition, and school plus home groups significantly reduced sugar intake. Finally, in a multi-center school intervention trial based in part on a previous study conducted by Perry, et al. (Luepker, et al., 1996), participants in the school plus parent intervention arm demonstrated greater positive changes in dietary knowledge (a secondary outcome), but not in dietary intake or serum cholesterol (primary outcomes), when compared to the participants in the school-only condition.
Nineteen studies used indirect methods to engage parents in intervention activities, while five used direct methods. Of the nineteen studies using indirect methods to engage parents, seven (37%) reported achieving statistically significant changes in the desired directions (Baranowski, et al., 2003b, Caballero, et al., 2003, Cullen, et al., 1997, Fitzgibbon, et al., 2005, O'Neil and Nicklas, 2002, Perry, et al., 1988, Reynolds, et al., 2000), seven (37%) reported mixed intervention outcomes (Baranowski, et al., 2000, Haerens, et al., 2006, Luepker, et al., 1996, Patrick, et al., 2006, Perry, et al., 1998, Trevino, et al., 2004, Vandongen, et al., 1995), and five (26%) reported no significant intervention effects (Bush, et al., 1989, Fitzgibbon, et al., 2006, Foster, et al., 2008, Lytle, et al., 2006, Neumark-Sztainer, et al., 2003). (Table 2) Of the five studies using direct methods to involve parents in the intervention, two reported positive outcomes (Epstein, et al., 2001, Haire-Joshu, et al., 2008)and the remaining three mixed effects (Nader, et al., 1989, Paineau, et al., 2008, Stolley and Fitzgibbon, 1997). Thus, a greater proportion (100%) of studies using direct methods achieved at least some dietary change (positive or mixed), while only 64% of studies using indirect methods achieved changes in dietary outcomes. There were no discernible patterns when outcomes were distributed across methods of dietary measurement and sample size (data not shown).
Publications varied widely with regard to reporting quality. Four publications reported ≥70% of the items on the CONSORT checklist (Haire-Joshu, et al., 2008, Luepker, et al., 1996, Paineau, et al., 2008, Trevino, et al., 2004). Item 4C (details on how adherence to protocol was assessed), Item 7 (sample size determination), Items 8-10 (randomization methods), 11A and 11B (blinding), Item 13 (flow of participants through the study), and Item 19 (adverse events) were the information most commonly omitted from the publications. (Table 3)
There were not enough studies that compared dietary interventions for children with and without parental components to adequately answer whether parent involvement enhanced program effectiveness (Research Question 1). Despite variability in the quality of reporting of the RCTs reviewed to address Research Question 2 (What type of parent involvement was most effective in achieving dietary outcomes?), interesting patterns emerged. Studies that used direct methods to engage parents were more likely to report positive or mixed results compared with those studies that used more indirect methods. Further, those studies that used indirect methods to involve parents but required children engage their parent in an activity were also more likely to report positive or mixed results, suggesting an intensity level that is adequate to result in significant change in children's dietary intake.
When dietary outcomes were cross-tabulated with methodological characteristics, there was no apparent pattern. It was unclear whether ‘direct’ interventions attracted those most interested in change (i.e. more motivated participants), or the intensity of the contact was sufficient to break through barriers preventing behavior changes (an intervention design factor). Similar trends were recently reported among interventions with family components intended to promote physical activity in children (O'Connor, et al., 2009), suggesting that direct involvement of parents in interventions targeting child dietary behavior need to be further evaluated via well-designed, adequately powered, randomized controlled trials.
Of concern was the lack of comprehensive and transparent reporting among the published interventions - only four of the reported studies met at least 70% of the CONSORT criteria for non-pharmacologic randomized controlled trials (Boutron, et al., 2008). Empirical evidence suggests that omitting information captured by the CONSORT checklist is associated with biased estimates of treatment effect, making it difficult to determine the reliability or relevance of findings (Altman, et al., 2001). We were unable to ascertain whether this was an issue in our review because of the limited number of publications meeting a majority of the reporting criteria.
There is a great need for development of more valid and reliable approaches for assessing dietary intake among children of all ages. Lack of uniformity in measurement of child dietary intake was also a troubling pattern that emerged from this review. While four commonly used methods of assessing dietary intake were used by the studies reviewed here (24-hour recalls, food frequency questionnaires, diet records, and staff observation), each varied slightly in methods, resulting in almost as many different measures of dietary outcome as studies reported. Different measurement methods yield different results (Stevens et al., 2007). The selection of a method for obtaining food intake data should be based on the research question, study design, and additional criteria regarding potential sources of error and problems that may occur due to socio-cultural characteristics of the participant population. For example, the food frequency questionnaire was designed to measure typical patterns of food intake and not necessarily intended to provide accurate quantitative measures of energy and nutrient intakes on an individual basis (Thompson and Byers, 1994). Further, while parents can report somewhat accurately on their child's behalf (Linneman et al., 2004), they report less accurately when children eat in settings outside the home (e.g. at school or in childcare settings) (Baranowski et al., 1991).
Interventions designed to impact child diet have largely taken place in school settings, which allows for large numbers of children to be reached, but with limited effects (Thomas, 2006). Strategies are needed that reach and impact a majority of children at a substantial and meaningful level. This review suggests that such strategies should aim to directly engage parents in ways to help support their child have more healthy dietary consumption patterns. Designing an effective nutrition intervention requires an understanding of psychosocial or environmental determinants of diet (Baranowski et al., 1997). Parents remain attractive targets for nutrition intervention programs because they act as nutrition “gatekeepers,” providing their children with ability and opportunity to make healthy food choices.
A potential barrier to implementing an effective parent-focused dietary intervention is a lack of theory-driven research that systematically evaluates the effects of specific parenting strategies (and in what context they are used) on child dietary behavior and weight. Research has begun to explore “effective food parenting” (O'Connor et al., 2010)with an emphasis on feeding styles (Hughes et al., 2005) and parenting practices (Hendy et al., 2009, Musher-Eizenman and Holub, 2007) and linking these strategies to child intake (O'Connor et al., 2009). Improving our understanding of this could inform policy and guide public health efforts.
This review has several limitations. Only published articles were reviewed which may bias the selection to more favorable outcomes, since interventions with null findings are less likely to be published than those with a positive effect (Doak et al., 2006). Only studies published in the English language were included, limiting the number of studies included outside of English-speaking countries. The CONSORT criteria allow for review of the quality of reporting, and are not a direct assessment of study design and analysis. Using this checklist to assess quality of reporting is also somewhat subjective given the possibility that users may interpret the criteria differently (despite definitions provided by CONSORT statement authors). Since the method of parental involvement that was reported in the publications only specified intensity of contact, intervention targets and intervention content must also be considered. It was impossible to ascertain either of these factors from the majority of studies in this review because of a lack of detailed reporting, often the result of word limits set by many medical and public health journals.
Currently, limited conclusions may be drawn regarding the best method to involve parents in changing child diet to prevent obesity and improve health. Indirect methods remain the most commonly used strategies to engage parents, however, direct methods of engagement show more promise and therefore, warrant further research.
Future research should specifically test a “parent effect” by designing methodologically rigorous studies with appropriate comparison groups. Different intensities of parental involvement should be investigated, and parent participation rates in intervention activities reported. Based on the CONSORT criteria, quality of reporting was generally inadequate and needs to be improved. A gold standard diet assessment method in children remains a significant methodology issue. Innovative ways to measure diet in real time should be developed to capture a more accurate representation of children's dietary intake. Finally, investigators should strive to use similar methods of dietary and adiposity measurement, making comparisons across studies possible and advancing this critical field of research.
This research was funded by a National Institute of Child Health and Human Development Training Grant 5T32HD007445, “Research Training in Maternal, Infant & Child Nutrition.” This work is also a publication of the United States Department of Agriculture (USDA/ARS) Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, and has been funded in part with federal funds from the USDA/ARS under Cooperative Agreement No. 58-6250-6001. The contents of this publication do not necessarily reflect the views of policies of the USDA nor does mention of trade names, commercial products, or organizations imply endorsement from the U.S. government.
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Melanie D. Hingle, University of Arizona, Department of Nutritional Sciences, Tucson, Arizona.
Teresia M. O'Connor, Baylor College of Medicine, Department of Pediatrics, USDA-ARS Children's Nutrition research Center, Houston, Texas.
Jayna M. Dave, USDA-ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX.
Tom Baranowski, Baylor College of Medicine, Department of Pediatrics, USDA-ARS Children's Nutrition Research Center, Houston, TX.