Five-Factor Model Personality Traits and the Objective and Subjective Experience of Body Weight

Journal of Personality ••:••, •• 2014 © 2014 Wiley Periodicals, Inc.

DOI: 10.1111/jopy.12143

Angelina R. Sutin and Antonio Terracciano Florida State University College of Medicine

Abstract Research on personality and adiposity has focused primarily on middle-aged and older adults.The present research sought to (a) replicate these associations in a young adult sample, (b) examine whether sex, race, or ethnicity moderate these associations, and (c) test whether personality is associated with the subjective experience of body weight and discrepancies between perceived and actual weight. Participants (N = 15,669; Mage = 29; 53% female; ∼40% ethnic/racial minority) from Wave 4 of the National Longitudinal Study of Adolescent Health completed a Five-Factor Model personality measure and reported their weight, height, and perception of weight category (e.g., overweight); trained staff measured participants’ height, weight, and waist circumference. Conscientiousness was associated with healthier weight, with a nearly 5 kg difference between the top and bottom quartiles. Neuroticism among women and Extraversion among men were associated with higher adiposity. Neuroticism was also associated with misperceived heavier weight, whereas Extraversion was associated with misperceived taller and leaner. The associations were similar across race/ethnic groups. Personality is associated with objective and subjective adiposity in young adulthood.Although modest, the effects are consistent with life span theories of personality, and the misperceptions are consistent with the conceptual worldviews associated with the traits.

It is estimated that approximately one in three American adults is obese (Flegal, Carroll, Kit, & Ogden, 2012). In addition to its effect on physical health (Wang, McPherson, Marsh, Gortmaker, & Brown, 2011), adiposity is implicated in psychological functioning. Body weight is, in part, physical evidence of an individual’s lifestyle (Mozaffarian, Hao, Rimm, Willett, & Hu, 2011), and, for many people, how they feel about themselves is interwoven with how they feel about their bodies (Tiggemann, 2005). The relation between psychological functioning and body weight is not unidirectional; psychological factors may likewise contribute to weight (Sutin & Zonderman, 2012). In particular, personality traits as defined by the Five-Factor Model (FFM) have been implicated in weight and weight gain (Jokela et al., 2013; Lahti et al., 2013), and weight has likewise been associated with trait development in adulthood (Sutin, Costa, et al., 2013). Such reciprocal relations suggest intimate transactions between mind and body. Much research on personality traits and body weight has focused on the association with body mass index (BMI) and other measures of adiposity (e.g., waist circumference). Less research has addressed whether personality traits are also associated with the subjective experience of body weight. In addition, most studies on personality and BMI have relied on predominantly older and predominantly White samples; less is known about whether there are similar associations in younger adulthood and across racial and ethnic minority populations.

To that end, the present research uses a large, diverse sample of young adults to examine the links between personality traits, measured adiposity, and subjective perceptions of body weight.

Personality Traits and Measured Adiposity Of the five traits, Conscientiousness—the tendency to be organized and disciplined—has the most consistent associations with BMI. Across different populations and measures of personality, higher Conscientiousness is associated with lower

This research uses data from Add Health, a program project directed by Kathleen Mullan Harris and designed by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris at the University of North Carolina at Chapel Hill, and funded by grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Special acknowledgment is due Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design. Information on how to obtain the Add Health data files is available on the Add Health website (http://www.cpc.unc.edu/addhealth). No direct support was received from grant P01-HD31921 for this analysis. Correspondence concerning this article should be addressed to Angelina R. Sutin, Florida State University College of Medicine, 1115 W. Call Street, Tallahassee, FL 32306. Email: [email protected].

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BMI (Chapman, Fiscella, Duberstein, Coletta, & Kawachi, 2009; Mõttus et al., 2013; Terracciano et al., 2009), lower risk of obesity (Jokela et al., 2013), and less weight gain across adulthood (Sutin, Ferrucci, Zonderman, & Terracciano, 2011). Conscientious individuals may weigh less because of their healthier lifestyle, including adherence to a healthy diet (Mõttus et al., 2013) and regular exercise (Hoyt, Rhodes, Hausenblas, & Giacobbi, 2009). The association between Neuroticism—the tendency to experience negative emotions—and body weight is more equivocal. Some studies find that individuals high in Neuroticism weigh more (Armon, Melamed, Shirom, Shapira, & Berliner, 2013) and are at greater risk of obesity (Magee & Heaven, 2011), but not all find this relation (Mõttus et al., 2013). There is also evidence that this relation may not be linear. Given that Neuroticism is a risk factor for eating disorders (Bulik et al., 2006), there may be a curvilinear association between Neuroticism and BMI. That is, those who are underweight, as well as those who are obese, may score higher in Neuroticism, obscuring the linear relation. As such, there may not be a simple, straightforward relation between Neuroticism and BMI. There is less evidence for the remaining three traits. The association between Extraversion—the tendency to be sociable—and BMI is negative in some samples (Kakizaki et al., 2008), positive in others (Armon et al., 2013; Sutin et al., 2011), and unrelated in yet others (Magee & Heaven, 2011). Some find a negative association between Openness— the tendency to be creative and open-minded—and BMI (Brummett et al., 2006; Magee & Heaven, 2011), and some find no relation (Chapman et al., 2009). Likewise, the association between Agreeableness—the tendency to be trusting and compassionate—and BMI is negative in some samples (Magee & Heaven, 2011) and unrelated in others (Armon et al., 2013). In addition to the main effect of personality on adiposity, the association between personality and BMI may vary by sex. A clear picture, however, has yet to emerge. Brummett and colleagues (2006), for example, found that Neuroticism was associated with higher BMI only for women, Extraversion was associated with higher BMI only for men, and that although Conscientiousness was associated with lower weight for both sexes, the association was stronger among women. These interactions have replicated in some samples (e.g., Jokela et al., 2013; Sutin et al., 2011) but not others (e.g., Terracciano et al., 2009; Magee & Heaven, 2011). In contrast to sex, no research has addressed directly whether the association between personality and adiposity varies by race and/or ethnicity. Some personality correlates of BMI, however, tend to be consistent across different populations (e.g., Conscientiousness and lower BMI among both rural Italians and urban Americans; Sutin et al., 2011; Terracciano et al., 2009; although not all find this relation; Shim et al., 2014). Other personality correlates tend to be more population specific (e.g., Extraversion is related to higher BMI among urban Americans but is unrelated to BMI among rural

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Italians). As such, the association between BMI and some traits may be more likely to vary by race/ethnicity than other traits.

Personality Traits and Subjective Body Weight There are a number of ways to conceptualize and measure the subjective experience of body weight. We focus on two: selfreported weight and height and perception of body weight category. It is often assumed that people do not answer honestly when asked about their weight, but there is a high correlation between reported and measured weight (r > .90) and reported and measured height (r > .90; McAdams, Van Dam, & Hu, 2007). These correlations indicate that even if people are not exactly accurate in how they report their measurements, they misreport them in a similar direction. That is, the relative ordering of individuals remains the same, even if there is bias in the mean level. As such, the correlations between personality and BMI based on self-reports should be similar to the correlations with measured BMI. These correlations, however, are not perfect, and the discrepancy between reported and measured weight/height is not random. In addition to demographic factors (Krul, Daanen, & Choi, 2011), misreported weight and height are associated with theoretically meaningful individual differences in psychological functioning (Sutin, 2013). For example, the worldviews of pessimists (who tend to see the worst) and optimists (who tend to see the best) shape the ways in which people report health-related information about themselves, including their weight: Individuals high in pessimism report that they weigh more than they actually weigh, whereas individuals high in optimism report that they weigh less than they actually weigh (Sutin, 2013). Other individual differences in psychological functioning are likely to be associated with this discrepancy, particularly Neuroticism and Extraversion, which are conceptually similar to pessimism and optimism. In addition, individuals who are conscientious tend to be precise and may thus be more accurate in how they report their weight and height. A second way to assess subjective body weight is to ask individuals to evaluate their weight category (e.g., overweight) and compare this perception with measured BMI categories. The concordance (or misperception) between perceived and measured weight category is one component of body image (Harris, King, & Gordon-Larsen, 2005). These selfperceptions are not always accurate, and there are consequences when perceptions do not match reality. These perceptions, for example, are associated with eating habits and physical activity, regardless of actual body weight: Adolescent girls who misperceive themselves as overweight engage in unhealthy dieting behavior, whereas adolescent girls who misperceive themselves as overweight do not engage in physical activity and do not monitor their food intake (Harris et al., 2005).

Personality and Body Weight

As with measured BMI and obesity, personality traits have been implicated in the subjective evaluation of body weight. Individuals high in Neuroticism, for example, tend to be dissatisfied with their bodies (Dionne & Davis, 2004), perceive a greater discrepancy between their actual and ideal bodies (Swami et al., 2013), and are more preoccupied with their weight (Davis, Shuster, Blackmore, & Fox, 2004), whereas individuals high in Extraversion report greater appreciation of their bodies, a greater congruence between actual and ideal body weight (Swami et al., 2013), and greater satisfaction with their appearance (Kvalem, von Soest, Roald, & Skolleborg, 2006). Less research has addressed how other traits are associated with aspects of body image, but given that conscientious individuals have a need to conform to rules and norms, they may be more likely to conform to the desirable weight category (i.e., normal weight). Research on subjective weight and body image has focused mostly on women. There are reasons for this singular focus. Women, for example, tend to feel worse about their bodies than men (Feingold & Mazzella, 1998), which increases risk for depression and health-risk behaviors (Johnson & Wardle, 2005). Despite mean-level differences between men and women, there is significant variability in subjective evaluations of the body within sex. Men do report discrepancies between their actual and ideal bodies, which is linked to depression (Olivardia, Pope, Borowiecki, & Cohane, 2004) and healthrisk behaviors (Kanayama, Barry, Hudson, & Pope, 2006). There are also mean-level differences in body image by ethnicity, although these differences tend to be small compared to differences between the sexes (Grabe & Hyde, 2006). Even with mean-level differences in body image, however, the predictors of body image may not differ by ethnicity or sex (Smith, Thompson, Raczynski, & Hilner,1999). Whether the association between personality traits and subjective body weight varies by sex and ethnicity has yet to be examined.

The Present Study The present research uses a large, diverse sample of young adults to address the relation between personality traits, objective and subjective adiposity, and discrepancies between actual and perceived body weight. First, we examine the associations between personality traits and measured BMI and waist circumference. Based on previous research, we expect individuals lower in Conscientiousness to have more adiposity. Given the mixed findings on the other four traits, we do not make specific predictions about their association with measured adiposity. Second, we examine whether the five traits are associated with misreporting body weight and height. Based on the finding that optimistic individuals perceive themselves as thinner and taller and pessimistic individuals perceive themselves as heavier and shorter (Sutin, 2013), we expect Extraversion and Neuroticism to show similar biases, respectively. Third, we examine how personality traits are associated with subjective body weight and discrepancies between perceived

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and actual body weight. Building on prior research on personality and body image (Swami et al., 2013), we expect that individuals high in Neuroticism will have greater discrepancies between their perceived and actual weight, whereas we expect the opposite associations for Extraversion and Conscientiousness. Finally, we examine demographic moderators of these associations. Specifically, we test whether the association between personality and BMI/subjective weight differs by sex and race/ethnicity. We construe these analyses as exploratory and do not make specific predictions.

METHOD Participants Participants were drawn from the National Longitudinal Study of Adolescent Health (Add Health). Participants in Add Health were recruited as a nationally representative sample of adolescents in the United States in grades 7–12 during the 1994– 1995 school year. The original sample has been followed up three times, with the fourth wave of data collection in 2008– 2009. The fourth wave was the first to include an FFM measure of personality traits (described below). A total of 15,669 participants had information available on personality and objective/subjective body weight. Due to missing data on some variables, the sample size ranged from 15,160 to 15,669. The results were identical when the analyses were restricted to only participants who had complete data on all study variables. The sample was, on average, 29 years old (Mage = 29.10, SD = 1.75; range = 25–34 years old), 53% female, 60.2% European American, 21.1% African American, 5.8% Asian American, 1.1% Native American, 7.9% other races, and 3.9% biracial; across all races, 15.9% of participants reported being of Hispanic origin. A previous study (Jokela et al., 2013) used a portion of the Add Health data (n = 4,957) as part of a meta-analysis on personality traits and obesity. The present research makes use of the full Add Health sample at Wave 4 (N = 15,669) and does not duplicate the analyses previously reported.

Measures Personality. Personality traits were assessed with the Mini International Personality Item Pool (Mini-IPIP; Donnellan, Oswald, Baird, & Lucas, 2006). This 20-item measure of the Big Five was developed for use in large-scale studies when time is limited. Each domain is measured with four items. Although the reliability tends to be lower than longer measures of the Big Five, the Mini-IPIP has demonstrated adequate reliability and validity in undergraduate populations (Donnellan et al., 2006), and specifically in Add Health (Baldasaro, Shanahan, & Bauer, 2013). In the current sample, the internal consistency alpha was .62 for Neuroticism, .71 for Extraversion, .65 for Openness, .70 for Agreeableness, and .65 for Conscientiousness.

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Adiposity. During the in-home interview, participants were asked to self-report their height and weight. Anthropometric measurements were taken by trained staff immediately after the interview. Participants were asked to remove their shoes and any bulky clothing. Height was measured to the nearest 0.5 cm using a steel tape measure, weight was measured to the nearest 0.1 kg using a Health-o-meter 844KL High Capacity Digital Bathroom Scale, and waist circumference was measured to the nearest 0.5 cm at the superior border of the iliac crest using a SECA 200 metric-increment circumference tape measure. Detailed information about the procedure for these measurements can be found in Entzel and colleagues (2009). Body mass index was derived in the standard way (kg/m2; Centers for Disease Control and Prevention, 2014) from both reported (M = 28.33, SD = 6.86) and measured (M = 29.14, SD = 7.54) weight and height. For some analyses, measured BMI was categorized into underweight (BMI < 18.5), normal weight (BMI = 18.5–24.99), overweight (BMI = 25–29.99), and obese (BMI ≥ 30). In this sample, 1.4% were underweight, 31.5% were normal weight, 30.1% were overweight, and 37% were obese. Men and women had a similar prevalence of obesity (36% and 38%, respectively), but women were more likely to be underweight (2% vs. 1%) or normal weight (34% vs. 28%), whereas men were more likely to be overweight (35% vs. 26%). These differences were statistically significant (χ2 = 202.34, p < .01). Misreported Weight/Height. Measured weight was subtracted from reported weight to assess misreported weight. Participants were classified into those who underestimated (n = 4,054) and overestimated (n = 2,161) their weight by at least 5 pounds, and those who reported their weight within 5 pounds of their actual weight (n = 9,037). Similarly, measured height was subtracted from reported height, and participants were classified into those who underestimated (n = 1,320) and overestimated (n = 4,063) their height by at least 1 inch, and those who were more accurate (n = 10,148). These cut points were chosen because previous research has indicated that the average reported weight is within 5 pounds of measured weight and the average reported height is within 1 inch of measured height (Krul et al., 2011). Perceived Weight Category. Perceived body weight category was assessed with the item “How do you think of yourself in terms of weight?” Participants responded on a scale ranging from 1 (very underweight) to 5 (very overweight). On average, participants reported that they were about average to slightly overweight (M = 3.62, SD = .84). Actual-Perceived Discrepancy. We followed Harris and colleagues’ (Harris et al., 2005) procedure to quantify the discrepancy between actual and perceived weight. Specifically, we coded measured BMI and subjective body weight into three categories: underweight, normal weight, and overweight for measured BMI and perceived underweight, perceived average

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weight, and perceived overweight for subjective body weight. From these categories, participants were classified into perceived heavier than actual weight (e.g., a participant of normal weight who perceived himself or herself to be overweight; n = 876), perceived lighter than actual weight (e.g., a participant who was overweight who perceived himself or herself to be normal weight; n = 3,232), and accurate (e.g., a participant who perceived and measured normal weight; n = 11,316). Discrepancy was also examined as a continuous variable (M = –.17, SD = .54). Positive values indicated participants perceived themselves as heavier than measured, whereas negative values indicated participants perceived themselves as lighter than measured.

Analytic Strategy We examined the association between personality traits and objective and subjective body weight in several ways. For objective body weight, we first used linear regression to predict the continuous measure of BMI and waist circumference from the five personality traits, controlling for age, sex, education, and race. We then used multivariate analysis of covariance (MANCOVA) to examine mean-level differences in personality across the four BMI categories, controlling for the same set of covariates. For subjective body weight, we again used linear regression to predict reported BMI and subjective weight from the personality traits, controlling for the demographic factors. We used logistic regression to examine whether the traits (independent variables) were associated with over- or underreporting weight and height compared to more accurate participants (dependent variables), and whether the traits (independent variables) were associated with perceiving one’s weight category as lighter or heavier than actual BMI category (dependent variables). We also ran the analyses using misreported weight/height and actual-perceived discrepancy as continuous variables. To examine whether these associations varied as a function of sex or race/ethnicity, we tested interactions between the traits and sex or race/ethnicity, controlling for the demographic variables and the main effect of personality. Due to the large sample size, we set p at .01.

RESULTS Measured Adiposity The associations between personality and measured adiposity are shown in Table 1. Consistent with previous research, Conscientiousness had the strongest and most consistent association with adiposity: Conscientious participants were leaner and had less abdominal adiposity. Participants in the lower quartile of this trait weighed, on average, nearly 5 kg more than participants in the highest quartile. There was also a small negative association between Agreeableness and adiposity;

Personality and Body Weight

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Table 1 Associations Between Personality Traits and Measured BMI Continuous Predictor Demographics Age Sex (female) Race African American Native American Asian American Multiracial Other Education Personality Neuroticism Extraversion Openness Agreeableness Conscientiousness

Categories

BMI

Waist

Underweight

Normal

Overweight

Obese

.05* .03*

.05* −.05*

28.60 (.12)* 74%*

28.96 (.02) 58%

29.15 (.03)* 45%*

29.19 (.02)* 55%*

.10* .04* −.03* .03* .04* −.11*

.04* .04* −.07* .01 .01 −.13*

21% 0% 9% 4% 3% 5.65 (.15)*

18% 1% 7% 4% 6% 6.00 (.03)

20%* 1% 6%* 4% 8%* 5.73 (.03)*

25%* 1% 4%* 4% 9%* 5.35 (.03)*

.02 .02 .00 −.02* −.09*

.02 .00 −.02 −.03* −.09*

10.65 (.18) 12.63 (.21)* 14.56 (.16) 15.21 (.16) 14.74 (.18)

10.40 (.04) 13.14 (.04) 14.56 (.03) 15.37 (.03) 14.87 (.04)

10.41 (.04) 13.28 (.04)* 14.44 (.04) 15.19 (.03)* 14.75 (.04)*

10.50 (.04) 13.27 (.04)* 14.48 (.03) 15.18 (.03)* 14.38 (.04)*

Note. BMI = body mass index. For the continuous analysis, ns range from 15,351 to 15,430. For the categorical analysis, n = 212 for underweight, n = 4,841 for normal weight, n = 4,619 for overweight, and n = 5,675 for obese.The sample size varies across analyses due to missing personality scores.Values for the continuous analysis are standardized beta coefficients from linear regressions. For the categorical analysis, values are estimated marginal means (standard errors) from MANCOVA. Both analyses control for age, sex, race, and education. For the categorical variables, male is the reference group for sex, and European American is the reference group for race. *p < .01.

antagonistic individuals weighed more. The mean-level differences in personality traits across the BMI categories paralleled the regression analyses: Participants who were overweight or obese tended to score lower in both Agreeableness and Conscientiousness than participants of normal weight (e.g., d = .18 for the difference between normal weight and obese for Conscientiousness). Although the linear association was not significant, overweight and obese participants scored higher in Extraversion, whereas underweight participants tended to be more introverted, compared to normal weight participants. The means for Neuroticism across the four BMI categories suggested a curvilinear association, but the means were not significantly different from each other. Several of these associations were moderated by sex. Neuroticism was unrelated to BMI/waist circumference among men, but women who reported a tendency to experience negative emotions had a higher BMI (βN x sex = .06, p < .01) and larger waist circumference (βN x sex = .05, p < .01) than more emotionally stable women. A similar pattern for Extraversion emerged in the opposite direction: Extraversion was unrelated to BMI or waist circumference among women, but extraverted men had both a higher BMI and larger waist circumference (βE x sex = –.03 and βE x sex = –.04, both ps < .01, respectively; the betas are negative because sex is coded as men = 0 and women = 1). Finally, sex moderated the association between Conscientiousness and BMI. A tendency to be organized and disciplined was associated with being leaner for both sexes, but the negative association was stronger among women (βC x sex = –.04, p < .01). Sex did not moderate the relation between Conscientiousness and waist circumference (βC x sex = –.02, ns).

There was less evidence that the association between personality traits and adiposity varied by race or ethnicity. The negative association between Conscientiousness and waist circumference was slightly stronger among Native American participants (βC x race = –.02, p < .01), and the negative association between Agreeableness and BMI did not hold for African American participants (βA x race = .03, p < .01). Hispanic ethnicity did not moderate any of the associations.

Subjective Weight The association between personality and measures of subjective body weight were similar to that of measured adiposity (Table 2). Conscientiousness correlated negatively with BMI derived from self-reported weight and height, an effect that was slightly stronger among women (βC x sex = –.03, p < .01). Similar to measured BMI, women who scored higher in Neuroticism had a higher self-reported BMI and perceived themselves to be heavier, whereas there was no association between Neuroticism and subjective weight for men (βN x sex = .05 and βN x sex = .07, both ps < .01, respectively); Extraversion likewise was associated with higher self-reported BMI among men, but not women (βE x sex = –.03, p < .01); sex did not moderate the association between Extraversion and perceived weight category. Similar to measured adiposity, there was a negative association between Agreeableness and reported BMI and subjective weight for all races/ethnicities, except for African American participants (both βA x race = .03, both ps < .01). In addition, the negative association between Agreeableness and reported BMI was slightly stronger for Asian American

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Table 2 Associations Between Personality Traits and Subjective Body Weight

Predictor Demographics Age Sex Race African American Native American Asian American Multiracial Other Education Personality Neuroticism Extraversion Openness Agreeableness Conscientiousness

Reported BMI

Perceived Weight Category

.05* .02

.05* .22*

.10* .04* −.04* .04* .04* −.11*

−.04* .02* −.01 .00 .04* −.03*

.02* .01 −.01 −.02 −.09*

.03* .00 .00 .00 −.08*

Note. BMI = body mass index.The ns range from 15,367 to 15,669 due to missing personality scores. Reported BMI is BMI derived from self-reported weight and height.Values are standardized beta coefficients from linear regressions controlling for age, sex, race, and education. For the categorical variables, male is the reference group for sex, and European American is the reference group for race. *p < .01.

participants (βA x race = –.02, p < .01). None of the associations were moderated by Hispanic ethnicity.

Misreported Weight/Height There was a strong correlation between reported and measured weight (r = .97) and height (r = .92), which indicated a high correspondence between participants’ reports and objective measurements. Similar to previous research on pessimism and optimism (Sutin, 2013), Neuroticism and Extraversion were associated with misreported weight (Table 3): Participants who had a tendency to experience negative emotions reported that they weighed at least 5 pounds more than measured, whereas participants who had a tendency to experience positive emotions reported that they weighed at least 5 pounds less than measured. Individuals who scored high in Extraversion also reported that they were taller than measured, as did participants higher in antagonism (low Agreeableness). Except for Agreeableness, these effects were also apparent in the analysis using the continuous measures of misreported weight and height. The association between Neuroticism and misreported weight was slightly stronger among Native American participants (βN x race = .02, p < .01), and there was a positive association between Neuroticism and overreported height among Asian American participants (βN x race = .02, p < .01), but otherwise these associations were not moderated by sex, race, or Hispanic ethnicity.

Table 3 Associations Between Personality Traits and Misreported Weight and Height Predictor

Overreported

Underreported

Continuous

Weight Demographics Age Sex (female) Race African American Native American Asian American Multiracial Other Education Personality Neuroticism Extraversion Openness Agreeableness Conscientiousness

.96 [.94, .99] .32 [.29, .36]*

1.00 [.98, 1.03] .88 [.81, .94]*

−.02 −.08*

1.66 [1.47, 1.86]* 1.42 [1.29, 1.55]* 1.10 [.68, 1.78] 1.32 [.94, 1.88] .93 [.74, 1.16] .82 [.69, .97] 1.25 [.99, 1.60] .93 [.76, 1.14] .90 [.74, 1.10] 1.08 [.94, 1.24] .86 [.84, .88] .92 [.91, .94]*

−.02 −.02 .01 .01 −.01 .00

1.14 [1.08, 1.20]* .96 [.92, 1.00] 1.02 [.97, 1.08] 1.08 [1.04, 1.12]* .99 [.94, 1.05] 1.04 [1.00, 1.08] .99 [.94, 1.04] .98 [.94, 1.02] .97 [.92, 1.02] .97 [.94, 1.01]

.03* −.03* −.02 .00 .00

Height Demographics Age Sex (female) Race African American Native American Asian American Multiracial Other Education Personality Neuroticism Extraversion Openness Agreeableness Conscientiousness

1.01 [.98, 1.03] .54 [.50, .58]*

1.01 [.98, 1.04] 1.48 [1.31, 1.67]*

.00 −.14*

1.31 [1.20, 1.44]* 1.64 [1.43, 1.87]* 1.00 [.70, 1.42] .94 [.54, 1.65] .81 [.68, .96] .52 [.37, .73]* 1.09 [.90, 1.31] .85 [.62, 1.18] 1.00 [.87, 1.16] 1.25 [1.02, 1.55] .92 [.90, .94]* .91 [.88, .93]*

.00 .00 .00 .00 .00 −.02*

1.01 [.97, 1.05] 1.00 [.90, 1.02] 1.06 [1.01, 1.10]* .96 [.90, 1.02] 1.03 [.99, 1.07] 1.00 [.94, 1.07] .94 [.90, .98]* .96 [.90, 1.03] 1.00 [.96, 1.04] .97 [.91, 1.03]

.00 .02* .01 −.01 .00

Note. n = 2,161 for overreported weight, n = 4,054 for underreported weight, and n = 9,037 for accurately reported weight. n = 4,063 for overreported height, n = 1,320 for underreported height, and n = 10,148 for accurately reported height. For the continuous analysis, ns range from 15,160 to 15,510 due to missing personality scores. Values for over- and underreported are odds ratios (95% confidence interval) from logistic regressions controlling for age, sex, race, and education.Values are per one standard deviation increase in personality.Values for the continuous analysis are standardized beta coefficients from linear regression controlling for the same set of covariates. For the categorical variables, male is the reference group for sex, and European American is the reference group for race. *p < .01.

Perceived-Assessed Weight Category Discrepancy Finally, we examined how personality was associated with discrepancies between self-perceptions of weight category and actual weight category (Table 4). Surprisingly, conscientious participants perceived themselves as a thinner weight category than they measured. This association was moderated by sex: Conscientious men tended to view themselves as leaner than measured (βC x sex = .04, p < .01). The logistic regressions also

Personality and Body Weight

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Table 4 Associations Between Personality Traits and Discrepancy Between Subjective Perception and Actual BMI Perceived Lighter

Perceived Heavier

Discrepancy

.99 [.97, 1.01] .25 [.23, .27]*

.97 [.93, 1.01] 5.09 [4.42, 6.25]*

.00 −.16*

1.87 [1.69, 2.06]* .42 [.34, .53]* .97 [.64, 1.45] .26 [.08, .83] .95 [.79, 1.15] 1.42 [1.10, 1.83]* 1.07 [.92, 1.26] .91 [.70, 1.20] 1.27 [1.03, 1.57] .70 [.47, 1.03] .96 [.94, .98]* 1.08 [1.05, 1.12]*

.07* −.01 .01 .01 .01 −.02*

1.00 [.95, 1.04] 1.09 [1.02, 1.17]* 1.02 [.98, 1.07] .93 [.87, .99] .96 [.92, 1.00] .99 [.92, 1.07] .96 [.92, 1.00] 1.02 [.95, 1.11] 1.14 [1.09, 1.19]* 1.05 [.98, 1.12]

.01 −.01 .01 .02 −.03*

Predictor Demographics Age Sex Race African American Native American Asian American Other Multiracial Education Personality Neuroticism Extraversion Openness Agreeableness Conscientiousness

Note. n = 3,232 for perceived lighter (e.g., individuals with measured BMI > 25 but perceived self to be normal weight), n = 876 for perceived heavier (e.g., individuals with measured BMI < 25 but perceived self to be overweight), and n = 11,316 for accurate perception.Values for perceived lighter and heavier are odds ratios (95% confidence interval) from logistic regressions controlling for age, sex, race, and education.Values are per one standard deviation increase in personality.Values for the discrepancy analysis are standardized beta coefficients from linear regression controlling for the same set of covariates. For the categorical variables, male is the reference group for sex, and European American is the reference group for race. *p < .01.

indicated that participants higher in Neuroticism were more likely to perceive themselves as heavier than they actually weighed. Neither race nor Hispanic ethnicity moderated the association between personality traits and the perceivedassessed discrepancies.

DISCUSSION Using a sample of over 15,000 participants, we built upon the literature on the association between personality traits and adiposity in several ways. First, previous research has focused primarily on middle-aged and older adults; we extended the association between personality and weight to young adults. Second, with our diverse sample we were able to examine whether the personality-adiposity associations varied across race and ethnicity. With few exceptions, the associations were similar across demographic groups. Third, we found that personality is also associated with two measures of subjective weight—the discrepancy between reported and measured adiposity and misperceived body weight category—in theoretically meaningful ways. Consistent with the growing body of evidence, in this large sample of young adults, Conscientiousness was associated with a healthier body weight. This association was pervasive: Using either BMI or waist circumference, across both sexes

and all of the racial and ethnic groups examined in this study, individuals high in Conscientiousness were leaner. Although modest, the effect size was of similar magnitude to what has been reported consistently in the literature, pointing to the remarkable replicability of this association across samples that differ in age, country of origin, and other demographic variables (e.g., Mõttus et al., 2013; Sutin et al., 2011; but see Shim et al., 2014). Conscientious individuals are organized and disciplined, and these general behavioral tendencies appear to extend to engaging in behaviors that are conducive to a healthy weight. For example, those who score high in Conscientiousness tend to exercise more frequently (Hoyt et al., 2009) and eat a healthier diet (Mõttus et al., 2013). In addition to this behavioral pathway, there may also be physiological pathways that link Conscientiousness and weight. For example, Conscientiousness is associated with better cardiorespiratory fitness (Terracciano et al., 2013) and healthier circulating levels of leptin (Sutin, Zonderman, et al., 2013), an adipose-derived hormone that helps regulate appetite. Conscientiousness was also associated with the subjective assessments of body weight in both expected and surprising ways. When asked to report their height and weight, individuals high in Conscientiousness perceived themselves to be of healthy weight and did not under- or overreport their weight or height. This trait, however, was associated with a greater discrepancy between perceived and actual body weight categories. That is, conscientious participants who were overweight perceived themselves to be of normal weight. From a theoretical perspective, individuals high in Conscientiousness adhere to societal expectations and may perceive themselves in the ways that are expected of them, a process that could extend to perceptions of their weight. It may also be the case that since conscientious individuals are in fact leaner than the average person, they may perceive themselves as lighter than they actually are, compared to what they see around them. A third possibility is that the association between Conscientiousness and misperception of body weight is spurious due to the inherent bias in BMI. That is, those who are conscientious, especially men, may be more muscular and thus have a higher BMI. In such cases, the subjective evaluation may be more accurate than the measure of BMI. In contrast to Conscientiousness, the association between Neuroticism and adiposity is less straightforward. Some studies have found this trait to be associated with BMI (Magee & Heaven, 2011), but not all find this relation (Mõttus et al., 2013). In the present research, we found that this association was moderated by sex: Neuroticism was associated with greater adiposity among women but not men. This finding replicates previous studies on middle-aged (Brummett et al., 2006) and older adults (Sutin et al., 2011), as well as conceptually similar constructs, such as depressive symptoms (Sutin & Zonderman, 2012). Differences in coping styles may be one mechanism that contributes to this difference across the sexes: Women may eat more in response to stress and negative emotions (Piquero, Fox, Piquero, Capowich, & Mazerolle, 2010),

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whereas men tend to engage in more activities (e.g., exercise) to regulate their negative mood (Angst et al., 2002). More research is needed to better understand how the association between Neuroticism and weight differs across the sexes. Individuals high in Neuroticism also tend to see themselves as heavier than they actually weigh. This effect was apparent for both types of discrepancies examined in this study: Individuals high in Neuroticism were more likely to report that they weighed at least 5 pounds more than they actually measured and were more likely to perceive themselves as overweight when they were actually normal weight. Interestingly, in contrast to measured and reported BMI, the effect for perceived weight category was not moderated by sex, which suggests that men who score high on Neuroticism, as well as women, are vulnerable to distorted perceptions of the body. Such distortions have consequences for both sexes, including unhealthy eating habits (Harris et al., 2005) and poor psychological health (Al Mamun et al., 2007). The association between Extraversion and measured adiposity was surprisingly complex. The analysis of BMI categories revealed a nonlinear effect not apparent in the continuous analysis: Underweight participants were particularly introverted, whereas overweight and obese participants were more extraverted. Previous studies have typically not had enough underweight participants to adequately test for nonlinear associations. Although Extraversion was unrelated to the continuous measures of adiposity, these associations were moderated by sex in the opposite direction of the pattern found for Neuroticism. That is, Extraversion was associated positively with BMI and waist circumference for men but not for women. Individuals consume more food when they eat with other people than when they eat by themselves (Hetherington, Anderson, Norton, & Newson, 2006), and men in particular may be more likely to consume more calories through alcohol. As with Neuroticism, this difference across the sexes has been found in some samples (e.g., Brummett et al., 2006; Jokela et al., 2013), but not in others (Sutin et al., 2011). The results were more straightforward and expected for the association between Extraversion and discrepancies between objective and subjective adiposity. Similar to optimism (Sutin, 2013), and consistent with their positive outlook on life, individuals high in Extraversion underreported their weight and overreported their height; that is, extraverted individuals presented themselves as thinner and taller than reality. And yet, there was little discrepancy between their perceived and actual BMI category. Fewer associations emerged for Agreeableness, and none emerged for Openness. Participants who were overweight or obese scored slightly higher on antagonism (low Agreeableness) than normal weight participants. Individuals who score high on antagonism tend to be at greater cardiovascular (Sutin, Scuteri, et al., 2010) and metabolic (Sutin, Costa, et al., 2010) risk, and excess body weight may be one factor that contributes to this association. Most studies, however, do not find antagonism to be associated with BMI (e.g., Armon et al., 2013).

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Of note, there were few differences in the associations across racial and ethnic groups. Hispanic ethnicity did not moderate any association between personality and either objective or subjective weight. The only consistent effect of race emerged for African Americans and Agreeableness: The negative association between Agreeableness and objective and subjective BMI did not hold for African American participants, whereas it did for the other racial groups in this study. Given the mixed literature on Agreeableness and weight, the evidence to date suggests that the links between personality and weight are likely to be similar across ethnic groups in the United States. It is also of note that despite the sex differences in the association between personality and adiposity, sex did not moderate the association between personality and discrepancy between perceived and actual body weight. This pattern suggests that the biases associated with the traits operate in similar ways for men and women, as well as across different racial and ethnic groups. Similar to previous research (McAdams et al., 2007), there was a high correlation between reported and measured weight and height in this sample. Even with correlations greater than .90, however, there are biases in how individuals report their physical measurements. In addition to demographic factors (Krul et al., 2011), personality is another factor that contributes to how individuals (mis)report information about themselves. This association has implications for using selfreported weight and height (and other subjective measures) in health-related research. For the most part, the relative ordering of individuals remains intact—individuals misreport their measurements in the same direction. And, indeed, the BMI correlates of personality were similar when using either measured or self-reported weight and height. These findings suggest that reported height/weight yield similar correlates to measured height/weight. The bias, however, may be a more significant problem for categorizing people—self-reports may over-categorize normal and overweight compared to overweight and obese, respectively (Meng, He, & Dixon, 2010). The present research contributes to theoretical models of personality and health. Many life span models theorize that personality starts to contribute to health in childhood and continues to be an important force through old age (Friedman, Kern, Hampson, & Duckworth, 2014; Moffitt et al., 2011). In the context of body weight, consistent with these models, Conscientiousness-related traits measured in childhood are associated with healthier childhood weight (Duckworth, Tsukayama, & Geier, 2010) and healthier weight gain (Schlam, Wilson, Shoda, Mischel, & Ayduk, 2013). Adult Conscientiousness has likewise been associated with obesity in older adulthood (Sutin et al., 2011). Surprisingly less research has addressed this association in early adulthood. We show that Conscientiousness is also associated with BMI in young adulthood, with an effect similar to that in older adulthood. This similarity suggests that the effect of Conscientiousness is not cumulative; the protective effect is stable and does not become stronger with age. BMI is also often hypothesized to be one

Personality and Body Weight

mediator between Conscientiousness and health outcomes (Hampson, Edmonds, Goldberg, Dubanoski, & Hillier, 2013). Individuals who are conscientious are of healthier weight in young adulthood, and this may be one mechanism that helps protect them against chronic diseases that often appear in middle age (e.g., type 2 diabetes). In addition to life span models of health, many models of personality hypothesize that traits should shape perceptions of the world in ways that are consistent with the content of the trait (John, Naumann, & Soto, 2008; McCrae & Costa, 2008). Neuroticism, for example, should be associated with perceiving the world in more negative ways, whereas Extraversion should be associated with more positive outlooks. Indeed, individuals tend to perceive themselves in ways consistent with these worldviews (Robins, Tracy, Trzesniewski, Potter, & Gosling, 2001). The present research indicates that these perceptions are not limited to psychological evaluations of the self, but extend to perceptions of the physical self. Perceptions of the physical self are thus shaped not only by the individual’s actual adiposity, but also by the individual’s psychological functioning. This link between Neuroticism and negative perceptions of the body also suggests one mechanism through which this trait may contribute to an increased risk of anorexia. The present study had several strengths, including a large and relatively diverse sample of young adults, an FFM measure of personality, and multiple measures of objective and subjective adiposity. There are also limitations that could be addressed in future research. First, this research extended the associations between personality and adiposity to young adults; however, with cross-sectional data, we could not examine the role of personality in changes in adiposity. Longitudinal research has generally found that personality is associated with changes in BMI across adulthood (e.g., Jokela et al., 2013; Sutin et al., 2011), but less research has addressed how these traits are associated with change across the transition from childhood to adolescence and the transition from adolescence to young adulthood. Both of these periods are critical periods for the development of obesity. Second, although this study used a valid measure of personality traits, we did not have a comprehensive measure that assessed the more specific aspects or facets of personality. A facet-level approach would provide a more nuanced understanding of the link between personality and adiposity. Third, Add Health did not assess other aspects of body image, such as body satisfaction or feeling ashamed of one’s body. Although we were able to examine the association between personality and subjective body weight, we could not take a comprehensive approach to body image. Body image is complex, and a more detailed assessment is needed to examine how personality is associated with other aspects of body image and how these associations may vary across sex and race/ethnicity. Finally, because this research is cross-sectional, it could not speak to the temporal relations between personality and adiposity. Given the reciprocal nature of personality and weight, it would be worthwhile

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to address the longitudinal relations between personality and both subjective and objective body weight. Finally, the associations reported in this research were modest. These effects, however, should be put into context. The etiology of adiposity is complex, ranging from genetics to public policy, and any individual risk factor is likely to only have a small effect. Indeed, all of the demographic factors had modest associations with BMI and were roughly comparable to that of Conscientiousness, the strongest personality correlate. The relation between Conscientiousness and BMI, for example, was twice as strong as the effect of age, three times as strong as the effect of sex, and nearly as strong as the effect of race and education. Misperception of the body is likewise complex, and a large effect for any single factor is unlikely to be replicable. Our results for Neuroticism and Extraversion and misperceived weight and height are consistent with previous findings using conceptually similar constructs on a very different population (older adults). These replicable findings indicate that personality contributes to how individuals perceive their bodies across the life span in conceptually meaningful ways and thus is unlikely to be spurious. In addition, even small effect sizes can have meaningful implications. For example, the association between BMI and single nucleotide polymorphisms, including those in the FTO gene (Frayling et al., 2007; Scuteri et al., 2007), is modest, but despite the small effect sizes, genetic studies are providing important new insights into the biological underpinning of obesity (e.g., Loos & Yeo, 2014). Similarly, the findings from this and related studies provide consistent evidence for the relation between personality traits and body weight. In sum, this study used a large sample with measured and subjective BMI to address the relations between FFM personality traits and adiposity. In this sample of young adults, we found associations consistent with effects found in older adults, which suggests the relation between personality and BMI starts early and persists across adulthood. Personality traits were also associated with subjective evaluations of the body. Personality thus contributes to both actual weight and how individuals subjectively perceive it.

Declaration of Conflicting Interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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