Overweight children habituate slower than non-overweight children to food

Reducing relative food reinforcement of infants using a music enrichment program: a randomized, controlled trial

BACKGROUND

Food reinforcement or one's motivation to eat may be established early in life; it might not be the food reinforcement per se that drives weight gain, but rather the imbalance between food and nonfood reinforcement.

OBJECTIVES

We implemented a 2-y randomized, controlled trial to assess the effects of a music enrichment program (music, n = 45) compared with an active play date control (control, n = 45) in 9- to 15-mo-old healthy infants who were strongly motivated to eat.

METHODS

The 12-mo intensive intervention phase included 4 semesters of Music Together® or a play date program (Winter, Spring, Summer, and Fall), comprised of once per week group meetings, followed by a 12-mo maintenance phase with monthly meetings. Parents were encouraged to listen to the Music Together® program CD or play with the play date group's toy with their infants at home, respectively. We performed a modified intention-to-treat analysis using all randomly assigned, non-excluded subjects for the outcome measures [relative reinforcing value of food (RRVfood), food reinforcement, music reinforcement, and weight-for-length z-score (WLZ)].

RESULTS

There were significant differential group changes across time for RRVfood (group × month; P = 0.016; Cohen's f2 = 0.034). The music group had significantly greater RRVfood decreases than the control group from baseline to the end of the intensive intervention phase (music change = -0.211; control change = -0.015; P = 0.002; Cohen's D = 0.379). However, these differences were not maintained during months 12-24 (music change = -0.187; control change = -0.143; P = 0.448; D = 0.087). We observed an overall moderation effect by sex for food reinforcement and WLZ. Boys in the music group had a significant attenuation in food reinforcement and WLZ compared with boys in the control group.

CONCLUSIONS

This study extends our knowledge in infant eating behavior by providing insight into the role of nonfood alternatives in altering one's motivation to eat. There may be sex differences in altering one's motivation to eat.This trial was registered at clinicaltrials.gov as NCT02936284.

Effect of Obesity Surgery on Taste

Obesity surgery is a highly efficacious treatment for obesity and its comorbidities. The underlying mechanisms of weight loss after obesity surgery are not yet fully understood. Changes to taste function could be a contributing factor. However, the pattern of change in different taste domains and among obesity surgery operations is not consistent in the literature. A systematic search was performed to identify all articles investigating gustation in human studies following bariatric procedures. A total of 3323 articles were identified after database searches, searching references and deduplication, and 17 articles were included. These articles provided evidence of changes in the sensory and reward domains of taste following obesity procedures. No study investigated the effect of obesity surgery on the physiological domain of taste. Taste detection sensitivity for sweetness increases shortly after Roux-en-Y gastric bypass. Additionally, patients have a reduced appetitive reward value to sweet stimuli. For the subgroup of patients who experience changes in their food preferences after Roux-en-Y gastric bypass or vertical sleeve gastrectomy, changes in taste function may be underlying mechanisms for changing food preferences which may lead to weight loss and its maintenance. However, data are heterogeneous; the potential effect dilutes over time and varies significantly between different procedures.

Food reinforcement and habituation to food are processes related to initiation and cessation of eating

An individual bout of eating involves cues to start eating, as well as cues to terminate eating. One process that determines initiation of eating is food reinforcement. Foods with high reinforcing value are also likely to be consumed in greater quantities. Research suggests both cross-sectional and prospective relationships between food reinforcement and obesity, food reinforcement is positively related to energy intake, and energy intake mediates the relationship between food reinforcement and obesity. A process related to cessation of eating is habituation. Habituation is a general behavioral process that describes a reduction in physiological or affective response to a stimulus, or a reduction in the behavioral responding to obtain a stimulus. Repeated exposure to the same food during a meal can result in habituation to that food and a reduction in consumption. Habituation is also cross-sectionally and prospectively related to body weight, as people who habituate slower consume more in a meal and are more overweight. Research from our laboratory has shown that these two processes independently influence eating, as they can account for almost 60% of the variance in ad libitum intake. In addition, habituation phenotypes show reliable relationships with reinforcing value, such that people who habituate faster also find food less reinforcing. Developing a better understanding of cues to start and stop eating is fundamental to understanding how to modify eating behavior. An overview of research on food reinforcement, habituation and food intake for people with a range of weight status and without eating disorders is provided, and ideas about integrating these two processes that are related to initiation and termination of a bout of eating are discussed.

Rationale and protocol for translating basic habituation research into family-based childhood obesity treatment: Families becoming healthy together study

This publication describes the rationale and protocol, including design, aims, intervention, and measures, of Families Becoming Healthy Together, a randomized clinical trial examining the effect of a limited RED (non-nutrient-dense, energy-dense) food variety prescription delivered within an 18-month family-based behavioral obesity treatment (FBT) on body mass index (BMI) and habituation rate to RED foods. One hundred fifty-six children (ages: 8-12 y; BMI: ≥ 85th percentile-for-age) and a caregiver (BMI: ≥ 25 kg/m2), both with overweight or obesity, will be randomized to one of two, interventions: FBT or FBT + Variety. All participants will receive 29 sessions of FBT and be prescribed the Traffic Light Diet (1000-1500 kcal/day, ≤ 2 RED food servings/day), and a physical activity goal (≥ 60 min/day [child] or 150 min/week [adult] of moderate-vigorous physical activity (MVPA)). FBT + Variety will also identify two RED foods, a dinner entrée and snack food, and develop meal plans that reduce variety of RED foods by regularly consuming these foods and limiting consumption of other RED foods. Measures of anthropometrics, dietary intake, habituation of salivary response to food cues, and physical activity will be assessed at 0, 6, 12, and 18-months. This study translates a line of basic behavioral research examining how dietary variety influences habituation into a dietary prescription that will be tested within an efficacy trial. It is hypothesized that a novel, limited dietary variety prescription within FBT should promote a faster food habituation rate, reducing energy intake and amplifying long-term weight loss in children.

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.

Smartphones are more reinforcing than food for students

College students engage in high-frequency smartphone use, despite potential negative consequences. One way to conceptualize this behavior is to consider it a highly reinforcing activity. Comparing motivation for smartphones to a powerful primary reinforcer, such as food, can establish their relative reinforcing value. This study investigated whether smartphones were more reinforcing than food, as well as the relationships between smartphone reinforcement, texting use, and smartphone motives. Participants were 76 college students (50% female, M_age = 18.9, SD = 0.99) who had no access to food for three hours and to their smartphones for two hours. After this modest deprivation period, participants worked for time to use their smartphones and 100-cal portions of their favorite snack food concurrently, with the work to obtain portions of both commodities increasing. The amount of smartphone use earned during the task was manipulated across groups (20, 30, 60, 120 s) to establish what amount of smartphone use was needed to motivate responding. Additionally, reinforcing efficacy of smartphones and food using a hypothetical purchase task and motivations for smartphone use was collected. Smartphones were more reinforcing than food using either measurement methodology (p's < 0.001). Smartphone reinforcement predicted number of text messages, controlling for age, sex, and family income. Positive smartphone use motives were associated with reinforcing efficacy of smartphones. These data show that smartphones are potent reinforcers, and are more reinforcing than food given modest food deprivation. These methods provide one important reason why people may use smartphones.

Food Intake and Eating Behavior After Bariatric Surgery

Obesity is an escalating global chronic disease. Bariatric surgery is a very efficacious treatment for obesity and its comorbidities. Alterations to gastrointestinal anatomy during bariatric surgery result in neurological and physiological changes affecting hypothalamic signaling, gut hormones, bile acids, and gut microbiota, which coalesce to exert a profound influence on eating behavior. A thorough understanding of the mechanisms underlying eating behavior is essential in the management of patients after bariatric surgery. Studies investigating candidate mechanisms have expanded dramatically in the last decade. Herein we review the proposed mechanisms governing changes in eating behavior, food intake, and body weight after bariatric surgery. Additive or synergistic effects of both conditioned and unconditioned factors likely account for the complete picture of changes in eating behavior. Considered application of strategies designed to support the underlying principles governing changes in eating behavior holds promise as a means of optimizing responses to surgery and long-term outcomes.

Playing with food: The effects of food pre-exposure on consumption in young children

Recent research has shown that pre-exposure to food can lead to reduced subsequent consumption in older children and adults when they focus on a task with a non-eating goal during exposure. One assumption is that the reduced consumption is a consequence of self-regulation that helps to concentrate on the task. Because self-regulatory mechanisms are still under development in young children, we studied the effects of food pre-exposure in young children under the age of six (N = 81). Children played a memory game with real sweets (food pre-exposure) or similar non-food stimuli (non-food pre-exposure) and we measured their subsequent food consumption. In contrast to the findings with older children in other studies, we found that pre-exposure led to an increase (not a decrease) in subsequent consumption. This effect was stronger among children with a higher BMI. Food exposure paradigms might not lead to the desired reduction in food intake in young children, whose BMI is positively associated with food reactivity. Thus, food exposure must continue to be considered a strong risk factor for obesity in young children.

Oral processing behaviours that promote children's energy intake are associated with parent-reported appetitive traits: Results from the GUSTO cohort

Oral processing behaviours associated with faster eating rates have been consistently linked to increased energy intakes, but little is known about their links to children's appetitive traits. This study used the Child Eating Behaviour Questionnaire (CEBQ) to explore cross-sectional and prospective associations between parent-reported appetitive traits and observed oral processing behaviours. Participants were 195 children from the Growing Up in Singapore Towards healthy Outcomes cohort, who participated in a video-recorded ad libitum lunch at 4.5 (Time 1) and 6 years (Time 2). Their mothers completed the CEBQ around the same time points. Children's bites, chews and swallows were coded, and used to calculate their eating rate, bite size, chews per bite, chew rate, oral exposure time and oral exposure per bite. At Time 1, children with higher scores in slowness in eating had lower eating and chew rates. At Time 2, higher scores for food enjoyment and lower for satiety responsiveness, slowness in eating, and food fussiness were linked with higher eating rates and greater energy intakes (r > 0.16, p < 0.05). Post-hoc analyses revealed that these associations were moderated by BMI and only present among children with higher BMI. Faster eating rates mediated the associations between greater food enjoyment, lower slowness in eating, lower food fussiness and higher intakes of energy. Children with higher slowness in eating scores had lower increases in eating rates over time, and children with higher BMI who had greater food enjoyment and food responsiveness scores had greater increases in eating rates over time. The findings suggest that oral processing behaviours linked with increased obesity risk may be underpinned by appetitive traits and may be one of the behavioural pathways through which these appetitive traits influence energy intakes.

Cue reactivity, habituation, and eating in the absence of hunger in children with loss of control eating and attention-deficit/hyperactivity disorder

OBJECTIVE

Childhood loss of control (LOC) eating and attention-deficit/hyperactivity disorder (ADHD) are highly comorbid conditions and present with disordered eating behaviors, such as overeating. This study sought to delineate shared and specific abnormalities in physiological, cognitive-motivational, and behavioral components of food-specific impulsivity in children with LOC eating and ADHD. Specifically, children's reactivity and habituation to food and eating in the absence of hunger were examined.

METHODS

Within this community-based study, four groups of 8-13-year-old children with LOC eating (n = 24), ADHD (n = 32), comorbid LOC eating/ADHD (n = 9), and matched controls (n = 34) received a standard laboratory test meal to establish satiety and were then exposed to their favorite snack food in a cue exposure/reactivity trial, while salivation and desire to eat were repeatedly assessed. Subsequently, they were offered a variety of snack foods ad libitum.

RESULTS

Children with LOC eating, ADHD, and LOC/ADHD did not differ from controls in salivary reactivity and habituation to food cues. Children with LOC eating and ADHD showed greater cue reactivity of the desire to eat than controls, but groups did not differ in its longer-term increments. At free access, only children with LOC/ADHD consumed significantly more energy than controls. Longer-term increments of desire to eat predicted greater energy intake beyond LOC/ADHD group status.

DISCUSSION

Desire to eat among children with comorbid LOC eating and ADHD was associated with overeating in the absence of hunger, which may contribute to excess weight gain. Delineation of the specific features of childhood LOC eating versus ADHD warrants further study.

Effects of Imagined Consumption and Simulated Eating Movements on Food Intake: Thoughts about Food Are Not Always of Advantage

Imagined food consumption is a method of elaborately imagining oneself eating a specific food that, when repeated 30 times, has been shown to decrease subsequent intake of the same food. The technique relies on a memory-based habituation process when behavioral and motivational responses to a stimulus decrease after its repeated presentation. Thus, repeatedly imagining food consumption leads to food-specific habituation effects. Large numbers of imagined consumption repetitions are effortful and time consuming and can be problematic when applied in interventions with the goal of reducing food intake. In the present study, we assessed the efficacy of the technique at smaller numbers of repetitions while testing motor simulation as a potential facilitator of the habituation-based consumption-reduction effect. 147 participants imagined eating chocolate pudding 15 or 3 consecutive times and simultaneously performed either facilitating or not-facilitating eating movements. Results showed that participants who imagined eating the chocolate pudding 15 times (M₁₅ = 178.20, SD₁₅ = 68.08) ate more of the pudding than those who imagined consuming it 3 times (M₃ = 150.73, SD₃ = 73.31). The nature of the motor movements that were performed did not impact this effect. The data suggest that the imagined food consumption technique can result in an unexpected increase in food consumption, when smaller numbers of imagination repetitions are performed.

Effect of Interpersonal and Cognitive Stressors on Habituation and the Utility of Heart Rate Variability to Measure Habituation

Habituation is a decrease in responding to a repeated stimulus. Operant responding and salivation measure habituation in eating behaviour research. Stress may increase eating by acting as a distractor, yielding spontaneous recovery and prolonging responding for food. Our research tested differences in the ability of cognitive and interpersonal stressors to recover responding for food. We also tested heart rate variability (HRV) as a measure of habituation. Twenty women worked for portions of macaroni and cheese for 15 trials on three separate laboratory visits. Between the 12th and 13th trial, one of three different stressor types (speech, stroop and subtraction) was presented during each visit. HRV was measured continuously throughout the laboratory visits. Responding for food declined across the 12 trials with no difference in rate of habituation by visit (p > 0.8) There was no difference between stressor type in the magnitude of spontaneous recovery after each stressor (p > 0.8). Rates of habituation of HRV variables correlated (p < 0.02) with the rate of operant responding habituation. Cognitive and interpersonal stressors do not differ in their ability to recover reduced responding for food. HRV variables may measure habituation to food similar to operant responding. Copyright © 2014 John Wiley & Sons, Ltd.

Pavlovian conditioning to hedonic food cues in overweight and lean individuals

Obese individuals develop heightened reactivity to environmental cues associated with hedonic foods through Pavlovian conditioning. This study examined differences between overweight (n = 16) and lean (n = 17) 18-26 year-olds in their acquisition of a swallowing response to visual cues paired with chocolate milk, tasteless water and no taste stimulus. We hypothesized that, compared to lean participants, overweight participants would demonstrate a heightened conditioned swallowing response to the visual cue paired with chocolate milk as well as a resistance to extinction of this response. Results showed that overweight participants swallowed more in response to the visual cue previously paired with chocolate than the cue previously paired with tasteless water (t(15) = -3.057, p = .008) while lean participants showed no cue discrimination (t(16) = -1.027, p = .320). The results evaluating the extinction hypothesis could not be evaluated, as the lean participants did not acquire a conditioned response. In evaluating the conditioned swallow response of overweight participants only, results indicated that there was not a significant decrease in swallowing to cues paired with chocolate milk or water, but overall, overweight participants swallowed more to cues paired with chocolate than cues paired with water. These are the first results to show differential acquisition of Pavlovian conditioned responding in overweight individuals compared to lean individuals, as well as differential conditioning to cues paired with hedonic food stimuli compared to cues paired with neutral stimuli.

Mental imagery interventions reduce subsequent food intake only when self-regulatory resources are available

Research has shown that imagining food consumption leads to food-specific habituation effects. In the present research, we replicated these effects and further examined whether the depletion of self-regulatory resources would reduce the habituation effects of imagined food consumption. Since self-regulatory resources have been shown to reduce habituation effects during the perception of emotional stimuli, we expected a reduction in habituation effects from imagined food consumption when self-regulatory resources were depleted. In Study 1, we replicated habituation effects as a response to imagining gummy bear consumption with a high (36) and medium number (18) of repetitions in a camouflaged taste test. Participants imagining gummy bear intake showed decreased food intake compared with participants who imagined putting a coin into a laundry machine. The number of repetitions did not significantly moderate the observed habituation effect. In Study 2, we investigated whether self-regulatory depletion would impede habituation effects evoked by the imagination of walnut consumption. Participants in a depleted state did not show a reduction in food intake after imagining walnut intake compared with participants in a non-depleted state. We discuss directions for future research and processes that might underlie the observed moderating effect of self-regulatory resources.

Saliva from obese individuals suppresses the release of aroma compounds from wine

Background

Recent evidence suggests that a lower extent of the retronasal aroma release correspond to a higher amount of ad libitum food intake. This has been regarded as one of the bases of behavioral choices towards food consumption in obese people. In this pilot study we investigated the hypothesis that saliva from obese individuals could be responsible for an alteration of the retro-nasal aroma release. We tested this hypothesis in vitro, by comparing the release of volatiles from a liquid food matrix (wine) after its interaction with saliva from 28 obese (O) and 28 normal-weight (N) individuals.

Methods and Findings

Amplicon sequencing of the 16S rRNA V4 region indicated that Firmicutes and Actinobacteria were more abundant in O, while Proteobacteria and Fusobacteria dominated in N. Streptococcaceae were significantly more abundant in the O subjects and constituted 34% and 19% on average of the saliva microbiota of O and N subjects, respectively. The Total Antioxidant Capacity was higher in O vs N saliva samples. A model mouth system was used to test whether the in-mouth wine aroma release differs after the interaction with O or N saliva. In O samples, a 18% to 60% significant decrease in the mean concentration of wine volatiles was detected as a result of interaction with saliva, compared with N. This suppression was linked to biochemical differences in O and N saliva composition, which include protein content.

Conclusion

Microbiological and biochemical differences were found in O vs N saliva samples. An impaired retronasal aroma release from white wine was detected in vitro and linked to compositional differences between saliva from obese and normal-weight subjects. Additional in vivo investigations on diverse food matrices could contribute to understanding whether a lower olfactory stimulation due to saliva composition can be a co-factor in the development/maintenance of obesity.

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.

Appetitive traits from infancy to adolescence: using behavioral and neural measures to investigate obesity risk

We come into the world with enduring predispositions towards food, which interact with environmental factors to influence our eating behaviors and weight trajectories. But our fates are not sealed - by learning more about this process we can identify ways to intervene. To advance this goal this we need to be able to assess appetitive traits such as food cue responsiveness and satiety sensitivity at different developmental stages. Assessment methods might include behavioral measures (e.g. eating behavior tests, psychometric questionnaires), but also biomarkers such as brain responses to food cues measured using fMRI. Evidence from infants, children and adolescents suggests that these indices of appetite differ not only with body weight, but also with familial obesity risk as assessed by parent weight, which reflects both genetic and environmental influences, and may provide a useful predictor of obesity development. Behavioral and neural approaches have great potential to inform each other: examining eating behavior can help us identify meaningful appetitive endophenotypes whose neural bases can be probed, while increasing knowledge of the shared neurobiology underlying appetite, obesity, and related behaviors and disorders may ultimately lead to innovative generalized interventions. Another challenge will be to combine comprehensive behavioral and neural assessments of appetitive traits with measures of relevant genetic and environmental factors within long-term prospective studies. This approach may help to identify the biobehavioral precursors of obesity, and lay the foundations for targeted neurobehavioral interventions that can interrupt the pathway to excess weight.

The non-advertising effects of screen-based sedentary activities on acute eating behaviours in children, adolescents, and young adults. A systematic review

Sedentary screen time may be an important determinant of childhood obesity. A number of potential mechanisms to explain the link between screen time and increased bodyweight have been proposed; however, the relationship appears to be best explained by the effects on dietary intake, which is attributed to either food advertising or effects independent of food advertising. Technological advances have allowed for greater accessibility and exposure to advertisement-free screen-based media. This review was conducted to systematically synthesise the evidence from laboratory based studies which have investigated the non-advertising effects of screen time (TV viewing, sedentary video games, and computer use) on dietary intake in children, adolescents, and young adults. MEDLINE, PubMed, PsychInfo, CINAHL, and Embase were searched from inception through 5 July 2013. Ten trials met the inclusion criteria and were included in the review. Risk of study bias was judged to range from low to high. Screen time in the absence of food advertising was consistently found to be associated with increased dietary intake compared with non-screen behaviours. Suggested explanations for this relationship included: distraction, interruption of physiologic food regulation, screen time as a conditioned cue to eat, disruption of memory formation, and the effects of the stress-induced reward system. Due to the limited number of high-quality studies available for this review, our findings are preliminary. More work is required to better establish the link between dietary intake and advertisement-free screen time and assess whether differences exist between the different screen-based activities.

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.

An exploration of salivation patterns in normal weight and obese children

We examined whether children's changes in salivary habituation to food vary based on weight status and/or allocating attention to a task. Children (31 non-overweight and 26 obese, ages 9-12 year) were presented with nine trials of a food stimulus and either listened to an audiobook (attention-demanding) or white noise (no-attention control). The salivary pattern differed significantly by weight status but not by condition or a condition by weight status interaction. This is the first study of salivary habituation in obese children; findings dovetail with an emerging set of evidence that obese individuals display distinctive biological responses to food.

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.

Habituation as a determinant of human food intake

Research has shown that animals and humans habituate on a variety of behavioral and physiological responses to repeated presentations of food cues, and habituation is related to amount of food consumed and cessation of eating. The purpose of this article is to provide an overview of experimental paradigms used to study habituation, integrate a theoretical approach to habituation to food based on memory and associative conditioning models, and review research on factors that influence habituation. Individual differences in habituation as they relate to obesity and eating disorders are reviewed, along with research on how individual differences in memory can influence habituation. Other associative conditioning approaches to ingestive behavior are reviewed, as well as how habituation provides novel approaches to preventing or treating obesity. Finally, new directions for habituation research are presented. Habituation provides a novel theoretical framework from which to understand factors that regulate ingestive behavior.

Variety influences habituation of motivated behavior for food and energy intake in children

BACKGROUND

Research has shown that variety reduces the rate of habituation, or a general reduction in the rate of responding, for low-energy-density (LED) and high-energy-density (HED) foods.

OBJECTIVE

We assessed whether the effects of variety on habituation of motivation to eat are different in overweight and lean children.

DESIGN

Overweight and lean children (n = 84) were randomly assigned to groups that varied as to whether they received their favorite or a variety of LED or HED foods.

RESULTS

Habituation was slower for overweight than for nonoverweight children (P = 0.008), for a variety of foods than for the same foods (P < 0.001), and for LED than for HED foods (P < 0.001). Energy intake was greater for overweight than for nonoverweight children provided with variety (P = 0.004) and was greater for overweight or nonoverweight children provided with the same food (P < 0.001). A variety of HED foods increased energy intake more than did the same HED foods (P < 0.001); this increase was greater than energy intake with the same or a variety of LED foods (P < 0.001). Children who sensitized, or showed an increase in responding before habituating, showed slower habituation (P < 0.001) and consumed more energy (P = 0.039) than did children who did not sensitize.

CONCLUSIONS

Habituation is influenced by variety of foods, and overweight children increase energy intake more with variety than do leaner children. Research is needed to evaluate mechanisms of how variety influences the motivation to eat and energy intake, and how the variety effect can be used to influence intake across multiple eating occasions in children.

Appetitive traits and child obesity: measurement, origins and implications for intervention

Childhood obesity has multiple causes, most of them capable of explaining only one part of the problem. The population-wide impact of sedentary lifestyles and availability of energy-dense food is undeniable, but substantial individual differences in body weight persist, suggesting that individuals respond differently to the 'obesogenic' environment. One plausible mechanism for this variation is the early expression of appetitive traits, including low responsiveness to internal satiety signals, high responsiveness to external food cues, high subjective reward experienced when eating liked foods and preferences for energy-dense foods. Case-control studies support the existence of abnormalities in these traits among obese children compared with normal-weight children, and correlations between psychometric measures of child appetite and child weight suggest that appetitive trait profiles may not only promote obesity but also protect against it. The origins of appetitive traits are as yet uncharted, but will include both genetic and environmental influences. Parental feeding style may affect the development of appetite but the exact nature of the relevant behaviours is unclear and many studies are cross-sectional or begin late in childhood, obscuring causal relationships. Future research should explore determinants and biological mechanisms by using prospective designs beginning early in life, measuring relevant biomarkers such as gut hormones and incorporating neuroimaging and genotyping technologies. Potential clinical applications include the identification of 'at risk' children early in life and interventions to modify appetitive traits or ameliorate their impact on intake and weight.

Sensitization and habituation of motivated behavior in overweight and non-overweight children

The rate of habituation to food is inversely related to energy intake, and overweight children may habituate slower to food and consume more energy. This study compared patterns of sensitization, as defined by an initial increase in operant or motivated responding for food, and habituation, defined by gradual reduction in responding, for macaroni and cheese and pizza in overweight and non-overweight 8-12 year-old children. Non-overweight children habituated faster to both foods than overweight children (p = 0.03). All children recovered motivated responding for a new food (chocolate). Overweight children consumed more energy than non-overweight children (p = 0.0004). Children who showed a sensitization in responding consumed more food (p = 0.001), and sensitization moderated the effect of overweight on habituation, with slower habituation for overweight children who sensitized (p < 0.0001). This study replicates previous data on overweight/non-overweight differences in habituation of food and of energy intake, and provides new information that individual differences in sensitization and habituation of motivated responding to food cues may be associated with a sustained motivation to eat, resulting in greater energy intake.

Dietary variety impairs habituation in children

OBJECTIVE

The purpose of these studies was to test the hypothesis that dietary variety decreases the rate of habituation and increases energy intake in children.

DESIGN

In Experiment 1, salivation in response to the same or a variety of food cues was measured followed by consumption of the study food(s). In Experiment 2, children responded in a computer task to earn points for the same or a variety of low or high energy density foods, which were then consumed.

MAIN OUTCOME MEASURES

Salivation, number of responses, and energy intake were measured.

RESULTS

Participants in the same groups habituated faster than those in the variety groups (p = .05), and in Experiment 2, the effect of variety was independent of energy density. Participants in the variety groups also consumed more energy than those in the same groups in both experiments (p = .05).

CONCLUSIONS

Dietary variety disrupted habituation and increased energy intake in children. In addition, the response to dietary variety was independent of energy density, suggesting that increasing variety of low energy density foods may increase consumption.

Dietary variety impairs habituation in children

OBJECTIVE

The purpose of these studies was to test the hypothesis that dietary variety decreases the rate of habituation and increases energy intake in children.

DESIGN

In Experiment 1, salivation in response to the same or a variety of food cues was measured followed by consumption of the study food(s). In Experiment 2, children responded in a computer task to earn points for the same or a variety of low or high energy density foods, which were then consumed.

MAIN OUTCOME MEASURES

Salivation, number of responses, and energy intake were measured.

RESULTS

Participants in the same groups habituated faster than those in the variety groups (p = .05), and in Experiment 2, the effect of variety was independent of energy density. Participants in the variety groups also consumed more energy than those in the same groups in both experiments (p = .05).

CONCLUSIONS

Dietary variety disrupted habituation and increased energy intake in children. In addition, the response to dietary variety was independent of energy density, suggesting that increasing variety of low energy density foods may increase consumption.