Introduction

Restrained eating (or chronic dieting) has been studied as an individual-difference variable since the mid-1970s (e.g., [1]). Many aspects of restrained eating have been investigated in the intervening years. One aspect that has received considerable attention in recent years is the question of whether and how restrained eaters respond differently from unrestrained eaters when confronted with food cues. Herman and Polivy [2] reviewed the research at that time and distinguished between sensory food cues and normative eating cues; it seems that restrained eaters are hyper-responsive to sensory food cues, but that both restrained and unrestrained eaters respond strongly to normative eating cues that indicate what and how much it is “appropriate” to eat. The present paper will update this review, focusing in particular on recent work (published since 2010) and discussing new directions taken by this research. We will examine evidence examining whether and to what extent restrained eaters respond differentially to food cues and to more remote cues about the food, such as labels indicating how healthy or energy dense the food is. We will examine food intake itself and also related responses such as attention and memory biases. We will also review recent research showing that diet cues, a particular subset of food-related cues, can curtail the excessive eating restrained eaters normally show in response to attractive food cues. Finally, we look at possible mediators or explanatory factors such as emotional responses and the role of goals, temptations, and one’s view of oneself as a dieter that might help us to understand the impact of food cues on restrained eaters, and on obese or overweight dieters in general.

Effects of Food Cues on Food Consumption

Several types of food cues have been studied for their effects on eating by restrained eaters. We will look at the effects of these cues on food intake before looking at other, non-eating behaviors affected by food cues.

Mere Presence of Food Cues

Many studies have confirmed that pre-exposing restrained eaters to attractive food cues leads to increased food consumption. (“Pre-exposure” refers to the situation in which the research participant is exposed to food cues for a period of time before being allowed to eat either that same food or some other food.) Several recent studies have looked at the pre-exposure scenario in more detail to try to understand the processes involved. For example, Shimizu and Wansink [3] had participants watch 30-min television programs containing either food-related content or non-food-related content and then offered them a bowl containing mini chocolate bars and a sugar-free soft candy, purportedly to see how the programing affected the taste of the sweets. Restrained eaters ate more after watching food-related programs, but unrestrained eaters were unaffected by program content. Seeing food even on television stimulated more eating only in restrained eaters. Veenstra and de Jong [4] found that restrained eaters exhibited stronger automatic liking responses to high-fat than to low-fat foods, and showed stronger approach tendencies to such foods, which may explain why seeing such foods elicited more eating from these individuals in the Shimuzu and Wansink study.

Although Herman and Polivy [2] identify portion size as a normative cue signaling that greater consumption is appropriate when portions are larger, consuming a large portion often has opposite effects on restrained eaters (whose diet is broken by a large portion, “releasing” additional intake) and unrestrained eaters (who compensate for a large initial portion by eating less subsequently) [5]. Polivy, Herman, and Deo [6] manipulated the perceived size of a portion of food served to participants by giving them a (normal-sized) slice of pizza but showing them either a smaller or larger slice purportedly being served to another person. Restrained eaters ate more cookies after a slice that they thought was large, whereas unrestrained eaters in the same condition reduced their subsequent cookie intake. Perceiving one’s portion as “large” thus promotes eating of a subsequent food by restrained but not unrestrained eaters.

The conditioning-based cue-reactivity model suggests that repeated exposure to a food cue while preventing the individual from eating the food should lessen restrained eaters’ heightened reactivity to such food cues [7]. To test this notion, the researchers exposed restrained and unrestrained eaters to chocolate cues either repeatedly or only once, without allowing the participants to eat the chocolate. Repeated exposure reduced cravings in unrestrained eaters but increased them in restrained eaters, who also tended to eat more after repeated exposure than after a single exposure (when they ate less than unrestrained eaters).

One recent study examined the extent to which exposure to attractive food cues might interfere with efforts to eat healthier foods [8]. Using hand-grip force as a measure of motivation to obtain pictured foods (rather than actual eating, in this case), the authors found that restrained, but not unrestrained eaters, reduced their grips for healthy food objects after exposure to more tempting, fattening food cues.

As should be clear from the descriptions of these studies, the focus is not simply on showing that food cues increase intake in restrained eaters, as this finding is well-replicated and accepted. The research has shifted to examine how food cues operate to influence restrained eaters’ food consumption. The kind of cues that are presented has become a further focus of interest, so in the next section, we examine the effect of specific health- and body-related food cues, which have interesting influences on restrained eaters.

Health-Related Food Cues

Various health-related food cues have been studied recently. Displaying energy values of foods, describing foods as healthy, along with package claims, nutrition claims, and brand names claiming better health status have all been used to present foods as healthy, diet-friendly, and good for the person. A different type of health-related eating cue involves presenting pictures of people (often media models) who have presumably eaten a food and are either thin, normal sized, or overweight. We will review both types of studies.

Gravel and colleagues described oatmeal cookies as either healthy, diet-friendly, or gourmet snacks before having restrained and unrestrained, overweight and normal-weight participants “taste and rate” the cookies [9]. The pattern of results was complex, but restrained eaters rated the “gourmet” cookies as most fattening, and all participants rated the “healthy” and “diet-friendly” cookies as significantly less fattening than those described as “gourmet.” However, the amount eaten was not affected by these labels, so the data do not replicate Provencher, Polivy, and Herman’s [10] finding that healthy labels led restrained eaters to eat more cookies. A later study replicated the effects of package labels and nutritional claims on the perceived healthfulness of the food for restrained eaters but not unrestrained eaters (although food intake was not measured) [11]. Similarly, giving brand and caloric/energy information affected how the cookies tasted to both restrained and unrestrained eaters [12], but restrained eaters ate more cookies from the healthy than the unhealthy brand unless the unhealthy ones were said to have fewer calories (lower energy density), in which case restrained eaters increased their consumption of those. Unrestrained eaters simply ate more of the healthy brand, regardless of caloric/energy information. These findings support previous work on calorie/energy labels on restaurant menus, wherein restrained eaters ordered salad if there were no labels, but shifted to pasta when the labels accurately indicated that the salad and the pasta were equal in energy density [13]. Labeling a food as healthy seems to make restrained eaters more likely to eat that food and often to eat more of it.

A recent study extended the use of healthy food labels by combining them with images of thin or normal-sized female models. Participants viewed images of the models and were then offered either a regular or diet-type snack. Restrained women chose the diet snack significantly more often after viewing either normal or thin-model images, whereas unrestrained eaters were more likely to choose the diet snack after viewing the thin models but not after viewing normal models. Seeing thin models thus seems to push even unrestrained eaters to seek foods labeled as diet-promoting [14]. On the other hand, focusing on thin media images, as opposed to seeing them more peripherally or inadvertently increased food consumption in restrained eaters [15], so how such cues are perceived appears to moderate their effects on restrained eaters. In fact, a study examining biases in attention and memory for body images among restrained and unrestrained eaters found that despite equivalent eye-gaze behavior (i.e., restrained eaters did not look longer at the thin media images) and a similar bias toward more attention to media images than to control images for both restrained and unrestrained eaters, restrained eaters outperformed unrestrained eaters on recognition of the images they had previously been shown [16]. Thus, restrained eaters seem to process food and body cues more deeply than do unrestrained eaters. Moreover, simply altering the extent to which restrained eaters are led to feel similar to the thin models in the images changes their reactions to the models, with those feeling similar to the models feeling better rather than worse about themselves [17].

Expectations may also influence responses to food cues. Fedoroff, Polivy, and Herman [18] previously showed that restrained eaters’ responses to food cues are specific to the cue presented, suggesting that expecting to receive that particular food may be at least partially responsible for the heightened response. Kemps and colleagues [19] tested this by showing participants photographs of healthy food (grapes), unhealthy food (cookies), or both grapes and cookies and told half the groups that they would be eating grapes and half that they would eat cookies. Half the participants were given the food that they expected and half received the food that they did not expect. There was a significant interaction between restraint status and expected food. Restrained and unrestrained participants who expected to taste the healthy grapes did not differ in their consumption of either food, but when unhealthy cookies were expected, restrained eaters ate less of both foods than did unrestrained eaters. The results were interpreted as supporting counteractive control theory [20] such that for restrained eaters, seeing and expecting to eat a tempting, diet-breaking food (cookies) may have triggered activation of their diet goal, thus limiting their food intake.

Diet Priming Cues

Despite the evidence that food cues increase intake in restrained eaters, some studies find that there is a subgroup of restrained eaters who are successful at restricting their intake and who react differently to attractive food cues. For these individuals, counteractive control theory [20] states that tempting food cues actually serve to activate their diet goals and remind them to control their eating. This research has sparked a flurry of studies investigating food cues that activate diet goals rather than eating goals. Papies and Hamstra [21] moved to a naturalistic environment and looked at the effect of adding a diet cue (a poster advertising a diet-friendly recipe) to the tempting smell of grilled chicken to see how many free meat snacks restrained and unrestrained customers ate. In the control condition (tempting cues only), restrained eaters ate more snacks than unrestrained eaters did, but they ate fewer snacks in the presence of the diet-priming cue whereas unrestrained eaters were unaffected by the diet cue. A more complex pattern of behavior was found in an investigation of desire for fattening foods in which participants viewed computer images of tempting or neutral food items. Attractive food cues led to reduced desire for fattening foods in normal-weight restrained eaters (when high- and low-calorie/energy dense foods were presented in a forced-choice measure) but greater desire in overweight restrained eaters. It must be remembered, however, that choosing foods in a forced-choice computer task is not necessarily the same as actually eating those or other foods.

Looking directly at eating after viewing a diet-friendly food cue, Buckland and colleagues [22] presented currently dieting restrained eaters and unrestrained non-dieters with a temptation cue (chocolate) and a diet-friendly food (orange) on two separate occasions. Intake after cue exposure was measured, with restrained eaters eating 60% less chocolate after viewing the diet-related cue than after the tempting cue, whereas unrestrained eaters were unaffected by which cue they had seen. To see if diet-friendly food cues are reminding dieters of their diet goals and enabling them to resist eating tempting foods, restrained and unrestrained eaters were again exposed to diet-friendly food cues, or were exposed to neutral, non-food items and subsequent intake of tempting snack food was assessed, along with diet cognitions, measured by responses to a lexical-decision task [23•]. Restrained eaters ate less after diet-friendly food cues than after neutral cues, but there were no significant results on the lexical-decision task. Finally, Kemps and colleagues [24] presented restrained and unrestrained eaters with either a tempting cue (photos of chocolate chip cookies), a diet-related cue (photos of grapes), or both, and assessed intake of either cookies or grapes. Restrained eaters ate less of both foods after exposure to the grapes photos than after viewing cookies either alone or with grapes, but unrestrained eaters were unaffected. The authors concluded that the context in which food cues are presented can affect how restrained eaters respond to them.

A different sort of diet prime, words related to a healthy body such as “slim” and “fit” versus neutral-word primes induced women to reduce their intake but did not affect males [25]. Restrained and unrestrained females were equally likely to consume less after healthy-body word primes.

Portion size has been described as both a sensory food cue and a social normative eating cue [26•]. Two recent studies investigated the effects of both portion size and diet primes on intake. Holden and Zlatevska [27], working to replicate studies showing that diet-conscious people eat more when portions are presented as multiple smaller units than when they are presented as larger whole units, found that the effect of partitioning a food into smaller pieces is greater when diet consciousness is manipulated than when it is simply measured. Those made highly diet conscious eat more when presented with smaller pieces than when presented with the larger, undivided food item. Moreover, such partitioning has the opposite effect on those who are not diet conscious, reducing their intake. Versluis and Papies [28] started with the opposite observation—namely that larger package sizes increase amount eaten, but that diet primes might curtail this effect. In two experiments, they found that showing participants either the cover of a dieting magazine or diet-related advertisements curtailed the expected increase in consumption associated with larger food portions (for both restrained and unrestrained eaters in the first experiment, but only for restrained eaters in the second).

In summary, the research on diet-related food cues indicates fairly consistently that such cues serve to reduce the impact of tempting food cues on restrained eaters, decreasing their intake of tempting foods. It is unclear, however, whether this effect is the same as counteractive control, wherein actual tempting foods reduce consumption. In summary, recent research on food cues seems to tilt more in favor of tempting food cues promoting increased food intake in restrained eaters, but cues related to diet-friendly foods, diets, or thin bodies seem to curtail eating even when restrained eaters would normally indulge.

Effects of Food Cues on Cognitive Functioning

Lately, there has been increasing focus on the extent to which restrained versus unrestrained eaters attend to, remember, and process food cues, rather than simply how much they eat after exposure to them. Whole literatures are appearing examining attention and memory biases using cognitive tasks and measures to see how restrained and unrestrained eaters differ in their cognitive responses and non-eating behaviors after exposure to food cues.

Attentional Bias

Do restrained and unrestrained eaters actually differ in the degree of attention they pay to food cues? Hollitt and colleagues [29] identified increased attention toward food stimuli as faster detection of and slower disengagement of attention from food cues. Female restrained and unrestrained eaters performed a visual search task to locate an odd-one-out target word embedded among a large number of distractor words. Restrained eaters did indeed locate the food word among the neutral distractors and the neutral word among the food distractors significantly faster than did unrestrained eaters, demonstrating an attentional bias toward food words. Restrained eaters, however, did not display an inability to disengage from such cues. In a Go/No-Go task utilizing pictures of fattening foods versus neutral objects, restrained eaters had longer reaction times than did unrestrained eaters only to food items, although they made fewer commission errors than did unrestrained eaters regardless of cue type [30]. The authors interpreted these findings as indicating a specific attention bias toward food stimuli. Similarly, restrained eaters in another study reacted more quickly to palatable food cues than to neutral cues or than unrestrained eaters reacted to the food cues [31].

Evidence of an attentional bias for food stimuli was also found in restrained eaters responding to a Rapid Serial Visual Presentation task using food and neutral pictures as targets or distractors [32]. Rigid (as opposed to flexible) restraint (i.e., rigidly adhering to a diet regime, without allowance for any transgressions) was strongly associated with an attentional bias to food and shape-related cues, and ultimately with less successful weight loss [33]. Restrained eaters who also scored low in disinhibition tendency (suggesting that they might be successful dieters) were less attentive to food cues when trying to remember a food or non-food cue, whereas those with a higher disinhibition tendency paid greater attention to food cues when they were primed [34]. Finally, Werthmann, Jansen, and Roefs [35] measured attentional biases toward fattening food cues and nonfood cues by eye movements and response latencies in a visual probe task and were able to reduce attentional bias in restrained eaters by inducing a healthy (as opposed to palatability) mindset in them before they saw the food cues.

It seems, then, that the attention bias to food cues exhibited by restrained eaters can be curtailed by more flexible restrained eating, lower disinhibitory tendencies, and healthy mindsets—that is, by the sorts of factors that promote more successful than unsuccessful dieting.

But not all findings show attentional bias. Female restrained and unrestrained eaters were presented with high- or low-calorie/energy food cues in a flanker task (presenting target cues in the midst of, or flanked by, competing or corresponding cues) to determine whether restrained eaters paid greater attention to fattening food cues [36]. When the task was performed after eating a snack, neither restrained nor unrestrained participants demonstrated an attentional bias toward fattening food cues, but when participants were hungry, restrained eaters exhibited response conflict only when low-calorie/energy targets were flanked by high-energy, palatable distractors, whereas unrestrained eaters were distracted by high-energy flanker cues regardless of the energy level of the target food. This study seems to say more about hungry participants’ responses to food cues than whether restrained and unrestrained eaters are differentially responsive to such cues. Similar failures to find attentional biases toward food cues in restrained eaters were reported by Hotham and colleagues [37] using a Stroop color-word task, Freijy, Mullan and Sharpe [38] with a dot-probe task and pictures versus words depicting high- versus low-calorie/energy foods, and by Yeomans and Brace [39] with a delayed-discounting task and a Go/No-Go task, as well as a measure of risky decision-making. The risky decision-making and delayed-discounting tasks were associated with disinhibition scores, especially following exposure to food cues, but there was no effect of cue exposure on the Go/No-Go food cues task, although restrained women were slower on this task overall. The authors offered no explanation for the discrepancy in these findings, but concluded that exposure to food cues generally increases the tendency of women who are potentially likely to overeat to respond impulsively to food.

A recent review of the literature pertaining to attentional biases toward food cues in not only restrained eaters, but in obese people and eating-disordered patients as well, concluded that there is evidence that such biases exist in these groups, but the evidence is contradictory to some extent, unlike the evidence for increased food intake when such a bias is present, which is more consistent [40•]. The recent studies reviewed above support this conclusion. Although not entirely consistent, the data do seem to support an attention bias in restrained eaters toward food cues, especially high-calorie/energy food cues. Some of the studies that did not find such an effect studied restrained eaters as identified by a questionnaire geared more toward identifying successful dieters (the Three Factor Eating Questionnaire, reference here) than the Herman and Polivy Restraint Scale, intended to identify dieters who fluctuate between restricting their intake and succumbing to temptations to eat. This is too complicated an issue to explore here, but the use of different scales for assessing restrained eating may account for at least some of the inconsistent data (see [41], for a discussion of the measurement of restrained eating).

One possible explanation for the attention bias and heightened intake of restrained eaters exposed to palatable food cues may be that they have stronger implicit and explicit preferences for such foods than do unrestrained eaters. Restrained eaters exhibited stronger implicit preferences for palatable foods, and both restrained and unrestrained eaters had greater negative implicit responses to fattening foods than to moderate- or low-calorie/energy foods [42]. Interestingly, the elevated explicit preferences for fattening foods that restrained eaters exhibit, especially following ego depletion (i.e., challenges to their self-control), can be reduced by self-affirmation exercises [43].

Memory

Like attentional biases, memory effects may reflect differential processing of food and weight-related stimuli by restrained versus unrestrained eaters. To test memory specificity, wherein a reduced ability to recall autobiographical experiences is an indication of problems in a specific domain, Ball et al. [44] asked participants to retrieve autobiographical memories in response to dieting and body-related cue words. Restrained eaters were less able than were unrestrained eaters to retrieve such memories. On the other hand, involuntary memories seem to be more likely to be triggered by primed activation so that even weak, almost imperceptible cues can render them conscious. Ball [45] found increased involuntary memories elicited by food cues and food-related situations for restrained eaters, suggesting that these individuals have a motivational bias toward food cues. Restrained and unrestrained eaters instructed to suppress thoughts about either food or animals or to monitor such thoughts were shown pictures of foods and animals. The restrained eaters remembered more food words than unrestrained eaters did, but did not, like unrestrained eaters, remember fewer food than animal words overall [46]. This pattern was interpreted as reflecting a (pictorial) food-related memory bias in restrained eaters. Finally, in the Higgs study et al. [34] described earlier, having participants hold food-related information in their working memories led restrained eaters to attend more to food than to non-food cues, whereas successful dieters (restrained eaters who scored low in disinhibition) paid less attention to food cues when trying to keep food-related information in their working memories.

Conclusions

Recent work on restrained eaters appears to support the idea that they are more responsive than are unrestrained eaters to food cues both in their eating behavior (increasing their intake in response to attractive food cues) and their attention and memory for food-related stimuli (see Table 1 for a summary). These effects are moderated, however, in complex ways. When the food cues indicate that the food is healthy, restrained eaters are more inclined to eat that food, sometimes eating significantly more of it. Diet-related cues, on the other hand, appear to encourage restrained eaters to control their eating, thus counteracting the effects of even tempting food cues if presented in the “right” circumstances. Expectations and the manner in which food- and body-related cues are viewed also have an impact on what effects such cues have on the behavior of restrained eaters. What all of this makes clear, however, is that restrained eaters pay more attention to food and diet-related cues than do unrestrained eaters. In fact, the literature indicates that restrained but not unrestrained eaters display an attentional bias toward food cues as well as selective memory for them. What remains to be determined, then, is the meaning of these effects. Do these biases spring directly from conflict between the eating- and diet-related goals of restrained eaters, as some have suggested [47•]? Or does this represent the development of a control-readiness strategy in which the dieter attempts to attend to powerful food cues in order to be proactive at overcoming their tempting aspects in the service of the larger weight-loss goal [48]? Or is there some other process underlying restrained eaters’ attentional bias toward food cues? Future research in this area will help to elucidate the causes and meanings of restrained eaters’ heightened attention to food and diet cues.

Table 1 Summary of major findings on restrained eating and food cues
Full size table