The Role of Social Norms in the Portion Size Effect: Reducing Normative Relevance Reduces the Effect of Portion Size on Consumption Decisions

Development and validation of an online tool to assess perceived portion size norms of discretionary foods

BACKGROUND

Perceived portion size norms (typical perception of how much of a given food individuals choose to eat at a single occasion) may have shifted towards larger sizes due to the ubiquity of large serving sizes. However, there is a lack of validated tools to assess such norms for energy-dense and nutrient-poor discretionary foods. This study aimed to develop and validate an online tool to examine the perceived portion size norms of discretionary foods.

METHODS

An online image-series tool of 15 commonly consumed discretionary foods was developed, with eight successive portion size options included for each food. Using a randomised-crossover design, adult consumers (18-65 years) completed the validation study in a laboratory session (April-May 2022) by reporting their perceived portion size norms for each food twice, once based on food images on a computer and another time based on equivalent real food portion size options at food stations in the laboratory. Agreement between methods for each test food was examined using cross-classification and intra-class correlation (ICC).

RESULTS

A sample of 114 subjects were recruited (mean age 24.8 years). Cross-classification indicated >90% of selections were matched in the same or adjacent portion size option. ICC was 0.85 across all foods, demonstrating a good level of agreement.

CONCLUSION

This novel online image-series tool developed to examine perceived portion size norms of discretionary foods showed good agreement with equivalent real food portion size options and may be valuable to investigate perceived portion size norms of common discretionary foods in future studies.

Psychological Pathways Through Which Social Norms and Social Identity Influence Eating Behavior: Testing a Conceptual Model

BACKGROUND

Although interventions frequently promote healthy eating, failing to consider psychosocial factors, such as social norms, may limit the effectiveness of these efforts. Perceived social norms are a well-documented determinant of eating behavior; however, there is limited understanding of the processes through which, and for whom, this relationship emerges. Using identity-based motivation as a theoretical framework, we present a conceptual model identifying one route through which descriptive social norms-beliefs about how others behave-predict eating behavior, and test whether this process varies across social identities (e.g., self-perceived weight status).

METHOD

Structured telephone interviews were conducted for a national sample of non-diabetic adults who identified as non-Hispanic White, non-Hispanic Black, or Mexican American (n = 990).

RESULTS

Multigroup SEM analysis comparing individuals who self-identified as overweight (versus "about the right weight" and underweight) demonstrated that perceiving descriptive social norms that people do not eat healthy foods predicted greater perceived barriers to eating healthy foods. Perceived barriers, in turn, predicted stronger beliefs that body weight is uncontrollable, and this relationship was stronger for participants who self-identified as overweight (relative to participants who did not identify as overweight). These beliefs subsequently predicted greater self-reported consumption of unhealthy foods (e.g., sweets), but did not predict consumption of fruits or vegetables.

CONCLUSIONS

This study extends our understanding of a psychosocial process that predicts consumption of unhealthy foods and underscores the importance of social identities for shaping responses to perceived norms.

Systematic review of the portion size norm of discretionary foods

CONTEXT

Portion size norm is described as the perception of how much of a given food people choose to eat. Reducing the portion size norm of foods that are high in saturated fat, added sugar, and added salt toward smaller sizes might be a potential strategy to promote appropriate portion size selections. However, an overview of existing portion size norms for discretionary foods has yet to be established.

OBJECTIVE

The aim of this systematic review was to examine the portion size norm of discretionary foods and assess the methodologies used to investigate the norm.

DATA SOURCES

The literature search was conducted in 6 databases following the PRISMA guidelines (from inception to January 2022).

DATA EXTRACTION

Forty studies were eligible and grouped into 3 categories by portion size norm measures: normal (n = 26), appropriate (n = 8), and preferred portion sizes (n = 3). Study quality was assessed using the Joanna Briggs Institute Critical Appraisal Tools.

DATA ANALYSIS

A wide range of portion sizes were considered normal for each food type, with means/medians varying from 2- to 4-fold among studies. Studies differed considerably in design, with variables including the setting, food type, food presentation, the manner in which portion-size-related questions were formulated, and the range and number of displayed serving size options. The quality of reviewed studies was mixed (25 studies had low or moderate risk of bias, 15 had high risk of bias), and the method of assessing portion size was not validated in 15 of 33 quantitative studies.

CONCLUSION

The assessment of portion size in future studies should be conducted using tools that are validated for the population of interest so that more definitive conclusions can be drawn regarding portion size norms for discretionary foods.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42021249911.

Can unexpected support promote environmental policy acceptability? An experimental investigation of norm source and strength

Two experiments tested how environmental policy acceptability of US conservatives and liberals was influenced by manipulating the level (minority vs. majority) and source (in-group vs. outgroup) of normative support for policy. Results from 928 MechanicalTurk users (Study 1: N = 268, Study 2: N = 660) indicated that when evaluating an in-group policy (that participants expect their own political group to support), communicating outgroup support increases acceptability compared with communicating in-group support. The outgroup norm has a positive indirect effect via the inference that the in-group is even more supportive of the policy than the outgroup is. In contrast, when evaluating an outgroup policy, communicating in-group support indirectly yields higher acceptability than communicating outgroup support, via the inference that the outgroup is more supportive than the in-group is. This effect mainly occurred for individuals with strong ideological identification and was independent of level of support (minority vs. majority). Results indicate that bipartisan support for environmental policies can be achieved by strategic communication of normative information about political groups.

Can Visual Cues to Portion Size Reduce the Number of Portions of Consumed? Two Randomized Controlled Trials

Background

Since 1950, the portion size of many snack foods has more than doubled and obesity rates have tripled. Portion size determines energy intake, often unwittingly.

Purpose

This paper tests whether salient visual cues to portion size on the packaging of high fat, sugar, or salty (HFSS) snacks can reduce consumption.

Methods

Two preregistered randomized controlled trials (N = 253 and N = 674) measured consumption in a lab and the home environment. Cues were salient, labeled stripes that demarcated single portions. Participants were randomized to cue condition or control. Consumption was measured without awareness.

Results

The main preregistered effect of the visual cue was not statistically significant. There was some variation by subgroup. In Study 1, men were more likely to eat the whole can of potato chips than women but significantly reduced consumption when visual cues were on the pack. The effect size was large: the number of men eating more than the recommended portion fell by 33%. Study 2 monitored household consumption of chocolate biscuits (cookies) sent to family homes in gift packs. Again, the main effect was nonsignificant but there was significant subgroup variation. When the person receiving the biscuits was female, households were more likely to eat more than the recommended portion per person per day, but less likely when the visual cues were displayed. The gender of the eaters was not known. The effect size was again large: the number of households eating more than the recommended portion fell by 26%. Households with children were also less likely to open packs with visual cues compared to control packs. Both studies recorded significant increases in the likelihood of observing serving size information, together with confusion about what it means.

Conclusions

The studies offer some evidence that salient visual cues could play a role in tackling the high consumption of unhealthy snacks, but the effects are confined to specific subgroups and warrant further investigation.

That's My Cue to Eat: A Systematic Review of the Persuasiveness of Front-of-Pack Cues on Food Packages for Children vs. Adults

Packaging is increasingly recognized as an essential component of any marketing strategy. Visual and informational front-of-pack cues constitute salient elements of the environment that may influence what and how much someone eats. Considering their overwhelming presence on packaging of non-core foods, front-of-pack cues may contribute to the growing rates of overweight and obesity in children and adults. We conducted a systematic review to summarize the evidence concerning the impact of front-of-pack cues on choices and eating behaviors. Four electronic databases were searched for experimental studies (2009-present). This resulted in the inclusion of 57 studies (in 43 articles). We identified studies on children (3-12 years) and adults (≥ 18 years), but no studies on adolescents (12-18 years). The results suggest that children and adults are susceptible to packaging cues, with most evidence supporting the impact of visual cues. More specifically, children more often choose products with a licensed endorser and eat more from packages portraying the product with an exaggerated portion size. Adults' eating behaviors are influenced by a range of other visual cues, mainly, package size and shape, and less so by informational cues such as labels.

The influence of front-of-pack portion size images on children's serving and intake of cereal

BACKGROUND

Consumption of large portions of energy-dense foods promotes weight gain in children. Breakfast cereal boxes often show portions much larger than the recommended serving size.

OBJECTIVE

This experimental study investigated whether front-of-package portion size depictions influence children's self-served portions and consumption.

METHODS

In a between-subjects design, 41 children aged 7-11 years (M= 9.0 ± 1.5y) served themselves breakfast cereal from a box, the front of which depicted either a recommended serving size of cereal (30g) or a larger, more typical front-of-pack portion (90g). Cereal served and consumed and total caloric intake (including milk) was recorded. Height and weight, demographic information and measures of children's food responsiveness and enjoyment of food were collected.

RESULTS

MANOVA revealed that children exposed to the larger portion size served themselves (+7g, 37%) and consumed (+6g, 63%) significantly more cereal than those exposed to the smaller portion. Despite this, overall caloric intake (milk included) did not differ between conditions, and no other measured variables (hunger, BMI) significantly affected the outcomes.

CONCLUSION

This study provides novel evidence of the influence portion-size depictions on food packaging have on children's eating behaviour. This offers possible avenues for intervention and policy change; however, more research is needed.

Portion size normality and additional within-meal food intake: two crossover laboratory experiments

Reducing food portion size could reduce energy intake. However, it is unclear at what point consumers respond to reductions by increasing intake of other foods. We predicted that a change in served portion size would only result in significant additional eating within the same meal if the resulting portion size was no longer visually perceived as 'normal'. Participants in two crossover experiments (Study 1: n 45; Study 2: n 37; adults, 51 % female) were served different-sized lunchtime portions on three occasions that were perceived by a previous sample of participants as 'large-normal', 'small-normal' and 'smaller than normal', respectively. Participants were able to serve themselves additional helpings of the same food (Study 1) or dessert items (Study 2). In Study 1 there was a small but significant increase in additional intake when participants were served the 'smaller than normal' compared with the 'small-normal' portion (m difference = 161 kJ, P = 0·002, d = 0·35), but there was no significant difference between the 'small-normal' and 'large-normal' conditions (m difference = 88 kJ, P = 0·08, d = 0·24). A similar pattern was observed in Study 2 (m difference = 149 kJ, P = 0·06, d = 0·18; m difference = 83 kJ, P = 0·26, d = 0·10). However, smaller portion sizes were each associated with a significant reduction in total meal intake. The findings provide preliminary evidence that reductions that result in portions appearing 'normal' in size may limit additional eating, but confirmatory research is needed.

When a portion becomes a norm: Exposure to a smaller vs. larger portion of food affects later food intake

BACKGROUND

Portion sizes in the food environment may communicate information about what constitutes a 'normal' amount of food to eat. Here we examined whether mere visual exposure to a smaller vs. larger portion size of snack food affects perceptions of how much a 'normal' sized portion is and how much people choose to eat of that food in future.

METHODS

Under the guise of a study on taste preference and personality, 104 female participants were randomly allocated to be exposed to either a smaller or larger portion size of snack food. Twenty-four hours later participants freely selected a portion of the snack food to consume and reported on their perception of what constituted a normal sized portion of the snack food.

RESULTS

Participants that were exposed to a smaller, as opposed to larger portion size subsequently believed that a normal portion of the snack food was smaller in size. Exposure to the smaller as opposed to the larger portion size also resulted in participants consuming less snack food the next day.

CONCLUSIONS

Environmental exposure to smaller, as opposed to larger portion sizes of food may change perceptions of what constitutes a normal amount of food to eat and affect the amount of food people choose to eat in future.

Lower socioeconomic status is associated with higher intended consumption from oversized portions of unhealthy food

Socioeconomic status is one of the strongest predictors of obesity, and of living in deprived neighbourhoods with unhealthy food environments. Little is known, however, about the psychological processes that translate features of such environments into socioeconomic differences in eating behaviour. One important feature of unhealthy food environments is the prevalence of oversized portions of unhealthy food. The present study tested whether individuals with lower socioeconomic status intend to consume more from large portions than those with higher socioeconomic status, and examined the psychological processes underlying this effect. A large-scale online experiment was conducted in which participants (N = 511) indicated how much they would eat from small and large portions of healthy and unhealthy snacks. The mediating effects of trait impulsivity and perceptions of how much was considered appropriate to eat were also assessed. Participants with lower socioeconomic status intended to eat more from the large portions than from the small portions of the unhealthy snacks, which would equate to a potential 15-22% increase in energy intake. These effects were partially mediated by trait impulsivity and perceptions of how much is appropriate to eat. These findings point to a significant health burden of low socioeconomic status: when exposed to unhealthy food environments, specific psychological processes might increase the amount of unhealthy food those with lower socioeconomic intend to consume. This study critically informs the emerging understanding of the psychology of socioeconomic status and eating behaviour.

Associations between local descriptive norms for overweight/obesity and insufficient fruit intake, individual-level diet, and 10-year change in body mass index and glycosylated haemoglobin in an Australian cohort

Background

Descriptive norms (what other people do) relate to individual-level dietary behaviour and health outcome including overweight and obesity. Descriptive norms vary across residential areas but the impact of spatial variation in norms on individual-level diet and health is poorly understood. This study assessed spatial associations between local descriptive norms for overweight/obesity and insufficient fruit intake (spatially-specific local prevalence), and individual-level dietary intakes (fruit, vegetable and sugary drinks) and 10-year change in body mass index (BMI) and glycosylated haemoglobin (HbA_1c).

Methods

HbA_1c and BMI were clinically measured three times over 10 years for a population-based adult cohort (n = 4056) in Adelaide, South Australia. Local descriptive norms for both overweight/obesity and insufficient fruit intake specific to each cohort participant were calculated as the prevalence of these factors, constructed from geocoded population surveillance data aggregated for 1600 m road-network buffers centred on cohort participants’ residential addresses. Latent growth models estimated the effect of local descriptive norms on dietary behaviours and change in HbA_1c and BMI, accounting for spatial clustering and covariates (individual-level age, sex, smoking status, employment and education, and area-level median household income).

Results

Local descriptive overweight/obesity norms were associated with individual-level fruit intake (inversely) and sugary drink consumption (positively), and worsening HbA_1c and BMI. Spatially-specific local norms for insufficient fruit intake were associated with individual-level fruit intake (inversely) and sugary drink consumption (positively) and worsening HbA_1c but not change in BMI. Individual-level fruit and vegetable intakes were not associated with change in HbA_1c or BMI. Sugary drink consumption was also not associated with change in HbA_1c but rather with increasing BMI.

Conclusion

Adverse local descriptive norms for overweight/obesity and insufficient fruit intake are associated with unhealthful dietary intakes and worsening HbA_1c and BMI. As such, spatial variation in lifestyle-related norms is an important consideration relevant to the design of population health interventions. Adverse local norms influence health behaviours and outcomes and stand to inhibit the effectiveness of traditional intervention efforts not spatially tailored to local population characteristics. Spatially targeted social de-normalisation strategies for regions with high levels of unhealthful norms may hold promise in concert with individual, environmental and policy intervention approaches.

Do Affective Variables Make a Difference in Consumers Behavior Toward Mobile Advertising?

Research into permission-based mobile marketing is increasingly common due to the widespread adoption of mobile technology and its use as a communication channel. Yet few studies have attempted to analyze the factors that determine attitudes toward mobile advertising while simultaneously considering: the links among them and consumers' intentions, behavior, and/or cognitive and affective variables simultaneously. The present research therefore sought to deepen understanding of the antecedents and consequences of attitudes toward permission-based mobile advertising. More specifically, it sought to identify the antecedents of attitudes toward mobile advertising and the bridges between these attitudes and consumers' intentions upon receiving advertising on their mobile devices. To this end, a causal model was proposed and tested with a sample of 612 mobile phone users that was collected from a panel of Spanish adults who receive advertising on their mobile phones in the form of SMS text messages. The structural model used was validated using the partial least squares (PLS) regression technique. The results show that the greatest influence was that exerted by positive emotions on feelings, suggesting that positive emotions have an indirect effect on attitude toward mobile advertising. This influence was even greater than their direct effect. Another important, though less powerful, effect was the influence of attitude on behavioral intentions to receive mobile advertising. In contrast, the influence of cognitive variables on attitude was less relevant.