Eating style, overeating, and overweight in a representative Dutch sample. Does external eating play a role?

Appetite 52 (2009) 380–387

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Eating style, overeating, and overweight in a representative Dutch sample. Does external eating play a role? Tatjana van Strien a,*, C. Peter Herman b, Marieke W. Verheijden c a Department of Clinical Psychology, Institute for Gender Studies and Behavioural Science Institute, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands b Department of Psychology, University of Toronto, Ont., Canada M5S3G3 c TNO Quality of Life/Prevention and Health, P.O. Box 2215, 2301 CE Leiden, The Netherlands

A R T I C L E I N F O

A B S T R A C T

Article history: Received 13 August 2008 Received in revised form 27 October 2008 Accepted 24 November 2008

This study examined which individuals in particular are susceptible or resistant to develop overweight in our current obesogenic environment. A cross-sectional study was conducted in a sample of 1342 people representative of the general population in the Netherlands. Overweight-level (normal body weight  17.5 BMI [weight in kilograms/height in meters squared, as self-reported] <25) versus overweight ((BMI  25)) and overeating, as measured by questionnaire, were assessed in relation to dietary restraint, emotional eating and external eating, as assessed with the Dutch Eating Behaviour Questionnaire. Both dietary restraint and emotional eating moderated the relationship between overconsumption and overweight, but that there was no (positive) main effect or moderator effect for external eating. It was concluded that dietary restraint may prevent people who overeat from getting overweight. An individual’s final level of body weight may possibly be determined more by people’s tendency toward emotional eating than by people’s sensitivity to environmental food cues. ß 2008 Elsevier Ltd. All rights reserved.

Keywords: Obesogenic environment Dietary restraint Emotional eating External eating Overeating Overweight

Overweight has a substantial genetic component but its dramatically increased prevalence in recent years must be attributed to environmental factors, possibly in interaction with metabolic and genetic susceptibilities (Ravussin & Bogardus, 2000). ‘‘Genes load the gun, but the environment pulls the trigger’’ (Bray, 1998). The current environment has been designated as obesogenic (Swinburn, Egger, & Raza, 1999), meaning that abundant availability, easy accessibility and aggressive marketing of foods, coupled with declines in physical activity (also encouraged by environmental affordances), encourage positive energy balance, weight gain and ultimately overweight. Despite the potency of the obesogenic environment, however, not all people become overweight; some remain lean. Clearly, individuals differ in their susceptibility to becoming overweight (in a weight-promoting environment) (Blundell et al., 2005). Susceptibility to weight gain and overweight may be understood at various levels, ranging from genetic, physiological, and metabolic to behavioural and psychological (Blundell et al., 2005). A recent review (Bryant, King, & Blundell, 2008) suggested that the behavioural trait of disinhibition may combine some of these levels, because individuals high in disinhibition may be characterized by stronger tendencies to overeat (Ouwens, Van Strien, & Van der Staak,

* Corresponding author. E-mail address: [email protected] (T. van Strien). 0195-6663/$ – see front matter ß 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2008.11.010

2003; Van Strien, Cleven, & Schippers, 2000), to make less healthful food choices (Contento, Zybert, & Williams, 2005), to more easily gain weight (Drapeuau et al., 2003), and to show various other responses related to the thrifty genotype (Bryant et al., 2008). The notion of the thrifty genotype, originally developed by Neel (1962), proposes that evolution has favoured genetic adaptations that allow humans to survive in periods of food shortages, including adaptations that allow them to rapidly lay down fat in times of food surplus. Disinhibition requires prior inhibition (i.e., restraint) by definition. See for example Polivy and Herman’s (1989) definition of disinhibition as: ‘‘. . .eating more as a result of the loosening of restraints in response to emotional distress, intoxication or preloading’’ (p. 342). However, because it is still unresolved whether restrained eating is a cause or consequence of overeating tendencies (Polivy & Herman, 1985; Van Strien, Van de Laar, et al., 2007), it may be preferable to use a phenomenological description of (over) eating.1 In close correspondence with the two psychological theories of the etiology of overeating, psychosomatic and externality theory (Bruch, 1973; Schachter, 1971), we may distinguish two overeating styles, emotional overeating (i.e., overeating in response to negative

1 See also Westenhoefer, Broeckmann, Mu¨nch, and Pudel (1994), who suggested renaming the Disinhibition scale of the TFEQ (Three Factor Eating Questionnaire) as ‘‘emotionally and externally triggered eating’’ (pp. 37–38).

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emotions such as anxiety or irritability) and external overeating (i.e., overeating in response to external food-related cues such as sight and smell of attractive food). Although emotional and external overeating often co-occur, they refer to independent constructs, and one type of overeating may be manifested independently of the other (Slochower, 1983; Van Strien, 2006; Van Strien, Schippers, & Cox, 1995). In the present study we examine the connection between disinhibition and overeating/overweight in terms of emotionally and externally driven overeating. According to psychosomatic theory (Bruch, 1973), emotional overeating is an inappropriate response to distress (Heatherton, Herman, & Polivy, 1991). Distress is associated with physiological reactions designed to prepare the individual for a fight-or-flight reaction (Cannon, 1915). It inhibits gastric motility (Carlson, 1916) and promotes the release of sugar into the bloodstream, thereby suppressing feelings of hunger (Schachter, Goldman, & Gordon, 1968). Because a reduction of intake during distress is considered to be the evolutionary adaptive and biologically ‘‘natural’’ response, it has been postulated that the ‘‘unnatural’’ response of emotional overeating is acquired (Wardle, 1990). It occurs in people who find it difficult to recognize whether they are hungry or satiated and/or who cannot distinguish hunger from other aversive internal states due to defective interoceptive awareness (Bruch, 1973) or alexithymia (Van Strien & Ouwens, 2007), possibly as a result of inappropriate learning experiences early in life (Snoek, Engels, Janssens, & Van Strien, 2007; Van Strien & Bazelier, 2007). Parental behaviour may contribute to the emergence of emotional overeating (Bruch, 1973; Snoek, Engels et al., 2007), particularly when controlling practices extend to the control of a child’s food intake (Carper, Orlet Fisher, & Birch, 2000; Van Strien & Bazelier, 2007), as when parents exercise pressure to eat or not eat or use food for comfort or as reward for good behaviour. When such parental food-controlling practices are frequent, children may develop poor interoceptive awareness, including difficulties in recognizing whether they are hungry or satiated or suffering from some other discomfort, which may result in a pattern of eating in response to any arousal state (i.e., emotional overeating). Externality theory (Schachter, 1971; see Herman, 2008, for an update, Spitzer & Rodin, 1981) posits, like psychosomatic theory, that external eaters are relatively insensitive to internal, physiological hunger and satiety signals. But in contrast to psychosomatic theory’s emphasis on personal, emotional factors, externality theory focuses on the external environment (esp. food cues) as a determinant of eating behaviour. External eaters overeat as a result of their elevated responsiveness to food-related cues in the immediate environment. A further important difference is that external eating, in contrast to emotional overeating, has been considered an evolutionarily adaptive response (Rodin, 1981, p. 361), which can be easily related to Neel’s (1962) thrifty-genotype concept. This concept suggests that evolution has favoured a genetic adaptation to allow humans to survive in the face of food scarcity and famine, by selective pressure on physiology and behaviour. These adaptations may have included promotion of fat disposition and encouragement of energy conservation. Also there may be selective pressure supporting opportunistic eating, the tendency to overeat whenever external food cues are present in the environment (Bryant et al., 2008; Polivy & Herman, 2006; Rodin, 1981). Only a limited number of studies have assessed associations of overeating and overweight with the disinhibition-related constructs of emotional and external eating (e.g., Burton, Smit, & Lighowler, 2007; Conner, Fitter, & Fletcher, 1999; Johansson, Ghaderi, & Andersson, 2004; Kra¨uchi, Reich, & Wirz, 1997; Lluch, Herbeth, Me´jean, & Siest, 2000; O’Connor, Jones, Conner, McMillan, & Ferguson, 2008; O’Connor & O’Connor, 2004; Van Strien, 2000, 2002; Van Strien, Herman, Engels, Larsen, Van Leeuwe, 2007; Van

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Strien, Van de Laar, et al., 2007; Van Strien & Ouwens, 2003; Van Strien & Van de Laar, 2008; Wardle, 1987; Wardle et al., 1992). The outcomes of these studies are mixed, possibly because some studies did not take into account that emotional and external eating often co-occur or that people may counteract their externally or emotionally induced tendency to overeat by imposing cognitive restraint on their food intake.2 Further, all studies may be criticized for not using representative samples. In the present study, using a sample of people representative of the general population in the Netherlands, we wanted to explore possible differences between overeating/overweight people and their non-overeating/normal-weight counterparts in terms of their dietary restraint, emotional eating, and external eating. A further aim was to explore possible individual and joint moderator effects of restrained, emotional and external eating on the relation between overconsumption and overweight level. Insight into these relationships in a representative Dutch sample may importantly advance our understanding of which individuals in particular are susceptible or resistant to developing overweight in a potentially weight-inducing dietary environment. Participants The participants were part of a larger cross-sectional study on knowledge and use of a Dutch mass media Balance Day campaign. This so-called ‘‘balance-day intervention’’ promotes moderation of food intake and/or increased physical activity in response to occasions of overeating. The sample was representative of the general population in the Netherlands and was recruited through a panel service agency. Questionnaires were made available to panel members until a sample was obtained consisting of 200 respondents less than 20 years of age, 800 respondents aged 20–40 years, and 200 respondents aged 41 and older. This recruitment strategy was designed to ensure sufficient response in the primary target group (i.e., people aged 20–40) of the Balance Day campaign. Within each age-group, recruitment efforts were continued until a sample representative for the distribution of sex, education level, ethnicity, and living region in The Netherlands was obtained. Twenty-two underweight participants (BMI [weight in kilograms/height in meters squared, as self-reported] <17.5) were excluded. The mean age of the remaining 1342 subjects (525 males and 845 females) was 33.6 (S.D. = 9.4) and the mean BMI was 25.4 (S.D. = 4.9). A total of 717 participants had a normal body weight (17.5 BMI <25) and 625 subjects were overweight (BMI  25). Measures (1) The Dutch Eating Behaviour Questionnaire (DEBQ; original Dutch version: Van Strien, Frijters, Bergers, & Defares, 1986a; official English version: Van Strien, 2002) has 33 items, forming three separate scales: emotional eating (13 items; e.g., ‘‘Do you have a desire to eat when you are irritated’’?), external eating (10 items; e.g., ‘‘If food smells and looks good, do you eat more than usual?’’), and restrained eating (10 items; e.g., ‘‘Do you try to eat less at mealtimes than you would like to eat?’’). Response categories range from 1 (‘never’) to 5 (‘very often’). Each of the scales displays good internal consistency and factorial validity (e.g., Van Strien, 1996; Van Strien, Frijters, Bergers, & Defares, 1986b, Van Strien, Herman, et al., 2007; Van Strien, Van de Laar, et al., 2007), and good validity for food consumption (Van 2 Whether restrained eating is a cause or consequence of overeating tendencies is as yet unresolved (Herman et al., 2005; Van Strien, Herman, et al., 2007; Van Strien, Van de Laar, et al., 2007). The fact is that restrained eating is often empirically linked to overeating tendencies and dietary restraint may therefore contaminate correlations between overeating tendencies, overeating and overweight.

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Table 1 Means, standard deviations and t-test for the sub-samples with low versus high overconsumption.a.

BMI-level DEBQ-R DEBQ-em DEBQ-ex Age Sexd Educatione

Low overconsumption, N = 530

High overconsumption, N = 813

Difference

Mean

S.D.

Mean

S.D.

T

0.37 2.36 2.08 2.61 34.41 0.57 1.88

0.48 0.84 0.77 0.58 10.51 0.49 0.74

0.53 2.86 2.65 2.95 33.15 0.64 2.08

0.50 0.72 0.83 0.55 8.64 0.48 0.72

db

p 5.83 11.16 12.79 10.98 2.39 2.63 5.10

0.33 0.65 0.71 0.56 0.14 0.09 0.28

<.001 <.001 <.001 <.001 <.05 (nsc) <.01 <.001

a Low overconsumption: less than once a month; high overconsumption: once a month or more (this corresponds to the median split of distribution of values to this question). b d = effect size by Cohen’s d. c Not significant after Bonferroni correction. d Dummy coded as 0 (males) and 1 (females). e Lower education (primary school, lower vocational education or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education or pre-university education = 2; higher education (higher vocational education or academic training) = 3.

Strien & Van de Laar, 2008). The reliabilities (Cronbach’s alpha) for the present sample were 0.96, 0.85 and 0.92 for emotional eating, external eating and restrained eating, respectively. (2) Overconsumption was measured with the question: ‘‘Can you indicate how often you eat or drink somewhat too much’’: (1) never. . . (6) more than twice a week.3 Subjects were classified as being a low versus high overconsumer if they reported overconsuming less than once a month versus once a month or more, which corresponded to the median split of responses to this question. Data-analysis All variables were tested for skewness and no problems were observed. Next, descriptive analyses were conducted to gather information about means, standard deviations and inter-correlations of the variables. The differences in the distribution of overconsumption and overweight-status (no overweight = 0 and overweight = 1) of the scores on restrained eating, emotional eating, external eating, age, sex (males = 0 and females = 1), and education were measured with an independent t-test, and effect sizes are also included. Effect sizes between 0.2 and 0.5 reflect a small effect, between 0.5 and 0.8, a moderate effect, and above 0.8, a large effect (Cohen, 1988). Owing to the numerous t-tests and correlations conducted, we report only those t-tests and correlations significant at the 1% level. Three hierarchical regression analyses were performed to examine the possible moderator effects of restrained eating, emotional eating, and external eating respectively, on the overconsumption–overweight relationship. In the first step we corrected for sex and education. Because of the high interrelation between emotional eating, external eating, and dietary restraint (see Table 3), we corrected for the other two eating types by forcing them in the second step of the analysis. The predictor variables in the various (four) steps are shown in Table 4. In a fourth hierarchical regression all possible moderators were simultaneously entered (see Table 4). To facilitate interpretation of interactions and reduce problematic collinearity between main effects and interaction terms, all variables were mean-deviated or centered prior to the regression analysis (i.e., the overall mean was subtracted from the values of a variable (Aiken & West, 1991; Whisman & McClelland, 2005). For the regression analyses an alpha level 3 Although we were not specifically interested in drinking, alcohol is highly caloric, so overindulgence in alcohol may be equivalent to overeating in terms of its effect on weight.

of .05 was used (Whisman & McClelland, 2005). All analyses were performed with SPSS 15.0. Results Mean differences Means and standard deviations of all variables may be found in Table 1 (low versus high overconsumers) and Table 2 (normalweight versus overweight participants). Except for age, means for the overconsumers were significantly higher on all variables, also for sex (see Table 1). The higher means on emotional and external eating can be interpreted as supporting the validity of the measure for ‘overconsumption’. Except for external eating and for sex, means of overweight participants were also higher on all variables (see Table 2). The effect sizes (d) indicated small- to medium-sized effects. Pearson correlations Table 3 presents Pearson correlation coefficients between all the variables in the present study. Of special interest for our purposes are the correlations between BMI and the measures for overeating (overconsumption, emotional eating and external eating) and for dietary restraint. Overconsumption, dietary restraint and emotional eating all showed significant, though moderate (r < .30) correlations with BMI, but external eating was Table 2 Means, standard deviations and t-test for the sub-samples of normal weight and overweight people.

Overconsumption DEBQ-R DEBQ-em DEBQ-ex Age Sex Educationb a

Normal weight (BMI < 25), N = 717

Overweight (BMI  25), N = 625

Difference

Mean

S.D.

Mean

S.D.

T

2.93 2.51 2.26 2.79 31.87 0.60 2.04

1.49 0.85 0.81 0.57 9.47 0.49 0.75

3.60 2.84 2.61 2.84 35.69 0.63 1.95

1.60 0.71 0.87 0.60 8.99 0.49 0.71

p 7.9 7.7 7.7 1.7 7.5 0.9 2.3

<.001 <.001 <.001 .092 <.001 .332 <.05 (nsc)

da 0.44 0.42 0.42 0.09 0.41 0.06 0.12

d = effect size by Cohen’s d (0.20 = small, 0.50 = medium, 0.80 = large). Lower education (primary school, lower vocational education or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education or pre-university education = 2; higher education (higher vocational education or academic training) = 3. c Not significant after Bonferroni correction. b

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Table 3 Pearson correlation coefficients. 1 1 2. 3 4 5 8 9 10

BMI Overconsumption DEBQ-R DEBQ-em DEBQ-ex Age Sex Educationa Mean S.D.

2

0.25* 0.22* 0.27* 0.05 0.23* 0.06 0.07 25.37 4.87

3

0.30* 0.40* 0.35* 0.04 0.09* 0.12* 3.21 1.58

0.39* 0.13* 0.11* 0.34* 0.18* 2.66 0.81

4

5

0.57* 0.08* 0.23* 0.07 2.42 0.85

0.20* 0.04 0.05 2.81 0.58

8

9

10

0.01 0.01 33.65 9.44

0.01 1.61 0.49

2.00 0.73

a Lower education (primary school, lower vocational education or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education or pre-university education) = 2; higher education (higher vocational education or academic training) = 3. * p < .01.

not significantly correlated with BMI. Of further interest are the significant interrelationships between overconsumption, restrained eating, emotional eating, and external eating (r  .30). Hierarchical regression analyses Table 4 shows the results of four separate hierarchical regression analyses. Education (step 1 in all four analyses) was significantly related to lower levels of overweight, but there were no main effects for sex. In the first regression analysis with dietary restraint as moderator variable, external eating, when controlling for emotional eating at step 2, was related to lower levels of overweight. Further, emotional eating, overconsumption and dietary restraint were all related to higher levels of overweight (steps 2 and 3). Finally, the relation between overconsumption and overweight level was significantly moderated by dietary restraint (step 4).

Table 4 Effects of individual and joint moderators on the relation between overconsumption and overweight-level. Step 1

B Intercept overweight level Sex Education

S.E.

Beta

p

.505 .028 .042

.060 .028 .019

.027 .062

<.001 .316 .023

Moderator effect of dietary restraint 2 DEBQ-ex DEBQ-em 3 Overconsumption DEBQ-R 4 DEBQ-R  overconsumption

.103 .170 .097 .099 .077

.028 .020 .029 .019 .034

.121 .291 .095 .161 .061

<.001 <.001 <.01 <.001 .023

Moderator effect of emotional eating 2 DEBQ-R DEBQ-ex 3 Overconsumption DEBQ-em 4 DEBQ-em  overconsumption

.149 .014 .097 .122 .075

.018 .023 .029 .021 .034

.241 .017 .095 .210 .059

<.001 .539 <.01 <.001 .027

Moderator effect of external eating 2 DEBQ-R DEBQ-em 3 Overconsumption DEBQ-ex 4 DEBQ-ex  overconsumption

.116 .091 .097 .104 .074

.019 .017 .029 .028 .047

.189 .157 .095 .122 .041

<.001 <.001 <.01 <.001 .117

Joint moderator effects of dietary restraint, 2 Overconsumption DEBQ-R DEBQ-em DEBQ-ex 3 DEBQ-R  overconsumption DEBQ-em  overconsumption DEBQ-ex  overconsumption

emotional and external eating .097 .029 .092 .099 .019 .161 .122 .021 .210 .104 .028 .122 .118 .037 .093 .118 .043 .093 .004 .056 .002

<.01 <.001 <.001 <.001 <.01 <.01 .946

As recommended by Holmbeck (2002), post hoc analyses were conducted to determine the nature of this significant interaction. Prior to these analyses, we created a high-dietary-restraint (i.e., centered dietary restraint – 1 S.D.) and low-dietary-restraint variable (i.e., centered dietary restraint + 1 S.D.) (Aiken & West, 1991). Each of these variables was then multiplied by the (centered) overconsumption variable to create interaction terms. With these variables, we conducted two regression analyses, each of which included the main effect for overconsumption, one of the conditional dietary restraint variables (high dietary restraint or low dietary restraint), and the interaction of the overconsumption and dietary restraint variable, thereby producing the slope for the high- and low-dietary-restraint conditions. The results of the regression for high dietary restraint indicated that degree of overconsumption was not significantly associated with overweight, [beta] = 0.03, p = 0.457. In contrast, results of the regression for low dietary restraint indicated that overconsumption was significantly associated with overweight, [beta] = .153, p < .001. Regression lines depicting raw overweight levels for high and low dietary restraint are plotted in Fig. 1. In the second regression analysis with emotional eating as moderator variable, external eating, when controlling for dietary restraint in step 2, was not related to higher levels of overweight.

Fig. 1. Regression lines for relations between overconsumption and overweightlevel (0 = no overweight and 1 = overweight) for high and low levels of dietaryrestraint. The slope for overconsumption was significant when dietary restraint was low ([beta] = 0.15, p < .001), but not significant when dietary restraint was high ([beta] = 0.03, p = 0.457).

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Further, dietary restraint, overconsumption, and emotional eating were all significantly related to higher levels of overweight (steps 2 and 3). Finally, the relation between overconsumption and overweight level was significantly moderated by emotional eating. To understand this interaction, we examined two regression equations each of which included the main effect for overconsumption, one of the conditional emotional-eating variables – high emotional overeating (i.e., centered emotional eating – 1 S.D.) or low emotional overeating (i.e., centered emotional eating + 1 S.D.) – and the interaction of the overconsumption and emotional eating variable, thereby producing the slope for the high- and lowemotional-eating conditions. The results of the regression for high emotional eating indicated that degree of overconsumption was significantly associated with overweight, [beta] = 0.17, p < .001. In contrast, results of the regression for low emotional eating indicated that overconsumption was not significantly associated with overweight, [beta] = .04, p = .280. Regression lines depicting raw overweight levels for high- and low-emotional eating are plotted in Fig. 2. In the third regression analysis with external eating as moderator variable, dietary restraint, emotional eating and overconsumption were all significantly related to higher levels of overweight (steps 2 and 3). External eating (at step 3) was significantly related to lower levels of overweight, and the relation between tendency to overeat and overweight level was not significantly moderated by external eating. Table 4 also shows the results of a fourth hierarchical regression analysis that examined the simultaneous impact of the three eating types as possible moderator variables on the relations between overconsumption and overweight. Overconsumption, dietary restraint and emotional eating were significantly related to higher levels of overweight, but external eating was significantly related to lower levels of overweight (see step 2). Further, both dietary restraint and emotional eating significantly moderated the relationship between overconsumption and overweight level, but external eating did not moderate this relationship. Highly similar results were obtained when possible underreporters of body weight were excluded from the analyses, and normal body weight was defined as a BMI below 24. (The definition of overweight remained the same: BMI  25).

Fig. 2. Regression lines for relations between overconsumption and overweightlevel (0 = no overweight and 1 = overweight) for high and low levels of emotional overeating. The slope for overconsumption was significant when emotional overeating was high ([beta] = 0.17, p < .001), but not significant when emotional overeating was low ([beta] = 0.04, p = .280).

Further, when also age was entered in step 1, the interaction effects of the eating types as individual moderators of the relationship between overconsumption and overweight level became borderline significant (p < .10). In the full model that examined the simultaneous impact of the three eating types as possible moderators of the relations between overconsumption and overweight level, however, the moderator effects of both dietary restraint and emotional eating remained significant even when age was also entered in step 1 (respectively: p < .01 and p < .05). We also conducted regression analyses, in which normal body weight was defined as a BMI below 24 (excluding possible underreporters of body weight) and obesity was defined as BMI  30 (excluding overweight persons). A total of 203 persons were obese. In this analysis the interaction effect of dietary restraint as individual moderator of the relationship between overconsumption and obesity level became non-significant (p = .285), but the interaction effect of emotional eating remained significant, as was also the case when age was entered in step 1. Additionally, in the full model that examined the simultaneous impact of the three eating types as possible moderators of the relations between overconsumption and obesity level, the moderator effects of both dietary restraint and emotional eating were significant (respectively: [beta = .106], p < .01 and [beta = 0.196], p < .001), and both moderator effects remained significant when age was also entered in step 1. [beta = .08], p < .05; [beta] = .18, p < .001 (Supplementary Table). Discussion In a sample of people representative of the general population in the Netherlands, the current research examined differences between high versus low overconsumers and between overweight versus normal-weight people in their degree of dietary restraint, emotional eating, and external eating. A further aim was to investigate possible individual and joint moderator effects of dietary restraint, emotional eating and external eating on the relations between overconsumption and overweight level. Before we discuss our main findings, we first summarize the results. High overconsumers differed from low overconsumers in that they were more often overweight, had higher degrees of dietary restraint and also had higher degrees of emotional and of external eating. They were also more often female, and also (remarkably) better educated. Not all of these factors translated themselves into overweight, though. Overweight people did differ from their normal-weight counterparts in that they reported higher frequencies of overconsumption, higher degrees of dietary restraint and also higher degrees of emotional eating. There was no difference in their degree of external eating, and there also was no sex difference or difference in education. Furthermore, overweight people were older. Overconsumption, dietary restraint, emotional eating, and external eating were all significantly interrelated, so (in hierarchical regression analyses) we examined possible main effects on overweight when the influence of the other variables was partialled out. Overconsumption, dietary restraint and emotional eating all retained significant positive main effects on overweight, but the main effect of external eating on overweight level became significantly negative (see Table 4, the fourth regression analysis, step 2). Next, possible moderator effects of the eating types on the relation between overconsumption and overweight level were examined. Both dietary restraint and emotional eating acted as moderator variables on the relationship between overconsumption and overweight level, and remained so when the simultaneous impact of the other eating types as possible moderator variables was examined. Overconsumption seemed to be more strongly

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related to overweight in people with lower levels of dietary restraint and in people with higher levels of emotional eating. The absence of difference between people with overweight and those with normal body weight in their degree of external eating may seem remarkable in view of the recent resurgence of interest in the possible role of external food cues in development of overweight (Burton et al., 2007; Herman & Polivy, 2008; Wansink, Payne, & Chandon, 2007). However, it is perhaps not so remarkable in light of similar results in various other studies (Lluch et al., 2000; Snoek, Van Strien, Janssen & Engels, 2007; Wardle, 1987; Wardle et al., 1992). In the study by Wardle (1987), overweight women were no more external than were those with normal body weight. In a further study involving British adolescents, Wardle et al. (1992) found that more external eaters, although they reported higher intakes of energy, were even slimmer. A highly similar result was found by Lluch et al. (2000) in the French Stanislas Family study. A large Dutch study (with over 10,000 adolescents) found a negative association between external eating and overweight level (Snoek, Van Strien et al., 2007). Taken together, these findings suggest that responsiveness to food cues may be a general characteristic and not specific to overweight people.4 This would support the suggestion by Rodin (1981) that external eating is an evolutionary adaptive response and that external eating may possibly be related to Neel’s (1962) thrifty genotype concept. These findings would further mean that one’s final level of body weight is possibly determined by variables other than one’s degree of external eating, such as physiological, psychological or environmental variables. One such variable may be dietary restraint, although in the present sample the main effect of external eating on overweight level remained non-significant when the influence of dietary restraint was partialled out (Table 4, second analysis, step 2). Another possible variable may be emotional eating, because the main effect of external eating on overweight level actually became negative when the influence of emotional eating was partialled out (Table 4, first analysis, step 2). We can only speculate on possible explanations for this finding; more research into this finding is needed. But emotional and external eating are highly interrelated (in the present study, r > .55) (see also Newman, O’Connor, & Conner, 2008; Slochower, 1983). And research into differences between emotional and external eating has determined that emotional eating and not external eating is associated with poor interoceptive awareness, high alexithymia, depression and problems with affect regulation (Van Strien, 2006). The lower association of external eating with abnormal/problem behaviour would suggest that external eating is associated with less resistance to change (for empirical support, see Van Strien, 2006; Van Strien & Van de Laar, 2008). The suggestion that external eating may be more easily controlled and therefore poses less of a risk for overweight may explain the negative association of external eating with overweight when the potential influence of emotional eating is partialled out. With regard to the moderator effect of dietary restraint, it should be noted that the DEBQ-R measures dietary restraint differently than does the Restraint Scale (Herman, Polivy, Pliner, Threlkeld, & Munic, 1978; Van Strien, Herman, et al., 2007; Van Strien, Van de Laar, et al., 2007). Research with the Restraint Scale has suggested that dietary restraint contributes to overeating and eating disorders (Herman, Polivy, & Leone, 2005). In contrast to the Restraint Scale, which measures predominantly unsuccessful dieting, the DEBQ-R measures a whole range of dieting, varying 4 Herman and Polivy (2008) have taken a different track, arguing that external food cues may be subdivided into two categories, one of which (normative cues) affects everyone regardless of weight and the other of which (sensory cues) affects people who are hungry (including dieters and many but not all overweight people).

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from ‘‘watching exactly what you eat’’ and/or moderation of food intake in response to occasions of overeating: ‘‘When you have eaten too much, do you eat less than usual the following day?’’ The moderator effect of dietary restraint in the present study, showing that overconsumption is less strongly related to overweight in people with higher levels of dietary restraint, suggests that people with high DEBQ restraint may have more success in avoiding overweight, because they tend to compensate for occasional bouts of overconsumption by eating less subsequently. The significant main effect of emotional eating on overweight, combined with the significant moderator effect of emotional eating on the relationship between overconsumption and overweight, would suggest an entirely different perspective on what exactly is so obesogenic about our present environment. Maybe we should look behind the Big Mac billboards and other ubiquitous food cues, although they probably present a precondition for any (over)eating, and focus our search on emotional eating. Interestingly, it turns out that the scores on emotional eating obtained in the present study were substantially higher (mean = 2.64, S.D. = 0.86) than were those that had been obtained in 1983 in a different but also representative Dutch sample (mean = 1.92; S.D. = 0.68) (see Van Strien et al., 1986b, Table 3). The effect size of the difference between the samples is 0.92, a large effect. Also, the current external and restrained eating scores were higher – the external eating mean = 2.81 (S.D. = 0.42) and the restrained eating mean = 2.64 (S.D. = 0.82) – than in the 1983 sample, where the external eating mean = 2.66 (S.D. = 0.54) and the restrained eating mean = 2.21 (S.D. = 0.91); but the effect sizes were 0.32 and 0.50, respectively, indicating only a small and a medium effect, respectively. So it seems that there has been a substantial increase in emotional eating in the last two decades, and that this increase has not been paralleled by a similarly large increase in external eating. Perhaps we should try to explain the current obesity epidemic from an emotion perspective. We do not know exactly why emotional eating has shown such an increase. Twenge (2000), however, showed that American adult and child samples increased almost a full standard deviation in anxiety between 1952 and 1993 (explaining about 20% variance in the trait). These increases do not necessarily level off when researchers stop sampling. Additionally, she found that economic factors seemed to play little role in the increased prevalence of anxiety; instead, decreases in social connectedness (divorce rate, percentage of people living alone) and increases in environmental dangers (violence, worry about war or women’s rights) seemed responsible. These trends may also hold true for the Netherlands. A further possible explanation is based on recent research in preadolescent children (Carper et al., 2000; Van Strien & Oosterveld, 2008; Wardle, Guthrie, Sanderson, & Rapoport, 2001). In young children, emotional eating is infrequent, with most young children showing a biologically natural reaction to emotional stressors (loss of appetite when feeling lonely, depressed or afraid). However, in the study by Van Strien and Oosterveld (2008), emotional eating was positively associated with spending much time with screen media (television for the girls; computers for the boys). This activity is often paired with mindless eating (i.e., eating during which one pays less attention to increasing feelings of fullness in the stomach), because one focuses on the television or computer screen.5 When mindless eating becomes a habit, children may lose appropriate awareness of hunger and satiety altogether and

5 It may be suggested that mindless eating is a proxy for external eating, a likely response to the ubiquitous advertising of food. However, in a study on preadolescent children only emotional eating, and not external eating, moderated the relationship between television viewing and snacking; television viewing was more strongly related to snacking in children with higher than with lower levels of emotional eating (Van Strien and Ouwens, submitted for publication).

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develop emotional eating. There has been a large increase in time spent with screen media (in the early 1980s most children did not even have a computer). Limitations A limitation of this study is that the data are cross-sectional and so we cannot draw any firm conclusions about the direction of the obtained associations. Further, all data were based on self-report, and it is possible that people may not be fully aware of their behaviour, such as whether they eat in response to external food cues or whether they engage in emotional eating. Another limitation of self-report is that we cannot rule out the possibility that, for reasons of social desirability, obese subjects may claim to be on a diet and may disavow emotional and external eating. These possibilities may have inflated dietary restraint scores and deflated emotional and external eating scores. Participants may also have under-reported body weight. Social desirability concerns, however, are not limited to studies that rely on self-report measures. Concerns about the impression that one is conveying may also affect behaviour in a direct tests of intake, and obese participants may be especially motivated to avoid overeating (Krantz, 1978). A strength of the study is the large data set and also the fact that the data were collected in a sample of people representative of the general population of the Netherlands. Further, we were encouraged by the finding of differences between normal-weight and overweight participants in reported overconsumption, indicating that the overweight people were prepared to admit their relatively high consumption (an admission that may be construed as an indicator of self-report validity). Further, the fact that the results did not change appreciably when possible under-reporters of body weight were excluded or, additionally, those with overweight were excluded gave us confidence in the validity of the present results. In conclusion, the present study, using large samples, allows us to draw certain conclusions with reasonable confidence. First, people who combine high overconsumption with high levels of dietary restraint may have more success in avoiding overweight than those who combine high overconsumption with low levels of dietary restraint. Second, particularly high emotional eaters seem at risk for developing overweight, because overconsumption seems to be more strongly related to overweight in people with high levels of emotional eating. Combined with the absence of a positive main effect or moderator effect for external eating, our data suggest that we may be well advised to seek an ‘‘emotional’’ explanation for the current obesity epidemic. Acknowledgements We thank Netherlands Nutrition Centre for allowing secondary data analyses and the Dutch Ministry of Health, Welfare and Sports for funding for Marieke Verheijden. References Aiken, L. S., & West, S. G. (1991). Multiple regression: testing and interpreting interactions. Thousand Oaks, CA: Sage. Blundell, J., Stubbs, R. J., Golding, C., Croden, F., Alam, R., Whybrow, S., et al. (2005). Resistance and susceptibility to weight gain: individual variability in response to a high fat diet. Physiology and Behavior, 86, 614–622. Bray, G. A. (1989). Contemporary diagnosis and management of obesity. Newton PA: Handbooks in Health care. Bruch, H. (1973). Eating disorders. New York: Basic Books. Bryant, E. J., King, N. A., & Blundell, J. E. (2008). Disinhibition: its effects on appetite and weight regulation. Obesity Reviews, 9, 409–419. Burton, P., Smit, H. J., & Lighowler, H. J. (2007). The influence of restrained and external eating patterns on overeating. Appetite, 49, 191–197. Cannon, W. B. (1915). Bodily changes in pain, hunger, fear and rage (2nd ed.). New York: Appleton.

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Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.appet.2008.11.010.