Research article
Self-efficacy and Norm Measures for Lunch Fruit and Vegetable Consumption are Reliable and Valid Among Fifth Grade Students

https://doi.org/10.1016/j.jneb.2006.06.006Get rights and content

Abstract

Objective

To determine the reliability and validity of a questionnaire measuring fruit and vegetable (FV) self-efficacy and social norms during school lunch among 5th graders.

Design

In this cross-sectional study, students completed lunch food records and a psychosocial questionnaire measuring school lunch FV self-efficacy and social norms regarding consumption during the fall and spring semesters. Test-retest reliability was assessed between fall and spring semesters. The measurement model was cross-validated in the spring data.

Setting

One middle school in Houston, Texas.

Participants

275 fifth graders in the 1998 fall semester and 262 of these fifth graders in the 1999 spring semester.

Main Outcome Measures

FV consumption and psychosocial variables.

Analyses

Principal components analyses, confirmatory factor analyses and bivariate correlations.

Results

Three scales were identified: Fruit Self-Efficacy, Vegetable Self-Efficacy, and FV Social Norms. FV self-efficacy were positively correlated with low-fat vegetable and fruit consumption. Social norms were positively correlated with total vegetable, low-fat vegetable, fruit and total FV consumption.

Conclusions and Implications

Self-efficacy and norms for eating FV at school lunch are related to lunch FV consumption. Increasing self-efficacy and social norms about consuming FV at school appears to be important targets to improve FV consumption.

Introduction

Fruit and vegetable (FV) consumption decreases the risk for chronic diseases, including heart disease and several cancers1, 2, 3, 4 and facilitates weight management.5 Despite these substantial health advantages, FV consumption among adolescents is less than recommended.6, 7, 8 Moreover, nearly 25% of vegetables consumed by adolescents are french fries,9 which have high levels of dietary fat.

Nationally, the National School Lunch Program (NSLP) daily provides approximately one-third of calories consumed by all NSLP participants.10 Although the one serving of fruit and the one vegetable serving usually included in the NSLP meal10, 11 provide a substantial percentage of the total FV consumed by elementary school students,12 FV consumption declines with age, even in the school environment.13, 14, 15, 16, 17 This decline is partly attributable to the NSLP-competing alternatives, such as the snack bar line that becomes available when students enter middle school.16, 17

There are multiple influences on adolescents’ eating behaviors, and the relationships can be complex.18 For the development of effective interventions designed to increase their consumption, identifying and understanding factors that influence FV consumption are necessary. Self-efficacy, or the belief in one’s ability to engage in a behavior, plays a key role in behavior effort and persistence.19 Social norms are what is or is not expected as appropriate behavior. Subjective norms are based on one’s judgment about whether or not others will approve of his or her behavior.20 Self-efficacy19 and social norms for eating FV influence consumption.21, 22 Although several investigations have examined the reliability and validity of questionnaires measuring self-efficacy and social norms for consuming FV in general, none has examined these variables specific to the school lunch setting, which poses substantial peer challenges and alternative food temptations. The present study examines the reliability and validity of a questionnaire that measured self-efficacy and social norms for consuming FV during school lunch among fifth grade students when they were first introduced to alternatives to the NSLP such as the school snack bar.

Section snippets

Methods

This study was approved by the Institutional Review Board of the University of Texas M. D. Anderson Cancer Center.

Data preparation

Analyses were conducted on data from the same students collected in 1998 (n=275) and 1999 (n=262). To minimize the effects of using 3-category and 4-category response scales, questionnaire items were normalized by subtracting the item mean from the participant’s item value and dividing the difference by the item standard deviation (ie, [participant’s item value − item mean]/SD), and items within scales were averaged. Servings of FV were summed for each day, and the mean number of servings for

Results

The respondents (N=275) were 42% male, 13% AA, 27% MA, 49% EA, and 11% AO (Table 2). The percentages by ethnicity were similar to those in the population, but the percentage of males was lower than in the population. Descriptive statistics were generated for fall 1998 lunch consumption data (bottom of Table 2). Average student consumption of FV and total FV at school lunch was less than one serving per day.

Factor loadings, Cronbach α reliabilities, scale test-retest, and scale means and

Discussion

This study examined the reliability and validity of an instrument measuring self-efficacy and social norms for eating FV at school lunch among fifth grade students who were recently introduced to NSLP alternatives. Confirmatory factor analyses were used to cross-validate that the factors emerging from the 1998 PCA would appropriately load on the respective latent variables using the spring 1999 data. Future research should explore the changes in self-efficacy and norms over time in the

Implications for research and practice

Self-efficacy and social norms for eating FV at school lunch demonstrated acceptable reliability and validity among fifth grade students. Interventions to increase FV consumption should increase school lunch FV self-efficacy. Strategies to alter norms so that they reflect desirable behaviors should be investigated. Future studies should focus on testing these social norm questions in different age groups to determine how social norms develop over time, and how they impact consumption.

Acknowledgments

This project has been funded in part by federal funds from the USDA/ARS under Cooperative Agreement No. 58-6250-6001. This work was also supported by grants CA88511 and CA88511-01S1 from the National Cancer Institute. The author wishes to thank Drs. Virginia Kennedy, Asha Kapadia, and Jeanne Martin of the University of Texas Health Science Center School of Public Health. This work is a publication of the USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of

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