A pilot study to investigate the effect of plate size on meal energy intake in normal weight and overweight/obese women

Food portion sizes: trends and drivers in an obesogenic environment

The prevalence of overweight and obesity in children and adults has increased worldwide. A strong environmental factor contributing to the obesity epidemic is food portion size (PS). This review evaluates the current evidence linking food PS to obesity, examines the effects of PS on energy intake (EI), and discusses the drivers of food PS selection. The leading causes of the rise in PS include globalisation, intensive farming methods, the impact of World War II, due to shortage of staple foods, and the notion of 'waste not, want not'. Large PS of energy-dense foods may stimulate overconsumption, leading to high EI levels. However, the studies have not shown a cause-and-effect relationship, due to confounding factors. Important mechanisms explaining the attractiveness of larger PS leading to higher EI levels are value for money, portion distortion, labels on food packaging, and tableware. Consumers depend on external rather than internal PS cues to guide consumption, irrespective of satiety levels. Further research is recommended on food consumption patterns to inform policymakers and provide information and insights about changes in diet.

Thinking about the bigger picture: Influence of holistic processing on the dishware size effect

Individuals vary in the extent to which they engage in holistic and analytic information processing styles. Holistic processing involves focusing on the interconnectivity and relatedness of items being evaluated, while analytic processing involves focusing on items being judged as discrete elements and independent of context. We examined the contribution of these basic processing styles to the dishware size effect, which proposes that food consumption patterns may be influenced by the size of the dishware (i.e., larger plates increase the amount of food consumed). We observed that participants self-served and consumed more food when using and eating from a larger plate (LP) compared with a smaller plate (SP) (p≤0.01). Importantly, participants who reported greater levels of holistic information processing related to attitudes towards contradictions and attention allocation exhibited smaller variations in portions of food self-served and consumed based on the dishware size used (SP vs. LP). These findings suggest that the susceptibility of individuals to the dishware size effect may be associated with an individual's dispositional tendency to process information in a holistic (vs. analytic) manner.

Impact of Portion Control Tools on Portion Size Awareness, Choice and Intake: Systematic Review and Meta-Analysis

Portion control utensils and reduced size tableware amongst other tools, have the potential to guide portion size intake but their effectiveness remains controversial. This review evaluated the breadth and effectiveness of existing portion control tools on learning/awareness of appropriate portion sizes (PS), PS choice, and PS consumption. Additional outcomes were energy intake and weight loss. Published records between 2006–2020 (n = 1241) were identified from PubMed and WoS, and 36 publications comparing the impact of portion control tools on awareness (n = 7 studies), selection/choice (n = 14), intake plus related measures (n = 21) and weight status (n = 9) were analyzed. Non-tableware tools included cooking utensils, educational aids and computerized applications. Tableware included mostly reduced-size and portion control/calibrated crockery/cutlery. Overall, 55% of studies reported a significant impact of using a tool (typically smaller bowl, fork or glass; or calibrated plate). A meta-analysis of 28 articles confirmed an overall effect of tool on food intake (d = –0.22; 95%CI: –0.38, –0.06; 21 comparisons), mostly driven by combinations of reduced-size bowls and spoons decreasing serving sizes (d = –0.48; 95%CI: –0.72, –0.24; 8 comparisons) and consumed amounts/energy (d = –0.22; 95%CI: –0.39, –0.05, 9 comparisons), but not by reduced-size plates (d = –0.03; 95%CI: –0.12, 0.06, 7 comparisons). Portion control tools marginally induced weight loss (d = –0.20; 95%CI: –0.37, –0.03; 9 comparisons), especially driven by calibrated tableware. No impact was detected on PS awareness; however, few studies quantified this outcome. Specific portion control tools may be helpful as potentially effective instruments for inclusion as part of weight loss interventions. Reduced size plates per se may not be as effective as previously suggested.

Do Adults Draw Differently-Sized Meals on Larger or Smaller Plates? Examining Plate Size in a Community Sample

Background

Prior research has reported that plate size may influence an individual's perceptions and recall of food and meal size. Therefore, manipulating plate size could influence projected meal quantities and portion size among community dwelling adults.

Methods

The present study interviewed 281 adult parents in their own homes in a medium-sized city in the United States. Participants were asked to accurately draw and label the foods they expected to eat for dinner that night, drawing on either a 23 cm or 28 cm paper plate. The respondents were then asked to label each food drawn in order to ensure proper recording of meals.

Results

Results showed clear differences in drawn food sizes between plate sizes as well as between sexes. Larger plates had about 24% more food drawn on them than small plates. Men drew their meals on 28 cm plates to be 37% larger than men who received 23 cm plates, while women with 28 cm plates drew their meals to be about 17% larger than women given 23 cm plates. Most (60%) of the overall differences in food size between plates came from the biggest food that was drawn. Women and men both drew bigger meat portions on 28 cm plates when compared to the meat portions on 23 cm plates.

Conclusions

Overall, these findings support the concept that adult participants' estimates of dinner meal size may be shaped by plate size. The effect of differing plate sizes appears to be more powerful for men than women, and may encourage greater food consumption among men, primarily as meat products.

Plate size and food consumption: a pre-registered experimental study in a general population sample

BACKGROUND

There is considerable uncertainty regarding the impact of tableware size on food consumption. Most existing studies have used small and unrepresentative samples and have not followed recommended procedures for randomised controlled trials, leading to increased risk of bias. In the first pre-registered study to date, we examined the impact on consumption of using larger versus smaller plates for self-served food. We also assessed impact on the underlying meal micro-structure, such as number of servings and eating rate, which has not previously been studied.

METHODS

The setting was a purpose-built naturalistic eating behaviour laboratory. A general population sample of 134 adult participants (aged 18-61 years) was randomly allocated to one of two groups varying in the size of plate used for self-serving lunch: large or small. The primary outcome was amount of food energy (kcal) consumed during a meal. Additionally, we assessed impact on meal micro-structure, and examined potential modifying effects of executive function, socio-economic position, and sensitivity to perceptual cues.

RESULTS

There was no clear evidence of a difference in consumption between the two groups: Cohen's d = 0.07 (95% CI [- 0.27, 0.41]), with participants in the large plate group consuming on average 19.2 (95% CI [- 76.5, 115.0]) more calories (3%) compared to the small plate group (large: mean (SD) = 644.1 (265.0) kcal, versus small: 624.9 (292.3) kcal). The difference between the groups was not modified by individual characteristics. There was no evidence of impact on meal micro-structure, with the exception of more food being left on the plate when larger plates were used.

CONCLUSIONS

This study suggests that previous meta-analyses of a low-quality body of evidence may have considerably overestimated the effects of plate size on consumption. However, the possibility of a clinically significant effect - in either direction - cannot be excluded. Well-conducted trials of tableware size in real-world field settings are now needed to determine whether changing the size of tableware has potential to contribute to efforts to reduce consumption at population-level.

TRIAL REGISTRATION

The study protocol ( https://osf.io/e3dfh/ ) and data analysis plan ( https://osf.io/sh5u7/ ) were pre-registered on the Open Science Framework.

Perceptions of tableware size in households of children and adolescents with obesity

PURPOSE

Portion size influences energy intake and is an important factor when developing weight management strategies. The effect of tableware on food intake is less clear, especially in children. To date, the relationship between the body weight of individuals and the tableware used in their households has not been investigated. The aim of this study was to analyze the sizes of tableware in households of children and adolescents with obesity (OBE) in comparison to participants with normal-weight matched for age and gender (NW).

METHODS

60 OBE (32 female, 26 male) and 27 NW (12 female, 15 male) aged between 9 and 17 years participated in a structured interview on the tableware used at home. Responses were standardized based on the selection of different sizes of tableware and everyday objects presented to the children.

RESULTS

In households of NW, larger plates and bowls were used during meals and desserts compared to OBE. OBE drank out of larger bottles. Shapes and sizes of drinkware, the number of children drinking out of bottles and the cutlery used during dessert did not differ between the groups.

CONCLUSIONS

Drinking out of large bottles may be an unfavourable habit of OBE if they contain sugar-rich liquids. The use of smaller plates and bowls of OBE may result in multiple helpings being consumed and so contribute to an overall increased portion size.

LEVEL OF EVIDENCE

Level V, Descriptive study.

Visual Cues and Food Intake: Distortion Power of Plate and Spoon Size on Overweight and Obese University Staff

Background:

This study was designed to evaluate the effect of the size of plate, spoon, and fork on food and energy intake during a meal in obese or overweight staff.

Methods:

This was a crossover randomized controlled trial that was conducted on 40 obese or overweight clerical staff of the university. The staff was invited to have lunch randomly, receiving either a large or a small set of plate, spoon, and fork. Washout period was 3 weeks, and the participants were then invited to have lunch in a second intervention period and received opposite sizes of dishes compared to the first period sizes. The meal was composed of roasted chicken (kebab), cooked rice, vegetable salad, dairy drink, and soda. Changes in food intake between large and small utensils (plate, spoon, and fork) were analyzed with paired t-test.

Results:

Rice intake using small or large eating utensils was different (P = 0.02). But total energy intake was not different. The Pearson correlation test demonstrated a positive and significant correlation between rice consumption and waist-to-hip ratio (P = 0.02). Soda (P = 0.02), carbohydrate (P = 0.01), and total energy intake (P = 0.03) were negatively correlated with the age of the participant.

Conclusions:

It seems that only the amount of grain products consumption changes with changing in dishware size with no significant effect on total energy intake. It is recommended that the independent effect of visual cues on food intake for foods with different textures be investigated in future studies.

The effect of the size of food containers on the selecting behavior of college students

The effect of container size of food and drinks as well as the effect of the variety of drinks on the selecting behaviors of male and female undergraduates were investigated in this research by manipulating the sizes of plates and glasses. The findings suggest that male students tended to choose smaller plates and preferred tall slender glasses that appeared to contain a greater volume of beverage compared to short wide glasses. In contrast, female students focused more on the quality of the food that they were interested in or attracted to rather than the quantity of food. Moreover, the findings showed that plates with or without a concentric circle have no influence on the selecting behaviors of male and female college students. Thus, male and female undergraduates have different selecting behaviors, and the effect of food container size showed distinct impacts on them.

Impact of glass shape on time taken to drink a soft drink: A laboratory-based experiment

BACKGROUND

Glassware design may affect drinking behaviour for alcoholic beverages, with glass shape and size influencing drinking speed and amount consumed. Uncertainty remains both about the extent to which these effects are restricted to alcohol and the underlying mechanisms. The primary aim of the current study was to examine the effect of differently shaped glasses on time taken to drink a soft drink. The secondary aim was to develop hypotheses about mechanisms concerning micro-drinking behaviours and perceptual effects.

METHOD

In a single-session experiment, 162 participants were randomised to receive 330ml of carbonated apple juice in a glass that was either inward-sloped, straight-sided, or outward-sloped. The primary outcome measure was total drinking time. Secondary outcome measures included micro-drinking behaviours (sip size, sip duration, interval duration), and perceptual measures (midpoint bias, drink enjoyment).

RESULTS

Participants drank 21.4% faster from the outward-sloped glass than from the straight-sided glass [95%CI: 0.2%,38.0%] in adjusted models. They were also 18.2% faster from the inward-sloped glass than the straight-sided glass, but this did not reach statistical significance with wide confidence intervals also consistent with slower drinking [95%CI: -3.8%,35.6%]. Larger sips were associated with faster drinking times (Pearson's r(162) = -.45, p < .001). The direction of effects suggested sips were larger from the outward-sloped and inward-sloped glasses, compared to the straight-sided glass (15.1%, 95%CI: -4.3%,38.0%; 19.4%, 95%CI: -0.5%,43.6%, respectively). There were no significant differences between glasses in mean sip or interval duration. Bias in midpoint estimation was greater for the outward-sloped glass (12.9ml, 95%CI: 6.6ml,19.2ml) than for the straight-sided glass, although the degree of bias was not associated with total drinking time (Pearson's r(162) = 0.01, p = .87).

DISCUSSION

Individuals drank a soft drink more quickly from an outward-sloped glass, relative to a straight-sided glass. Micro-drinking behaviours, such as sip size, are promising candidates for underlying mechanisms.

The effects of bowl size and portion size on food intake and fullness ratings in a sample of Japanese men

OBJECTIVE

Portion sizes and bowl sizes may be related to food intake and perceived fullness. The objective of the present study was to investigate the effects of portion size and bowl size and possible interactions between these variables on food intake and fullness in a sample of Japanese men.

DESIGN

Participants ate four different experimental meals across four weeks and completed questionnaires about their fullness using a visual analogue scale administered before and after meals. The four meal patterns included consistent portions of several foods commonly eaten together in typical Japanese meals, along with 150 g of rice served in a small rice bowl (diameter of 11·5 cm), 150 g of rice served in a large rice bowl (diameter of 13·5 cm), 250 g of rice served in a small rice bowl or 250 g of rice served in a large rice bowl.

SETTING

Tokyo.SubjectTwenty-one adult men participated in the study.

RESULTS

Portion size had a significant main effect on rice intake (F (1,20)=83, P<0·001) and fullness (F (1,20)=8·0, P=0·010), but no significant effects of bowl size on the outcome variables were found. The interactions between portion size and bowl size on intake and fullness were not significant.

CONCLUSIONS

The sample of Japanese men showed an influence of portion size on food intake. Further research is needed to clarify the combined effects of bowl size and portion size on intake and fullness.

How does plate size affect estimated satiation and intake for individuals in normal-weight and overweight groups?

OBJECTIVE

Manipulating plate sizes could possibly introduce perceptual biases for judging food satiation and intake, which is thought to be related to the Delbeouf illusion - a visual illusion based on the perceived size of one object related to another. This study was to investigate whether an association exists between an individual's susceptibility to the plate-size-effect and their weight status (i.e. normal-weight versus overweight).

METHODS

The study assessed the effect of plate size amongst normal-weight (N = 124) and overweight (N = 79) New Zealand Europeans. All participants were asked to rate estimated satiation (ES) and intake (EI) on Visual Analogue Scales for 20 food images, which comprised photographs of ten different dishes placed on large versus small plates. These responses were analysed by mixed-model ANCOVA.

RESULTS

The results showed that the plate size had significant effects on ES (F_{(1, 1986)} = 19.14, p < 0.001) and EI (F_(1,1986) = 5.25; p = 0.048), with the small plate associated with higher ES and lower EI than the large plate. Significant differences in ES and EI were also evident across the weight groups (ES: F_(1,1986) = 4.26, p = 0.039; EI: F_(1,1986) = 42.22, p < 0.001), with the normal-weight group reported higher ES and lower EI than the overweight group. Furthermore, the weight group and the plate-size-effect were found to be involved in a significant interaction for EI. Post-hoc tests showed that the plate size only had a significant effect for the normal-weight group (p < 0.05), but not for the overweight group.

CONCLUSIONS

Overall, the study demonstrated that the normal-weight and overweight group differed in their susceptibilities to the plate-size-effect (reflected by EI). This study revealed some potential moderators for the plate-size-effect, such as the type of dish, and its associated appeal and familiarity, and provided useful indications about the effectiveness of small plates for food reduction.

Effect of plate size on meal energy intake in normal weight women

BACKGROUND/OBJECTIVES

Use of smaller plates to control food intake is a commonly recommended strategy for restricting energy intake, despite conflicting results. Therefore, the aim of this study was to examine whether or not three different sizes of plates influence energy intake during a multi-itemed buffet meal in normal weight women.

SUBJECTS/METHODS

This was a cross-over study conducted on 37 female participants aged 19-25 years with normal BMI levels. Participants were recruited from Hacettepe University and the surrounding community. On experimental days, participants ate a standard breakfast and were then randomly assigned to eat lunch using a small (19 cm), medium (23 cm), or large (28 cm) diameter plate. Visual analogue scale (VAS) scores on sensory and satiety outcomes were measured for all meals. Energy and macronutrient intakes during lunch were recorded.

RESULTS

There was no evidence that use of a smaller plate size reduced energy or specific macronutrient intake during the free choice lunch meal. Multiple visits to the serving table were not associated with energy or macronutrient intake. Plate size did not affect VAS scores during the test days.

CONCLUSIONS

Plate size did not influence energy intake, meal composition, or palatability in normal weight women during a multi-itemed open buffet lunch. Studies in natural settings at the population level are needed to clarify current outcomes.

Portion size: what we know and what we need to know

There is increasing evidence that the portion sizes of many foods have increased and in a laboratory at least this increases the amount eaten. The conclusions are, however, limited by the complexity of the phenomenon. There is a need to consider meals freely chosen over a prolonged period when a range of foods of different energy densities are available. A range of factors will influence the size of the portion size chosen: amongst others packaging, labeling, advertising, and the unit size rather than portion size of the food item. The way portion size interacts with the multitude of factors that determine food intake needs to be established. In particular, the role of portion size on energy intake should be examined as many confounding variables exist and we must be clear that it is portion size that is the major problem. If the approach is to make a practical contribution, then methods of changing portion sizes will need to be developed. This may prove to be a problem in a free market, as it is to be expected that customers will resist the introduction of smaller portion sizes, given that value for money is an important motivator.

Contextual and environmental influences on reported dietary energy intake at evening eating occasions

OBJECTIVE

This study sought to determine the simultaneous effect of immediate eating environment variables; portion size, plate size, proximity to food, variety of food, side serves of salad/vegetables and presence of distraction on dietary energy intake (EI), of a reported evening meal, in the participants' real world setting.

DESIGN

A retrospective computer assisted telephone interview collected data on ten immediate eating environment variables, covariates and a 24-hour dietary recall of EI at an evening meal. Multiple regression analysis was conducted to determine relationships of these variables with EI. Significant (P<0.05) standardised beta coefficients (β) are reported.

SETTING

Australia wide, participants' homes.

SUBJECTS

Australian adult males and females (n 150) aged 18-65years.

RESULTS

Of the immediate eating environment variables, the absence of salads/vegetables (β=0.237), increased food variety (β=0.208), presence of music (β=0.207), and the consumption of pre-plated (as opposed to self-served) meals (β=0.195) had a positive association with EI, explaining 16.3% of the variance. Of the covariates, being male was the strongest predictor of EI (β=0.242); and hunger score also had a positive relationship with EI (β=0.190), explaining 17.5% of the variance.

CONCLUSION

This study provides evidence that some immediate food environment variables at an evening eating occasion are associated with EI. Findings suggest there are several strategies that people could implement to assist in controlling their EI and help address over consumption.

Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco

BACKGROUND

Overeating and harmful alcohol and tobacco use have been linked to the aetiology of various non-communicable diseases, which are among the leading global causes of morbidity and premature mortality. As people are repeatedly exposed to varying sizes and shapes of food, alcohol and tobacco products in environments such as shops, restaurants, bars and homes, this has stimulated public health policy interest in product size and shape as potential targets for intervention.

OBJECTIVES

1) To assess the effects of interventions involving exposure to different sizes or sets of physical dimensions of a portion, package, individual unit or item of tableware on unregulated selection or consumption of food, alcohol or tobacco products in adults and children.2) To assess the extent to which these effects may be modified by study, intervention and participant characteristics.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE, PsycINFO, eight other published or grey literature databases, trial registries and key websites up to November 2012, followed by citation searches and contacts with study authors. This original search identified eligible studies published up to July 2013, which are fully incorporated into the review. We conducted an updated search up to 30 January 2015 but further eligible studies are not yet fully incorporated due to their minimal potential to change the conclusions.

SELECTION CRITERIA

Randomised controlled trials with between-subjects (parallel-group) or within-subjects (cross-over) designs, conducted in laboratory or field settings, in adults or children. Eligible studies compared at least two groups of participants, each exposed to a different size or shape of a portion of a food (including non-alcoholic beverages), alcohol or tobacco product, its package or individual unit size, or of an item of tableware used to consume it, and included a measure of unregulated selection or consumption of food, alcohol or tobacco.

DATA COLLECTION AND ANALYSIS

We applied standard Cochrane methods to select eligible studies for inclusion and to collect data and assess risk of bias. We calculated study-level effect sizes as standardised mean differences (SMDs) between comparison groups, measured as quantities selected or consumed. We combined these results using random-effects meta-analysis models to estimate summary effect sizes (SMDs with 95% confidence intervals (CIs)) for each outcome for size and shape comparisons. We rated the overall quality of evidence using the GRADE system. Finally, we used meta-regression analysis to investigate statistical associations between summary effect sizes and variant study, intervention or participant characteristics.

MAIN RESULTS

The current version of this review includes 72 studies, published between 1978 and July 2013, assessed as being at overall unclear or high risk of bias with respect to selection and consumption outcomes. Ninety-six per cent of included studies (69/72) manipulated food products and 4% (3/72) manipulated cigarettes. No included studies manipulated alcohol products. Forty-nine per cent (35/72) manipulated portion size, 14% (10/72) package size and 21% (15/72) tableware size or shape. More studies investigated effects among adults (76% (55/72)) than children and all studies were conducted in high-income countries - predominantly in the USA (81% (58/72)). Sources of funding were reported for the majority of studies, with no evidence of funding by agencies with possible commercial interests in their results.A meta-analysis of 86 independent comparisons from 58 studies (6603 participants) found a small to moderate effect of portion, package, individual unit or tableware size on consumption of food (SMD 0.38, 95% CI 0.29 to 0.46), providing moderate quality evidence that exposure to larger sizes increased quantities of food consumed among children (SMD 0.21, 95% CI 0.10 to 0.31) and adults (SMD 0.46, 95% CI 0.40 to 0.52). The size of this effect suggests that, if sustained reductions in exposure to larger-sized food portions, packages and tableware could be achieved across the whole diet, this could reduce average daily energy consumed from food by between 144 and 228 kcal (8.5% to 13.5% from a baseline of 1689 kcal) among UK children and adults. A meta-analysis of six independent comparisons from three studies (108 participants) found low quality evidence for no difference in the effect of cigarette length on consumption (SMD 0.25, 95% CI -0.14 to 0.65).One included study (50 participants) estimated a large effect on consumption of exposure to differently shaped tableware (SMD 1.17, 95% CI 0.57 to 1.78), rated as very low quality evidence that exposure to shorter, wider bottles (versus taller, narrower bottles) increased quantities of water consumed by young adult participants.A meta-analysis of 13 independent comparisons from 10 studies (1164 participants) found a small to moderate effect of portion or tableware size on selection of food (SMD 0.42, 95% CI 0.24 to 0.59), rated as moderate quality evidence that exposure to larger sizes increased the quantities of food people selected for subsequent consumption. This effect was present among adults (SMD 0.55, 95% CI 0.35 to 0.75) but not children (SMD 0.14, 95% CI -0.06 to 0.34).In addition, a meta-analysis of three independent comparisons from three studies (232 participants) found a very large effect of exposure to differently shaped tableware on selection of non-alcoholic beverages (SMD 1.47, 95% CI 0.52 to 2.43), rated as low quality evidence that exposure to shorter, wider (versus taller, narrower) glasses or bottles increased the quantities selected for subsequent consumption among adults (SMD 2.31, 95% CI 1.79 to 2.83) and children (SMD 1.03, 95% CI 0.41 to 1.65).

AUTHORS' CONCLUSIONS

This review found that people consistently consume more food and drink when offered larger-sized portions, packages or tableware than when offered smaller-sized versions. This suggests that policies and practices that successfully reduce the size, availability and appeal of larger-sized portions, packages, individual units and tableware can contribute to meaningful reductions in the quantities of food (including non-alcoholic beverages) people select and consume in the immediate and short term. However, it is uncertain whether reducing portions at the smaller end of the size range can be as effective in reducing food consumption as reductions at the larger end of the range. We are unable to highlight clear implications for tobacco or alcohol policy due to identified gaps in the current evidence base.

Eating under observation: a systematic review and meta-analysis of the effect that heightened awareness of observation has on laboratory measured energy intake

BACKGROUND

Laboratory paradigms are commonly used to study human energy intake. However, the extent to which participants believe their eating behavior is being measured may affect energy intake and is a methodologic factor that has received little consideration.

OBJECTIVE

Our main objective was to examine available evidence for the effect that heightened awareness of observation has on energy intake in a laboratory setting.

DESIGN

We systematically reviewed laboratory studies that allowed for experimental examination of the effect that heightened awareness of observation has on energy intake. From these experimental studies we combined effect estimates using inverse variance meta-analysis, calculating the standardized mean difference (SMD) in energy intake between heightened-awareness and control conditions and qualitatively synthesized potential moderators of this effect.

RESULTS

Nine studies, providing 22 comparisons, were eligible for inclusion. These studies largely sampled young women and examined the energy intake of energy-dense snack foods. Evidence indicated that heightened awareness of observation was associated with reduced energy intake when compared with the control condition (random-effects SMD: 0.45; 95% CI: 0.25, 0.66; P < 0.0001). We found little evidence that the type of experimental manipulation used to heighten awareness moderated the overall effect.

CONCLUSIONS

The available evidence to date suggests that heightened awareness of observation reduces energy intake in a laboratory setting. These findings suggest that laboratory studies should attempt to minimize the degree to which participants are aware that their eating behavior is being measured.

Is level of intuitive eating associated with plate size effects?

OBJECTIVE

Intuitive eating is an eating approach that emphasizes increased focus on internal hunger and fullness cues to regulate eating behavior; thus, successful intuitive eating should curb the influence of environmental factors such as plate and portion size on consumption. The current study examined whether self-reported levels of intuitive eating moderated the influence of portion size on college students' food consumption during an afternoon meal of pasta and tomato sauce.

METHOD

Participants (N=137, 63.5% female) were randomly assigned to either a large plate (12-inch) or small plate (8-inch) external cue condition. All participants fasted for four daytime hours, completed the Intuitive Eating Scale, and then were asked to rate a meal of pasta and tomato sauce on different dimensions of taste. Participants were told that they could eat as much pasta as they would like.

RESULTS

Higher levels of intuitive eating were associated with greater food consumption. At the mean level of intuitive eating, participants ate more pasta in the large plate condition. Furthermore, the influence of plate size on food consumption increased as levels of intuitive eating increased.

DISCUSSION

Individuals who report high levels of intuitive eating may be more likely to eat an objectively larger amount of food in a permissive food environment, and may have implications for eating approaches that promote eating in response to internal hunger and fullness cues.

Visual illusions and inattention: Their association with adiposity among adolescent girls

The Delboeuf concentric circle illusion is frequently invoked as an explanation for the hypothesized association between dinner plate size and overeating. We examined its association with adiposity among 162 girls, aged 14-18 years. We also examined the association of adiposity with neural and behavioral responses during a separate visual discrimination task. The analysis showed that girls with a body mass index percentile ≥ 85, or with greater triceps skinfold thickness, exhibited less sensitivity to the Delboeuf illusion than girls with normal adiposity. The excess adiposity group also exhibited significantly smaller electroencephalographic responses and more errors during the separate visual discrimination task. In combination, the findings from the two tasks suggest that girls with an elevated body mass are less sensitive to visual cues in their environment. The implications of these findings for weight loss education should be considered.

Dishware size and snack food intake in a between-subjects laboratory experiment

OBJECTIVE

The use of smaller dishware as a way of reducing food consumption has intuitive appeal and is recommended to the general public. Recent experimental studies have failed to find an effect of plate size on food intake, although the methods used across studies have varied. The aim of the present study was to examine the effect that bowl size had on snack food consumption in a 'typical' snacking context (snacking while watching television).

DESIGN

Between-subjects.

SETTING

Laboratory experiment.

SUBJECTS

Sixty-one adult participants served themselves and ate popcorn while watching television. Participants were randomly assigned to serve themselves with and eat from either a small or a large bowl.

RESULTS

The use of a smaller bowl size did not reduce food consumption. Unexpectedly, participants in the small bowl condition tended to consume more popcorn (34·0 g) than participants in the large bowl condition (24·9 g; 37 % increase, d=0·5), although the statistical significance of this difference depended on whether analyses were adjusted to account for participant characteristics (e.g. gender) associated with food intake (P=0·02) or not (P=0·07).

CONCLUSIONS

Counter to widely held belief, the use of a smaller bowl did not reduce snack food intake. Public health recommendations advising the use of smaller dishware to reduce food consumption are premature, as this strategy may not be effective.

Weighing the Evidence of Common Beliefs in Obesity Research

Obesity is a topic on which many views are strongly held in the absence of scientific evidence to support those views, and some views are strongly held despite evidence to contradict those views. We refer to the former as "presumptions" and the latter as "myths." Here, we present nine myths and 10 presumptions surrounding the effects of rapid weight loss; setting realistic goals in weight loss therapy; stage of change or readiness to lose weight; physical education classes; breastfeeding; daily self-weighing; genetic contribution to obesity; the "Freshman 15"; food deserts; regularly eating (versus skipping) breakfast; eating close to bedtime; eating more fruits and vegetables; weight cycling (i.e., yo-yo dieting); snacking; built environment; reducing screen time in childhood obesity; portion size; participation in family mealtime; and drinking water as a means of weight loss. For each of these, we describe the belief and present evidence that the belief is widely held or stated, reasons to support the conjecture that the belief might be true, evidence to directly support or refute the belief, and findings from randomized controlled trials, if available. We conclude with a discussion of the implications of these determinations, conjecture on why so many myths and presumptions exist, and suggestions for limiting the spread of these and other unsubstantiated beliefs about the obesity domain.

Using plate mapping to examine portion size and plate composition for large and small divided plates

Does the size of a plate influence the serving of all items equally, or does it influence the serving of some foods - such as meat versus vegetables - differently? To examine this question, we used the new method of plate mapping, where people drew a meal on a paper plate to examine sensitivity to small versus large three-compartment divided plates in portion size and meal composition in a sample of 109 university students. The total drawn meal area was 37% bigger on large plates than small plates, which showed that the portion of plate coverage did not differ by plate size. Men and women drew bigger vegetable portions and men drew bigger meat portions on large plates when compared to small plates. These results suggest that men and women are differentially sensitive to plate size for overall meal size and for meal composition. Implications for decreasing portion size and improving meal balance are that plate size may influence portion size and change the proportions of foods served.

Mechanisms of the portion size effect. What is known and where do we go from here?

Childhood obesity is a persistent problem worldwide, and of particular concern in the United States. Clarifying the role of the food environment in promoting overeating is an important step toward reducing the prevalence of obesity. One potential contributor to the obesity epidemic is the increased portion sizes of foods commonly served. Portion sizes of foods served both at home and away from home have dramatically increased over the past 40 years. Consistently, short-term studies have demonstrated that increasing portion size leads to increased food intake in adults and children, a phenomenon known as the portion size effect. However, the mechanisms underlying this effect are poorly understood. Understanding these mechanisms could assist in clarifying the relationship between portion size and weight status and help inform the development of effective obesity interventions. First, we review the role of visual cues, such as plate size, unit, and utensil size as a potential moderator of the portion size effect. In addition, we discuss meal microstructure components including bite size, rate, and frequency, as these may be altered in response to different portion sizes. We also review theories that implicate post-ingestive, flavor-nutrient learning as a key moderator of the portion size effect. Furthermore, we present preliminary data from an ongoing study that is applying neuroimaging to better understand these mechanisms and identify modifiable child characteristics that could be targeted in obesity interventions. Our tentative findings suggest that individual differences in cognitive (e.g. loss of control eating) and neural responses to food cues may be critical in understanding the mechanisms of the portion size effect. To advance this research area, studies that integrate measures of individual subject-level differences with assessment of food-related characteristics are needed.

Will smaller plates lead to smaller waists? A systematic review and meta-analysis of the effect that experimental manipulation of dishware size has on energy consumption

It has been suggested that providing consumers with smaller dishware may prove an effective way of helping people eat less and preventing weight gain, but experimental evidence supporting this has been mixed. The objective of the present work was to examine the current evidence base for whether experimentally manipulated differences in dishware size influence food consumption. We systematically reviewed studies that experimentally manipulated the dishware size participants served themselves at a meal with and measured subsequent food intake. We used inverse variance meta-analysis, calculating the standardized mean difference (SMD) in food intake between smaller and larger dishware size conditions. Nine experiments from eight publications were eligible for inclusion. The majority of experiments found no significance difference in food intake when participants ate from smaller vs. larger dishware. With all available data included, analysis indicated a marginal effect of dishware size on food intake, with larger dishware size associated with greater intake. However, this effect was small and there was a large amount of heterogeneity across studies (SMD: -0.18, 95% confidence interval: -0.35, 0.00, I(2) = 77%). Evidence to date does not show that dishware size has a consistent effect on food intake, so recommendations surrounding the use of smaller plates/dishware to improve public health may be premature.

The influence of plate size on meal composition. Literature review and experiment

Environmental factors, such as the size of containers, can influence our energy intake. Even though different sized food containers are often recommended to control portion sizes, the evidence to support this is contradictory. In the present study, we conducted a literature review and a controlled laboratory experiment to investigate whether plate size influences the composition of a meal and the total meal energy. The results of the review suggest that distraction factors, the type of container, the food-serving mode (self-service or being served) and the type of food offered all influenced the results observed in the various published studies. For the experiment in this study, eighty-three participants were individually invited to serve themselves a lunch from a buffet containing 55 replica food items. Either a standard size plate (27 cm) or a large plate (32 cm) was provided to the participants. The results of the experiment suggest that the plate size had no significant effect on the total energy of the meal (F(1,81) =0.782, P> .05). However, participants using a large plate served themselves significantly more vegetables (F(1,81) =4.786, P< .05), particularly vegetables generally eaten as side dishes (F(1,81) =6.804, P< .05). Therefore, reducing the plate size does not seem to be an appropriate intervention to reduce the total energy intake in order to promote weight loss. Rather, using a large plate might be a simple and inexpensive strategy to increase vegetable consumption.

Serving size guidance for consumers: is it effective?

Larger portion sizes (PS) may be inciting over-eating and contributing to obesity rates. Currently, there is a paucity of data on the effectiveness of serving size (SS) guidance. The aims of the present review are to evaluate SS guidance; the understanding, usability and acceptability of such guidance, its impact on consumers and potential barriers to its uptake. A sample of worldwide SS guidance schemes (n 87) were identified using targeted and untargeted searches, overall these were found to communicate various inconsistent and often conflicting messages about PS selection. The available data suggest that consumers have difficulty in understanding terms such as 'portion size' and 'serving size', as these tend to be used interchangeably. In addition, discrepancies between recommended SS and those present on food labels add to the confusion. Consumers generally understand and visualise SS best when expressed in terms of household measures rather than actual weights. Only a limited number of studies have examined the direct impact of SS guidance on consumer behaviour with equivocal results. Although consumers recognise that guidance on selecting SS would be helpful, they are often unwilling to act on such guidance. The challenge of achieving consumer adherence to SS guidance is formidable due to several barriers including chronic exposure to larger PS, distorted consumption norms and perceptions, the habit of 'cleaning one's plate' and language barriers for ethnic minorities. In conclusion, the impact of SS guidance on consumers merits further investigation to ensure that future guidance resonates with consumers by being more understandable, usable and acceptable.