Priming food intake with weight control cues: systematic review with a meta-analysis

Exploring Whether Weight-Related Cues Affect Food Intake in Older Adults with Dementia

Purpose

Past research has shown that exposure to the image of a slim person reduces food consumption among young adults. However, it remains unknown whether this paradigm could be adapted and applied to increase food intake among older adults with dementia by exposing them to the image of a higher-weight person to mitigate weight loss and malnutrition. The present study explored whether weight-related visual cues affect the amount of food consumed by older adults with dementia.

Participants and Methods

In the experiment, twenty-one elderly people with dementia living in a nursing home were visually exposed to one of four conditions (a cartoon image of a normal-weight chef, a higher-weight chef, a flower or no image) during real-life daily lunch situations over the course of four weeks, during which each condition was presented for one week.

Results

Results demonstrate that participants finished their meals more frequently when they were exposed to the image of the higher-weight chef than when they were not exposed to any images.

Conclusion

These results suggest that exposure to a cartoon chef character representing a stereotyped social group related to body weight activates the stereotype and increases stereotype-consistent behavior in older adults with dementia. The present findings will contribute to understanding the effect of visual information on eating behavior and to designing eating environments which facilitate sufficient nutrition intake among older adults with dementia.

Autobiographical memory specificity and restrained eating: examining the influence of priming with images of healthy and unhealthy foods

BACKGROUND

Dietary restraint has been linked to deficits in the ability to recall detailed memories of personally experienced events (referred to as autobiographical memory specificity). As priming with healthy foods increases the salience of restraint it would be expected to lead to greater deficits in memory specificity.

OBJECTIVE

To determine if priming word cues with images of healthy or unhealthy foods would influence the specificity of memory retrieval, and if deficits in memory specificity would be more evident in those reporting higher levels of dietary restraint, or currently dieting.

METHODS

Sixty female undergraduates self-reported if they were currently dieting and completed measures of mood, restraint, and disinhibition, and a modified version of the autobiographical memory task. Participants were presented with positive and negative words (unrelated to eating concerns) and asked to retrieve a specific memory in response to each cue. A food image was shown prior to each word cue; half of the participants were primed with images of healthy foods and half with images of unhealthy foods.

RESULTS

As expected, participants primed with healthy foods retrieved fewer specific memories than did those primed with unhealthy foods. However, neither restraint nor current dieting behaviour was associated with memory specificity.

CONCLUSIONS

Differences in memory specificity between the priming conditions cannot be explained in terms of increased salience of restraint. However, it is plausible that unhealthy images led to an increase in positive affect, which in turn improved memory specificity.

LEVEL OF EVIDENCE

Level I: Evidence obtained from: at least one properly designed experimental study.

The Effect of Augmented Reality and Privacy Priming in a Fashion-Related App: An Application of Technology Acceptance Model

In this research, we tested (a) the effects of augmented reality (AR) and (b) how the effects of AR could be moderated by privacy perceptions. We used a 2 eyewear app type (AR vs. non-AR) by 2 privacy priming (prime vs. no prime) between-subject experimental design, and 114 Korean adults participated in the experiment. Results showed that AR had a main effect on perceived ease of use but not on perceived usefulness. Instead, the effect of AR on perceived usefulness was moderated by privacy priming such that the positive effect of AR on perceived usefulness was weaker when privacy concern was salient. Moreover, the results provided support for a moderated mediation model in which the indirect effect of AR on intent to use the app via perceived usefulness was moderated by privacy priming. Theoretical and practical implications are discussed.

Usability Testing an mHealth Program with Tailored Motivational Messages for Early Adolescents

Obesity among children is a rising concern throughout the world. In the U.S., rates of childhood obesity are the highest among children from diverse and economically disadvantaged households. Obesity in adolescence increases the risk of negative physical and psychological health consequences. Mobile-app-based health interventions have been found to be an effective tool to encourage children to adopt a healthier living style. A novel mobile app prototype was developed for early adolescents to communicate with and engage them interactively about healthy eating and active living. To test the app's usability, students from a U.S. middle school, with a majority of children from low-income families, were recruited to use the app and report their feedback. The usability testing results confirmed that the app was equally well received by participants of different genders, normal weight versus overweight/obesity, and amounts of screen time. Study participants also provided overwhelming positive feedback for the embedded and tailored motivational messages that encourage healthy eating and active living. The conceptualization of the app prototype was guided by the self-determination theory, social cognitive theory, and priming theory, in addition to incorporating evidence-based obesity prevention principles. This prototype, hence, provides a valid platform for building theory-based behavioral interventions.

Calorie reformulation: a systematic review and meta-analysis examining the effect of manipulating food energy density on daily energy intake

BACKGROUND

Dietary energy density is thought to be a contributor to obesity, but the extent to which different magnitudes and types of reductions to food energy density decreases daily energy intake is unclear. The primary objective was to systematically review and meta-analyse experimental studies that have examined the effect that manipulating energy density of food has on total daily energy intake. Secondary objectives were to examine moderators of the effect that altering energy density has on daily energy intake and effects on body weight.

METHODS

A systematic review and multi-level meta-analysis of studies on human participants that used an experimental design to manipulate the energy density of foods served and measured energy intake for a minimum of 1 day.

RESULTS

Thirty-one eligible studies sampling both children (n = 4) and adults (n = 27) contributed 90 effects comparing the effect of higher vs. lower energy density of served food on daily energy intake to the primary meta-analysis. Lower energy density of food was associated with a large decrease in daily energy intake (SMD = - 1.002 [95% CI: - 0.745 to - 1.266]). Findings were consistent across studies that did vs. did not manipulate macronutrient content to vary energy density. The relation between decreasing energy density and daily energy intake tended to be strong and linear, whereby compensation for decreases to energy density of foods (i.e. by eating more at other meals) was minimal. Meta-analysis of (n = 5) studies indicated that serving lower energy dense food tended to be associated with greater weight loss than serving higher energy dense food, but this difference was not significant (- 0.7 kg difference in weight change, 95% CIs: - 1.34, 0.04).

CONCLUSIONS

Decreasing the energy density of food can substantially reduce daily energy intake and may therefore be an effective public health approach to reducing population level energy intake.

TRIAL REGISTRATION

Registered on PROSPERO ( CRD42020223973 ).

Battle of the primes - The effect and interplay of health and hedonic primes on food choice

People making food choices are often exposed to different cues that can activate relevant goals that influence the choice outcome. Hedonic goals are frequently primed by advertising while health policy enlists primes that activate health goals in the moment of food decision-making - e.g., healthy food labels. However, little is known about the effect of such goal-priming cues on the population level and how people respond when exposed to both types of primes simultaneously. The results of this study, based on a large, representative sample (N = 1200), show no effect of health-goal priming on healthy food choices. Being exposed to a sole hedonic prime, however, reduces healthy choices by 3%. This effect completely disappeared when both primes were presented at the same time. All effects remained insensitive to people's gender, hunger status, level of dietary restraint, and BMI. These findings cast doubt over the effectiveness of health goal primes as a tool to increase healthy food choices but suggest a protective effect against competing hedonic primes and could thereby prevent less healthy choices.

Examining the neural correlates of goal priming with the NeuroShop, a novel virtual reality fMRI paradigm

OBJECTIVE

Health goal priming has been shown to stimulate healthy food choices by activating an individual's weight-control goal. The present study combined fMRI with a novel virtual reality food choice task to elucidate the underlying neural mechanisms of health goal priming. Previous research has suggested that the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) play a role in the incorporation of health considerations into the food choice process. Responses may be more representative for those found in real life when assessed in an environment similar to the actual choice environment. Therefore, the first aim of the study was to explore if a novel virtual reality food choice task is sufficiently sensitive to detect basic valuation processes in food choice. The second aim was to examine whether increased activation in the dlPFC drives the effects of health goal priming.

METHODS

Fifty-six female participants performed an fMRI food choice task embedded in a virtual supermarket environment. They chose between perceived healthy and unhealthy products in a health prime, hedonic prime, and non-food control condition, while activation in brain areas involved in self-control and valuation (vmPFC, dlPFC) was assessed.

RESULTS

There were no differences in relative preference for perceived healthy products over unhealthy products between the conditions. There were also no main effects of prime condition on brain activation in the vmPFC and dPFC during food choice. Across conditions, activation in the vmPFC correlated with the tastiness of the chosen product during food choice.

CONCLUSIONS

Although the study does not provide support for health goal priming triggering neural self-control mechanisms, results did show that virtual reality has potential for a more realistic fMRI food choice paradigm.

Incidental exposure to hedonic and healthy food features affects food preferences one day later

Memories acquired incidentally from exposure to food information in the environment may often become active to later affect food preferences. Because conscious use of these memories is not requested or required, these incidental learning effects constitute a form of indirect memory. In an experiment using a novel food preference paradigm (n = 617), we found that brief incidental exposure to hedonic versus healthy food features indirectly affected food preferences a day later, explaining approximately 10% of the variance in preferences for tasty versus healthy foods. It follows that brief incidental exposure to food information can affect food preferences indirectly for at least a day. When hedonic and health exposure were each compared to a no-exposure baseline, a general effect of hedonic exposure emerged across individuals, whereas health exposure only affected food preferences for high-BMI individuals. This pattern suggests that focusing attention on hedonic food features engages common affective processes across the general population, whereas focusing attention on healthy food features engages eating restraint goals associated with high BMI. Additionally, incidental exposure to food features primarily changed preferences for infrequently consumed foods, having less impact on habitually consumed foods. These findings offer insight into how hedonic information in the obesogenic food environment contributes to unhealthy eating behavior that leads to overweight and obesity. These findings further motivate the development of interventions that counteract the effects of exposure to hedonic food information and that broaden the effects of exposure to healthy food information.

The influence of supraliminal priming on energy density of food selection: a randomised control trial

Background

Many people exercise because they know it is good for their health. Although this is true, it can make us feel deserving of a reward and lead us to eat more indulgent, less healthy food than if we had not done any exercise. Generally, lower energy-dense (LED) foods are recognised as healthier choices than higher energy-dense (HED) options. Despite our intention to make healthy choices, seeing tempting higher-calorie foods on offer often side-tracks us. Priming is a psychological tool that makes specific changes to our environment that remind us of our motivation to be healthy. This makes it easier to choose a healthier option, by nudging us towards it without us even realising. However, it is currently unclear which method of priming achieves the best results.

Aims

Our study explores whether priming people to expect they will receive LED food leads them to make this healthier choice after exercise, even when also offered tempting less healthy HED foods at the moment of selection.

Methods

Our study observed the foods selected by university athletes after their sports matches. Before the match, half of the participants were primed by asking them to choose a LED snack from the options we offered, which they would receive after the match. The remaining half of participants were not asked this same question. To distract the athletes from our observation of their food choices, participants completed a task prior to choosing their snack, which was disguised as a ‘thank you’ for taking part.

Results

Overall, we found the priming group did not choose LED foods significantly more than the control group, hence priming did not increase LED food selection.

Conclusion

Importantly, our results indicate that priming must be more noticeable to achieve its goal. Additionally, we demonstrated that priming may be less successful for young athletic individuals, compared to older and more overweight adults recruited in other studies. This highlights the importance of studying a broader demographic range of individuals from the general population. We support future research into this area, which will help us to tweak priming to achieve the best outcomes.

Trial registration

ISRCTN Registry, ISRCTN74601698. Date registered: 02/10/2020 (retrospectively registered).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40359-021-00554-1.

Effect of food variety on intake of a meal: a systematic review and meta-analysis

BACKGROUND

Many studies have shown that food variety-the presence of multiple foods and/or sensory characteristics within and across meals-increases intake. However, studies report mixed findings, and effect size remains unclear.

OBJECTIVES

A systematic review and meta-analysis were conducted to 1) synthesize data across experimental studies that examined effects of variety on total meal intake, relative to a control condition with comparatively less variety; 2) quantify support for this effect; and 3) assist in the identification of important moderating factors (registration: CRD42019153585).

METHODS

In November 2019, we searched the following databases for relevant experimental studies, published in English from 1980, with human participants: PubMed, Cochrane Library, Web of Science, ClinicalTrials.gov, PsycINFO, and OpenGrey. This search was updated in September 2020. Means, standard deviations, and sample sizes were extracted from included articles, and Hedges' g was used to calculate effect sizes. Risk of bias was assessed using the Cochrane Collaboration's tool.

RESULTS

Of 7259 references identified in an initial search, 34 articles consisting of 37 studies contained sufficient information for review, and data from 30 studies (39 comparisons) were included in the meta-analysis. Results from a random-effects model showed a significant small to medium effect of variety on intake (in weight and energy), with greater variety being associated with increased consumption (Hedges' g = 0.405; 95% CI: 0.259, 0.552). However, heterogeneity was considerable across studies (I2 = 84%), and this was unexplained by subgroup analyses based on form of variety, test foods, sensory characteristics, age, sex, and body weight.

CONCLUSIONS

Our findings support the conclusion that variety is a robust driver of food intake. However, risk of bias was high across studies, and this review highlights methodologic limitations of studies. It is recommended that further attention is given to the development of preregistered, well-powered randomized controlled studies in eating behavior research.

Targeting automatic processes to reduce unhealthy behaviours: a process framework

While previous frameworks to address health behaviours through targeting underlying automatic processes have stimulated an improved understanding of related interventions, deciding between intervention strategies often remains essentially arbitrary and atheoretical. Making considered decisions has likely been hampered by the lack of a framework that guides the selection of different intervention strategies targeting automatic processes to reduce unhealthy behaviours. We propose a process framework to fulfil this need, building upon the process model of emotion regulation. This framework differentiates types of intervention strategies along the timeline of the unfolding automatic response, distinguishing between three broad classes of intervention strategies - direct antecedent, indirect antecedent, and response-focused. Antecedent-focused strategies aim to prevent the exposure to or activation of automatic responses directly through the avoidance of unwanted stimulus-response associations (i.e., situation modification or situation-specific response selection), or indirectly through automatising self-control (i.e., attentional deployment or cognitive change). Response-focused strategies aim to directly downregulate automatic unwanted responses (i.e., response modulation). Three main working hypotheses derived from this process framework provide practical guidance for selecting interventions, but await direct testing in future studies.

A Dieting Facilitator on the Fridge Door: Can Dieters Deliberately Apply Environmental Dieting Cues to Lose Weight?

Individuals exposed to dieting-related environmental cues have been repeatedly shown to be better able to resist tempting food. This especially applies to restrained eaters who hold a chronic dieting goal. Thus far, mainly short-term effects of environmental dieting cues have been examined and the individuals were typically unaware of being influenced. Yet, it is unclear whether individuals can deliberately apply environmental dieting cues for themselves to facilitate the pursuit of the longer-term goal of losing weight. The present longitudinal study applied a 2 (cue: visually dieting-related vs. visually neutral cue) × 2 (awareness: being aware vs. not being aware of the cue’s facilitating influence) between-subjects design for 6 months (N = 166 participants who started the study; M_age = 47.85 years; 69.9% female; M_BMI = 29.07 kg/m²). Our results provide preliminary indications that cue, awareness, and restrained eating interact. The results suggest that high (vs. low) restrained eaters could deliberately apply environmental dieting cues for themselves to facilitate losing weight. However, further studies are needed to explore the effects of environmental dieting cues over a longer period of time.

Restrained eaters' consumption of dietary forbidden and permitted foods after exposure to incidental fitness cues

The purpose of this research is to investigate the influence of incidental fitness cues on caloric food intake in restrained (vs. unrestrained) eaters. The authors show that the effect of incidental fitness cues (made salient via a priming procedure in a seemingly unrelated study prior to the main study) on caloric food intake differs between dietary forbidden and permitted foods. For food that is perceived as dietary forbidden, calorie intake decreases if restrained eaters are incidentally primed with fitness. In contrast, calorie intake of dietary permitted food increases for restrained eaters in response to incidental fitness primes. The study extends prior research on priming effects on eating behavior and derives important implications on how to help restrained eaters control energy intake.

Implicit food odour priming effects on reactivity and inhibitory control towards foods

The food environment can interact with cognitive processing and influence eating behaviour. Our objective was to characterize the impact of implicit olfactory priming on inhibitory control towards food, in groups with different weight status. Ninety-one adults completed a modified Affective Shifting Task: they had to detect target stimuli and ignore distractor stimuli while being primed with non-attentively perceived odours. We measured reactivity and inhibitory control towards food pictures. Priming effects were observed on reactivity: participants with overweight and obesity were slower when primed with pear and pound cake odour respectively. Common inhibitory control patterns toward foods were observed between groups. We suggest that non-attentively perceived food cues influence bottom-up processing by activating distinguished mental representations according to weight status. Also, our data show that cognitive load influences inhibitory control toward foods. Those results contribute to understanding how the environment can influence eating behaviour in individuals with obesity.