Journal of Pediatric Psychology Advance Access originally published online on April 19, 2007
Journal of Pediatric Psychology 2007 32(7):783-793; doi:10.1093/jpepsy/jsm017
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Effects of Modifying Physical Activity and Sedentary Behavior on Psychosocial Adjustment in Overweight/Obese Children
1Mental Health Research, Children's Hospital of Eastern Ontario Research Institute, 2School of Human Kinetics, University of Ottawa, 3Department of Paediatrics, University of Ottawa, 4Department of Psychology, Carleton University, and 5Chalmers Research Group, Children's Hospital of Eastern Ontario Research Institute
All correspondence concerning this article should be addressed to Gary S. Goldfield, PhD, C. Psych, Senior Investigator, Children's Hospital of Eastern Ontario Research Institute, Mental Health Research, 401 Smyth Rd., Ottawa, ON Canada K1H 8L1. E-mail: ggoldfield{at}cheo.on.ca.
| Abstract |
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Objectives To evaluate the relationship between changes in physical activity (PA), sedentary behavior, and physical self-perceptions and global self-worth in 30, 812 years old, overweight/obese children (13 boys, 17 girls). Methods Secondary analyses from a randomized controlled trial designed to increase PA and reduce sedentary behavior. PA was measured by accelerometers worn by participants every day for 8 weeks. Sedentary behavior, defined as minutes per day spent in television viewing, was assessed by self-report. Results Increases in PA were associated with increases in perceived physical conditioning (r = .54, p < .01), body satisfaction (r = .55, p < .01), and overall physical self-worth (r = .44, p < .05) independent of changes in body mass index (BMI). Reductions in TV viewing were also related to increased physical and global self-worth. Conclusions Increases in PA are associated with improvements in physical self-perceptions but not global self-worth, while reductions in TV viewing are associated with increased physical and global self-worth, and these psychosocial benefits appear to be independent of changes in adiposity.
Key words: children; obesity; overweight; physical activity; sedentary behavior; self-esteem; self-perceptions; TV; youth..
Child obesity is increasingly being recognized as a global epidemic (Tremblay & Willms, 2000
One of the most reliable psychological correlates relating to physical self-perceptions in obese children is body dissatisfaction or physical appearance esteem. Mounting evidence from systematic reviews indicates that overweight/obese children, especially girls, exhibit greater dissatisfaction than normal-weight peers in clinical and community-based samples (Ricciardelli & McCabe, 2001
; Wardle & Cooke, 2005
). This is clinically significant because body dissatisfaction is not only a consequence of obesity; it is directly related to unhealthy restrictive dieting behaviors that are cross-sectionally and prospectively related to weight gain in youth (Field et al., 2003
) and adults (French et al., 1994
). Thus, lifestyle intervention that enhances body image and other physical self-perceptions should not only provide psychological benefits, but these benefits may translate to more sustained PA and improved eating behavior needed to induce negative energy balance and weight loss. Increasing PA and reducing sedentary behavior in overweight/obese youth may be one method of achieving these aims (Biddle, Sallis, & Cavill, 1998
).
Obese children are a group who may particularly benefit from increased energy expenditure from physical activity given that they are less physically active (Bar-Or et al., 1998
; Sallis et al., 1992
) and less fit (Johnson et al., 2000
; Mamalakis, Kafatos, Manios, Anagnostopoulou, & Apostolaki, 2000
) than nonobese children, and because obesity and sedentary lifestyles track from childhood to adulthood (Stark, Atkins, Wolff, & Douglas, 1981
). In addition, TV watching is a sedentary behavior that consumes a large part of children's leisure time (Gortmaker et al., 1996
; Olds, Ridley, Dolman, 2006
), and is cross-sectionally (Andersen, Crespo, Bartlett, Cheskin, & Pratt, 1998
; Hancox & Poulton, 2006
) and prospectively related to the development of obesity in children (Gortmaker et al., 1996
) and adults (Viner & Cole, 2005
), and negatively correlated with physical activity (Andersen et al., 1998
; Janssen et al., 2005a
) and fitness (Durant, Baranowski, Johnson, & Thompson, 1994
). Moreover, physically active children report greater body satisfaction, self-esteem, and physical self-perceptions than sedentary peers (Biddle et al., 1998
), and increasing PA and exercise improves global self-esteem in youth (Ekeland, Heian, Hagen, Abbott, & Nordheim, 2004
). Importantly, there is evidence that the psychological benefits of increased PA in youth are often independent of changes in body mass (Ekeland et al., 2004
), but this issue needs further study.
Using sedentary behavior to reinforce physical activity, a behavior modification technique known as the premack principle (Premack, 1959
), increases PA and reduces sedentary behavior in normal-weight and obese children in the laboratory (Goldfield, Kalakanis, Ernst, & Epstein, 2000
; Saelens & Epstein, 1998
), as well as adiposity in obese children in the natural environment (Faith et al., 2001
; Goldfield et al., 2006
). Very few clinical trials have examined the effects of modifying PA and sedentary behavior on psychological well-being in overweight/obese children, as most of this research has utilized cross-sectional samples or epidemiological cohorts rather than randomized controlled trial designs. Thus, the aim of this study was to examine the effects of an intervention designed to increase PA while reducing TV viewing (Goldfield et al., 2006
) on changes in physical self-perceptions and global self-worth in overweight/obese children, and evaluate the degree to which this relationship is influenced by changes in body composition. We predicted that increases in PA rather than reductions in sedentary behavior would predict improvements in body image and other physical self-perceptions and global self-esteem, and this relationship would exist independent of body composition change. It was also of interest to examine the degree to which changes in intensity of PA related to changes in psychosocial adjustment.
| Methods |
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The criteria to define overweight and obesity used in this study are based on the International Obesity Task Force guidelines (www.iotf.org), which differ from the Center for Disease Control definition stating that BMI above the 85th percentile for age and sex is considered "at risk of overweight" and BMI above the 95th BMI is "overweight" (www.cdc.gov). Forty-six children were screened for eligibility. Thirty, 812 years old overweight/obese children who participated with their parents in an 8-week PA randomized control trial met the following inclusion criteria: (a) 812 years old children with a BMI of 85th95th BMI percentile (overweight) or greater than 95th BMI percentile (obese) for age and sex (Kuczmarski, Ogden, Guo, et al, 2002
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Design and Procedures
The randomized controlled trial was conducted at the Children's Hospital of Eastern Ontario from September 2003 to June 2004. Thirty families were randomized to PA monitoring and feedback plus reinforcement (TV access) (open-loop feedback + reinforcement, n = 14) versus PA monitoring and feedback only (open-loop feedback alone, n = 16). None of the participants dropped out of the study. Children in both groups were provided objective feedback on their PA by wearing a PA monitor (BioTrainer; Individual Monitoring Systems, Baltimore, MD, USA). However, children in the open-loop feedback plus reinforcement group were rewarded with access to television based on the amount of PA accumulated, whereby 400 activity counts on the activity monitors, equivalent to about 1 h of moderate to vigorous PA (MVPA; Goldfield et al., 2006
Children in the open-loop feedback control group were provided feedback on PA but did not have the token TV devices, hence had free access to TV. These children were required to visit the laboratory for activity monitor downloading according to the same schedule as the intervention group. Families in this group were not given any activity goals to avoid confounding goals with the effects of the feedback from activity monitors. More specific information of the trial methodology and procedures are reported elsewhere (Goldfield et al., 2006
).
Measurement
Demographics were evaluated by self-report and socioeconomic status was assessed by the sum of parental income. Medical history and current medical problems or physical conditions that contraindicate PA were evaluated by self-report and clinical interview.
Body Composition
Child weight was assessed to the nearest 0.1 kg with subjects wearing light clothing without shoes using a calibrated balance beam scale. Height was assessed using a Health-O-Meter stadiometer. Height and body weight were measured at baseline and 8-week follow-up assessment and used to determine BMI defined as weight in kg over height in m2 (kg/m2). We chose to use BMI rather than z-BMI in light of new research indicating that traditional BMI is more sensitive to change over time than z-BMI (Cole, Faith, Pietrobelli, & Heo, 2005
), making it more suitable to evaluate intervention effects.
Measurement of Daily PA
PA was objectively measured by the BioTrainer® (IM Systems, Baltimore, MD, USA), a small, unobtrusive accelerometer validated under laboratory and field conditions (Welk, Blair, Wood, Jones, & Thompson, 2000
), that has detected significant increases in PA in clinical outcome research (Andersen et al., 1999
). The BioTrainer® provides minute-by-minute measures of PA, and thus can provide information on when children are active and not active, and the intensity of activity performed. Total activity counts, average daily activity counts, time spent in MVPA (35.9 METS), and vigorous physical activity (VPA
6 METS) (Pate et al., 1995
) were calculated from data downloaded from the Biotrainer® at 7-day baseline, bi-weekly during the intervention, and 8-week posttreatment.
Self-reported Behaviors
The Past Day Physical Activity recall (PD-PAR), a valid self-report measure of PA in children (Weston, Petosa, & Pate, 1997
), including obese children, was used in combination with the BioTrainer® to indicate what children were doing when they were active and sedentary. Participants were asked to use the PD-PAR daily to record all targeted and nontargeted forms of sedentary behaviors, as well as physical activities throughout each day of the week during baseline and posttreatment assessment periods, as well as daily during the intervention. The PD-PAR was also used with interviews at screening to assess eligibility. Children self-reported the amount of time they wore the activity monitor by writing the time of day they put the monitor on and when they took it off, using a self-report form prepared by the investigative team. The self-reported activity was compared with the objective activity monitors to verify accuracy of reporting when activity monitors were worn, and discrepancies between self-report and activity monitors were addressed with families in the bi-weekly meetings.
Physical Self-perceptions
Physical self-perceptions were assessed using the Physical Self-Perception Profile for Children (PSPP-C; Fox & Corbin, 1989
; Eklund, 1997
). This 36-item inventory is designed to measure children's perceived competence in five domains of functioning: Sport, Physical Conditioning, Body Appearance, Strength, and a higher order constructthe Physical Self-Worth scale. The Harter Global Self-Esteem subscale (Harter, 1985
) was added to evaluate the extent to which the child likes himself/herself as a person and is happy with the way he/she is. As such, this dimension constitutes a global dimension of one's self-worth as a person, rather than domain-specific competency or adequacy. These domains were discriminated from each other through factor analytic procedures (Fox & Corbin, 1989
). The PSPP-C adopts a response format that includes both positively and negatively worded phrases to control for socially desirable responses. Each response has two components whereby children first choose the direction and then the intensity of their response. For example, they would first circle one of the following two statements that is most true of themselves: "some kids are often unhappy with themselves" BUT "other kids are pretty pleased with themselves." The second step in completing responses would be to rate whether the statement circled is "sort of true for me" or "really true for me." Items are scored on a 4-point rating scale (14), with higher numbers reflecting greater competence and self-esteem.
Analytic Plan
The relationship between changes in overall PA and self-perceptions and the degree to which this relationship is influenced by changes in body composition were evaluated in two ways. First, between-group changes on the six domains of physical and global self-perceptions were evaluated using an intention to treat approach with a mixed analysis of variance and covariance models. The ANOVA/ANCOVA consisted of a between-subjects factor of group (open-loop feedback + reinforcements vs. open-loop feedback only), as well as a repeated measures factor of Time (Baseline vs. Posttreatment), with the six domains of physical self-perceptions serving as the dependent measures, and baseline BMI as a covariate. A significant Group x Time interaction and post hoc tests using Fisher's exact tests were used to determine if the intervention provided psychosocial benefits independent of BMI. Two, prepost change scores were created, and the magnitude of correlation between the changes in overall PA (total counts per day), minutes per day in MVPA, minutes per day in VPA, targeted sedentary behavior, and self-perceptions were evaluated by Pearson Product Moment correlations with and without partialing out changes in BMI. In addition, correlations between changes in BMI and physical self-perceptions were also conducted. In all analyses, we used two-tailed alpha values set at 0.05. Statistical analyses were conducted using the Statistical Package for the Social Sciences (SPSS 13.0).
| Results |
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Demographic and anthropometric characteristics of the sample are reported in Table I. No group differences emerged on these variables.
ANOVAs yielded significant Group x Time interactions indicating that, compared with controls, the intervention group demonstrated significantly greater changes in total physical activity counts [F(3, 84) = 3.79, p < .05], and time spent in MVPA [F(3, 84) = 2.8, p < .05]. The Group x Time interaction for VPA was not significant.
There was a significant Group x Time interaction on several dependent measures. Controlling for BMI at baseline, the intervention group exhibited significantly greater improvements in perceived Physical Conditioning [F(1, 27) = 4.5, p = .036], Body Appearance [F(1, 27) = 4.0, p = .04], and Physical Self-Worth [F(1, 27) = 4.8, p = .02] compared with controls. Between-group differences on the Sport, Strength, and Global Self-Esteem were not statistically significant. The results of analyses of physical self-perception scales are shown in Table II. Neither the main effects of time nor group were significant for any of the dependent measures when controlled for BMI.
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Correlational analyses indicated that increases in PA were associated with increases in Body Appearance (r = .43, p = .017), Condition (r = .38, p = .04), and Physical Self-Worth (r = .44, p = .01). As shown in Table III, these relationships remained significant after controlling for changes in BMI. Changes in PA were not associated with changes in Strength, or Global self-Esteem. Changes in targeted sedentary behavior (i.e., TV viewing) were not related to changes in physical self-perceptions when BMI was not controlled for, but were inversely related to Physical Self-Worth (r = .38, p = .05) and Global Self-Esteem (r = .36, p = .05) when BMI was statistically controlled for. The improvements in self-perceptions were more strongly correlated with overall volume (total counts) of PA rather than intensity, as shown in Table III.
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A significant Group x Time interaction emerged for BMI [F(1, 28) = 3.9, p < .05] indicating greater improvements for intervention group (pre: 28.9 ± 6.2; post: 28.3 ± 6.6) compared with control (pre: 28.2 ± 3.0; post: 28.5 ± 3.1). Changes in BMI were not related to changes in physical self-perceptions (Table IV).
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| Discussion |
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To our knowledge, this is the first study to examine the effects of open-loop feedback to increase PA on psychosocial adjustment in overweight/obese children. Data from the current study indicate that increases in overall PA are associated with improvements in Body Satisfaction, perceived Physical Conditioning, and perceived Physical Self-Worth, and these psychological benefits were independent of reductions in BMI.
Despite the study intervention not resulting in "visible" change in BMI (Goldfield et al., 2006
), there remained a relationship between increased PA and improved body appearance esteem. This finding, previously reported in youth (Kirkcaldy, Shephard, & Siefen, 2002
), has important clinical implications. Many overweight children experience weight-based teasing (Puhl & Brownell, 2001
), which likely serves to exacerbate body dissatisfaction that is already prevalent in this population (Wardle & Cooke, 2005
). It is interesting to note that while one may expect self-esteem to increase in association with improved body satisfaction, our data indicate that increased PA was only associated with improved physical, but not global, self-worth, highlighting that the correlation between body esteem and self-esteem is not linear or symmetrical in overweight/obese children (Wardle & Cooke, 2005
). The fact that PA was associated with increased body image and several other domains of self-perception, but not global self-esteem, is inconsistent with systematic review findings indicating PA increases self-esteem and emotional well-being in children (Ekeland et al., 2004
; Gruber, 1986
). Perhaps this discrepancy in findings is due, in part, to the fact that most trials included in these reviews were not based on clinical samples of obese children. It appears that the current sample of overweight/obese children may be evaluating their global self-worth on many domains that extend well beyond merely PA and body image. This self-perception may provide psychological advantages given that over investment in body weight and shape is associated with increased risk of engaging in unhealthy eating and weight control practices, and full-blown eating disorders (American Psychiatric Association, 1994
). Given that many obese children presenting for treatment have difficulty losing weight and maintaining the losses, it is encouraging to note that body image and physical self-worth can be enhanced, independent of weight loss simply by getting overweight children more physically active. Moreover, given that body dissatisfaction often elicits restrained eating or dieting for weight loss in overweight children (Casper & Offer, 1990
; Field et al., 1999
), combined with evidence that dieting leads to weight gain in youth (Field et al., 2003
; Shunk & Birch, 2004
), future research is needed to determine whether improved body image resulting from increased PA in overweight children translates to healthier eating behavior and weight management.
Our findings indicating that increases in PA were associated with increases in physical self-perceptions, independent of BMI, is consistent with previous research in mainly normal-weight children (Crocker et al., 2000
) and adolescents (Crocker et al., 2003
), and provides evidence that PA interventions can be empowering in the context of perceived competence in physical abilities in overweight/obese children. This finding is important knowing that physical self-worth is predictive of subsequent PA and sport participation (Biddle et al., 2001
), which may provide greater opportunity to increase energy expenditure needed for weight loss or weight maintenance throughout growth in this patient population.
Today's children spend more time watching TV and playing video games than any other activity besides sleeping (The Annenberg Public Policy Center of the University of Pennsylvania, 1997
), and obese children, in particular, spend more time in these sedentary activities (Dietz & Gortmaker, 1985
). Interestingly, reductions in TV viewing were associated with improvements in physical and global self-worth, but only when changes in BMI were statistically controlled. To the best of our knowledge, we are the first to document a relationship between reduced TV viewing and increased global self-worth in this population. One possible explanation for this finding may be that successfully reducing TV viewing may have enhanced feelings of self-discipline or self-control that psychologically empowered children to feel better about themselves. Additionally, children and youth are particularly vulnerable to the messages conveyed through TV, which have been shown to adversely influence their self-image and aggressive behaviors (American Academy of Pediatrics, 2001
). Therefore, a reduction in viewing time may increase self-esteem by reducing exposure to unhealthy messages and unrealistic body images displayed on TV. Alternatively, reductions in TV viewing may conceivably lead to improved physical and global self-worth by increasing PA (Epstein, Roemmich, Paluch, & Raynor, 2005
). However, our data indicate that improved global self-worth was not related to changes in PA; thus, given the multidimensional nature of self-esteem, increasing PA alone may not be sufficient to increase global self-esteem in overweight and obese children.
Regardless of the mechanism, the finding that reducing TV is predictive of improved self-esteem is important because good self-esteem is a predictor of physical health (Rhee, Holditch-Davis, & Miles, 2005
) and is also a well-accepted measure of psychosocial health in youth (Rotenberg et al., 2004
). Moreover, self-esteem has reliably been shown to predispose to, or buffer against, the development of numerous psychiatric disorders, including eating disorders (Fairburn, Welch, Doll, Davies, & O'Connor, 1997
). Future research is needed to replicate and further understand how reductions in TV viewing are associated with enhanced self-esteem in overweight children.
The relationship between changes in intensity of PA and physical self-perceptions and global self-esteem in overweight/obese children has not been well studied. Our data indicate that overall volume (total counts) of PA was more closely associated with improvements in physical self-worth than MVPA, and in fact, there was virtually no relationship between changes in VPA and self-perceptions. Research suggests that obese children find it more difficult to sustain bouts of higher intensity PA than normal-weight children (Dishman, 1991
; therefore, attempting to be active at these intensities may be disempowering and affect adherence resulting in reduced physical self-perceptions. Conversely, increasing volume of PA at lower intensities may provide a sense of mastery and empowerment in relation to physical competencies. This finding, if replicated, has clinical relevance in that overall volume of PA in youth may be more important for providing psychosocial health benefits than higher intensity PA designed to improve fitness (Rowland & Freedson, 1994
). In addition, encouraging overweight/obese children to engage in higher volume, lighter intensity PA may be a more realistic goal that would likely yield better adherence and may contribute to weight control (Rowlands, Eston, & Ingledew, 1997
).
This study has several limitations. Although novel research questions were posed, the small sample size makes it difficult to evaluate how generalizable these results are to preadolescent overweight/obese children. The sample size of primarily Caucasian children also precludes a meaningful evaluation of how gender or ethnicity influence the relationship between activity changes and psychosocial adjustment. Although changes in relationships were evaluated longitudinally, the study period was only 8-weeks and long-term follow up with multiple evaluations are needed to better determine how changes in volume and intensity of PA performed predict changes in physical and global self-worth in this population, and whether these changes are maintained after the intervention is stopped.
In summary, data from the current study indicate that increases in overall volume (total counts) of PA are associated with improvements in perceived physical conditioning, body satisfaction, and overall physical self-worth, and these improvements in psychosocial adjustment were not due to changes in body composition. Improvements in physical self-perceptions were more closely related to overall volume (total activity counts) of PA than intensity of PA, but this finding needs replication with larger samples and less sedentary children who engage in greater amounts of MVPA and VPA. Reductions in TV viewing were associated with increases in physical and global self-worth, independent of changes in BMI, thereby identifying additional psychological health benefits of reducing reinforcing sedentary behavior. Collectively, our findings indicate that behavioral interventions that increase PA and reduce TV viewing may be effective in improving weight control, and may also provide concomitant psychosocial benefits to a pediatric population in need. Future research incorporating longitudinal designs with multiple follow-ups are needed to more accurately determine whether changes in activity provide psychosocial benefits, or whether improvements in psychosocial functioning lead to increased PA and reduced sedentary behavior, or both.
| Acknowledgments |
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This research is supported, in part, by a New Investigator Award and clinical trial grant from the Canadian Institutes of Health Research (CIHR) awarded to Dr Gary Goldfield. The authors would like to thank Dr Hollie Raynor, and Paula Cloutier for providing constructive feedback on previous versions of this manuscript.
Conflict of interest: None declared.
Received May 31, 2006; revision received February 20, 2007; accepted February 20, 2007
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