What constitutes food variety? Stimulus specificity of food

Individual Differences in Plate Wasting Behavior: The Roles of Dispositional Greed, Impulsivity, Food Satisfaction, and Ecolabeling

This study examines the effects of dispositional greed, impulsivity, food satisfaction, and ecolabeling on consumers' plate waste in all-inclusive hotels. Using a moderated mediation research model, a cross-sectional survey was conducted among 1253 tourists of different nationalities, all staying in five-star hotels in Alanya, Türkiye. The results show that both dispositional greed and impulsivity positively predict and significantly contribute to plate waste. Conversely, food satisfaction was found to be an influential variable that moderates the effects of greed and impulsivity on plate waste, highlighting its critical role in waste reduction strategies. Ecolabels, despite their intended purpose, were not found to have a significant impact on consumer attitudes toward plate waste. Future research is encouraged to explore strategies to counteract dispositional greed and impulsivity, given their significant impact on plate waste behavior. At the same time, refining methods to promote food satisfaction and the effective use of ecolabels may contribute significantly to reducing plate waste in all-inclusive resorts. This research contributes to our understanding of the psychological factors that influence consumer behavior in buffet settings and provides guidance to hospitality industry practitioners seeking to reduce waste.

Outcome devaluation by specific satiety disrupts sensory-specific Pavlovian-to-instrumental transfer

Reward predictive cues can selectively motivate instrumental behaviors that predict the same rewarding outcomes, an effect known as specific Pavlovian-to-instrumental transfer (PIT). This selective effect is thought to be mediated by a representation of the sensory specific properties of an outcome, that has become associated with both the Pavlovian cue and the instrumental response during initial learning. Specific satiety is a common method of outcome devaluation that reduces an outcome's value but might also lead to the habituation of the outcome's sensory properties. Previous research has demonstrated that specific PIT is insensitive to changes in specific outcome value following taste aversion devaluation, as well as general satiety manipulations, and therefore specific satiety should not disrupt specific PIT by reducing outcome value. The present rodent experiments used a specific satiety devaluation procedure immediately prior to a specific PIT test to show that habituation of these outcome specific sensory representations can disrupt its efficacy as a stimulus and abolish the specific PIT effect. Experiment 1 employed a two-lever choice test to show that a non-devalued stimulus supports specific PIT, whereas a devalued stimulus abolished the specific PIT effect. Experiment 2 replicated this procedure while controlling for response competition by using a single-lever test to confirm that a devalued stimulus abolishes the specific PIT effect. These findings demonstrate that specific satiety can disrupt the ability of an outcome specific representation to support specific PIT. Given previous findings that specific PIT is insensitive to changes in outcome value by general satiety and taste aversion devaluation, this suggests that specific satiety devaluation might disrupt the use of sensory specific outcome representations to guide behavior via a mechanism that is independent of the outcome's current value.

Habituation as an underlying mechanism for Sensory Specific Satiety: An assessment using flavor consumption and preference in rats

Sensory specific satiety refers to a decline in the hedonic value of the sensory properties of a particular food as it is consumed. This phenomenon is characterized by a decrement in responding as a consequence of repeated exposure, is stimulus specific, and recovers after time. All these characteristics are shared with the habituation phenomenon and for this reason, habituation has been proposed as the underlying mechanism that explains this eating regulatory system. However, several studies conducted with human models have yielded mixed results. Using rats as experimental subjects, the present study tested the following three characteristics of habituation within a Sensory Specific Satiety (SSS) framework: spontaneous recovery, dishabituation and the distractor effect. Experiment 1 demonstrated the basic effect of SSS and its spontaneous recovery over time. In Experiment 2 we found that the presentation of a dishabituator after a pre-feeding procedure had no impact on the SSS effect. Finally, in Experiment 3 the presence of a distractor during a pre-feeding procedure did not alter the expression of SSS. These results challenge the idea that SSS constitutes a typical case of habituation, at least with the procedure used here.

High reinforcing value of food is related to slow habituation to food

BACKGROUND

The rate of habituation to food and reinforcing value of food are processes that are related to food intake and body weight. Reinforcing value of food provides an index of the motivation to eat, while habituation provides an index on how repeated presentations of food relate to reduced behavioral and physiological responses to that food.

OBJECTIVE

To investigate the relationship between habituation phenotypes to salty, sweet and savory foods and reinforcing value of those foods.

DESIGN

A sample of 229 8-12-year-old children at risk for obesity completed reinforcing value and habituation tasks for foods that varied in savory, sweet or salty tastes. Multivariate Group Based Trajectory Modeling was used to create four unique patterns of habitation to foods based on detailed 10 s epochs of responding for food over a 24 min task. Differences in reinforcing value of food were assessed for these habituation phenotypes.

RESULTS

Results showed a graded relationship between the overall habituation phenotypes and reinforcing value of food, as those with the relatively flat habituation phenotype found food more reinforcing than those with phenotypes that showed rapidly decelerating responding across all taste categories.

CONCLUSIONS

Those who habituated slower found food more reinforcing than those with a rapid habituation phenotype. Implications of these phenotypes for understanding how habituation relates to food intake are discussed.

Preliminary Evaluations of Habituation of Operant Responding for Sensory Stimuli in Humans

Research suggests that repetitive reinforcers wane in their ability to maintain operant behavior in a manner consistent with habituation. Weaker reinforcers, including sensory stimuli common in human work, may be most impacted by repetition. The present research examined within-session operant responding patterns for visual stimuli in humans from two experiments assessing multiple characteristics of habituation. In Experiment 1, declines in reinforced responding were assessed and stimulus specificity was evaluated to test habituation's contribution to these declines. Seventy-three participants completed two visits, both including a reinforcement paradigm using pictures. With repetition, operant responding declined. The stimulus specificity manipulation did not enhance responding, suggesting that habituation did not contribute to response declines. Several methodological concerns may have contributed to the absence of a stimulus specificity effect. Experiment 2 assessed a separate habituation characteristic, rate of stimulation, to address these methodological concerns and further evaluate habituation. Twenty-eight participants completed the reinforcement paradigm over three visits. Decline in responding was partially supported, but the rate of stimulation did not alter declines. In sum, habituation's contribution to within-session declines for sensory reinforcers was not evident in either experiment. These results suggest that assessment of habituation of sensory reinforcers in humans may require parametric evaluation.

Sensory variety in shape and color influences fruit and vegetable intake, liking, and purchase intentions in some subsets of adults: a randomized pilot experiment

Dietary variety increases food intake, but it is unclear if sensory differences elicit increases in eating-related behaviors. Using a 4×3 between-subject pilot experiment, we examined if increasing sensory variety (control, color, shape, both color and shape) and priming individuals to notice differences or similarities in the foods (positive, neutral, negative) influenced ad libitum proximal intake, liking, and willingness to purchase pears and peppers among 164 Greater Boston adults >18y/o. MANOVA was used to examine associations between sensory variety (independent variable) and six dependent measures. We tested for interactions between sensory variety condition and individual-level factors that may influence food intake. There was no main effect of sensory variety condition for any dependent measure. However, interactions between sensory variety condition and age, overweight status, and prime were detected. Adults with overweight (vs. adults of normal weight) ate more pear with color variety (7.2 vs. 4.4 oz, p=0.01). Pear intake was also higher among adults with overweight in the color variety (7.2 oz) vs. combination variety (4.4 oz) condition. Adults ≥36y/o ate more peppers (3.5 oz) in the color variety condition versus other conditions (2.1-2.2 oz, p=0.04). Participants primed to notice differences were more willing to purchase pears in the color variety (5.0 ± 0.5) versus control (3.7 ± 0.5) condition. Color variety may modestly increase proximal intake, liking, and purchase intentions for fruits and vegetables in some subsets of adults. Our preliminary findings encourage more research to determine if color variety can be used to improve diet quality of targeted populations.

Incentive motivation in pet dogs - preference for constant vs varied food rewards

Recently, there has been a move towards positive reinforcement using food rewards in animal training. By definition, rewards function as reinforcers if they increase or maintain the frequency of behaviour that they follow. However, in operant conditioning tasks animals frequently show systematic changes in performance - in particular a reduction in responding over time. One suggested strategy to avoid such performance decrements is to provide a variety of food rewards, rather than the same food reward in all trials. The enhancement of appetitive behaviour and consumption by reward variation is referred to as 'variety effect'. We investigated whether dogs preferred a variable or a constant food reward in a concurrent two-choice test. Of 16 dogs, six subjects showed a significant preference for the varied food reward and six for the constant food reward, while four dogs exhibited no significant preference for either option. At the group level, there was a significant effect of block: preference for the varied food reward increased across six blocks of ten trials each. Thus, although some individuals may prefer a single, favourite food reward in the short term, introducing variation in reward types may maintain dogs' motivation in operant tasks over a longer time period.

Effect of exposure to similar flavours in sensory specific satiety: Implications for eating behaviour

Sensory-specific satiety (SSS) refers to a decline in pleasantness of eaten foods in comparison to other non-ingested meals. Although SSS is specific to the eaten food, it can also generalize to other meals that share similar properties to the satiated food. It is possible that this phenomenon could become more specific after extensive experience, as repeated exposure to an assortment of similar food could cause perceptual learning (i.e. an increase in the distinctiveness of each specific item). This in turn would reduce generalization from the consumed food to other similar products, so they will be more readily consumed. To assess this hypothesis, two experiments were carried out using rats as experimental subjects and flavoured solutions as stimuli. In Experiment 1 our main goal was to find the basic SSS effect with two different solutions. As expected, the results showed that rats tended to consume a higher amount of non-sated solutions in comparison to sated ones. Experiment 2 evaluated how repeated exposure to two similar solutions affected generalization of the SSS. Results showed that rats that did not have extensive exposure to the flavoured solutions showed no preference for the non-sated drink. However, rats that had repeated exposure to the flavours showed SSS. The results suggest that easy and continuous access to a high variety of similar unhealthy foods might have long-term effects on food consumption, and highlight a potential mechanism linking obesogenic environments with dietary habits.

Understanding the Relationship Between Food Variety, Food Intake, and Energy Balance

PURPOSE OF REVIEW

In accordance with US dietary guidance, incorporating variety into the diet can align with energy balance, though greater food variety in some categories may make energy balance more challenging. Thus, experimental and epidemiologic evidence is summarized on the relationship between food variety, food and energy intake, and energy balance.

RECENT FINDINGS

Lab-based, experimental research consistently demonstrates that greater variety within foods or sensory characteristics of food increases food and energy intake within an eating occasion. Epidemiologic evidence is less consistent, potentially driven by differing methodologies, particularly in defining and measuring food variety. Moreover, the effect of variety on energy balance appears to be moderated by food energy density. Integrating insights from experimental and epidemiologic research are essential for strengthening food variety guidance including developing evidence-based definitions of food variety, understanding moderators of the relationship, and developing practical guidance interpretable to consumers.

Comparison of three nudge interventions (priming, default option, and perceived variety) to promote vegetable consumption in a self-service buffet setting

BACKGROUND

Dietary choices in out-of-home eating are key for individual as well as for public health. These dietary choices are caused by a wide array of determinants, one of which is automatic decision-making. Nudging is attracting considerable interest due to its understanding and application of heuristic biases among consumers. The aim of this study is to test and compare three nudges in promoting vegetable consumption among test persons in a food lab-based experiment.

METHODS

The initial sample consisted of 88 participants recruited in Copenhagen, Denmark. Each study participant was randomly assigned to one of the three experiments: priming, default and perceived variety. The priming arm of the experiment consisted of creating a leafy environment with green plants and an odour of herbs. In the default arm of the experiment, the salad was pre-portioned into a bowl containing 200g of vegetables. The third experiment divided the pre-mixed salad into each of its components, to increase the visual variety of vegetables, yet not providing an actual increase in items. Each individual was partaking twice thus serving as her/his own control, randomly assigned to start with control or experimental setting.

RESULTS

The default experiment successfully increased the energy intake from vegetables among the study participants (124 kcal vs. 90 kcal in control, p<0.01). Both the priming condition and perceived variety reduced the total energy intake among the study participants (169 kcal, p<0.01 and 124 kcal, p<0.01, respectively), mainly through a decrease in the meat-based meal component.

CONCLUSIONS

Considerable progress has been made with regard to understanding the use of nudging in promoting a healthier meal composition, including increasing vegetable intake. This study suggests that the nature of a nudge-based intervention can have different effects, whether it is increasing intake of healthy components, or limiting intake of unhealthy meal components. This work has demonstrated that consumer behaviour can be influenced without restricting or providing incentives for behaviour change. The present findings have promising application to the foodservice sector.

Behavioral sensitization of the reinforcing value of food: What food and drugs have in common

Sensitization is a basic property of the nervous system whereby repeated exposure to a stimulus results in an increase in responding to that stimulus. This increase in responding contributes to difficulty with treatment of drug abuse, as stimuli associated with substance use become signals or triggers for drug craving and relapse. Our work over the past decade has applied the theoretical framework of incentive sensitization to overeating. We have shown, in several studies, that lean adults do not commonly demonstrate behavioral sensitization after repeated exposure to snack food, but a subset of obese adults reliably does. This review will discuss this change in behavioral response to repeated consumption of snack food in obese individuals and apply the theoretical framework of incentive sensitization to drugs of abuse to high fat/high sugar snack foods. We will also show data that suggest that behavioral sensitization to repeated administration of snack food is predictive of weight gain, which may enhance its utility as a diagnostic tool for identifying at-risk individuals for obesity. Finally, we will discuss the future directions of this line of research, including studying the phenomenon in children and adolescents and determining if similar principles can be used to increase motivation to eat healthier food. A combination of reductions in unhealthy food intake and increases and healthy food intake is necessary to reduce obesity rates and improve health.

Seasoning ingredient variety, but not quality, is associated with greater intake of beans and rice among urban Costa Rican adults

Exposure to a variety of flavors may promote food enjoyment, but few studies have examined the relationship between food seasoning and food intake. We hypothesized that using a higher variety (number) of 11 seasonings to prepare 2 staple foods (beans, white rice) would be associated with intake of those foods in a population-based case-control study of Costa Rican adults in urban vs rural areas (n=1025), where cooking and dietary practices differ. Participants were surveyed about the variety of seasoning ingredients added when preparing beans or rice. Ingredients were also categorized by their dietary quality (healthfulness), and scores for seasoning variety and quality were created. Multivariable linear regression was used to determine the association between variety and quality scores (continuously and in tertiles (T)) and intake of each staple food. Seasoning variety was positively associated with daily servings of beans (β=.02, P=.01; 1.31 and 1.23 servings/day in T2 and T3 versus 1.02 servings/day in T1, P<.05) and rice (β=.04, P=.005) in the urban areas only. No differences in ingredient quality across increasing intakes of beans or rice were noted, and the joint associations between variety and quality were not significant. In conclusion, a greater variety, but not quality, of seasoning ingredients was positively associated with intakes of beans and rice in urban Costa Rican adults. Our results suggest that increasing the variety of seasonings added to beans may be a culturally-appropriate strategy to improve intake of this healthy staple food among urban Costa Rican adults.

Variety, palatability, and obesity

Among the key characteristics of the Western obesogenic food environment is a highly palatable and varied food supply. Laboratory investigations of eating behavior in both humans and animals established key roles for palatability and variety in stimulating appetite, delaying satiety, and promoting excessive energy intake. There is a robust effect of food palatability and variety on short-term food intake, and increased variety and palatability also cause weight gain in animal models. However, laboratory paradigms do not replicate the complexities of eating in a natural setting, and there is a shortage of evidence to estimate the magnitude of effects on weight in humans. There are substantial individual differences in susceptibility to the palatability effect and this may be a key determinant in individual vulnerability to weight gain. The understanding of pathways through which palatability and variety can affect eating is advancing, and epidemiologic and intervention studies are needed to translate laboratory findings into applications in public health or clinical domains, and to establish whether there is a role for greater regulation of the food environment in tackling increases in obesity.

Colour, pleasantness, and consumption behaviour within a meal

It is often claimed that colour (e.g., in a meal) affects consumption behaviour. However, just how strong is the evidence in support of this claim, and what are the underlying mechanisms? It has been shown that not only the colour itself, but also the variety and the arrangement of the differently-coloured components in a meal influence consumers' ratings of the pleasantness of a meal (across time) and, to a certain extent, might even affect their consumption behaviour as well. Typically, eating the same food constantly or repeatedly leads to a decrease in its perceived pleasantness, which, as a consequence, might lead to decreased intake of that food. However, variation within a meal (in one or several sensory attributes, or holistically) has been shown to slow down this process. In this review, we first briefly summarize the literature on how general variety in a meal influences these variables and the major theories that have been put forward by researchers to explain them. We then go on to evaluate the evidence of these effects based mainly on the colour of the food explaining the different processes that might affect colour-based sensory-specific satiety and, in more detail, consumption behaviour. In addition, we also discuss the overlap in the definitions of these terms and provide additional hypothesis as to why, in some cases, the opposite pattern of results has been observed.

Habituation of reinforcer effectiveness

In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE) that links behavioral- and neural-based explanations of reinforcement. We argue that HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009; Rankin etal., 2009). We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow) normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect “accelerated-HRE.” Consideration of HRE is important for the development of effective reinforcement-based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior.

Food characteristics, long-term habituation and energy intake. Laboratory and field studies

Greater food variety is related to increased energy intake, and one approach to reduce food intake is to reduce food variety. The effects of varying the variety of foods at the dinner meal to reduce energy intake was assessed in laboratory and field experiments. Experiment 1 randomly assigned 31 overweight children to one of three conditions that provided one laboratory meal per day over a week. Conditions were the SAME macaroni and cheese, SIMILAR types of macaroni and cheese, or a VARIETY of high-energy-dense foods. On days 1 and 5 all children consumed the same macaroni and cheese meal. Results showed significant differences in energy consumed between SAME and SIMILAR versus VARIETY from day 1 to 5, with SAME and SIMILAR decreasing and VARIETY increasing energy intake. Trials to habituation, a potential mechanism for the variety effect, showed the same pattern of between group differences as energy intake. Experiment 2 randomly assigned 30 overweight children to conditions that provided the SAME, SIMILAR or VARIETY of high-energy-dense entrees along with a variety of low-energy-dense dinner entrees to eat in their homes for 4 weeks. Results showed significant between group differences in energy intake across weeks, with significant decreases over weeks for the SAME and SIMILAR versus VARIETY groups. The pattern of results across the experiments shows the same pattern of reduction in energy intake if children eat the same or similar characteristics of foods (types of macaroni and cheese), which may provide ideas about how to develop dietary variety prescriptions that can reduce intake and be tested in clinical trials.

Vegetable variety: an effective strategy to increase vegetable intake in adults

Effective strategies are needed to increase vegetable intake in accordance with health recommendations. Previous research has shown that increasing the variety of foods leads to increased consumption, yet this strategy has not been investigated for promoting vegetable intake. This crossover study, conducted in 2008 and 2009, tested whether filling half the plate with a variety of vegetables influences vegetable consumption and meal energy intake. Once a week for 4 weeks, a meal of pasta and cooked vegetables was consumed ad libitum by 66 adults (34 women, 32 men). The meals were varied in the type of vegetables offered: at three meals 600 g of a single vegetable was served (broccoli, carrots, or snap peas) and at one meal 200 g of each of the three vegetables was served side by side. Data were analyzed using a mixed linear model with repeated measures. In this study, serving a variety of vegetables increased vegetable intake at the meal (P<0.0001). Subjects ate more vegetables when served the variety than when served any single type; the mean increase was 48±6 g, or more than one-half serving. This increase remained significant when intake of the variety of vegetables was compared with the preferred vegetable of each participant (mean 25±8 g; P=0.002). Vegetable intake was not significantly related to energy intake at the meal. The results of this study demonstrate that increasing the variety of low-energy-dense vegetables served at a meal can be used as a strategy to increase vegetable intake.

Contextual influences on eating behaviours: heuristic processing and dietary choices

This paper reviews some of the evidence that dietary behaviours are, in large part, the consequence of automatic responses to contextual food cues, many of which lead to increased caloric consumption and poor dietary choices. We describe studies that illustrate how these automatic mechanisms underlie eating behaviours, as well as evidence that individuals are subject to inherent cognitive limitations, and mostly lack the capacity to consistently recognize, ignore or resist contextual cues that encourage eating. Restaurants and grocery stores are the primary settings from which people obtain food. These settings are often designed to maximize sales of food by strategically placing and promoting items to encourage impulse purchases. Although a great deal of marketing research is proprietary, this paper describes some of the published studies that indicate that changes in superficial characteristics of food products, including packaging and portion sizes, design, salience, health claims and labelling, strongly influence food choices and consumption in ways for which people generally lack insight. We discuss whether contextual influences might be considered environmental risk factors from which individuals may need the kinds of protections that fall under the mission of public health.

Can limiting dietary variety assist with reducing energy intake and weight loss?

Due to the high prevalence of overweight and obesity, developing strategies to improve weight loss and weight loss maintenance is imperative. One dietary environmental variable that has received little attention in being targeted in an intervention to assist with obesity treatment is dietary variety. Experimental research has consistently shown that greater dietary variety increases consumption, with the effect of variety on consumption hypothesized to be a consequence of the differential experience of the more varied sensory properties of food under those conditions with greater dietary variety. As reduced energy intake is required for weight loss, limiting variety, particularly in food groups that are high in energy-density and low in nutrient-density, may assist with reducing energy intake and improving weight loss. A series of investigations, both observational and experimental, were conducted to examine if limiting variety in an energy-dense, non-nutrient-dense food group, snack foods (i.e., cookies, chips), assisted with reducing energy intake of the food group and improving weight loss. Results of the investigations suggest that a prescription for limiting variety in a food group can be implemented during obesity treatment, limiting variety is associated with the occurrence of monotony, and that reducing food group variety is related to decreased consumption of that food group. Future research is needed to ascertain the long-term effect of prescriptions targeting dietary variety on weight loss and weight loss maintenance.

Slow rates of habituation predict greater zBMI gains over 12 months in lean children

Slow rates of habituation are cross-sectionally related to greater energy intake and body weight. The present study is designed to assess whether slow rates of habituation are prospectively related to zBMI change over a 12 month period in 66 lean 8-12 year-old children, and whether the rate of habituation is a stable behavioral phenotype. Results showed that slower rates of habituation predicted greater zBMI change, controlling for child sex, age, initial zBMI, dietary awareness and minority status. In addition, the rate of habituation was stable over the year of observation. These data suggest that slow rates of habituation may be a risk factor for weight gain and the development of obesity. Future research is needed to understand the mechanism for this effect, and assess whether the habituation phenotype interacts with other behavioral phenotypes, such as food reinforcement, to influence increases in zBMI.

Long-term habituation to food in obese and nonobese women

BACKGROUND

Habituation is a form of learning in which repeated exposure to a stimulus leads to a decrease in responding. Eating involves repeated presentation of the same food stimulus in a meal, and habituation is reliably observed within a meal such that faster rates of habituation are associated with less energy intake. It is possible that repeated presentation of the same food over days will lead to long-term habituation, such that subjects habituate to foods repeated over meals. However, no research on long-term habituation to food in humans has been conducted.

OBJECTIVE

The current study was designed to assess long-term habituation in 16 obese and 16 nonobese premenopausal women.

DESIGN

Obese and nonobese women (aged 20-50 y) were randomly assigned to receive a macaroni and cheese meal presented 5 times, either daily for 1 wk or once per week for 5 wk.

RESULTS

In both obese and nonobese women, daily presentation of food resulted in faster habituation and less energy intake than did once-weekly presentation of food.

CONCLUSIONS

Long-term habituation was observed when the same food was presented at daily meals but not when presented once weekly for 5 wk. These results provide the first evidence of long-term habituation to food in women and show that memory of food over daily meals can increase the rate of habituation and reduce energy intake. This trial was registered at clinicaltrials.gov as NCT01208870.

Relationship between food habituation and reinforcing efficacy of food

Reinforcing value and habituation are two processes that have been used to study eating behaviors, but no research has examined their relationship, how they relate to energy intake, and whether they respond in a similar manner to food deprivation. Twenty-two female subjects were randomized to food deprived or non-deprived conditions, and assessed for food reinforcement, habituation to food and ad libitum eating. Results showed food reinforcement and habituation are correlated (r = 0.62, p = 0.002) and both independently predict energy intake. Hierarchical regression showed that the rate of habituation accounted for 30 percent of the variance in eating (p = 0.008), and adding food reinforcement increased the amount of variance accounted for up to 57.5 percent (p < 0.05). This suggests that both processes may influence energy intake in a meal.