Visual exposure to large and small portion sizes and perceptions of portion size normality: Three experimental studies

Portion-control tableware differentially impacts eating behaviour in women with and without overweight

Portion control tableware has been described as a potentially effective approach for weight management, however the mechanisms by which these tools work remain unknown. We explored the processes by which a portion control (calibrated) plate with visual stimuli for starch, protein and vegetable amounts modulates food intake, satiety and meal eating behaviour. Sixty-five women (34 with overweight/obesity) participated in a counterbalanced cross-over trial in the laboratory, where they self-served and ate a hot meal including rice, meatballs and vegetables, once with a calibrated plate and once with a conventional (control) plate. A sub-sample of 31 women provided blood samples to measure the cephalic phase response to the meal. Effects of plate type were tested through linear mixed-effect models. Meal portion sizes (mean ± SD) were smaller for the calibrated compared with the control plate (served: 296 ± 69 vs 317 ± 78 g; consumed: 287 ± 71 vs 309 ± 79 g respectively), especially consumed rice (69 ± 24 vs 88 ± 30 g) (p < 0.05 for all comparisons). The calibrated plate significantly reduced bite size (3.4 ± 1.0 vs 3.7 ± 1.0 g; p < 0.01) in all women and eating rate (32.9 ± 9.5 vs 33.7 ± 9.2 g/min; p < 0.05), in lean women. Despite this, some women compensated for the reduced intake over the 8 h following the meal. Pancreatic polypeptide and ghrelin levels increased post-prandially with the calibrated plate but changes were not robust. Plate type had no influence on insulin, glucose levels, or memory for portion size. Meal size was reduced by a portion-control plate with visual stimuli for appropriate amounts of starch, protein and vegetables, potentially because of the reduced self-served portion size and the resulting reduced bite size. Sustained effects may require the continued use of the plate for long-term impact.

Development and validation of a new methodological platform to measure behavioral, cognitive, and physiological responses to food interventions in real time

To fully understand the causes and mechanisms involved in overeating and obesity, measures of both cognitive and physiological determinants of eating behavior need to be integrated. Effectively synchronizing behavioral measures such as meal micro-structure (e.g., eating speed), cognitive processing of sensory stimuli, and metabolic parameters, can be complex. However, this step is central to understanding the impact of food interventions on body weight. In this paper, we provide an overview of the existing gaps in eating behavior research and describe the development and validation of a new methodological platform to address some of these issues. As part of a controlled trial, 76 men and women self-served and consumed food from a buffet, using a portion-control plate with visual stimuli for appropriate amounts of main food groups, or a conventional plate, on two different days, in a random order. In both sessions participants completed behavioral and cognitive tests using a novel methodological platform that measured gaze movement (as a proxy for visual attention), eating rate and bite size, memory for portion sizes, subjective appetite and portion-size perceptions. In a sub-sample of women, hormonal secretion in response to the meal was also measured. The novel platform showed a significant improvement in meal micro-structure measures from published data (13 vs. 33% failure rate) and high comparability between an automated gaze mapping protocol vs. manual coding for eye-tracking studies involving an eating test (ICC between methods 0.85; 90% CI 0.74, 0.92). This trial was registered at Clinical Trials.gov with Identifier NCT03610776.

Exposure to images showing (non)adherence to physical distancing rules: Effect on adherence behavior and perceived social norms

Introduction

Adherence to behavioral measures such as physical distancing are key to mitigating the effects of viral pandemics such as the COVID-19 pandemic. Adherence depends in part on people’s perception of what others do (descriptive norms) or approve of (injunctive norms). This study examines the effects that exposure to images depicting people following or breaking physical distancing rules have on perceptions of descriptive and injunctive norms and subsequent adherence behavior.

Methods

An online between-subjects experiment (n = 315) was conducted, in which participants were exposed to a set of five photographs of different public spaces in which people either did or did not adhere to physical distancing rules (pre-registration: https://www.osf.io/uek2p). Participants’ adherence behavior was measured using a triangulation of measures (incentivized online behavioral task, vignettes, intention measure). Perceptions of relevant social norms were also measured.

Results

Mann-Whitney tests showed no effects of condition on perceptions of descriptive and injunctive norms or on adherence behavior. Linear regressions showed that both component paths of the indirect effect (condition on norm perceptions, and norm perceptions on adherence behavior) were non-significant, hence mediation analyses were not conducted.

Conclusions

Exposure to images of people following (compared to breaking) physical distancing rules did not affect adherence to such rules or perceived norms. We surmise that a single exposure to such images, especially in the context of COVID-19, is insufficient to affect behavior. We therefore recommend performing a comparable experiment in which participants are exposed repeatedly to images showing people (non)adhering to a specific behavior in a particular context for a longer period.

Designing for downsizing: Home-based barriers and facilitators to reduce portion sizes for children

Evidence confirms that parents know that they should limit non-core foods for their children since these tend to be high in energy density (HED), fat, salt and sugar. However, it is unclear how knowledge of portion size limits, such as the 100 kcal guide from Public Health England are applied in practice. To observe in real-time children’s home food environment related to portion control and to explore with parents their reported portion size strategies, a mixed methods study was designed. Families with children aged 1–5 years were recruited (n = 21) to a three-part study: (1) to complete questionnaires and interviews on household food intake and portion control; (2) to report daily food intake for 4 days (n = 13) for one parent and their child(ren); (3) to observe home-based food provisioning via videorecording during dinner, breakfast and snack time (n = 6). Although the problem of large portion sizes of HED foods was recognised by mothers, strategies to downsize portions were not necessarily applied at home, as revealed in home observations and diaries. A mismatch between what was observed at home, what was reported in food diaries and what was said in interviews became apparent for some families. Mothers reported the need for greater support and guidance to downsize HED foods since they relied on pre-packaging as a guide to intake. Education and engagement were identified as important parameters for downsizing by mothers. One strategy which could be explored and applied by manufacturers is packaging design to faciliate the 100 kcal guidance using physical and engaging ways to assist parents in downsizing HED foods for their children. To facilitate effective government communication, innovative packaging design can be used to convey clear guidance and to tailor portion size messages for children. Packaging design, alongside government recommendations, can support parents’ goals to achieve healthy eating and can reinforce guidance for portion norms through innovation involving learning, playful engagement, and interaction.

Estimation of meal portions in bulimia nervosa compared to anorexia nervosa and healthy controls

PURPOSE

Bulimia nervosa (BN) and anorexia nervosa (AN) are potentially life-threatening eating disorders (ED) that primarily affect young people, mostly women. The central common pathology is linked to the relationship with food and with abnormalities in food intake. A previous study indicated that individuals with AN tend to overestimate food portion sizes compared to healthy controls (HC), but no study has investigated these patterns in BN, which was the objective of this study.

METHODS

Women with BN (27), AN (28), and HC (27) were asked to rate different meal portion sizes in two conditions: as if they were supposed to eat them (intent-to-eat condition) or in general (general condition). BN results were compared to HC and AN using mixed model analyses.

RESULTS

BN showed larger estimations compared to HC, while smaller estimations compared to AN. These differences were found mostly for intermediate portion sizes. No difference for conditions (intent-to-eat; general) was found between groups.

CONCLUSION

When estimating food portion sizes, individuals with BN seem to fall intermediately between HC and AN. ED symptoms in BN were most strongly associated with higher portion estimation. This might therefore reflect one aspect of the cognitive distortions typically seen also in AN. A therapeutic option could include the frequent visual exposure to increasing portions of food, what may serve to recalibrate visual perceptions of what a "normal-sized" portion of food looks like.

LEVEL OF EVIDENCE

Level II: Evidence obtained from well-designed controlled trials without randomization.

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.

Gender, Age, Hunger, and Body Mass Index as Factors Influencing Portion Size Estimation and Ideal Portion Sizes

Portion sizes of meals have been becoming progressively larger which contributes to the onset of obesity. So far, little research has been done on the influence of body weight on portion size preferences. Therefore, we assessed whether Body Mass Index (BMI), as well as other selected factors, contribute to the estimation of food portions weight and the subjective perception of portion sizes. Through online questionnaires, the participants were asked to estimate the weight of pictured foods in the first study. In the second study, the participants indicated how the depicted varying portion sizes of different meals relate to their actual consumed real-life portion sizes. A total of 725 and 436 individuals were included in the statistical analysis in the first and second study, respectively. BMI and gender had a small effect on the capacity to estimate the weight of foods. The main predictor for portion size choices was the factor gender with men estimating ideal portion sizes as larger than women. Further, age and hunger together with external and restrictive eating behaviors were among the deciding factors for portion size choices. As expected, externally motivated eaters chose bigger portions while restrictive individual smaller ones. Gender- and age-related differences in portion size preferences likely reflect distinct energy requirements. The individuals with a higher BMI do not differ strongly from other BMI groups in their portion-related preferences. Therefore, other factors such as meal frequency, snacking, or a lifestyle, may contribute more to the onset, development, and maintenance of overweight.

Olfactory and Gustatory Supra-Threshold Sensitivities Are Linked to Ad Libitum Snack Choice

Snacking is a common eating habit in the modern food environment. Individual snack choices vary substantially, with sweet versus savoury snacks linked to differential health outcomes. The role of olfactory and gustatory sensitivities in snack choices and consumption is yet to be tested. A total of 70 Caucasian young males (age: 21−39 years; BMI: 20.5−40.5 kg∙m−2) were tested for their supra-threshold sensitivities to sweet and savoury associated odours and tastants (vanillin, methional; sucrose, NaCl). The participants also attended an ad libitum task in which their intakes of sweet and savoury snacks were recorded and analysed. Univariate and multivariate analyses were used to test for relationships between odour/taste sensitivities and sweet versus savoury snack intake. Results indicated that individual sensitivities to sweet-associated stimuli (e.g., vanillin, sucrose) were negatively linked with intake of the congruent (e.g., sweet) snacks and positively linked with incongruent (e.g., savoury) snacks (p < 0.05). These differences were reflected by energy intake rather than consumption weight (p > 0.05). This study outlines the fundamental roles of olfactory and gustatory sensitivities in snack choices and offers novel insights into inter-individual variability in snack consumption.

Is a 'culture of plus-size women' the independent effect of neighborhood disadvantage on female BMI? A cross-sectional study in two Chilean Municipalities

Research has shown that neighborhood disadvantage has an effect on BMI that is independent of individual disadvantage, much more pronounced in women than in men. The mechanisms that explain this gender-specific effect are not yet clear. Since women's body size dissatisfaction is closely linked to gender differences in BMI inequalities, the independent effect of neighborhood disadvantage on female BMI may relate to a local culture of acceptance of female large bodies, that could influence women's parameters for body size dissatisfaction. This study explored how the relation between female BMI, neighborhood income, individual income and education is influenced by body size dissatisfaction in a random sample of 882 women aged 20-60 that reside in two Chilean Municipalities. Data have a two level structure (women nested in 17 neighborhoods); it was collected by direct survey, height and weight were measured with portable instruments. Disadvantaged neighborhoods house mainly poor and low educated women, whereas the wealthier ones were inhabited mostly by affluent women with postsecondary education. The proportion of women without a husband/partner and with more than three children in disadvantaged neighborhoods was higher than better off areas. Multilevel linear regression showed that neighborhood disadvantage had an effect on female BMI that was independent of women's income and education, which was explained by body size dissatisfaction. The mean BMI for body size satisfaction among women in disadvantaged neighborhoods was 2 kg/m² higher than in affluent areas, which suggests that a 'culture of plus-size women' would emerge in urban clusters of poverty. The findings signal that neighborhood effects on BMI would relate to the socioeconomic polarization of urban areas, with marked concentrations of poverty and wealth, and might be explained by the psychosocial pathways associated to social disadvantage that act in addition to the effects of material conditions to influence people's health.

Impact of bottle size on in-home consumption of wine: a randomized controlled cross-over trial

AIM

To assess the impact of purchasing wine in 50 cl bottles compared with 75 cl bottles on the amount of wine consumed at home.

DESIGN

Cross-over randomized controlled trial with a 'usual behaviour' period of a maximum of 3 weeks between conditions.

SETTING

Households in the United Kingdom.

PARTICIPANTS

One hundred and eighty-six households that consumed between two and eight 75 cl bottles of wine each week.

INTERVENTION

Households were randomized to the order in which they purchased wine in two bottle sizes. During two 14-day intervention periods, households purchased a pre-set volume of wine-based on their baseline self-reported weekly consumption-in either 75 cl bottles or 50 cl bottles. On days 7 and 14 of each study period, participating households sent photographs of each purchased wine bottle.

MEASUREMENTS

The primary outcome was the volume of study wine in millilitres (ml) consumed during each study period estimated through returned photographs. The secondary outcome was the rate of consumption measured by the mean number of days taken to drink 1.5 litres from each bottle size.

FINDINGS

One hundred and sixty-six of 186 enrolled households satisfactorily completed the study. After accounting for pre-specified covariates, 191.1 ml [95% confidence interval (CI) = 42.03-339.2] or 4.5% (95% CI = 1.0-7.9%) more wine was consumed per 14-day period from 75-cl bottles than from 50-cl bottles. Consumption was 5.8% faster (95% CI = -10.9 to -0.4%) from 75 cl bottles than from 50 cl bottles.

CONCLUSIONS

Consuming wine at home from 50 cl bottles, compared with 75 cl bottles, may reduce both amount consumed and rate of consumption.

How do patients with eating disorders perceive and evaluate food portion sizes? A systematic review

OBJECTIVE

The selection of adequate portion sizes plays a key role in the nutritional treatment of eating disorders (EDs). There is limited knowledge concerning the estimation of portion sizes in individuals with EDs.

METHOD

We performed a systematic review according to the PRISMA statement to synthesise current evidence in this field. Of N = 584 hits, four full-texts were included in the qualitative synthesis.

RESULTS

While patients with anorexia nervosa (AN) tend to overestimate the size of energy-dense food items and small to medium sized meal portions, they do not show a different estimation compared to healthy controls when judging the amount of food pieces. Large portion sizes were associated with increased anxiety in patients with AN.

DISCUSSION

The overestimation of food portion sizes seems to be driven by attitudinal and/or higher cognitive factors associated with AN. Differences between the studies are discussed and suggestions for future studies are given.

Usability of Food Size Aids in Mobile Dietary Reporting Apps for Young Adults: Randomized Controlled Trial

Background

Young adults are more likely to use self-managed dietary reporting apps. However, there is scant research examining the user experience of different measurement approaches for mobile dietary reporting apps when dealing with a wide variety of food shapes and container sizes.

Objective

Field user experience testing was conducted under actual meal conditions to assess the accuracy, efficiency, and subjective reaction of three food portion measurement methods embedded in a developed mobile app. Key-in–based aid (KBA), commonly used in many current apps, relies on the user’s ability to key in volumes or weights. Photo-based aid (PBA) extends traditional assessment methods, allowing users to scroll, observe, and select a reduced-size image from a set of options. Gesture-based aid (GBA) is a new experimental approach in which the user makes finger movements on the screen to roughly describe food portion boundaries accompanied by a background reference.

Methods

A group of 124 young adults aged 19 to 26 years was recruited for a head-to-head randomized comparison and divided into 3 groups: a KBA (n=42) control group and PBA (n=41) and GBA (n=41) experimental groups. In total, 3 meals (ie, breakfast, lunch, and dinner) were served in a university cafeteria. Participants were provided with 25 dishes and beverages for selection, with a variety of food shapes and containers that reflect everyday life conditions. The accuracy of and time spent on realistic interaction during food portion estimation and the subjective reaction of each aid were recorded and analyzed.

Results

Participants in the KBA group provided the highest accuracy in terms of hash brown weight (P=.004) and outperformed PBA or GBA for many soft drinks in cups. PBA had the best results for a cylindrical hot dog (P<.001), irregularly shaped pork chop (P<.001), and green tea beverage (660 mL; P<.001). GBA outperformed PBA for most drinks, and GBA outperformed KBA for some vegetables. The GBA group spent significantly more time assessing food items than the KBA and PBA groups. For each aid, the overall subjective reaction based on the score of the System Usability Scale was not significantly different.

Conclusions

Experimental results show that each aid had some distinguishing advantages. In terms of user acceptance, participants considered all 3 aids to be usable. Furthermore, users’ subjective opinions regarding measurement accuracy contradicted the empirical findings. Future work will consider the use of each aid based on food or container shape and integrate the various advantages of the 3 different aids for better results. Our findings on the use of portion size aids are based on realistic and diverse food items, providing a useful reference for future app improvement of an effective, evidence-based, and acceptable feature.

Trial Registration

International Standard Randomized Controlled Trial Registry ISRCTN36710750; http://www.controlled-trials.com/ISRCTN36710750.

Impact of bottle size on in-home consumption of wine: feasibility and acceptability randomised cross-over study

Background

Reducing alcohol consumption across populations would prevent many non-communicable diseases. Large packages increase food and non-alcoholic drink consumption and large glasses increase wine consumption. Smaller bottles may reduce alcohol consumption but their impact is uncertain. This study aims to (i) explore the feasibility and acceptability of conducting a large-scale randomised study to assess the impact of bottle size on in-home wine consumption and (ii) estimate the effect size and variance of the intervention on consumption to inform the design of future studies.

Methods

Cross-over randomised study in which 16 households in Cambridge, England, consuming at least two 750-ml bottles of wine each week, received a pre-set volume of wine biweekly for 4 weeks, in 750-ml and 375-ml bottles, in random order. Consumption was assessed by recording the number of empty and partially full bottles at the end of each biweekly period. At the end of the study, household representatives were interviewed about their experiences of participating in the study.

Results

The study procedures proved feasible. Comparable to similar trials, 14% of identified eligible households (18/125) consented to participate in the study. Attrition between consent and study completion was 11% (2/18) and 0% between study periods and 13% of households (2/16) correctly identified the study aim. The study procedures were considered acceptable. After adjusting for guest and out-of-home consumption, the difference in consumption between the 750-ml (3385.2 ml; SD = 1698.5) and 375-ml bottles (3376.7 ml; SD = 1719.0) was 8.4 ml (SD = 1235.4; 95%CI − 596.9, 613.8). Results suggest a possible order effect, with households receiving the 375-ml bottles first consuming more wine out of the 750-ml bottles and vice versa. This might also reflect an increase in consumption with study duration. Households receiving the 375-ml bottles first (6315.9 ml; SD = 3293.5) also drank less wine overall than those receiving the 750-ml bottles first (7335.4 ml; SD = 3735.4).

Discussion

The findings support the feasibility and acceptability of running a large-scale randomised study to assess the impact of bottle size on in-home wine consumption. Due to the heterogeneous patterning of results, a future study will be powered using the variance observed in the current study to detect a meaningful reduction of 250 ml of wine when consumed from smaller compared with larger bottles.

Trial registration

Open Science Framework (OSF): rmk43; May 23, 2017.

Served Portion Sizes Affect Later Food Intake Through Social Consumption Norms

Portion sizes of commercially available foods have increased, and there is evidence that exposure to portion sizes recalibrates what is perceived as 'normal' and subsequently, how much food is selected and consumed. The present study aims to explore the role of social (descriptive and injunctive) and personal portion size norms in this effect. Across two experiments, participants were either visually exposed to (Study 1, N = 329) or actually served (Study 2, N = 132) a smaller or larger than normal food portion. After 24 h, participants reported their intended consumption (Study 1) or served themselves and consumed (Study 2) a portion of that food and reported perceived portion size norms. In Study 1, visual exposure to portion size did not significantly affect intended consumption and perceived portion size norms. In Study 2, participants consumed a smaller portion of food when they were served a smaller rather than a larger portion the previous day, which was mediated by perceived descriptive and injunctive social (but not personal) portion size norms. Results suggest that being served (but not mere visual exposure to) smaller (relative to larger) portions changes perceived social norms about portion size and this may reduce future consumption of that food.

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.

A review of evidence supporting current strategies, challenges, and opportunities to reduce portion sizes

Although there is considerable evidence for the portion-size effect and its potential impact on health, much of this has not been successfully applied to help consumers reduce portion sizes. The objective of this review is to provide an update on the strength of evidence supporting strategies with potential to reduce portion sizes across individuals and eating contexts. Three levels of action are considered: food-level strategies (targeting commercial snack and meal portion sizes, packaging, food labels, tableware, and food sensory properties), individual-level strategies (targeting eating rate and bite size, portion norms, plate-cleaning tendencies, and cognitive processes), and population approaches (targeting the physical, social, and economic environment and health policy). Food- and individual-level strategies are associated with small to moderate effects; however, in isolation, none seem to have sufficient impact on food intake to reverse the portion-size effect and its consequences. Wider changes to the portion-size environment will be necessary to support individual- and food-level strategies leading to portion control.

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.

Exploring the Experiences of People with Obesity Using Portion Control Tools-A Qualitative Study

Large portion sizes increase consumption and eating smaller portions is recommended as a weight control strategy. However, many people report difficulties enacting this advice. This study examined the experience of individuals using two commercially available portion-control tools to try to manage their weight. In a crossover design, 29 adults with obesity (18 women) who had attended a previous weight loss intervention in the community were invited to use two portion-control tool sets over a period of four weeks (two weeks each) and to complete a semi-structured questionnaire about their experience. The tools were a guided crockery set (sector plate, calibrated bowl, and calibrated glass) and a set of calibrated serving spoons (one for starch, one for protein, and one for vegetables). Data were analyzed using thematic framework analysis. A key theme was related to the educational benefits of the tools, such as generating awareness, guidance, and gaining an independent ability to judge appropriate portions. Other key themes were tool usability, acceptability, and feasibility of usage. Barriers identified by participants included unclear markings/instructions and the inconvenience of using the tool when eating away from home. Overall, the tools were perceived to be educationally useful, easy to use, and potentially effective for learning to control portions, which suggested that these instruments could help in weight management interventions alongside other strategies. Elements of the tool design could influence the ability of participants to adhere to using the tool, and hence allow the educational effect to be mediated.

Potential moderators of the portion size effect

AIM

The robust effect of portion size on intake has led to growing interest in why individuals consume more food when served larger portions. A number of explanations have been proposed, and this review aims to provide insight into potential underlying factors by summarizing recent studies testing moderators of the portion size effect.

SUMMARY OF FINDINGS

Provision of portion size information, such as through labeling or training in portion control, failed to attenuate food intake in response to increasing meal size. This indicates that a lack of knowledge about appropriate portions may not be sufficient to explain the portion size effect. In contrast, there is evidence for a role of decision making in the response to large portions, with value being one consideration of importance. The portion size effect may be more closely related to the inherent value of food than monetary value, since provision of the opportunity to take away uneaten food after a meal, which can reduce food waste, attenuated the portion size effect but variations in pricing did not. A number of studies also support an influence of orosensory processing on the portion size effect; large portions have been shown to relate to increased bite size and faster eating rate. Reduced oral processing time when consuming large portions could contribute to the effect by delaying sensory-specific satiety. Findings from a recent study supported this by demonstrating that sensory-specific satiety did not differ between larger and smaller portions despite substantial differences in intake.

CONCLUSIONS

A number of moderators of the portion size effect have been identified, including factors related to the environment, the food, and the individual. It is likely that multiple variables contribute to the response to large portions. Future research should aim to determine the relative contribution of explanatory variables across different contexts and individuals.

Visual perceptions of portion size normality and intended food consumption: A norm range model

•Smaller portion sizes are associated with lower energy intake.•We test a norm range model of the portion size effect on intended intake.•A wide range of portion sizes were perceived as normal.•Portions perceived as normal did not prompt intended compensatory eating.•Portions perceived as smaller than normal prompted intended compensation.

The Cognitive Control of Eating and Body Weight: It's More Than What You "Think"

Over the past decade, a great deal of research has established the importance of cognitive processes in the control of energy intake and body weight. The present paper begins by identifying several of these cognitive processes. We then summarize evidence from human and nonhuman animal models, which shows how excess intake of obesity-promoting Western diet (WD) may have deleterious effects on these cognitive control processes. Findings that these effects may be manifested as early-life deficits in cognitive functioning and may also be associated with the emergence of serious late-life cognitive impairment are described. Consistent with these possibilities, we review evidence, obtained primarily from rodent models, that consuming a WD is associated with the emergence of pathophysiologies in the hippocampus, an important brain substrate for learning, memory, and cognition. The implications of this research for mechanism are discussed within the context of a “vicious-cycle model,” which describes how eating a WD could impair hippocampal function, producing cognitive deficits that promote increased WD intake and body weight gain, which could contribute to further hippocampal dysfunction, cognitive decline, and excess eating and weight gain.

The Feasibility and Acceptability of Two Methods of Snack Portion Control in United Kingdom (UK) Preschool Children: Reduction and Replacement

Large portions of high energy dense (HED) snacks are offered to children from a young age and are pervasive in our food environment. This study aimed to explore the feasibility, acceptability, and preliminary efficacy of two strategies of snack portion control: reduction and replacement. Forty-six mother-child dyads aged 22⁻56 months (36.6 ± 9.5 m, 48% female) completed a three-week intervention. In week 1 (baseline) no changes were made to the child's diet; week 2 (acclimation) children received a standardised selection of HED snacks, and in week 3 (intervention) participants were randomly assigned to snack replacement (n = 24) or snack reduction (n = 22). Snack replacement involved swapping HED snacks for fruits and vegetables, whilst snack reduction involved reducing the size of HED snacks by 50%. Food and energy intake were measured using a weighed food diary for four consecutive days. Snack replacement resulted in more positive changes to children's diets; vegetable intake increased (p < 0.01), and total daily energy intake decreased when compared to snack reduction (p < 0.05). Mothers expressed a more favourable attitude to snack replacement, although snack reduction was also well received by mothers. Despite increased preliminary efficacy of snack replacement on dietary intake, both strategies were feasible and acceptable. The current pilot study provides the necessary information to inform the design of future interventions.

Combating Excessive Eating: A Role for Four Evidence-Based Remedies

OBJECTIVE

The aim of this study is to review the control of energy balance and outline some causes of and remedies for excessive energy intake.

METHODS

A narrative review was conducted.

RESULTS

There is negative feedback control of energy intake and body weight, but, nonetheless, energy intake is only loosely coupled with energy expenditure. Consequently, we are vulnerable to eating in excess of energy requirements. In this context, energy density, portion size, and habitual meal patterns have strong influences on energy intake and, accordingly, can be targeted to reduce energy intake. For example, energy density can be reduced without much affecting food reward (approximately the pleasure gained from eating) because their relationship is such that reward value is affected relatively little by increments in energy density above 1.5 kcal/g. This and other strategies that increase reward per calorie eaten may be superior to increasing the satiety effect of products because fullness is not inherently rewarding. Low-calorie sweeteners provide a means to reduce energy density while largely preserving food or beverage reward value. Consistent with this, consumption of low-calorie sweeteners compared with consumption of sugars has been found to reduce energy intake and body weight.

CONCLUSIONS

Understanding what causes excessive eating also provides insights into how to combat this problem.

Doggy bags and downsizing: Packaging uneaten food to go after a meal attenuates the portion size effect in women

Serving larger portions leads to increased food and energy intake, but little is known about strategies to moderate this response. This study tested how the effect of portion size on meal intake was influenced by providing the option to take away uneaten food in a "doggy bag" (to-go container). Women were randomly assigned to one of two subject groups: a To-Go Group (n = 27) that was informed before each meal that their leftover food would be packaged to take away after the meal, and a Control Group (n = 26) that was not given this option. In a crossover design, subjects came to the lab once a week for four weeks to eat a dinner composed of five foods. Across meals, the portion size of all foods was varied (100%, 125%, 150%, and 175% of baseline). Results showed that the portion size effect, defined as the trajectory of intake across the weight of food served, differed significantly by subject group (P ≤ 0.025). In the Control Group, increasing the portion size of all foods led to substantial increases in intake (P < 0.0001); for every 100 g added to the baseline portion, women in this group consumed an additional mean (±SEM) of 64 ± 12 g of food and 90 ± 19 kcal, until intake leveled off. In contrast, intake of women in the To-Go Group increased by only 17 ± 12 g and 19 ± 18 kcal for every additional 100 g served; these increases did not differ significantly from zero (P > 0.15). Thus, the effect of portion size on intake was attenuated in the To-Go Group compared to the Control Group. These data indicate that packaging uneaten food after a meal could be an effective strategy to reduce overconsumption from large portions.

Understanding the science of portion control and the art of downsizing

Offering large portions of high-energy-dense (HED) foods increases overall intake in children and adults. This is known as the portion size effect (PSE). It is robust, reliable and enduring. Over time, the PSE may facilitate overeating and ultimately positive energy balance. Therefore, it is important to understand what drives the PSE and what might be done to counter the effects of an environment promoting large portions, especially in children. Explanations for the PSE are many and diverse, ranging from consumer error in estimating portion size to simple heuristics such as cleaning the plate or eating in accordance with consumption norms. However, individual characteristics and hedonic processes influence the PSE, suggesting a more complex explanation than error or heuristics. Here PSE studies are reviewed to identify interventions that can be used to downsize portions of HED foods, with a focus on children who are still learning about social norms for portion size. Although the scientific evidence for the PSE is robust, there is still a need for creative downsizing solutions to facilitate portion control as children and adolescents establish their eating habits.

Fairness-Based Tasks for Assessing Children's Perceptions of Food Quantities and Associations with Portion Selection

It is critical to develop ecologically valid experimental methods to assess consumers’ food-related behaviors. Ad libitum approaches are often used but may not be appropriate for studies with children or with products that are not typically consumed until the individual feels full. The current study presents novel methods to assess children’s size perception and portion preference for gummy candies. In the first study, 62 children (30 boys, 32 girls) aged 6 to 9 years completed two matching tasks: one using pictures on a computer screen, and a similar task where the products were physically manipulated. Results of the two matching tasks were correlated, demonstrating that a computer-based approach could be used to predict the factors influencing children’s perception of food amount: the number, size, and shape of pieces. In the second study, a portioning measure was developed to investigate whether the factors identified in the matching tasks were confirmed in a task that more closely represented portion selection in the real world. The effects observed in the matching tasks could not be replicated in the portioning task. The size of each item had no significant impact on the portion selection, suggesting that it may be possible to reduce the size of pieces in snacks where multiple pieces are typically consumed without negatively impacting perceived quantity in children, thus offering a promising strategy to nudge children toward choosing smaller portions.

Portion size and later food intake: evidence on the "normalizing" effect of reducing food portion sizes

Background

Historical increases in the size of commercially available food products have been linked to the emergence of a worldwide obesity crisis. Although the acute effect that portion size has on food intake is well established, the effect that exposure to smaller portion sizes has on future portion size selection has not been examined.

Objective

We tested whether reducing a food portion size "renormalizes" perceptions of what constitutes a normal amount of that food to eat and results in people selecting and consuming smaller portions of that food in the future.

Design

Across 3 experiments, participants were served a larger or smaller portion of food. In experiments 1 and 2, participants selected and consumed a portion of that food 24 h later. In experiment 3, participants reported on their preferred ideal portion size of that food after 1 wk.

Results

The consumption of a smaller, as opposed to a larger, portion size of a food resulted in participants believing a "normal"-sized portion was smaller (experiments 1-3, P ≤ 0.001), consuming less of that food 1 d later (experiments 1-2, P ≤ 0.003), and displaying a tendency toward choosing a smaller ideal portion of that food 1 wk later (experiment 3, P = 0.07), although the latter finding was not significant.

Conclusion

Because consumer preferences appear to be driven by environmental influences, reducing food portion sizes may recalibrate perceptions of what constitutes a "normal" amount of food to eat and, in doing so, decrease how much consumers choose to eat. This trial was registered at www.clinicaltrials.gov as NCT03241576.

Research into food portion size: methodological aspects and applications

Portion sizes for certain foods have been increasing dramatically in recent years alongside obesity rates, concurring with the phenomenon of the portion size effect (more is consumed when more is offered). Portion size may be defined based on different purposes such as for dietary assessment, or therapeutic advice or food labelling, resulting in a variety of measurement methods and specifications. This situation has resulted in disagreements on establishing portion size recommendations by manufacturers, food distributors, restaurants, health professionals and policy makers, contributing to confusion amongst consumers on the amounts of food to be consumed, and potentially increasing the likelihood of overeating and other obesity-related behaviours. Such variability is also reflected in the research field making comparison across studies on portion size difficult. The aim of this review is to provide an overview of definitions and methods used in research to evaluate portion-size related outcomes, including methods to estimate amounts consumed by individuals as part of dietary assessment; methods to analyse cognitive mechanisms related to portion size behaviour; and methods to evaluate the impact of portion size manipulations as well as individual plus environmental factors on portion size behaviour. Special attention has been paid to behavioural studies exploring portion size cognitive processes given the lack of previous methodological reviews in this area. This information may help researchers, clinicians and other stakeholders to establish clearer definitions of portion size in their respective areas of work and to standardise methods to analyse portion size effects.

Overweight but unseen: a review of the underestimation of weight status and a visual normalization theory

Although overweight and obesity are widespread across most of the developed world, a considerable body of research has now accumulated, which suggests that adiposity often goes undetected. A substantial proportion of individuals with overweight or obesity do not identify they are overweight, and large numbers of parents of children with overweight or obesity fail to identify their child as being overweight. Lay people and medical practitioners are also now poor at identifying overweight and obesity in others. A visual normalization theory of the under-detection of overweight and obesity is proposed. This theory is based on the notion that weight status is judged relative to visual body size norms. Because larger body sizes are now common, this has caused a recalibration to the range of body sizes that are perceived as being 'normal' and increased the visual threshold for what constitutes 'overweight'. Evidence is reviewed that indicates this process has played a significant role in the under-detection of overweight and obesity. The public health relevance of the under-detection of overweight and obesity is also discussed.

The bogus taste test: Validity as a measure of laboratory food intake

Because overconsumption of food contributes to ill health, understanding what affects how much people eat is of importance. The ‘bogus’ taste test is a measure widely used in eating behaviour research to identify factors that may have a causal effect on food intake. However, there has been no examination of the validity of the bogus taste test as a measure of food intake. We conducted a participant level analysis of 31 published laboratory studies that used the taste test to measure food intake. We assessed whether the taste test was sensitive to experimental manipulations hypothesized to increase or decrease food intake. We examined construct validity by testing whether participant sex, hunger and liking of taste test food were associated with the amount of food consumed in the taste test. In addition, we also examined whether BMI (body mass index), trait measures of dietary restraint and over-eating in response to palatable food cues were associated with food consumption. Results indicated that the taste test was sensitive to experimental manipulations hypothesized to increase or decrease food intake. Factors that were reliably associated with increased consumption during the taste test were being male, have a higher baseline hunger, liking of the taste test food and a greater tendency to overeat in response to palatable food cues, whereas trait dietary restraint and BMI were not. These results indicate that the bogus taste test is likely to be a valid measure of food intake and can be used to identify factors that have a causal effect on food intake.

What can the food and drink industry do to help achieve the 5% free sugars goal?

AIMS

To contribute evidence and make recommendations to assist in achieving free sugars reduction, with due consideration to the broader picture of weight management and dietary quality.

METHODS

An expert workshop in July 2016 addressed options outlined in the Public Health England report 'Sugar reduction: The evidence for action' that related directly to the food industry. Panel members contributed expertise in food technology, public heath nutrition, marketing, communications, psychology and behaviour. Recommendations were directed towards reformulation, reduced portion sizes, labelling and consumer education. These were evaluated based on their feasibility, likely consumer acceptability, efficacy and cost.

RESULTS

The panel agreed that the 5% target for energy from free sugars is unlikely to be achievable by the UK population in the near future, but a gradual reduction from average current level of intake is feasible. Progress requires collaborations between government, food industry, non-government organisations, health professionals, educators and consumers. Reformulation should start with the main contributors of free sugars in the diet, prioritising those products high in free sugars and relatively low in micronutrients. There is most potential for replacing free sugars in beverages using high-potency sweeteners and possibly via gradual reduction in sweetness levels. However, reformulation alone, with its inherent practical difficulties, will not achieve the desired reduction in free sugars. Food manufacturers and the out-of-home sector can help consumers by providing smaller portions. Labelling of free sugars would extend choice and encourage reformulation; however, government needs to assist industry by addressing current analytical and regulatory problems. There are also opportunities for multi-agency collaboration to develop tools/communications based on the Eatwell Guide, to help consumers understand the principles of a varied, healthy, balanced diet.

CONCLUSION

Multiple strategies will be required to achieve a reduction in free sugars intake to attain the 5% energy target. The panel produced consensus statements with recommendations as to how this might be achieved.

Acceptability and potential effectiveness of commercial portion control tools amongst people with obesity

Exposure to large portion sizes is a risk factor for obesity. Specifically designed tableware may modulate how much is eaten and help with portion control. We examined the experience of using a guided crockery set (CS) and a calibrated serving spoon set (SS) by individuals trying to manage their weight. Twenty-nine obese adults who had completed 7-12 weeks of a community weight-loss programme were invited to use both tools for 2 weeks each, in a crossover design, with minimal health professional contact. A paper-based questionnaire was used to collect data on acceptance, perceived changes in portion size, frequency, and type of meal when the tool was used. Scores describing acceptance, ease of use and perceived effectiveness were derived from five-point Likert scales from which binary indicators (high/low) were analysed using logistic regression. Mean acceptance, ease of use and perceived effectiveness were moderate to high (3·7-4·4 points). Tool type did not have an impact on indicators of acceptance, ease of use and perceived effectiveness (P>0·32 for all comparisons); 55 % of participants used the CS on most days v. 21 % for the SS. The CS was used for all meals, whereas the SS was mostly used for evening meals. Self-selected portion sizes increased for vegetables and decreased for chips and potatoes with both tools. Participants rated both tools as equally acceptable, easy to use and with similar perceived effectiveness. Formal trials to evaluate the impact of such tools on weight control are warranted.

Does wine glass size influence sales for on-site consumption? A multiple treatment reversal design

Background

Wine glass size can influence both perceptions of portion size and the amount poured, but its impact upon purchasing and consumption is unknown. This study aimed to examine the impact of wine glass size on wine sales for on-site consumption, keeping portion size constant.

Methods

In one establishment (with separate bar and restaurant areas) in Cambridge, England, wine glass size (Standard; Larger; Smaller) was changed over eight fortnightly periods. The bar and restaurant differ in wine sales by the glass vs. by the bottle (93 % vs. 63 % by the glass respectively).

Results

Daily wine volume purchased was 9.4 % (95 % CI: 1.9, 17.5) higher when sold in larger compared to standard-sized glasses. This effect seemed principally driven by sales in the bar area (bar: 14.4 % [3.3, 26.7]; restaurant: 8.2 % [−2.5, 20.1]). Findings were inconclusive as to whether sales were different with smaller vs. standard-sized glasses.

Conclusions

The size of glasses in which wine is sold, keeping the portion size constant, can affect consumption, with larger glasses increasing consumption. The hypothesised mechanisms for these differential effects need to be tested in a replication study. If replicated, policy implications could include considering glass size amongst alcohol licensing requirements.

Trial registration

ISRCTN registry: ISRCTN12018175. Registered 12^th May 2015.