Evidence of a self-serving bias in people's attributions for their food intake.

People often fail to acknowledge external influences on their food intake, but there might be some circumstances in which people are willing to report that those external factors influenced their behavior. This study examined whether participants who believed that they had overeaten would indicate that the portion size they were served influenced their food intake. Participants (119 women) ate a pasta lunch at two separate sessions, one week apart. At the second session, participants were randomly assigned to receive either a regular portion of pasta (the same portion as the first session) or a large portion of pasta (a portion that was twice the size), and to receive false feedback about their food intake indicating that they had either eaten about the same as or substantially more than they had at the previous session. Participants were then asked to indicate the extent to which the amount of food served influenced how much they ate at that second session. Compared to participants who were informed that they had eaten the same amount across the two sessions, those who were informed that they ate more at the second session reported a stronger influence of the amount of food served if they also received a large portion of pasta, but not if they received a regular portion of pasta. These findings suggest that the willingness to implicate external influences (e.g., portion size) on one's food intake may be driven by a self-serving bias, providing an "excuse" for overeating. However, the external cue must be salient enough to be a plausible explanation for one's behavior.

Influence of social-normative information on the modeling of food-related decisions.

Social modeling is a powerful influence on people's food intake: When there is a clear and consistent norm, people eat more when eating with someone who eats a lot and eat less when eating with someone who eats only a little. In three studies, the present research examined how clear versus ambiguous social-normative information influences the modeling of food-related decisions. Using a novel online decision-making paradigm, female participants (total N = 1042) were provided with information about how many cookies previous participants had supposedly selected (no information was provided in the control condition), and then decided how many cookies they would choose for a snack. When there was a clear and consistent norm, the typical social modeling effect was observed. When there was a small number of "dissenters" whose responses conflicted with the norm set by the majority, participants' cookie selection still conformed to the behaviour of the majority (Studies 1 and 2). It was only when the behaviour of the previous participants was highly ambiguous that participants behaved as if they had been given no normative information (Study 3). By demonstrating that, except in extreme cases, people use the available information to discern a social norm that influences their behaviour, these findings highlight the power of social norms related to food-related decisions.

What is restrained eating and how do we identify it?

Defining and measuring such qualities as restrained eating or dieting may require more than simply administering questionnaires and assuming that we are identifying the population that we wish to study. Different questionnaires may identify different types of restrained eaters, and even deciding what restrained eating consists of is a complicated endeavor. We discuss how to define and measure restrained eating, specifying key attributes, and acknowledging the problems inherent in relying on self-report instruments. We conclude that given the difficulties in defining such constructs as restrained eating, we need to specify more clearly exactly what our research questions are, in order to be sure that we are identifying the populations with the attributes necessary to answer those questions.

Modeling of food intake among restrained and unrestrained eaters.

The Theory of Normal Eating suggests that how much others eat sets an upper limit for how much it is appropriate to eat. This study tested the hypothesis that restrained eaters, who typically eat less than they want to, would be more responsive to a high-intake norm than would unrestrained eaters. Data were combined from 8 experimental studies (total N = 735 female participants; 305 restrained eaters, 430 unrestrained eaters). Each study: (a) included a low-intake norm, a high-intake norm, and a no-norm control condition; (b) measured participants' food intake; and (c) included the Restraint Scale as a measure of dietary restraint. There were no differences between restrained unrestrained eaters in the no-norm control condition or in the magnitude of the inhibition effect (i.e., the difference between the low-intake norm condition and the control condition). There was, however, a restraint difference in the magnitude of the augmentation effect (i.e., the difference between the high-intake norm condition and the control condition). Restrained eaters showed a larger augmentation effect (d = 0.58; 95% CI = 0.29, 0.87) than did unrestrained eaters (d = 0.20; 95% CI = -0.05, 0.45). Social norms provide an upper limit for acceptable food intake, with high-intake norms permitting (but not requiring) individuals to indulge themselves. The fact that restrained eaters were more responsive to the high-intake norm than were unrestrained eaters suggests that the high-intake norm gives restrained eaters permission to indulge when they typically eat less than they want to.

It's all in the timing: The effect of a healthy food cue on food choices from a pictorial menu.

The contemporary food-rich environment has been consistently linked to unhealthy eating. Emerging research suggests that changing the presentation context of unhealthy foods by introducing a subtle nudge in the form of a healthy food cue may promote healthier dietary choices. This study investigated the effect of the timing of a healthy food cue (before or simultaneously with food options) on food choices. Participants (n = 210) were presented with a pictorial café-style menu displaying a healthy food cue (basket of fruit and vegetables) either on the menu cover or inside the menu, or they received a control menu. Participants were asked to make one choice from each of three menu sections (meals, beverages, afters), and then completed a measure of dietary restraint. As predicted, participants chose a greater proportion of healthy food from the healthy-cue-before menu compared to both the healthy-cue-simultaneous and control menus. Furthermore, this effect was stronger for restrained eaters. The findings demonstrate that the timing of presentation of a healthy food cue is critical, and could be used to inform the design of menus in real-world environments, such as cafés and fast-food outlets, to promote healthier dietary choices.

Two observational studies examining the effect of a social norm and a health message on the purchase of vegetables in student canteen settings.

There is some evidence from laboratory-based studies that descriptive social-norm messages are associated with increased consumption of vegetables, but evidence of their effectiveness in real-world settings is limited. In two observational field studies taking an ecological approach, a vegetable-related social norm (e.g. "Did you know that most students here choose to eat vegetables with their meal?"), and a health message (e.g. "Did you know that students who choose to eat vegetables have a lower risk of heart disease?") were displayed in two different student canteens. Purchases were observed during three stages: baseline, intervention (when the posters were displayed) and immediate post-intervention (when the posters had been removed). Study 1 (n = 7598) observed the purchase of meals containing a portion of vegetables and Study 2 (n = 4052) observed the purchase of side portions of vegetables. In Study 1, relative to baseline, the social-norms intervention was associated with an increase in purchases of vegetables (from 63% to 68% of meals; OR = 1.24, CI = 1.03-1.49), which was sustained post-intervention (67% of meals; OR = 0.96, CI = 0.80-1.15). There was no effect of the health message (75% of meals at baseline, and 74% during the intervention; OR = 0.98, CI = 0.83-1.15). In Study 2, relative to baseline, there was an effect of both the social norm (22.9% of meals at baseline, rising to 32.5% during the intervention; OR = 1.62, CI = 1.27-2.05) and health message (rising from 43.8% at baseline to 52.8%; OR = 0.59, CI = 0.46-0.75). The increase was not sustained post-intervention for the social norm intervention (22.1%; OR = 0.59, CI = 0.46-0.75), but was sustained for the health intervention (48.1%; OR = 0.83, CI = 0.67-1.02). These results support further testing of the effectiveness of such messages in encouraging healthier eating and indicate the need for larger-scale testing at multiple sites using a randomised-controlled design.

Are there different types of dieters? A review of personality and dietary restraint.

We review the research on the association between personality and dietary restraint as measured by commonly-used self-report assessment instruments (Restraint Scale, TFEQ, DEBQ, and EDE-Q). In order to expand our understanding of the potentially different types of dieters, we examine the different personality profiles that emerge from existing studies of restraint and personality, including associations between restraint and body dissatisfaction and body focus, self-esteem, neuroticism, sensation seeking, impulsivity, perfectionism and narcissism. This research provides some preliminary evidence that different measures of restraint are associated not only with different eating behaviours, but that they capture different personality profiles.

The persistence of and resistance to social norms regarding the appropriate amount to Eat: A preliminary investigation.

We conducted a preliminary investigation on the resistance to, and persistence of, social influence regarding the appropriate amount to eat, defined in terms of eating an amount similar to that eaten by a confederate. Participants ate pizza both alone and in the presence of remote confederates presenting either a high or low eating norm. In the portion of the experiment examining resistance to social influence, participants given an initial opportunity to form a personal eating norm by eating alone for one session in the absence of social influence were no more resistant to low eating norms than were those who had no such opportunity; however, those who ate alone for two or three prior sessions did show resistance. For the high eating norm, it took three eating alone sessions to create resistance. In the portion of the experiment examining persistence of social influence, when participants ate alone following a session with norm-setting remote confederates, the effect of the social influence persisted. However, the persistence effect varied by norm and weakened over time. Participants modeled a low eating norm for only one additional session and the size of the effect was markedly weaker. By contrast, the high norm persisted for all of the remaining sessions. Thus, individuals' social influence histories can affect their eating.

Hunger, taste, and normative cues in predictions about food intake.

Normative eating cues (portion size, social factors) have a powerful impact on people's food intake, but people often fail to acknowledge the influence of these cues, instead explaining their food intake in terms of internal (hunger) or sensory (taste) cues. This study examined whether the same biases apply when making predictions about how much food a person would eat. Participants (n = 364) read a series of vignettes describing an eating scenario and predicted how much food the target person would eat in each situation. Some scenarios consisted of a single eating cue (hunger, taste, or a normative cue) that would be expected to increase intake (e.g., high hunger) or decrease intake (e.g., a companion who eats very little). Other scenarios combined two cues that were in conflict with one another (e.g., high hunger + a companion who eats very little). In the cue-conflict scenarios involving an inhibitory internal/sensory cue (e.g., low hunger) with an augmenting normative cue (e.g., a companion who eats a lot), participants predicted a low level of food intake, suggesting a bias toward the internal/sensory cue. For scenarios involving an augmenting internal/sensory cue (e.g., high hunger) and an inhibitory normative cue (e.g., a companion who eats very little), participants predicted an intermediate level of food intake, suggesting that they were influenced by both the internal/sensory and normative cue. Overall, predictions about food intake tend to reflect a general bias toward internal/sensory cues, but also include normative cues when those cues are inhibitory. If people are systematically biased toward internal, sensory, and inhibitory cues, then they may underestimate how much food they or other people will eat in many situations, particularly when normative cues promoting eating are present.

The role of expectations in the effect of food cue exposure on intake.

Pre-exposure to food cues has often been shown to increase food intake, especially in restrained eaters. This study investigated the role of expectations in the effect of such pre-exposure on food intake. A sample of 88 undergraduate women was exposed to visual food cues (photos of grapes and chocolate-chip cookies). In a 2 × 2 × 2 design, participants were explicitly told to expect that they would be tasting and rating either grapes or chocolate-chip cookies. Participants subsequently completed an ostensible taste test, in which they tasted and rated either grapes or cookies, such that half were given the food that they had been led to expect and the other half were given the other food. Participants' restraint status (restrained versus unrestrained) was based on their scores on the Revised Restraint Scale (Herman & Polivy, 1980). A significant interaction between expected food and restraint status was found. When participants were led to expect that they would be tasting grapes, restrained and unrestrained eaters did not differ in their subsequent consumption (of either grapes or cookies). However, when participants were led to expect that they would be tasting cookies, restrained eaters ate significantly less (of both grapes and cookies) than did unrestrained eaters, even though craving ratings were similarly elevated for both restrained and unrestrained eaters. The findings are consistent with counteractive control theory in that restrained eaters who expected to eat a high caloric food may have been able to activate their dieting goal, thereby limiting their food intake. The findings further point to an important role for expectations in the understanding and regulation of food intake in restrained eaters.

The social facilitation of eating. A review.

The social facilitation of eating (i.e., people eating more in groups than when alone) has been studied for about three decades now. In this paper, we review the empirical research (diary studies, observational studies, and experimental studies) of social facilitation, attending to factors that increase or decrease socially facilitated eating. We also review the various explanations (e.g., "time extension") that have been offered for the effect and offer our own speculations as to the underlying mechanisms. Further, we discuss promising directions for future research on the social facilitation of eating.

Dietary restraint and body mass change. A 3-year follow up study in a representative Dutch sample.

OBJECTIVE: To determine in a representative Dutch sample the association of dietary restraint, Concern for Dieting, and Weight Fluctuation with subsequent change in body mass index (BMI; in kg/m(2)) in addition to possible moderator effects of sex, level of education, age category, ethnicity, overweight level and physical activity. DESIGN: In a longitudinal study in a representative Dutch sample consisting of 675 participants (331 females, 344 males), dietary restraint (including Concern for Dieting and Weight Fluctuation) was assessed with the Restraint Scale at baseline, and also self-reported weight and height. Three years later, weight and height were also assessed. RESULTS: Dietary restraint was significantly associated with an increase in BMI after three years (B=.272, p=001). Inspection of the significant moderator effect of sex (B=-.387, p=.012) indicated that dietary restraint was significantly associated with increases in BMI only in females. There was no main effect for Concern for Dieting (p=.091). There was a moderator effect of sex on the association between Concern for Dieting and BMI change (B=-.424; p=.002): initial concern for dieting was positively associated with subsequent body mass gain only in women. Weight Fluctuation was significantly associated with an increase in BMI after three years (B=.162, p=008) and sex did not moderate this association. There were no moderator effects for level of education, age category, ethnicity, overweight level and physical activity. CONCLUSION: Dietary restraint and Concern for Dieting are associated with increases in BMI only in females. Weight Fluctuation is associated with increases in BMI in both males and females.

The power of social influence over food intake: examining the effects of attentional bias and impulsivity.

Numerous studies have shown that people adjust their intake directly to that of their eating companions. A potential explanation for this modelling effect is that the eating behaviour of others operates as an external eating cue that stimulates food intake. The present study explored whether this cue-reactive mechanism can account for modelling effects on intake. It was investigated whether attentional bias towards dynamic eating cues and impulsivity would influence the degree of modelling. Participants completed one individual session and one session in which an experimental confederate accompanied them. In the first session, eye movements were recorded as an index of attentional bias to dynamic eating cues. In addition, self-reported impulsivity and response inhibition were assessed. The second session employed a between-participants design with three experimental conditions in which participants were exposed to a same-sex confederate instructed to eat nothing, a low or a large amount of M&Ms. A total of eighty-five young women participated. The participants' self-reported impulsivity determined the occurrence of modelling; only low-impulsive women adjusted their intake to that of their eating companion. Attention towards eating cues and response inhibition, however, did not moderate modelling of food intake. The present study suggests that cue-reactive mechanisms may not underlie modelling of food intake. Instead, the results emphasise the importance of social norms in explaining modelling effects, whereas it is suggested that the degree of impulsivity may play a role in whether or not women adhere to the intake norms set by their eating companion.

Emotional stimuli exert parallel effects on attention and memory.

Because emotional and neutral stimuli typically differ on non-emotional dimensions, it has been difficult to determine conclusively which factors underlie the ability of emotional stimuli to enhance immediate long-term memory. Here we induced arousal by varying participants' goals, a method that removes many potential confounds between emotional and non-emotional items. Hungry and sated participants encoded food and clothing images under divided attention conditions. Sated participants attended to and recalled food and clothing images equivalently. Hungry participants performed worse on the concurrent tone-discrimination task when they viewed food relative to clothing images, suggesting enhanced attention to food images, and they recalled more food than clothing images. A follow-up regression analysis of the factors predicting memory for individual pictures revealed that food images had parallel effects on attention and memory in hungry participants, so that enhanced attention to food images did not predict their enhanced memory. We suggest that immediate long-term memory for food is enhanced in the hungry state because hunger leads to more distinctive processing of food images rendering them more accessible during retrieval.

How much should I eat? Situational norms affect young women's food intake during meal time.

Portion size and the intake of others have been found to influence people's food intake. No study, however, has tested the potential influences of both types of situational norms on intake during the same eating occasion. We experimentally tested the effects of manipulating portion size and the intake of others on young women's meal intake during a 20 min eating opportunity. An experimental design with a three (confederate's intake: small, standard, large) by two (portion size: small, standard) between-participants design was used. A total of eighty-five young women participated. Portion size and the confederate's intake both influenced young women's intake. Participants consumed more when offered a larger portion than when offered a smaller portion, and they also ate more when their eating companion ate more. The present results indicate that the effects of portion size and the intake of others were independent but additive. Thus, both types of situational norms might independently guide an individual's intake during a single eating occasion.

Eating style, overeating and weight gain. A prospective 2-year follow-up study in a representative Dutch sample.

This study examined which individuals are particularly at risk for developing overweight and whether there are behavioral lifestyle factors that may attenuate this susceptibility. A prospective study with a 2-year follow-up was conducted in a sample representative of the general population of The Netherlands (n=590). Body mass change (self-reported) was assessed in relation to overeating and change in physical activity (both self-reported), dietary restraint, emotional eating, and external eating, as assessed by the Dutch Eating Behavior Questionnaire. There was a consistent main (suppressive) effect of increased physical activity on BMI change. Only emotional eating and external eating moderated the relation between overeating and body mass change. However, the interaction effect of external eating became borderline significant with Yes or No meaningful weight gain (weight gain >3%) as dependent variable. It was concluded that whilst increasing physical activity may attenuate weight gain, particularly high emotional eaters seem at risk for developing overweight, because overconsumption seems to be more strongly related to weight gain in people with high degrees of emotional eating.

"Healthy," "diet," or "hedonic". How nutrition claims affect food-related perceptions and intake?

The main purpose of this study was to investigate the impact of nutrition claims on food perceptions and intake among adult men and women, during ad libitum snacks. In a three (healthy vs. diet vs. hedonic) by two (normal-weight vs. overweight/obese) by two (unrestrained vs. restrained eaters) factorial design, 164 men and 188 women were invited to taste and rate oatmeal-raisin cookies. Despite the fact that the cookies were the same in all conditions, they were perceived as being healthier in the "healthy" condition than in the "diet" and "hedonic" conditions. The caloric content was estimated as higher by participants in the "hedonic" than in the "healthy" condition, by women than by men, and by restrained than by unrestrained eaters. Although measured ad libitum cookie intake did not differ as a function of experimental condition, overweight restrained men ate more than did women from each BMI and restraint category. Conversely, overweight restrained women ate less than did men from each BMI and restraint category. In conclusion, our manipulations of healthiness and "fatteningness" of food were effective in changing perceptions, but were not in changing behavior.

Moderation of distress-induced eating by emotional eating scores.

Earlier studies assessing the possible moderator effect of self-reported emotional eating on the relation between stress and actual food intake have obtained mixed results. The null findings in some of these studies might be attributed to misclassification of participants due to the use of the median splits and/or insufficient participants with extreme scores. The objective of the two current studies was to test whether it is possible to predict distress-induced eating with a self-report emotional eating scale by using extreme scorers. In study 1 (n=45) we used a between-subjects design and emotional eating was assessed after food intake during a negative or a neutral mood (induced by a movie). In study 2 (n=47) we used a within-subjects design and emotional eating was assessed well before food intake, which occurred after a control or stress task (Trier Social Stress Task). The main outcome measure was actual food intake. In both studies self-reported emotional eating significantly moderated the relation between distress and food intake. As expected, low emotional eaters ate less during the sad movie or after stress than during the neutral movie or after the control task, whereas high emotional eaters ate more. No such moderator effect was found for emotional eating in the entire sample (n=124) of study 1 using the median-split procedure or the full range of emotional eating scores. We conclude that it is possible to predict distress-induced food intake using self-reports of emotional eating provided that the participants have sufficiently extreme emotional eating scores.