Comparing Japanese College Students’ and U.S. College Students’ Disordered Eating,Distress,and Psychological Inflexibility

Abstract

The present study investigated whether psychological inflexibility is related to disordered eating in Japanese undergraduate students and compared the strength and pattern of the associations with effects in a sample of undergraduate students from the United States. Data from 200 Japanese (n_female = 100) and 481 U.S. (n_female = 380) college students were used. Contrary to prediction, female gender and higher body mass index (BMI), but not psychological inflexibility, were uniquely related to higher levels of disordered eating while controlling for age and psychological distress in the Japanese group. In the U.S. group, greater psychological inflexibility was the only variable that was uniquely related to higher levels of disordered eating after controlling for other study variables. Our findings suggest that psychological inflexibility may not be a useful concept for understanding disordered eating within Japanese college students.

Keywords

Japanese college students U.S. college students disordered eating psychological distress psychological inflexibility experiential avoidance

Disordered eating (Ackard, Fulkerson, & Neumark-Sztainer, 2007; Stice, 2002; Williamson, Gleaves, & Stewart, 2005) refers to an array of psychological symptoms, ranging from subclinical levels of dieting, compensatory behaviors, and body image dissatisfaction to clinical levels of anorexia nervosa (AN) and bulimia nervosa (BN). Over the past three decades, disordered eating concerns have become increasingly pervasive in Japan, especially among adolescent girls and young adult women (Chisuwa & O’Dea, 2010; Nakai, 2012; Nishizawa, Tomisawa, & Igarashi, 2006). Lifetime prevalence rates are 0.03% to 0.2% for AN, and 1.9% to 2.9% for BN (Chisuwa & O’Dea, 2010). Nearly 15 % of female Japanese college students endorse moderate levels of disordered eating symptoms, and 5% endorse clinical levels (Makino, Hashizume, Yasushi, Tsuboi, & Dennerstein, 2006). Several psychosocial factors are found to be associated with disordered eating in Japanese samples. These include female gender (Nishizawa et al., 2006); body mass index (BMI; Kayano et al., 2008); the “tripartite influence” of the family, peers, and media (Yamamiya, Shroff, & Thompson, 2008); difficulty in identifying and describing one’s own emotions (Kiyotaki & Yokoyama, 2006); body dissatisfaction (Mukai, Kambara, & Sasaki, 1998); and the need for social approval (Kiyotaki & Yokoyama, 2006; Mukai et al., 1998).

Psychological Inflexibility and Disordered Eating

The psychological inflexibility model (Hayes, Luoma, Bond, Masuda, & Lillis, 2006; Hayes, Villatte, Levin, & Hildebrandt, 2011) is a transdiagnostic cognitive behavior therapy (CBT) account of psychopathology, which is applicable to disordered eating (Manlick, Cochran, & Koon, 2013; Merwin et al., 2011). The model stems from a basic theory of complex human behavior, called relational frame theory (Hayes, Barnes-Holmes, & Roche, 2001), and its applied work, called acceptance and commitment therapy (ACT; Hayes, Strosahl, & Wilson, 2012). Psychological inflexibility is conceptualized as an overall maladaptive emotion and behavior regulation pattern marked by unwillingness to remain in contact with distressing thoughts, feelings, memories, and other private experiences combined with diminished daily functioning (Bond et al., 2011; Latzman & Masuda, 2013). This model conceptualizes disordered eating symptoms as a set of psychological events reflecting the patterns of deliberate efforts to down-regulate and control unwanted internal experiences (e.g., body dissatisfaction, frustration, depression). A growing body of evidence supports the conceptual applicability to disordered eating (Fulton et al., 2012; Hayaki, 2009; Lavender, Jardin, & Anderson, 2009; Masuda, Price, & Latzman, 2012; Rawal, Park, & Williams, 2010; Schmidt & Treasure, 2006).

Psychological Inflexibility and Disordered Eating in Japanese

Research, although still limited, suggests the applicability of the psychological inflexibility model to Japanese individuals and to their disordered eating (Kishita, Tamamoto, & Shimada, 2008; Masuda, Muto, Hayes, & Lillis, 2008; Muto, Hayes, & Jeffcoat, 2011; Shima, Yanagihara, Kawai, & Kumano, 2013). Consistent with findings in Western countries (Hayes et al., 2006; Hayes et al., 2011), psychological inflexibility is positively associated with a range of psychological distress outcomes, such as anxiety and depression, among Japanese individuals (Kishita et al., 2008; Shima et al., 2013). Psychological inflexibility was also found to mediate treatment outcomes in an ACT-based bibliotherapy with Japanese international students studying in the United States (Muto et al., 2011). Relevant to the present study, maladaptive regulation patterns captured by the construct of psychological inflexibility, such as emotional- and avoidance-focused coping strategies (Nagata, Matsuyama, Kiriike, Iketani, & Oshima, 2000) and difficulty in identifying feelings (Kiyotaki & Yokoyama, 2006), have been shown to be associated with disordered eating in Japanese women. Finally, a case study with a 23-year-old Japanese woman demonstrated that improvement in disordered eating concerns paralleled reduction in psychological inflexibility throughout the course of 26 sessions of individual ACT over a period of 10 months (Masuda et al., 2008). In sum, extant literature points to psychological inflexibility as a useful concept in understanding disordered eating in Japanese individuals. An important next step in research is to examine the applicability of the link between psychological inflexibility and disordered eating to a larger sample of Japanese individuals.

Present Study

The primary aim of the present study was to investigate whether psychological inflexibility is related to disordered eating in Japanese undergraduate students and to compare the strength and pattern of the associations with those in U.S. counterparts. We selected a U.S. sample as a comparison group because the conceptual link between psychological inflexibility and disordered eating is primarily drawn from findings in U.S. samples (Fulton et al., 2012; Lavender et al., 2009). This cross-cultural comparison also allows for investigating the relative extent to which maladaptive regulation would be a central feature of disordered eating in a Japanese sample, especially when controlling for the effects of other key demographic and psychological factors. Given extant literature (Kiyotaki & Yokoyama, 2006; Masuda et al., 2008; Nagata et al., 2000), we predicted that greater psychological inflexibility would be related to greater disordered eating in the Japanese group after controlling for age, gender, BMI, and psychological distress. We also expected that greater psychological inflexibility would be related to greater disordered eating in the U.S. group after controlling for these study variables.

Method

Participants

Participants were 200 college students from Japan and 481 college students from the United States who were recruited from their campuses to participate in the present study. Ages among the Japanese college students ranged from 18 to 46 years (M = 20.35, SD = 2.39), and the sample was equally split by gender with 100 male participants and 100 female participants. For the Japanese sample, BMI scores were calculated using participants’ self-report of height and weight, weight (kg) / (height [m])². The average BMI score for the Japanese sample fell within the “normal” range (BMI between 18.5 and 24.9) and ranged from 16.37 to 35.43 (M = 20.38; SD = 2.36).

The U.S. sample ranged in age from 16 to 57 (M = 21.23; SD = 5.51). The majority of participants in the U.S. group were female (79.0%, n = 380), with the remainder identifying as male (21.0%, n = 101). The U.S. sample was ethnically diverse; 36.2% (n = 174) identified as European American, 30.6% (n = 147) as African American, 18.9% (n = 127) as Asian American, 7.1% (n = 34) as Latino/a, 3.1% (n = 15) as Bi-racial, 0.6% (n = 3) as Native American, 0.2% (n = 1) as Pacific Islander, and finally, 3.3% (n = 16) as “Other/not specified.” For the U.S. sample, BMI scores were computed using participants’ self-report of height and weight, weight (lb) / (height [in])² × 703. The average BMI score for the U.S. group was also within the “normal” range (M = 23.61; SD = 5.14) and ranged from 13.39 to 52.35.

Procedure

All procedures for both study sites were approved by their respective Institutional Review Boards, and consent was obtained from all participants. Participants were recruited separately at their universities for participation in the present study. Participants in the Japanese sample were recruited from a university in a metropolitan area of Japan to take a short, paper-and-pencil questionnaire; the Japanese versions of the self-report measures were used for these participants (see below). Participants in the U.S. sample were recruited from their undergraduate psychology courses at a large metropolitan university in the southeastern United States and received course credit for participation. The U.S. participants anonymously completed their consent forms and measures through the university’s online survey portal.

Measures

Disordered eating

For the U.S. sample, the Eating Attitudes Test−26 (EAT-26; Garner, Olmsted, Bohr, & Garfinkel, 1982) was used to measure disordered eating symptoms. The EAT-26 is a 26-item measure of behaviors and attitudes indicating possible eating disorder pathology, such as preoccupation with the idea of being thinner and avoiding certain kinds of food (e.g., foods high in carbohydrates). Following the guideline by Garner and colleague (1982), all items are scored on a 6-point Likert scale: never (0), rarely (0), sometimes (0), often (1), very often (2), or always (3). Total scores on the EAT-26 range from 0 to 78, with higher scores indicating more problematic eating behaviors and attitudes. The clinical cut-off score of EAT-26 is 20. The EAT-26 has good psychometric properties; it has excellent internal consistency (α = .90; Garner et al., 1982), has been accurate in correctly classifying women with and without eating disorders (Garner & Garfinkel, 1979), and correlates with measures of body dissatisfaction, inaccurate body size estimates, and negative body image (Garner et al., 1982). Cronbach’s alpha for the U.S. group in the present study was .90.

The Japanese-translated version of EAT-26 was used for the Japanese sample (Mukai, Crago, & Shisslak, 1994). The scale was originally developed though back-translation and is one of the most widely used self-report measures of eating disturbance in Japan; it has adequate internal consistency (i.e., Cronbach’s α = .79) in a sample of Japanese college women (Mukai et al., 1998). The clinical cut-off score of the Japanese version is also set at 20. Cronbach’s alpha of the measure for the Japanese group was .80 in the present study.

Psychological distress

The General Health Questionnaire–12 (GHQ-12; Goldberg, 1978) is a brief, 12-item measure assessing general mental health difficulties common to many psychological disorders such as anxiety and depression. Items query the frequency of behaviors and distress indicative of poor mental health, such as difficulty making decisions over the past few weeks. Items are coded on a 4-point Likert scale from 0 (not at all) to 3 (much more than usual). Total scores on the GHQ-12 range from 0 to 36, with higher scores indicating more current mental health difficulty. The GHQ-12 has evidenced adequate reliability (α = .73-.76) and validity in previous samples of adult nonclinical individuals (Bond & Bunce, 2000). Cronbach’s alpha for the U.S. group in the present study was .87.

The Japanese-translated version of GHQ-12 was used for the Japanese sample (Nakagawa & Daibo, 1982, 1985). The scale was originally developed through back-translation (Nakagawa & Daibo, 1982), and it has been validated as a measure of psychological distress and social dysfunction within Japanese adult populations with Cronbach’s alphas of .83 to .85 (Doi & Minowa, 2003). Cronbach’s alpha in the present study was .81 for the Japanese group.

Psychological inflexibility

The Acceptance and Action Questionnaire–II (AAQ-II; Bond et al., 2011) is a 7-item measure of psychological inflexibility, defined as the inability to confront uncomfortable or difficult private experiences (e.g., thoughts and emotions) in the process of behaving consistently with one’s individual values. It was originally developed as a 10-item questionnaire, and 3 items were later dropped for the final version (Bond et al., 2011). Items are rated on a 7-point Likert scale from 1 (never true) to 7 (always true). Total scores on this measure range from 7 to 49, and higher scores indicate more psychological inflexibility, while lower scores indicate more psychological flexibility. The AAQ-II has shown strong psychometric properties, including adequate to good reliability (α = .78-.87) and convergent validity, as evidenced by correlations with a number of metrics of psychological distress (Bond et al., 2011). Cronbach’s alpha for the U.S. group in the present study was .92.

Using the 10-item AAQ-II (Bond et al., 2011), the items of Japanese AAQ-II was initially developed through back-translation (Kishita et al., 2008). Following the seven-item version of AAQ-II recommended by Bond and colleagues (2011), the corresponding seven items of Japanese AAQ-II were selected, and then tested for its factor structure through promax-rotated exploratory factor models using maximum-likelihood estimation (Shima et al., 2013). Consistent with the English version of AAQ-II, the analyses revealed a one-factor solution to best fit the data. The Japanese AAQ-II has demonstrated adequate internal consistency with Cronbach’s alpha of .88 as well as adequate convergent validity as evidenced by correlations with a range of metrics of psychological distress, including depression and rumination (Shima et al., 2013). Cronbach’s alpha in the present study was .84 for the Japanese group.

Model Fit

Models including age, gender, BMI, psychological distress, and psychological inflexibility as predictors of disordered eating were tested using path analysis with maximum-likelihood estimation in the Mplus 6 software program (Muthén & Muthén, 1998-2010). A model with separate parameters for the Japanese and U.S. samples was fit to the data first, and then a series of models in which different parameters were constrained to be equal across the two nationalities were estimated. Several model fit indices were used to evaluate the fit of the data to the models. The χ² difference test was used to compare the fits of these models. A nonsignificant difference in the χ² values for two models indicates that the model with parameters constrained across nationalities provides a fit that is not significantly worse than the model with all parameters free to vary across nationalities. This more restrictive and parsimonious model is generally preferred. The Bayesian Information Criterion (BIC; Schwarz, 1978) is an alternative to the χ² difference test that is less influenced by large sample sizes and thus is less prone to rejecting a more restrictive model when deviations between the baseline and restricted model are relatively small. However, the BIC penalizes considerably for model complexity. The Sample Size Adjusted Bayesian Information Criterion (SABIC) is similar to BIC but does not penalize as highly for model complexity. Lower values of BIC and SABIC are preferred. Bentler’s Comparative Fit Index (CFI; Bentler, 1990) is a relative fit index with values above .95 indicating a good fitting model (Hu & Bentler, 1999). Finally, the Root Mean Square Error of Approximation (RMSEA) is a widely used measure of fit; values of .01, .05, and .08 indicate excellent, good, and mediocre fit, respectively (MacCallum, Browne, & Sugawara, 1996). Standardized parameter estimates for the paths are also reported and interpreted.

Results

Preliminary Analyses

Means and standard deviations of all measures by nationality and gender are presented in Table 1. A multivariate analysis of covariance (MANCOVA) with nationality and gender as between-subject factors and age as a covariate was performed on BMI, disordered eating (EAT-26), psychological distress (GHQ-12), and psychological inflexibility (AAQ-II). Significant effects were followed by pairwise comparisons with a Bonferroni correction. The Japanese group had significantly lower BMI, lower disordered eating, greater psychological distress, and greater psychological inflexibility than the U.S. group. The female group (across nationalities) had greater disordered eating, greater psychological distress, and greater psychological inflexibility than the male group.

Table 1.

Means and Standard Deviations of Study Variables by Nationality and Gender.

	Japanese			United States			Combined
	Male (n = 100)	Female (n = 100)	Total (n = 200)	Male (n = 101)	Female (n = 380)	Total (n = 481)	Male (n = 201)	Female (n = 480)	Total (n = 681)
BMI	20.82 (2.83)	19.95 (1.67)	20.39_a (2.36)	23.65 (5.02)	23.60 (5.19)	23.61_b (5.15)	22.24 (4.31)	22.84 (4.91)	22.66 (4.74)
Disordered eating (EAT-26)	5.10 (4.83)	9.26 (8.61)	7.18_a (7.27)	9.87 (13.42)	10.09 (10.49)	10.05_b (11.15)	7.76_c (10.91)	9.91_d (10.12)	9.28 (10.40)
Psychological distress (GHQ-12)	13.45 (5.19)	15.53 (6.40)	14.49_a (5.90)	11.06 (6.19)	11.97 (6.45)	11.77_b (6.40)	12.25_c (5.83)	12.71_d (6.59)	12.58 (6.37)
Psychological inflexibility (AAQ-II)	22.64 (7.47)	24.47 (7.82)	23.56_a (7.68)	18.60 (8.91)	20.10 (9.16)	19.79_b (9.12)	20.61_c (8.45)	21.01_d (9.06)	20.89 (8.88)

Note. Letters a and b within rows denote significant nationality differences; letters c and d within rows denote significant nationality differences. MANCOVA results: for nationality, F(4, 673) = 28.51, p < .001, F_BMI (1, 676) = 59.16, p < .001, d = .80, F_EAT-26 (1, 676) = 10.20, p < .01, d = .30, F_GHQ-12 (1, 676) = 26.94, p < .01, d = .44, F_AAQ-II (1, 676) = 26.62, p < .01, p < .01, d = .45; for gender, F(4, 673) = 3.01, p < .05, F_EAT-26 (1, 676) = 5.62, p < .05, d = .20, F_GHQ-12 (1, 676) = 6.97, p < .01, d = .07, F_AAQ-II (1, 676) = 4.32, p < .05, d = .05. The gender by nationality interaction was not significant, F(4, 673) = 1.73, p = .14. For all pairwise comparisons, p < .01. BMI = body mass index; EAT-26= Eating Attitudes Test−26; GHQ = General Health Questionnaire; AAQ-II = Acceptance and Action Questionnaire−II.

Associations Among Study Variables

Bivariate correlations among the study variables by nationality are shown in Table 2. In the Japanese group, greater disordered eating was associated with greater psychological distress, greater psychological inflexibility, female gender, and greater BMI. In the U.S. group, disordered eating was positively associated with psychological distress and psychological inflexibility.

Table 2.

Zero-Order Relations Between All Variables by Nationality.

	1	2	3	4	5
Japanese (n = 200)
1. Disordered eating (EAT-26)	—
2. Psychological distress (GHQ-12)	.21**	—
3. Psychological inflexibility (AAQ-II)	.22**	.51**	—
4. Age	−.07	−.07	−.12	—
5. Gender	.29**	.18*	.12	−.09	—
6. BMI	.16*	.03	.06	.06	−.19**
United States (n = 481)
1. Disordered eating (EAT-26)	—
2. Psychological distress (GHQ-12)	.16**	—
3. Psychological inflexibility (AAQ-II)	.31**	.60**	—
4. Age	−.07	−.04	−.10*	—
5. Gender	.01	.06	.07	.00	—
6. BMI	−.01	−.03	−.04	.20**	−.00

Note. EAT-26 = Eating Attitudes Test−26; GHQ = General Health Questionnaire; AAQ-II = Acceptance and Action Questionnaire−II; BMI = body mass index.

p < .05. **p < .01.

Path Models With Psychological Inflexibility as a Predictor of Disordered Eating

The model in which eating disorder symptoms were regressed on age, gender, BMI, psychological distress, and psychological inflexibility was fit to the data with parameters free to differ for the Japanese and U.S. samples. The standardized parameter estimates for this model are presented in Figure 1. Higher BMI and female gender, but not psychological inflexibility, are significant predictors of higher levels of disordered eating in the Japanese sample, while psychological inflexibility is a significant predictor of higher levels of disordered eating in the U.S. sample.

Figure 1.

The Effects of the Predictors on Disordered Eating for the U.S. and Japanese Samples.

Fit indices comparing this model (with parameters free to vary across nationalities) to models with parameters constrained across nationalities are presented in Table 3. The comparative fit indices show that the best-fitting model is one in which the effects of gender, BMI, and psychological inflexibility on disordered eating symptoms are different for the Japanese and U.S. samples and other effects are constrained to be equal across the two samples.¹ This model accounted for a significant proportion of the variance in disordered eating behavior for both the U.S. (11%) and Japanese (12%) samples.

Table 3.

Fit Indices for Models Constraining Parameters Across Nationality.

	$χ_{diff}^{2}$ test statistics
Model	Δχ²	Δdf	p	BIC	SABIC	CFI	RMSEA (90% CI)
1. All parameters unconstrained				23,267.10	23,184.54
2. All parameters constrained	141.34	6	<.001	23,369.12	23,305.62	.00	.25 [.22, .29]
3. Parameter for eating sx on age constrained	0.03	1	.86	23,260.58	23,181.20	1.00	.00 [.00, .08]
4. Parameter for eating sx on gender constrained	7.81	1	.005	23,268.36	23,188.98	.92	.14 [.06, .24]
5. Parameter for eating sx on PD constrained	1.01	1	.31	23,261.56	23,182.18	1.00	.01 [.00, .14]
6. Parameter for eating sx on BMI constrained	7.39	1	.007	23,267.93	23,188.55	.92	.14 [.06, .23]
7. Parameter for eating sx on PI constrained	8.71	1	.003	23,269.26	23,189.88	.91	.14 [.07, .25]
8. Parameters for eating sx on age and PD constrained	1.01	2	.60	23,255.04	23,178.83	1.00	.00 [.00, .09]

Note. Bolding indicates the best fitting model. BIC = Bayesian Information Criterion; SABIC = Sample Size Adjusted Bayesian Information Criterion; CFI = Comparative Fit Index; RMSEA = Root Mean Square Error of Approximation; CI = confidence interval; PD = psychological distress; BMI = body mass index; PI = Psychological inflexibility.

Discussion

The present study investigated whether psychological inflexibility is related to disordered eating in Japanese undergraduate students and compared the strength and pattern of the associations with those in U.S. counterparts. As predicted, the bivariate correlation showed a significant positive correlation between psychological inflexibility and disordered eating in the Japanese group. However, unlike our prediction, psychological inflexibility was no longer related to disordered eating in the group after controlling for age, gender, BMI, and psychological distress: Only being female and having a higher BMI were uniquely associated with greater disordered eating. Conversely, psychological inflexibility was uniquely associated with disordered eating in the U.S. group after controlling for other study variables.

These findings suggest disordered eating in the Japanese group was qualitatively distinct from that in U.S. group. More specifically, unlike the U.S. group, a general tendency toward maladaptive emotion and behavior regulation may not be a central feature of disordered eating in the Japanese group after taking into account gender and BMI. This is somewhat surprising as psychological inflexibility has been found to be a maladaptive process pervasive across a wide range of psychopathology in Western countries (Hayes et al., 2006; Hayes, Wilson, Gifford, Follette, & Strosahl, 1996; Kashdan, Barrios, Forsyth, & Steger, 2006), including disordered eating (Fulton et al., 2012; Masuda, Boone, & Timko, 2011; Rawal et al., 2010) as well as preliminary findings suggesting that there is a link between psychological inflexibility and disordered eating in Japanese samples (Kiyotaki & Yokoyama, 2006; Masuda et al., 2008; Nagata et al., 2000). Given these findings, future research should further investigate psychological inflexibility and its role in disordered eating behavior with Japanese samples.

Recently, researchers have argued that disordered eating involves maladaptive emotion and behavior regulation processes, but that the construct of psychological inflexibility may be too generic to fully capture the processes specific to disordered eating (Lillis & Hayes, 2008; Sandoz, Wilson, Merwin, & Kate Kellum, 2013; Wendell, Masuda, & Le, 2012). Partially in response to these concerns, measures of psychological inflexibility specific to body image and disordered eating (Ferreira, Pinto-Gouveia, & Duarte, 2011; Lillis & Hayes, 2008; Wendell et al., 2012) have been developed in recent years, and they have been shown to be more powerful predictors of disordered eating than general measures of psychological inflexibility (Lillis & Hayes, 2008; Sandoz et al., 2013). As such, future studies should investigate disordered-eating-specific psychological inflexibility and its relations to a range of disordered eating symptoms in Japanese samples to investigate the link between emotion regulation and disordered eating in this group. It is also important for these studies to account for gender in these analyses.

Alternatively, disordered eating in the Japanese group may involve perceived sociocultural pressure more so than internalizing maladaptive emotion and behavior regulation. For example, it is possible that gender and BMI are relevant to disordered eating in Japanese individuals partially because these constructs reflect perceived sociocultural pressures to have an ideal body shape to be socially accepted (Chisuwa & O’Dea, 2010; Kiyotaki & Yokoyama, 2006; Mukai et al., 1998). In fact, previous studies with Japanese adolescent and young adult samples (Kayano et al., 2008; Nishizawa et al., 2006; Yamamiya et al., 2008) posit that perceived sociocultural pressure from family, peers, and the media triggers disordered eating by promoting the thin-ideal and social comparison. Similarly, the significant effects of gender and BMI found in the Japanese group, but not in the U.S. group, may be attributable to differential levels of perceived social pressure given a collective nature of Japanese culture (Kitayama, Markus, Matsumoto, & Norasakkunkit, 1997; Kitayama, Mesquita, & Karasawa, 2006). As such, it may be worthy of investigating the role of aforementioned sociocultural factors on disordered eating in the Japanese participants.

The present investigation has several notable limitations. The external validity of the current study is limited given that data were derived from Japanese undergraduates attending a university in an urban area of Japan as well as U.S. undergraduate counterparts attending an urban area university in the southeastern United States. From a sociocultural perspective, some demographic factors, such as gender role identification, regional context, sexual orientation, and university culture, are likely to shape the variables of interest in systematic ways (Striegel-Moore & Bulik, 2007; Strong, Williamson, Netemeyer, & Geer, 2000). The number of variables included in the study was intentionally restricted to obtain a preliminary understanding of the association between psychological inflexibility and disordered eating while controlling for key demographic variables and psychological distress.

Another set of limitations is drawn primarily from the present methodology and data collection methods. First, discrepancy in the data collection method between Japanese and U.S. samples might have affected the cross-national differences in study variables. Second, as mentioned above, the present study followed the clinically inclined guideline for calculating the EAT-26 total scores. However, other studies have used the sum of coded raw scores to avoid possible skewness in the distribution of scores (Mazzeo, 1999; Tylka & Subich, 2004). Finally, the study is a cross-sectional investigation. The analytic strategy of the present study is sufficient for investigating associations between the variables of interest, but does not permit drawing causal inferences or inferences about functional associations among the variables.

Despite these limitations, the present study extends the existing literature by suggesting that general psychological inflexibility may not be a useful concept in understanding the disordered eating of Japanese college students. Instead, gender and BMI are the only unique predictors of disordered eating in the group. Future studies should examine why gender and BMI, but not psychological inflexibility, are related to disordered eating. We hope that the present findings contribute to the understanding and, perhaps, treatment of Japanese college students with disordered eating concerns.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Notes

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