关键词: "瘦理想"社会规范, 积极身体意象, 自我差异, 纠正误解, 榜样

Abstract: Under the influence of the mass media, many individuals have embraced the “thin-ideal” social norm, wherein people accept and adhere to the behavioral norm that perceives thinness as the ideal body type. This trend has resulted in many young adults compromising their positive body image and adopting unhealthy weight loss practices, such as reducing their caloric intake. Based on the self-discrepancy theory, this paper proposes that the thin-ideal social norm will strengthen the thin-ideal self-concept, which will amplify any existing discrepancy between the ideal self and the actual self, ultimately diminishing the individual’s positive body image. In that light, the present research explored the effects of social norm interventions on improving young adults’ positive body image and increasing their caloric intake. The findings suggest that interventions that address misconceptions, particularly when combined with role models, yield more favorable outcomes than interventions that focus solely on correcting misunderstandings within the social norm framework do.
The present research comprised one questionnaire study and three intervention studies, involving 612 participants. Study 1 examined the mediating role of body mass index (BMI) self-discrepancy in the relationship between the thin-ideal social norm and a positive body image. Two hundred eleven participants (113 females, aged 22.31 ± 2.10 years) completed questionnaires assessing their perceptions of the social norms, their BMI self-discrepancy, and their positive body image. Studies 2~4 were dedicated to practical interventions. In Study 2, 117 participants (79 females, aged 22.56 ± 2.28 years) received either interventions that addressed misinformation about social norms, or no information. The participants reported their positive body image at the beginning and end of the study, along with their caloric intake over 4 days. Study 3 involved 155 participants (111 females, aged 22.06 ± 2.13 years) who were randomly assigned to one of three interventions: correcting misunderstandings alone, combining that intervention with role models, or no intervention. As was the case with Study 2, the participants reported their positive body image and caloric intake over 4 days. In Study 4, 147 participants (89 females, aged 22.57 ± 2.10 years) were randomly assigned to one of three interventions that were similar to those in Study 3 but spanned 10 days. Those participants reported their body image at two time points and their caloric intake at five time points.
Study 1 revealed that self-discrepancy partially mediated the relationship between the social norms of the thin ideal and body image. Specifically, both the thin-ideal descriptive and injunctive social norms could reduce body image by increasing the self-discrepancy between ideal BMI and real BMI. Building upon Study 1, Study 2 revealed that the instructive social norm intervention demonstrated a positive impact on caloric intake, compared with no intervention, but not on positive body image, and its effectiveness was limited to correcting misunderstandings. Motivated by the insights from Study 2, Studies 3 and 4 advanced the research by adopting more robust descriptive social norm interventions and also employing descriptive social norm interventions that incorporated role models. Study 3 showed that both interventions had better effects on positive body image and caloric intake than no intervention did. In Study 4, among groups adhering to restrictive diets, the application of the norm-based intervention did not yield a significant improvement in positive body image. However, the findings suggest that the descriptive social norm interventions which incorporated role models exhibited not only a better impact but also a more sustained and prolonged duration of intervention effectiveness on caloric intake.
This research contributes valuable insights into thin-ideal social norms. It suggests a more effective intervention strategy that provides practical recommendations which are applicable to individuals, role models, and commercial organizations.

Key words: "thin-ideal" social norm, positive body image, self-discrepancy, correcting misperception, role model