Introduction

The rate of pediatric obesity has risen significantly in the United States¹ to the point at which 17% of children ages 2-19 were obese and an additional 15% were overweight in 2007-2008². This epidemic has become a major public health concern, as childhood obesity has been linked to many adverse health consequences, including juvenile hypertension, elevated cholesterol levels, orthopedic abnormalities, type II diabetes mellitus, gallstones, asthma, and sleep disorders, to name a few³. Prevention programs for children and adolescents have so far had limited success^4,5. Thus, research is necessary to examine individual difference characteristics that contribute to the development of pediatric obesity and barriers to its treatment. This study intends to determine whether weight misperception may be an important factor in understanding the high prevalence of adolescent obesity.

Weight underestimation among a multiethnic sample of overweight U.S. adolescents (BMI at or above the 85 ^th percentile) was found to be common, with 61% of males and 40% of females underestimating their actual weight status⁶. This finding is indicative of an ongoing trend among many Americans with overweight who have inaccurate self-perceptions of their weights^7-10. Furthermore, many parents have been found to underestimate the weight status of both their child and adolescent offspring^11-13, which thereby suggests a potential mechanism for transmitting an inaccurate gauge for healthy weight status to their children.

In adults, the tendency to misperceive one’s weight varies substantially across demographic factors, with men, those with lower socioeconomic status, Hispanics, and African-Americans more likely to underestimate their overweight status^10,14,15. Similar to adults, there is some evidence that gender, race, and family factors play an important role in adolescent weight perception^16,17. However, Yan et al⁶ found only gender differences and no race or socioeconomic status associations with weight status misperception in their multiethnic sample of adolescents.

This study seeks to add to the current literature by determining associations between weight misperception and specific adolescent health behaviors, such as physical activity and nutrition, among individuals with obesity. Across healthy and unhealthy adolescent populations, weight loss efforts are strongly related to adolescents’ perceptions of themselves as overweight^15,18. Therefore, underestimation of overweight status might reduce the likelihood that adolescents with overweight would participate in healthy behaviors that could promote weight loss. This hypothesis suggests a direct perception-behavior relationship.

Alternatively, evidence that self-efficacy predicts adolescent participation in a range of health behaviors, including exercise, smoking, AIDS prevention, and diet^19-22, points to self-efficacy as a factor that may mediate the perception-behavior link. Thus, an opposing hypothesis exists such that accurate perception of obesity status could undermine self-efficacy to engage in health behaviors such as physical activity, thereby reducing the likelihood of participation in healthy activities. That is, they may view their overweight status as an impediment to their participation in health behaviors. In either case, an opportunity exists to gain a better understanding of relations between weight perception, self-efficacy, and health behaviors among obese adolescents.

Purpose

The primary goal of this study was to test two hypotheses that examine associations between weight self-perception and participation in health behaviors among obese adolescents: 1) a direct weight perception-behavior relationship, with weight underestimation expected to decrease the likelihood of participation in health behaviors linked to weight management; and 2) a mediating effect of self-efficacy, such that accurate recognition of one’s obese status is expected to correlate with lower self-efficacy in one’s ability to participate in health behaviors, thereby reducing the likelihood of actual participation in these behaviors. To test these hypotheses, we measured self-reported readiness to participate in four areas of health behavior (i.e., physical activity, healthy diet, weight management, and overall healthy lifestyle) among adolescents who are obese. We also explored effects of hypothesized moderating (i.e., gender and grade level) variables in the relationship between weight perception and health behaviors.

Methods

Participants

Measures

BMI

Procedure

Statistical Analysis

Results

Among the 1,210 obese students, ¬18% (N = 217) underestimated their weight status as normal or underweight. Males (23%; N = 166) were more likely than females (10%; N = 51) to underestimate their weight status, Χ² (1) = 34.03, r ² = .03. The 7 ^th graders (21%; N = 121) were more likely than 11 ^th graders (15%; N = 96) to underestimate their obese status, Χ² (1) = 8.26, r ² = .01. The underestimators (M = 29.5, SD = 3.1) had significantly lower BMI’s than the accurate reporters (M = 33.1, SD = 4.9), t (1,208) = 10.35, Cohen’s d ^{= .78.}

Health Behaviors

The distributions of self-reported rates of readiness to participate in health behavior are presented in Table 1.

Figure 1

Table 1: Associations between Self-reported Participation in Health Behaviors and Weight Perception

The underestimators reported higher rates of physical activity, eating healthy food, healthy weight management, and an overall healthier lifestyle than those with accurate report.

Self-Efficacy

As predicted, the underestimators reported greater self-efficacy in their ability to engage in each of the four health behaviors than those with accurate self-report (see Table 2).

Figure 2

Table 2: Associations between Self-efficacy in Health Behavior Participation and Weight Perception

Consistent with the differences in their average BMI’s, more than twice the proportion of underestimators compared to accurate self-reporters expressed strong self-efficacy (“I can do it, no problem”) with healthy weight management. Self-efficacy was also found to be significantly associated with self-reported participation in each of the corresponding health behaviors. The results of this series of χ² tests are presented in Table 3.

Figure 3

Table 3: Associations between Self-reported Participation in Health Behaviors and Self-efficacy

Logistic Regression Models

In the fourth and final step of the mediational analysis, a series of four logistic regression analyses were run to determine the influence of self-efficacy on the associations between weight perception and self-reported health behavior participation. A null effect for weight perception on physical activity and healthy diet, respectively, was found when self-efficacy was entered into these logistic regression equations, indicating that self-efficacy mediates the relationship between weight perception and these two outcomes (see Figure 1).

Figure 1. Observed Models in which Self-efficacy Significantly Mediated the Relationship Between Weight Perception and Health Behaviors.

Figure 4

Figure 1a. Physical Activity

Figure 5

Figure 1b. Healthy Diet

In contrast, although a null effect was not found for weight management and overall healthy lifestyle when self-efficacy was entered into those two equations, the shift in parameter estimates of exp(β) towards unity indicates partial mediational effects²⁷. The β odds are presented in Table 4.

Figure 6

Table 4: Logistic Regression Modeling Results for Health Behavior Participation

Gender And Grade Level

Discussion

This study intended to determine the association between weight perception and health behavior participation among obese adolescents. Two competing hypotheses were tested: (1) underestimation is associated with decreased participation through a direct perception-behavior link and (2) accurate perception is associated with decreased participation through the mediating effect of self-efficacy. Weight underestimation was observed in 18% of participants, which was a substantial reduction in prevalence from the 2009 Yan et al.⁶ study that included a multiethnic sample of both overweight and obese adolescents. The decision to include only obese students in this sample may have reduced the rate of misperception as intended. The data refuted the first hypothesis, but generally supported the second hypothesis. Underestimators reported rates of participation in four health behaviors (physical activity, healthy diet, weight management, overall healthy lifestyle) that were 16-33% higher than the accurate reporters.

Consistent with the second hypothesis, self-efficacy was shown to be positively associated with both weight underestimation (r ² range of .04 to .11) and self-reported health behavior participation (r ² range of .10 to .21), respectively. Self-efficacy fully mediated the relationships between weight perception and physical activity and healthy diet, respectively, and was a partial mediator of the relationships with weight management and overall healthy lifestyle.

Although self-efficacy appears to be a key mediating factor between weight underestimation and self-reported health behavior participation, other mediators not accounted for in this dataset could be involved. One speculative hypothesis comes from the finding that intrinsic motivation (e.g., fitness, recreation, etc.) predicts exercise and general quality of life, whereas extrinsic motivation (e.g., weight loss, attractiveness) is negatively associated with these outcomes¹⁷. Without an accurate recognition of their obese status, it would seem that underestimators would be more likely to participate in health behaviors for intrinsic reasons other than weight loss. On the other hand, those who recognize that they are obese may tend to be interested in health behaviors for the specific purpose of trying to lose weight, which is an extrinsic source of motivation that negatively predicts actual exercise participation.

Body dissatisfaction could be another mediating factor in the relationship between weight underestimation and health behavior participation. Presumably, those who identified themselves as overweight would be more at-risk for lower body satisfaction. Although body dissatisfaction has been shown to be associated with unhealthy weight loss efforts, such as binge eating and smoking, it predicts lower levels of healthy weight loss behaviors, such as fruit and vegetable intake and physical activity²⁸.

Consistent with previous adolescent research⁶, the males who were obese were more likely to underestimate their weight status than the females. Also, the 7 ^th graders were more prone to underestimate their obese status than the 11 ^th graders, perhaps suggesting that weight self-awareness is more accurate among older than younger adolescents. Yet in our multivariate analyses, grade level appeared to be a more influential moderator of health behavior than gender (see Table 4).

Limitations

The most significant limitation of this study was the lack of available psychometric data for the self-report measure. Although the PWP items that are intended to measure health behavior participation, self-efficacy, and interest have strong content validity, they are not standardized measurements of these constructs. The authors emphasize that the use of this self-report measure enabled an initial investigation into variables of interest that have potential to inform and improve future obesity research and prevention efforts.

The use of self-report in itself is another limitation of the study. Although self-report is commonly used to determine levels of health behavior participation, it is susceptible to the influence of a number of cognitive and situational factors that could reduce reliability and validity of this key variable²⁹. In this study, there is a possibility of a spurious, bidirectional relationship with self-reported weight. That is, self-reported weight status may have been influenced by reporting biases other than actual weight perception, such as an optimistic view of reality or concern with impression management (i.e., the desire to look “good’). From the perspective of cognitive dissonance theory³⁰, for example, participants may have strived to maintain cognitive consistency by reporting health behavior levels that were correspondent to their self-images. Also, those who underestimated their weight status may just have been less accurate overall in their self-report, which could have also led to skewed self-reported participation rates.

The use of nurse-obtained BMI was a strength of this study because adolescents, particularly those who are obese or overweight, tend to under-report their body weight, which can lead to an underestimation of the prevalence of overweight and obesity^31,32. On the other hand, although BMI is considered a valid indicator of adiposity in adolescents^33,34, a flaw of the measure is that it does not take into account body frame and muscularity. Therefore, the use of BMI to assess adiposity could result in the erroneous categorization of some muscular and broad-shouldered athletic students as obese.

Both the underestimators and accurate reporters had average BMI’s within the obese range. However, consistent with the underestimators’ assertion of healthier weight status, they had lower BMI’s than the accurate reporters. It makes intuitive sense that the students with lower levels of obesity who are somewhat closer to the cut-off for normal weight status would be more prone to weight underestimation those with a greater degree of obesity. It is also possible that a portion of the heightened participation in health behaviors among underestimators may have been due to the limitations of BMI as a measure of obesity in adolescents, rather than a direct perception-behavior relationship. In addition to improved assessment of health behavior participation, future study in this area will benefit from including multiple fitness indicators.

Other limitations included the correlational nature of the analyses, thereby precluding any conclusions about the causal relationships among variables. The sample was obtained from a predominantly rural school district and therefore cannot be assumed to be representative of the U.S. adolescent population. Furthermore, due to the school districts’ concerns with privacy issues, there were no racial or socioeconomic data available to further determine generalizability and the potential influence of these important variables. Interpretation of these findings is also limited to 7 ^th and 11 ^th graders and the results cannot be assumed to be representative of the entire adolescent developmental spectrum.

Implications

Despite this study’s limitations, results supported a hypothesis about the role of weight perception in a sample of obese adolescents. The associations between accurate self-perception and lower rates of health behaviors and lower self-efficacy in one’s ability to participate in these behaviors suggest a potential mechanism that may create barriers to weight loss efforts among some obese adolescents. The proposed mechanism may be similar to the stereotype threat that has been found to lead to the underperformance of minority students on academic skills tests when their minority status is made salient. Similar observations have been observed among female students who have demonstrated underperformance on math tests when their self-awareness of their gender status is raised³⁵. The strong associations between self-efficacy and participation in healthy weight loss behaviors suggest that this factor may deserve special focus in prevention and intervention efforts. As further indication of the importance of this variable, self-efficacy was found to at least partially mediate the relationship between weight perception and the health behaviors.

We speculate that interventions that foster self-efficacy in regard to weight loss behaviors may be a relatively more effective strategy than focusing on increasing self-awareness of obesity and the associated risks. Programs that provide opportunities for supervised instruction and coaching while supporting and encouraging student participation may be particularly beneficial for adolescents who are self-aware of their obese status. Research on stereotype threat offers encouraging support for the notion that relatively straightforward steps can be taken to overcome negative self-perceptions^36,37, which suggests that it would be possible to reduce the potential deleterious influence of self-perception on health behavior participation. Also, given that self-recognition of one’s obesity status does not render adolescents more likely to participate in health behaviors, interventions should seek to tap into and to further develop the intrinsic motivations, such as enjoyment, competition, and opportunity for socialization, that may be more important in facilitating participation. Nonetheless, the direct effects of both weight perception and self-efficacy should be considered when attempting to understand and predict which obese adolescents are likely to engage in health behaviors.

This study has provided preliminary insights into the relationship between obesity and weight perception among adolescents, but the implications of the findings should remain tentative at this point due to the limitations of this study design. It is uncertain whether weight perception has played a meaningful role in contributing to the current adolescent obesity epidemic. Future studies are necessary to further determine and the most effective ways for intervention efforts to address the issue of misperception.

Acknowledgements

The authors want to thank Donna Decker, Jack Dennis, Elizabeth Hanna, and Joseph Glutting for their assistance with this manuscript. This project was completed to meet the research requirement for Dr. Thunfors’ clinical psychology internship at Temple University’s College of Health Professions.