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Self-identities and BMI of Minnesotan Soy Consumers and Non-consumers Tamara Schryver,* Chery Smith,* and Melanie Wall†

Abstract SCHRYVER, TAMARA, CHERY SMITH, AND MELANIE WALL. Self-identities and BMI of Minnesotan soy consumers and non-consumers. Obesity. 2007;15: 1101–1106. Objective: The purpose of this study was to identify selfidentities among mainstream and natural foods shoppers and the relationship of these self-identities to soy consumption and BMI. We hypothesized that soy consumers (SCs) would have lower BMIs than non-consumers (NCs) and that persons who self-identify themselves as SCs, natural foods, organic foods, health conscious, whole foods consumers, and vegetarians would have higher intakes of soy. Research Methods and Procedures: A validated soy foods frequency questionnaire was administered to 298 adult mainstream and natural foods grocery store shoppers in Minneapolis/St. Paul, MN. An additional survey gathered information on consumers’ self-identification with several dietary and lifestyle descriptors. Principal component analysis was used to extract factors representing overarching self-identities. Correlation coefficients between derived scales for each factor and BMI and soy servings per week were generated using a Spearman correlation. One-way ANOVA was used to test significance between derived scales for factors and demographic variables and store type. Multiple regression models were used to test association between derived scales and BMI and soy servings per week while adjusting for demographic covariates. Results: Asians and those who shopped at natural food grocery stores consumed more soy foods and had lower BMIs than other ethnicities or those who shopped at mainstream grocery stores. Five overarching self-identities were found: vegetarian, mainstream, nouveau gourmet, pleasure, and bargain. Vegetarian and nouveau gourmet self-identi-

Received for review June 27, 2005. Accepted in final form November 11, 2006. *Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota; and †Department of Biostatistics, University of Minnesota, Minneapolis, Minnesota. Address correspondence to Chery Smith, Department of Food Science and Nutrition, Room 161, University of Minnesota, 1334 Eckles Avenue, St. Paul, MN 55108. E-mail: [email protected] Copyright © 2007 NAASO

ties consumed significantly greater amounts of soy foods and had significantly lower BMIs, whereas mainstream self-identities consumed significantly less soy foods and had significantly higher BMIs. Discussion: Self-identities influence soy food consumption and BMI. Key words: soy, self-identity, consumption, BMI, shopping

Introduction Self-identity is the self-image that people assign to themselves to define their views and place in society (1) and, when examined in the context of eating behavior, appears to drive distinct dietary eating patterns that confer health benefits or risks including the maintenance of body weight (2). Self-identity is not only important in terms of predicting current food choices, but it also appears to initiate and sustain change in patterns of eating related to permanent weight loss (3). Evidence suggests regular soy consumers (SCs)1 have lower BMIs than non-consumers (NCs) (4), although in human weight loss studies designed to compare soy-based diets with casein or traditional-based diets, there is generally no difference in weight loss between the two (5). Regular soy consumption may be an indicator of a healthy lifestyle that includes management of BMI. The purpose of this study was to identify patterns of self-identity among mainstream and natural foods shoppers and the relationship of these patterns to actual soy consumption and BMI using factor analysis [principal component analysis (PCA)]. We hypothesized that SCs would have lower BMIs than NCs and that persons who self-identify themselves as SCs, natural foods consumers, organic foods consumers, health conscious consumers, whole foods consumers, and vegetarian or vegan would have higher intakes of soy foods. The relevance of this study is that it describes

1 Nonstandard abbreviations: SC, soy consumer; NC, non-consumer; PCA, principal component analysis.

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Self-Identities and BMI of Soy Consumers, Schryver, Smith, and Wall

self-identities of SCs and NCs as they relate to BMI, which could be useful in determining long-term indicators of successful weight maintenance.

Research Methods and Procedures Two hundred ninety-eight adults completed soy behavior and consumption surveys in three mainstream and two natural food cooperatives within Minneapolis/St. Paul, MN. Content of the survey tool was developed based on a review of the literature and 12 focus groups conducted with SCs and NCs (6). The survey was evaluated for content and face validity,2 breadth of coverage, readability (Flesch-Kincaid readability grade level was 5), and reliability using the test-retest method and was shown to be a valid and reliable tool for measuring self-identities. Demographic information collected included age, gender, ethnicity, income, and education. Participants were asked to rate their level of agreement using a five-point Likert scale with statements like “I consider myself a health conscious consumer,” “a vegetarian or vegan,” “a fast food consumer,” and so on, for 16 types of self-identities. Soy consumption was assessed using a validated soy foods frequency questionnaire (7), which was shortened to exclude soy sauce and soy supplements because soy sauce is a food of minimal nutritional value and soy supplements are not foods. On completion of the survey, participants’ heights and weights were taken. This study was approved by the University of Minnesota’s Institutional Review Board for Research involving Human Subjects. Data were analyzed using the SPSS/PC statistical program (version 10.0 for Windows; SPSS, Inc., Chicago, IL). Data on soy servings per week were non-normally distributed; therefore, a square root transformation was applied before analysis. One-way ANOVA was used to test for mean differences in soy servings per week and BMI by demographic variables. A Pearson correlation matrix comparing BMI and soy servings per week was generated, and tests for significant correlation were performed. PCA was used to extract the initial factors using an orthogonal rotation. PCA input variables were each of the 16 self-identities. Correlation coefficients between derived scales for each factor and BMI and soy servings per week were generated using a Spearman correlation. One-way ANOVA was used to test significance between derived scales for factors and demographic variables and store type. Multiple regression models were used to test association between derived scales for factors and the two outcomes, BMI and soy servings per week, while adjusting for demographic covariates. All hypotheses were tested at the p ⬍ 0.05 level of significance. 2 Content validity refers to the degree to which the scores yielded by a test adequately represent the content, or conceptual domain, that these scores purport to measure. Face validity is only a casual, subjective inspection of the test items to judge whether they cover the content that the test purports to measure (19).

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Results The majority of participants were white with at least some college or technical school education, and income levels were well distributed (Table 1). Asians consumed significantly more soy foods than other ethnic groups, selfdefined SCs consumed significantly more soy foods than NCs, and those who shopped at natural food cooperatives had higher levels of soy consumption compared with mainstream grocery store shoppers (Table 1). The mean BMI for the total sample was 27.2 ⫾ 5.8, with 57% of the sample categorized as overweight or obese (Table 1). Asians and self-defined SCs had significantly lower BMIs than blacks or other ethnicities and NCs did, whereas those shopping at a natural foods cooperative had significantly lower BMIs than those shopping at a mainstream grocery store (Table 1). BMI was significantly negatively correlated with health consciousness, vegetarian, natural foods, organic, and soy foods self-identities and significantly positively correlated with traditional, mainstream, fast foods, and bargain selfidentities. Soy consumption was significantly positively correlated with health conscious, vegetarian, whole foods, natural, organic, soy foods, religious, and gourmet selfidentities but significantly negatively correlated with traditional and mainstream self-identities and BMI. The five factors retained explained 60.8% of the total variability (Table 2). The proportion of variance explained by each factor was 17.1%, 14.3%, 13.9%, 8.3%, and 7.2%, for Factors 1 through 5, respectively. Factor 1 was labeled vegetarian, and the associated scale contained health conscious, vegetarian, and soy foods self-identities. Factor 2 was labeled mainstream, and the scale contained convenience, traditional, mainstream, fast foods, and sweet and salty self-identities. Factor 3 was labeled nouveau gourmet, and the derived scale included whole foods, natural foods, organic foods, and gourmet self-identities. The scale from Factor 4 contained pleasure and picky and religious selfidentities in the negative direction, which was subsequently named pleasure, whereas factor 5 contained only the bargain self-identity and was labeled bargain. There was a significant positive correlation between BMI and the mainstream and bargain factors, whereas a significant negative correlation existed between BMI and the vegetarian and nouveau gourmet factors. Soy consumption was directly correlated to the vegetarian and nouveau gourmet factors but inversely correlated to the mainstream factor. The vegetarian factor was significantly higher in women than men. There was a significant decrease in the mainstream factor with increasing age and a significant increase in the nouveau gourmet factor with increasing age. The pleasure factor was significantly higher for whites and other race ethnicities compared with blacks and Asians. The bargain factor was significantly lower for Asians compared with whites, blacks, and other race ethnicities. Education was significantly associated with an increase in the vege-


Table 1. Distribution of demographic characteristics, mean soy servings per week, and BMI in study sample Variable Total Gender Men Women Age 17 to 34 yrs 35 to 49 yrs 50 to 64 yrs 65 to 80 yrs Ethnicity/race§ White Black Asian Other* Education ⬍12th grade Completed high school Some college/technical school Completed college/technical school Completed graduate/professional school Income§ ⬍$10,000 $10,000 to $19,999 $20,000 to $39,999 $40,000 to $59,999 $60,000 to $84,999 ⬎$85,000 Store type Mainstream grocery Natural foods cooperative Self-identification as soy consumer Soy foods consumer Non-soy foods consumer

N

%

Mean soy servings/wk†‡

298

Mean BMI†

2.76 ⫾ 2.69

27.17 ⫾ 5.75

131 167

44.0 56.0

2.62 ⫾ 2.95 2.86 ⫾ 2.50

27.26 ⫾ 5.28 27.10 ⫾ 6.10

129 81 72 16

43.3 27.2 24.2 5.4

2.79 ⫾ 3.02 2.53 ⫾ 2.59 2.96 ⫾ 2.66 2.92 ⫾ 1.19

25.72 ⫾ 4.76a 28.02 ⫾ 5.86b 28.04 ⫾ 6.21b 30.67 ⫾ 7.52b

234 30 16 17

78.5 10.0 5.4 5.7

2.25 ⫾ 1.99a 4.12 ⫾ 5.57a 11.02 ⫾ 6.00b 2.31 ⫾ 1.54a

26.97 ⫾ 5.59ab 29.10 ⫾ 5.69a 24.08 ⫾ 4.00b 29.52 ⫾ 7.85a

6 23 93 111

2.0 7.7 31.2 37.2

3.03 ⫾ 4.54 2.46 ⫾ 3.84 2.89 ⫾ 3.28 2.10 ⫾ 1.77

27.18 ⫾ 7.81 28.04 ⫾ 6.59 27.42 ⫾ 6.59 26.72 ⫾ 4.82

65

21.8

4.00 ⫾ 2.86

27.27 ⫾ 5.75

31 40 69 73 38 38

10.4 13.4 23.2 24.5 12.8 12.8

1.93 ⫾ 1.85 3.06 ⫾ 2.79 4.12 ⫾ 4.37 2.59 ⫾ 2.25 1.39 ⫾ 1.21 2.92 ⫾ 2.92

26.09 ⫾ 5.41a 25.94 ⫾ 5.09ab 28.37 ⫾ 5.86ab 26.42 ⫾ 5.32a 29.80 ⫾ 7.18b 26.52 ⫾ 4.26ab

174 124

58.4 41.6

2.25 ⫾ 3.03a 3.53 ⫾ 2.16b

28.10 ⫾ 5.92a 25.86 ⫾ 5.25b

94 204

31.5 68.5

8.76 ⫾ 1.61a 1.12 ⫾ 1.64b

25.52 ⫾ 4.93a 27.93 ⫾ 5.94b

SD, standard deviation. ab Values not sharing the same superscript denote significant differences among variables within the same column. * Other includes Hispanic, American Indian, and mixed/other. † Mean ⫾ SD. ‡ Mean ⫾ SD values computed using transformed data. § One person did not respond to the ethnicity question, and nine people did not respond to the income question.

tarian, nouveau gourmet, and pleasure factors and significantly associated with a decrease in the mainstream and bargain factors. Increasing income was significantly associated with a decrease in the bargain factor. All factors were

statistically significantly different between mainstream grocery and natural foods cooperative shoppers, with the vegetarian, nouveau gourmet, and pleasure factors being higher in natural foods cooperative shoppers and mainstream and OBESITY Vol. 15 No. 5 May 2007

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Table 2. Rotated factor loadings for sub-identities identified by principal component analysis* Factor 1: vegetarian

Factor 2: mainstream

Factor 3: noveau gourmet

Factor 4: pleasure

Factor 5: bargain

17.14

14.29

13.86

8.30

7.18

0.43† 0.82† ⫺0.01 0.34 ⫺0.73 0.47 0.47 ⫺0.42 0.73† 0.06 ⫺0.03 ⫺0.30 ⫺0.02 0.03 0.03 ⫺0.03

⫺0.33 ⫺0.06 0.74† ⫺0.25 0.44† ⫺0.20 ⫺0.16 0.40† 0.16 0.08 0.24 0.79† 0.58† 0.29 0.07 ⫺0.11

0.43 0.10 ⫺0.17 0.44† 0.05 0.62† 0.62† ⫺0.05 0.37 0.18 ⫺0.10 ⫺0.14 ⫺0.25 0.26 0.04 0.83†

0.13 ⫺0.16 ⫺0.13 0.10 ⫺0.13 0.16 0.24 ⫺0.16 0.10 0.42† ⫺0.75† 0.01 0.53 ⫺0.30† 0.14 ⫺0.01

⫺0.01 0.06 0.07 0.01 0.03 ⫺0.27 ⫺0.31 0.27 0.04 0.14 0.03 ⫺0.01 0.08 0.08 0.91† 0.17

Variance explained (%) Factor loadings Health conscious identity Vegetarian identity Convenience identity Whole foods identity Traditional foods identity Natural foods identity Organic foods identity Mainstream identity Soy foods consumer Pleasure identity Picky identity Fast foods identity Sweet and salty identity Religious identity Bargain identity Gourmet identity

* Varimax rotation with Kaiser normalization. † Item included in the derived scale for the respective factor.

bargain factors being low. After adjusting for gender, age, race, education, and income, the vegetarian, mainstream, and nouveau gourmet factors were still significantly associated (in the expected directions) with BMI and soy consumption, but the bargain factor was no longer significantly associated with BMI.

Discussion This study investigated self-identities of SCs and NCs in mainstream and natural foods grocery stores and identified five major dimensions to eating patterns, vegetarian, mainstream, nouveau gourmet, pleasure, and bargain, and their relationship to BMI and weekly soy consumption. The major findings from the factor analysis were as follows: The vegetarian factor, which combined the health conscious, vegetarian, and soy food consumer identities, was associated with decreased BMI and increased soy foods consumption. The mainstream factor, which combined the convenience, traditional foods, mainstream, fast foods, and sweet and salty consumer identities, was associated with increased BMI and decreased soy food consumption. The nouveau gourmet factor, which combined the whole foods, natural foods, organic foods, and gourmet identities, was found to be associated with decreased BMI and increased soy food 1104


consumption. Natural foods shoppers scored higher on the vegetarian, nouveau gourmet, and pleasure factors and had higher intakes of soy and lower BMIs than mainstream grocery shoppers. To our knowledge, this is the first study to identify self-identity eating patterns of SCs and NCs and how they relate to BMI and actual soy consumption. The vegetarian factor contained subidentities of eating patterns indicative of an all-encompassing lifestyle that focused on personal health and a philosophy related to vegetarianism. Past research on food choice determinants has found associations between health consciousness and vegetarianism (8 –10), vegetarianism and soy intake (11,12), and health consciousness and soy intake (13). This reinforces the cohesiveness of this study’s factor loadings for the vegetarian factor and suggests that it may be possible to use one overarching eating pattern to explain coexisting self-identity eating patterns. Further, although regular soy consumption, vegetarianism, and health consciousness have individually been associated with a lower BMI (14 –18), this study is the first to relate all of them to a lower BMI and actual soy consumption as measured by the soy foods frequency questionnaire. The vegetarian eating pattern may be a way to organize values that people not only believe are important, but believe are relevant in defining their own


sense of being. Weight control and regular soy consumption seem to be beneficial by-products of this self-identity eating pattern rather than actual endpoints. In contrast, the mainstream factor was comprised of the convenience, traditional, mainstream, fast foods, and sweet and salty subidentities. Soy consumption was significantly lower in the mainstream factor, suggesting a lack of familiarity or comfort with soy or a dislike that resulted in an exclusion of soy foods from the eating pattern. Although mainstream and traditional foods are not inherently higher in calories than other foods, the higher BMI found in the mainstream eating pattern is most likely a reflection of the inverse correlation between health consciousness and each of the subidentities contained with the mainstream factor. This implies that the health conscious subidentity, which had a high factor loading for the vegetarian eating pattern but low factor loading for mainstream eating pattern, carried with it some parameter of weight control. Soy consumption was found to increase with rising nouveau gourmet factor scores, which implies that vegetarians are not the only sector of consumers to enjoy soy food consumption. The nouveau gourmet factor appears to be an eating pattern that emphasizes non-traditional food choices, captured by the subidentities of whole foods, natural foods, and organic foods, as a way to enhance advanced food preparation skills. In addition, soy foods may be viewed as more of a gourmet-type food, which ensures a degree of regular consumption. The differences among self-identity eating patterns between mainstream and natural foods cooperative shoppers corresponded well to their respective store type. Natural foods cooperative shoppers had higher vegetarian, nouveau gourmet, and pleasure factor scores and lower mainstream and bargain factor scores than mainstream grocery shoppers. Additionally, they consumed significantly more soy foods than mainstream grocery shoppers consume and had lower BMIs. However, soy foods were equally available for purchase in the mainstream grocery store the survey was conducted in and had the same depth of variety and quantity of products compared with the natural foods cooperative, yet soy consumption, the vegetarian and nouveau gourmet self-identities, and BMI were more favorable in the natural foods cooperative. Fifty percent of consumers in the mainstream grocery store consumed one or more servings of soy foods per week compared with 68% of consumers in the natural foods cooperative. Store type (natural food cooperatives vs. mainstream grocery stores) may provide additional insight about a shopper’s eating patterns. However, it is unclear whether store type could be used as a means to provide eating patterns information for all members of the household. More research is needed to determine whether shopper self-identities affect family member self-identities.

Our study indicates that the construct of self-identity can be applied to eating and shopping behavior, and the eating patterns we derived showed meaningful associations with soy consumption and weight. Although using a cross-sectional study design and a convenience sample are study limitations, this study takes an original approach to examining the relation between self-identity eating patterns and weight, and the findings suggest that future interventions should consider consumer shopping behavior and possibly store type.

Acknowledgments We thank Mississippi Market, St. Paul, MN, and Roundy’s Inc./Rainbow Food grocery stores, Minneapolis/ St. Paul, MN, for allowing us to conduct focus groups in their stores. We thank all the participants for generously agreeing to participate in our study. Student salary was paid, in part, by the Agricultural Experiment Station of the University of Minnesota. No additional funding was received for this project. References 1. Goyder J. Measuring social identities: problems and progress. Intl J Publ Opin Res. 2003;15:180 –91. 2. Newby PK, Tucker KL. Empirically derived eating patterns using factor or cluster analysis: a review. Nutr Rev. 2004;62: 177–203. 3. Kearney MH, O’Sullivan J. Identity shifts as turning points in health behavior change. Western J Nursing Res. 2003;25: 134 –52. 4. Greenwood DC, Cade JE, Draper A, Barrett JH, Calvert C, Greenhalgh A. Seven unique food consumption patterns identified among women in the UK Women’s Cohort Study. European J Clin Nutr. 2000;54:314 –20. 5. Anderson JW, Luan J, Hoie LH. Structured weight-loss programs: meta-analysis of weight loss at 24 weeks and assessment of effects of intervention intensity. Adv Therapy. 2004;21:61–75. 6. Schrvyer T, Smith C. Attitudes and behaviors of soy consumers versus non-consumers in natural foods or mainstream grocery stores towards soy food consumption. J Nutr Educ Behav. 2005;37:292–9. 7. Frankenfeld CL, Patterson RE, Kalhorn TF, Skor HE, Howald WN, Lampe JW. Validation of soy food frequency questionnaire with plasma concentrations of isoflavones in US adults. J Am Diet Assoc. 2002;102:1407–13. 8. Lea E, Worsley A. Benefits and barriers to consumption of a vegetarian diet in Australia. Public Health Nutr. 2003;6:505– 11. 9. Lindeman M, Stark K. Pleasure, pursuit of health or negotiation of identity? Personality correlates of food choice motives among young and middle-aged women. Appetite. 1999; 33:141– 61.


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