The Desire to Eat in the Presence of Obese Or Normal-Weight Eaters As a Function of Their Emotional Facial Expression

nature publishing group articles Behavior and Psychology

The Desire to Eat in the Presence of Obese or Normal-weight Eaters as a Function of Their Emotional Facial Expression

[Q1] Laétitia Barthomeuf1,2, Sylvie Rousset2 and Sylvie Droit-Volet1

The aim of this study was to investigate whether the eating desire would be lower in the presence of facial expression of an obese than of a normal-weight eater in participants who were or not themselves obese. Normal-weight and obese participants assessed their desire to eat liked and disliked foods. These foods were presented alone and with a normal-weight and obese eater expressing pleasure, disgust, or neutrality. Results showed that, compared with a normal-weight eater, perceiving an obese eater decreased the viewer’s desire to eat, whatever his/her facial expression. Thus, pleasant faces of normal weight but not of obese eaters increased the eating desire. Furthermore, the influence of eater’s facial expressions did not differ as a function of the participants’ BMIs. These data were discussed in the framework of the embodiment theory of emotion and of their implications in terms of nutritional education, either by enabling people to learn to like certain unpalatable foods or by helping them moderate their food intake simply through the sight of an obese eater.

Obesity (2009) doi:10.1038/oby.2009.357

INTRODUCTiON obesity is considered as a form of social deviance (9), and Social cues are important determinants of eating behavior. It has obese individuals are repeatedly targets of social stigmatiza- been shown that individuals eat more and spend more time eat- tion (10). Obesity is associated with a wide variety of negative ing in the presence of others than alone (1,2). However, recent characteristics such as laziness, lack of willpower, or ugliness studies have also revealed the important role of other people’s (11). It is also associated with eating disorders (12) and rep- emotional facial expressions on our own eating behavior. When resents a serious risk to health (diabetes, hypertension, heart participants perceived another eater expressing either disgust or disease, etc.). Thus, watching obese people should also activate neutrality, their desire to eat liked foods decreased (3–5). In con- the idea that too much eating is bad for health, even if the eater trast, when the eater expressed pleasure, the desire to eat disliked is expressing pleasure. Due to negative characteristics attrib- foods increased. In the theoretical framework of the embodi- uted to obese people and their eating-related behavior, we may ment theories (6), this is explained by the perception of other’s assume that participants have less desire to eat when in the emotional facial expression that induced the same emotion in the presence of obese compared to normal-weight eaters, and this observer by an automatic imitation of this facial expression. This even if he/she expressed a positive emotion. imitation activates the mirror neuron system that produces the However, people’s attitude toward obese people may depend sensorimotor experience in the observer of perceived emotion on the group to which they themselves belong, i.e., whether (7). For example, it has been shown that the same brain areas (the they are or are not themselves obese. Various studies in social left anterior insula and the right anterior cingulate cortex) were psychology have shown that people identify more with and are activated both when the individuals observed disgust in others more influenced by the members of their own group (e.g., race, and when they experienced disgust themselves (8). gender) (in-group members) than those of other groups (out- However, the influence of the other on eating behavior may group members) (13). Thus, in line with this in-group effect, also differ as a function of the eater’s BMI. The purpose of viewing an obese eater might decrease the desire to eat, but to a this original study was to examine whether individuals have lesser extent in obese participants (in-group advantage) than in less desire to eat with obese people than with normal-weight normal-weight participants (out-group). However, as discussed people. No study has attempted to examine this topic. In our further latter, an alternative assumption might be that there diet-conscious society, which preaches the ideal of thinness, would be no in-group advantage for obesity. There is evidence

1Laboratoire de Psychologie Sociale et Cognitive, UMR 6024, CNRS, Université Blaise Pascal, Clermont-Ferrand, France; 2Institut National de la Recherche Agronomique, UMR 1019, Centre de Recherche en Nutrition Humaine d’Auvergne, Clermont-Ferrand, France. Correspondence: Sylvie Droit-Volet ([email protected]) Received 5 March 2009; accepted 2 September 2009; advance online publication 00 Month 2009. doi:10.1038/oby.2009.357

obesity 1 articles Behavior and Psychology that obese and normal-weight individuals share the same nega- Table 1 Means and standard deviations of the evaluation of tive stereotypical beliefs about fat people (10). Consequently, the “to like” emotion toward the food pictures on the 7-point the decrease in the desire to eat when faced by an obese eater liking scale, from 0 “I do not feel this emotion” to 6 “I feel it could be similar whatever the participant’s BMI. very strongly” In sum, our study was aimed to investigate whether the Food picture Mean SD influence of emotions (disgust, neutrality, pleasure) expressed Chocolate 4.2 1.6 by another eater on the participant’s own desire to eat varies as Bread 4.6 1.4 a function of the eater’s BMI. We expected that eating desire Cream cake 4.7 1.6 would be lower in the presence of the facial expression of an Cooked sausage with vegetables 2.1 1.8 obese rather than of a normal-weight eater. Furthermore, we crossed the group membership of the eaters and participants in Black pudding 1.9 2.1 order to highlight the any potential in-group advantage (obese Kidneys 2.0 2.0 participants/obese eater). The in-group advantage would be observed if the eating desire of obese participants was greater the highest emotional scores were selected. However, unlike in the case in the presence of an obese eater than of a normal-weight eater. of the normal-weight models, it was difficult to find two obese females However, obesity is also associated with other symptoms, such who portrayed all three emotional expressions well. We were therefore obliged to select three obese women instead of two in order to obtain the as depression (14), restriction (15), and hyperempathy (16). right scores for each emotional expression (Table 2). Furthermore, the We therefore measured these possible moderator variables. We selected photographs of obese eaters were assessed by a fluorescence- also measured the degree of hunger in order to predict distor- activated cell sorting coder (18). tions in the evaluation of eating desire. In addition, the participants were asked to complete four questionnaires. The beck depression inventory 13) (19) which assesses depressive symptoms on 13 items. This questionnaire provides a depression score METHODS AND PROCEDURES between 0 and 39, allowing a classification of individuals as no depres- Participants sion (0–3), mild depression (4–7), moderate depression (8–15), or severe Seventy-five subjects (41 women and 34 men aged from 19 to 37 years depression (>16). The Dutch Eating Behavior Questionnaire (20) assesses (28.5 ± 4.9)) were recruited in Clermont-Ferrand through advertis- restrained eating on 10 items and provides a score of restriction between 0 ing in the local newspapers. Based on their BMI, they were assigned and 5. The empathy quotient (EQ) (21) assesses the ability to understand either to the obese group (BMI >30) or to normal-weight group (BMI and share another person’s feelings. The EQ ranges from 0 to 80. Between between 19.5 and 24.9). There were 37 normal-weight participants (20 0 and 32 the EQ is weak; between 33 and 52, it is average; between 53 and women, BMI = 21.1 ± 1.8, and 17 men, BMI = 22.6 ± 1.6), and 38 obese 63, it is above average; and between 64 and 80, the EQ is very high. The participants (21 women, BMI = 34.1 ± 3.1, and 17 men, BMI = 33.7 ± last questionnaire assesses the sensation of hunger with a hunger score 3.4). None of the participants were receiving medical treatment. They of between 1 and 7 (22). participated for a payment of €10. Procedure The participants completed the four questionnaires presented in ran- Materials dom order, and performed the eating desire test. The questionnaire-test The participants were seated in front of a computer screen in a labora- order was counterbalanced. tory setting. The stimuli consisted of photographs of six different food In the eating desire test, the participants assessed the intensity of their products presented on the computer screen: three liked (chocolate, desire to eat the food products shown in each of the photographs, on a French bread, cream cake) and three disliked (cooked sausage with veg- horizontal nonstructured scale (from the left, “I have no desire to eat,” to etables, kidneys, black pudding). These liked and disliked foods have the right, “I have a great desire to eat”). The scores varied between 0 and been pretested by Gil et al. (17). In this study, young adults rated the 10. They were two series of photographs (food presented alone vs. food intensity of the emotion “to like,” aroused by each photograph of 13 presented with an eater), with the series order being counterbalanced different food products, on a 7-point scale, from 0 “I do not feel this across subjects. The first series consisted of the six different photographs, emotion” to 6 “I feel it very strongly. The three liked foods used in the one for each food product presented alone (three liked and three dis- present study received the highest mean ratings, and the three disliked liked). The second series consisted of 72 different photographs (4 × 3 × foods the lowest mean ratings (Table 1). 6), i.e., four eaters (two normal-weight and two obese, one of each sex) There were also photographs of eight eaters seated at a table: two men for each of the three emotional expressions (disgust, neutrality, and pleas- and two women for each BMI. Each eater expressed three different emo- ure), and for all six food products. Within each series, the photographs tions: pleasure, neutrality, and disgust. Each of the six food products was were presented in random order. presented with an eater expressing each facial expression (Figure 1). For the four normal-weight eaters, the emotional faces had been pretested and selected for the quality and the intensity of the expressed emotions RESULTS in Rousset et al.’s (4) (Table 2). The emotional faces for the obese eat- Depressive symptoms scores ers were tested in the present study. Sixteen obese models, eight men (age = 30.3 ± 3.4, BMI = 33.6 ± 2.8) and eight women (age = 28.4 ± 4.2, In our study, the mean depressive symptoms score for the obese BMI = 32.8 ± 3.7) were photographed expressing three different emo- participants (mean = 7.04) indicated that they were suffering tional expressions (i.e., pleasure, neutrality, and disgust) in the same from mild depression whereas the normal-weight participants conditions as those used by Rousset et al. (4). These photographs were were not depressive (mean = 2.48). The ANOVA run on these evaluated by 32 additional participants (age = 23.47 ± 4.1, BMI = 21 ± scores with the participants’ BMI and sex as between-subject 1.9). They rated each face on the basis of nine emotions (anger, disgust, fear, sadness, guilt, surprise, interest, satisfaction, pleasure, and neutral- factors found a main effect of BMI,F (1, 71) = 17.24, P < 0.001, ity) on a 7-point scale from 0 “the face does not express this emotion” to but no main effect of sex, nor any interaction between BMI and 6 “the face strongly expresses this emotion.” The photographs obtaining sex, F(1, 71) = 0.06, F(1, 71) = 0.001, respectively, all P > 0.05.

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Figure 1 Examples of normal-weight and obese eater with expressions of disgust, neutrality and pleasure toward the three liked and the three disliked foods.

Table 2 Means and standard deviations of the intensity of the This confirmed that the depression score was higher for the perceived emotions of the four normal-weight eaters and the obese than for the normal-weight participants. As indicated by five obese eaters which best expressed disgust, neutrality and the Pearson correlation coefficient, there was a positive corre- pleasure on a 7-point scale, from 0 “the face does not express lation between the BMI and the depression scores, r = 0.43, P < this emotion” to 6 “the face strongly expresses this emotion.” 0.01: the higher the BMI score was, the greater the symptoms Emotional expressions of depression. Pleasure Neutrality Disgust Selected eatera Mean s.d. Mean s.d. Mean s.d. Restrained eating scores Normal-weight men The ANOVA carried out on the restrained eating scores M1 5.1 1.6 3.7 1.7 4.7 1.1 revealed a main effect of BMI,F (1, 71) = 20.32, and of sex, F(1, 71) = 13.76, all P < 0.001, but no interaction between these M2 4.1 1.7 3.0 1.9 5.4 1.0 two variables, F(1, 71) = 0.24, P > 0.5. Thus, the restrained eat- Normal-weight women ing score was higher in women than in men (2.83 vs. 2.34). W1 4.9 1.5 3.8 2.1 5.1 1.4 Similarly, the obese participants had a higher restrained eating W3 5.3 1.0 3.7 2.1 4.9 1.1 score than the normal-weight participants (2.88 vs. 2.29). There Obese men was a positive correlation between the BMI and the restrained M10 5.1 1.6 4.1 1.7 5.2 1.1 eating score, r = 0.46, P < 0.01, with BMI scores corresponding to more restrained eating behavior. M13 5.2 1.7 5.5 1.9 5.9 1.0

Obese women EQs W1 — — 4.1 2.1 5.3 1.4 The ANOVA run on the EQs indicated a main effect of BMI, W6 5.6 1.0 4.2 2.1 — — F(1, 71) = 6.56, and of sex, F(1, 71) = 6.85, all P < 0.05, but no W7 5.5 1.5 — — 5.1 1.1 interaction between these two variables, F(1, 71) = 0.88, P > aThe first character indicates the sex (M for men and W for women) andthe 0.05. Thus, women had a higher EQ than men (33.09 vs. 29.29), second character, the number of the selected eater. and obese participants than normal-weight participants (33.05 obesity 3 articles Behavior and Psychology vs. 29.33). There was a positive correlation between the BMI was conducted using depression as a predictor variable of the and the EQ, r = 0.27, P < 0.05, with higher BMIs corresponding desire to eat the liked or disliked foods and was run for each to higher EQs. emotional facial expression. The results showed that depressive symptoms only significantly predicted a decrease in the Hunger scores desire to eat the disliked foods when the eaters expressed dis- The ANOVA carried out on the hunger scores revealed neither gust. Thus, the more depressive the participants were, the more a main effect of sex,F (1, 71) = 0.23, or of BMI, F(1, 71) = 3.30, sensitive they were to the emotion of disgust expressed by the nor a BMI × sex interaction, F(1, 71) = 0.02, all P > 0.05. In line eater toward disliked foods and the more their own desire to with these results, there was no correlation between the BMI eat decreased, R2 = 0.06, P < 0.05. Depression scores were not and the hunger score, r = −0.15, P > 0.05. significantly correlated with the other variables. To summarize, the BMI was significantly correlated The ANCOVA also revealed a significant interaction between with depressive symptoms, restrained eating and empathy. food category, facial expressions, eater’s BMI, eater’s sex and Consequently, these three different scores were introduced as participant’s BMI, F(2, 142) = 2.86, P < 0.05. In contrast, the covariates into the subsequent analyses of variances. However, effect of participant’s sex did not reach significance and was only depression had a significant effect. The other two covari- not involved in any interaction. Consequently, this factor was ates were therefore removed from the analyses and the presen- removed from the subsequent analyses which were then per- tation of the results. formed separately for each facial expression. In the case of the disgusted faces, the ANOVA performed Desire to eat food products in a nonsocial context: on the difference scores between food presented with an eater Foods presented alone expressing disgust and food presented alone revealed no main An analysis of Covariance (ANCOVA) was run on the eating effect of participant’s BMI, or any interaction involving this fac- desire score for the food presented alone with the participant’s tor. In contrast, there was a significant main effect of eater’s sex, BMI and sex as between-subjects factors and food category (liked F(1, 73) = 5.64, P < 0.05, but no interaction involving this factor. vs. disliked) as within-subjects factor, and depression as covari- The one-sample t-tests revealed that the difference scores were ate. This ANCOVA revealed a main effect of depressive symp- significantly lower than zero both for the men eaters, t(74) = toms, F(1, 68) = 4.66, P < 0.05, but no significant interaction −4.89, and for the women eaters, t(74) = −5.46, all P < 0.001. involving this factor. However, the correlation between depres- Thus, the desire to eat was lower when the eater expressed dis- sive symptoms and the desire to eat food presented alone did not gust, and more so when the disgust was expressed by a woman reach significance, r = 0.16, P > 0.05. The results also indicated (−0.81) than a man (−0.69). In addition, there was a significant a significant main effect of food category, F(1, 68) = 3.90, P = interaction between food category and the eater’s BMI, F(1, 73) 0.05, and a significant food category × participant’s sex interac- = 6.92, P < 0.05 (Figure 2). This interaction indicated that the tion, F(1, 68) = 4.93, P < 0.05, but no significant main effect of desire to eat the liked foods in the presence of a disgusted face sex, F(1, 68) = 1.16, P > 0.05. Thus, this interaction indicated that again decreased more in the presence of an obese eater (−1.06) the desire to eat the liked foods tended to be higher in the women than of a normal-weight eater (−0.78). This phenomenon was than in the men (6.56 vs. 5.81), F(1, 73) = 3.10, P = 0.08. In con- observed for all the participants, both normal-weight and trast, the desire to eat the disliked foods was similar in both the obese. The difference scores were significantly lower than zero women and the men (2.06 vs. 2.56), F(1, 73) = 1.08, P > 0.05. for both the normal-weight eater, t(74) = −4.08, and the obese There was no main effect of BMI,F (1, 68) = 0.14, P > 0.05, or any eater, t(74) = −4.46, all P < 0.001. In contrast, the desire to eat interaction involving this factor. Thus, the desire to eat foods did the disliked foods did not differ depending on the eater’s BMI, not differ as a function of the individual’s body weight. F(1, 74) = 0.93, P > 0.05. The difference scores were significantly lower than zero in both the BMI groups, i.e., the normal-weight Desire to eat food products in a social context: eaters, t(74) = −4.15, and the obese eaters, t(74) = −3.86, all P < effects of facial expressions 0.001. Thus, compared to food presented alone, a disgusted face We calculated the difference between the scores obtained for decreased the desire to eat both liked and disliked foods, but, in the desire to eat food presented with an eater (social con- the case of the liked foods, did so to a greater extent when the text) and food presented alone (nonsocial context). A gen- disgust was expressed by an obese eater. eral repeated ANCOVA was run on these difference scores In the case of the neutral faces, the ANOVA run on the dif- with food category, facial expressions, and eater’s BMI and ference of expressed eating desire between food presented sex as within-subjects factors, participant’s BMI and sex as with an eater expressing neutrality and food presented alone between-subject factors, and depression as covariate factors. indicated no main effect of participant’s BMI, nor any interac- This ANCOVA revealed no main effect of depressive symp- tion involving this factor. The only significant interaction was toms but instead a significant depressive symptoms × food between food category and eater’s BMI, F(1, 73) = 4.61, P < category × facial expression interaction, F(2, 140) = 3.18, P < 0.05 (Figure 3). For the disliked foods, the difference in desire 0.05. To study this interaction, we performed a linear regres- to eat in the presence of neutral faces and food presented alone sion analysis designed to investigate the proportion of vari- was similar for the normal-weight eater (−0.24) and the obese ance accounted for by depressive symptoms. This analysis eater (−0.23), F(1, 74) = 0.07, P > 0.05. The one-sample t-tests

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Disgusted faces Pleasant faces 1.5 1

1 0.5 0.5

Liked s score 0 Liked

Disliked ce 0 Disliked Normal-weight eaterObese eater

−0.5 eren ff Difference scores Di −1 −0.5

−1.5 Normal-weight eater Obese eater −1 Figure 2 Means and standard deviations of the difference in scores Figure 4 Means and standard deviations of the difference in scores between food presented with disgusted faces of a normal-weight and between food presented with pleasant faces of a normal-weight and obese eater and food presented alone. obese eater and food presented alone.

Neutral faces 1 liked and disliked foods increased when only the normal-weight participants were in the presence of a pleasant face. 0.5 DiSCUSSiON scores Liked

ce 0 Disliked Our study showed that the participants’ desire to eat was affected eren

ff by the emotions expressed by the other eaters. Compared with Di −0.5 foods presented alone, neutral and disgusted faces decreased the participants’ desire to eat, whereas pleasant faces increased

−1 it. This result is consistent with those obtained by Barthomeuf Normal-weight eaterObese eater et al. (3) which showed that viewing a person expressing pleas- Figure 3 Means and standard deviations of the difference in scores ure in eating increases the desire to eat whereas seeing a per- between food presented with neutral faces of a normal-weight and son expressing disgust decreases it. According to embodiment obese eater and food presented alone. theory (6), the effect of the perception of facial expressions on the perceiver’s behavior is explained through the perceiver’s revealed that the difference scores were significantly lower than automatic imitation of the perceived emotions. As set out in zero for the normal-weight eaters, t(74) = −2.04, P < 0.05, and our introduction, the afferent feedback from imitation induced marginally lower than zero for the obese eaters, t(74) = −1.71, the perceived emotion in the observer. However, the fact that P = 0.09, thus indicating that, in the case of the disliked foods, the effect of the eater’s facial expressions was modulated by the both the normal-weight and obese participants’ desire to eat status of the eaters (obese or not) and the category of foods decreased in the presence of neutral faces when compared to (liked vs disliked) partly calls into question the conceptualiza- a presentation of the food without an eater. In the case of the tion of the embodiment process in terms of a simple automatic liked foods, the desire to eat was lower in the presence of an imitation mechanism. Indeed, our study showed that the pho- obese eater with a neutral facial expression (−0.42) than in the tograph of a pleasant face still increased the desire to eat the presence of a normal-weight eater (−0.23), F(1, 74) = 4.78, P < liked foods but only when the face was that of a normal-weight 0.05. The one-samplet -tests revealed that the difference scores eater. The disgusted faces also decreased the desire to eat both did not differ from zero for the normal-weight eaters, t(74) = liked and disliked foods, but this decrease in the case of the −1.57, P > 0.05, but were significantly lower than zero for the liked foods was greater when the eater was obese than when obese eaters, t(74) = −2.40, P < 0.05. Thus, the desire to eat the he/she was normal-weight. Consequently, the eater’s BMI liked foods decreased in the presence of an obese eater for all played a critical role in the effect of emotional facial expres- the participants, both normal-weight and obese. sions on the desire to eat. This BMI-related influence may be Finally, in the case of the pleasant faces, the ANOVA run on the consequence of the stereotypes associated with obese peo- the difference scores revealed a significant main effect of eater’s ple. Some studies have shown that normal-weight participants BMI, F(1, 73) = 4.14, P < 0.05, but no other main effect and no considered obese individuals to be less intelligent, less willing, interaction (Figure 4). Thus, whatever the food category and the more angry, ashamed, and greedy than normal-weight people participant’s BMI, the desire to eat was greater in the presence of (10). Obesity is also associated with eating disorders (12) and a pleasant facial expression worn by a normal-weight eater than a risk to health. Thus, watching obese people should also acti- by an obese one (0.33 vs. 0.20). The one-sample t-tests revealed vate the idea that too much eating is bad for health, even if that the difference scores were greater than zero for the normal- the eater is expressing pleasure. The characteristics attributed weight eaters, t(74) = 2.73, P < 0.01, but that they did not differ to obese people should therefore have moderated the process from zero for the obese eaters, t(74) = 1.72, P > 0.05. Therefore, of embodying other people’s emotions by activating a nega- compared with food presented alone, the desire to eat both the tive assessment of the food or the food-related behavior. This obesity 5 articles Behavior and Psychology explained why the participants were less eager to eat in the grant from the French National Research Agency (ANR Blan06-2-145908 presence of obese eaters. FaceExpress). In addition, our results revealed no in-group advantage for the DiSCLOSURE obese participants. Instead of feeling an increase in the desire The authors declared no conflict of interest. to eat in the presence of an obese eater as was observed for the normal-weight participants in the presence of another normal- © 2009 The Obesity Society weight eater (3,4), the obese participants were negatively influ- REFERENCES enced by the presence of individuals belonging to the same 1. Bell R, Pliner PL. Time to eat: the relationship between the number of people category. Numerous studies have showed that stigmatized groups eating and meal duration in three lunch settings. Appetite 2003;41:215–218. develop a positive, collective identity that fosters both awareness 2. Clendennen VI, Herman PC, Polivy J. Social facilitation of eating among of discrimination and group pride and which allows them to friends and strangers. Appetite 1994;23:1–13. 3. Barthomeuf L, Rousset S, Droit-Volet S. Emotion and food. Do the emotions sustain their self-esteem (23). 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Future research could attempt to body weight on implicit and explicit antifat bias. Obes Res 2006;14:440–447. generalize these results to the case of real food intake. 25. Hale WW 3rd. Judgment of facial expressions and depression persistence. Psychiatry Res 1998;80:265–274. ACKNOWLEDGmENTS 26. Christakis NA, Fowler JH. Th spread of obesity in a large social network over We thank Laurie Mondillon for assessing the obese facial expressions 32 years. N Engl J Med 2007;357:370–379. with fluorescence-activated cell sorting, and Aurore Bernard for the 27. Marcelino AS, Adam AS, Couronne T, Köster EP, Sieffermann JM. Internal and taking of photographs of obese eaters. This research was supported by a external determinants of eating initiation in humans. Appetite 2001;36:9–14.

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