Smaller Food Item Sizes of Snack Foods Influence Reduced Portions and Caloric Intake in Young Adults

The effect of discretionary snack consumption on overall energy intake, weight status, and diet quality: A systematic review

The consumption frequency and portion size of discretionary snacks are thought to contribute to a greater food intake and risk of overweight or obesity in the developed world but evidence from epidemiological studies is inconclusive. To investigate this, we systematically evaluated evidence on the effects of discretionary snack consumption on weight status, energy intake, and diet quality. Articles involving discretionary snacks reported against the outcome measures of any primary, peer-reviewed study using human participants from free-living conditions for all age groups were included. A total of 14,780 titles were identified and 40 eligible publications were identified. Three key outcomes were reported: weight status (n = 35), energy intake (n = 11), and diet quality (n = 3). Increased discretionary snack consumption may contribute modestly to energy intake, however, there is a lack of consistent associations with increased weight/BMI. Although cross-sectional analyses offered conflicting findings, longitudinal studies in adults showed a consistent positive relationship between discretionary snack intake and increasing weight or body mass index. Given that experimental findings suggest reducing the size of discretionary snacks could lead to decreased consumption and subsequent energy intake, food policy makers and manufacturers may find it valuable to consider altering the portion and/or packaging size of discretionary snacks.

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.

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.

Snack Package Size and Variety Differentially Influence Energy Intake and Food Choices in Healthy Adults

BACKGROUND

While energy and nutritional content of snacks can contribute to overconsumption, other factors within the modern food environment may also influence the amount and types of snacks consumed.

OBJECTIVES

The aim was to examine whether snack package size and variety influence free-living snacking behavior in healthy adults. The impact of intuitive eating score on snacking behavior was also examined.

METHODS

Thirty adults [age: 23.6 ± 0.8 y; BMI (kg/m2): 22.8 ± 0.5] participated in a randomized crossover-design study. Participants were provided, in randomized order, with the following isocaloric snack exposures to consume for 3 d/exposure-1) CONTROL: highly appealing/appetizing snacks (e.g., dessert snacks, candy, savory snacks, fruits and vegetables, protein snacks); 2) LARGE-PACKAGE: similar snacks as CONTROL but in larger package sizes; and 3) VARIETY: larger variety of snacks. The primary outcomes included the 3-d average ad libitum snack energy, macronutrient content, and food choices for each snack exposure. The secondary outcome was the intuitive eating score and snacking behavior.

RESULTS

LARGE-PACKAGE increased snack intake by 11.9% (1150 ± 81 kcal) compared with CONTROL (1030 ± 71 kcal, P = 0.04), whereas VARIETY snack intake (1030 ± 69 kcal) was no different from CONTROL (P = 1.0). LARGE-PACKAGE increased consumption of desserts compared with CONTROL (P = 0.03) and VARIETY (P = 0.02). Alternately, VARIETY increased consumption of fruits and vegetables compared with LARGE-PACKAGE (P = 0.01) and CONTROL (P = 0.01). Intuitive eating score was not significantly associated with snack intake or snack choice (all, P > 0.05).

CONCLUSIONS

Snack package size and variety differentially influence energy intake and food choices in healthy adults. This trial was registered atclinicaltrials.gov (NCT03940105).

Is the Suppression Effect of the Color Red on Snack Food Consumption Reliable?

Two articles hypothesized that exposure to the color red would induce a state of avoidance motivation and reported that snack food consumption was decreased when the food was served on red plates, relative to white and blue plates. The current experiment combined their procedures and approximately tripled their group sizes. Participants were provided with pretzels on red, white, or blue plates in a mock sensory analysis task. The results indicated that more pretzels were consumed when presented on red plates, in direct contradiction of previous results. Alternative explanations, such as group differences in hunger or preference for pretzels, could not account for the results. The facilitation effect of red indicates that the color red does not always reduce snack food consumption and suggests that the reported inhibitory effect of red on snack consumption may not be reliable.

Subtle sensory and labeling modifications have minimal impact on expected appetitive sensations in chewy bars

Given the contribution of frequent hunger and overeating to the rising incidence of obesity, strategies to increase the satiating and satiety-inducing properties of snacks and meals are needed. In this study, we conducted three experiments to explore the contribution of sensory and labeling modifications to expected satiation and satiety in a popular and versatile snack: a chewy bar. For each experiment, we chose subtle interventions that could be incorporated into a variety of products without requiring significant reformulation. In experiment one, participants evaluated ten chewy bar samples (five flavors, two peanut form conditions) and rated five expected appetitive sensations. In experiment two, participants viewed one of six packaging images with various labeling interventions (control, protein bar label, "good for you" logo, meal bar label, calorie content logo, and "satisfies hunger longer" logo). The strongest sensory and labeling interventions from the first two experiments were combined and simultaneously evaluated in experiment three. Although we did not detect any significant effects of sensory or labeling modifications in any of the experiments, exploratory post-hoc analysis suggested that whole peanuts suppressed expected hunger and increased expected fullness, and that protein labeling increased expected satiety. Additionally, through a penalty-benefit analysis of check-all-that-apply (CATA) product characteristics, we identified several attributes that consumers may positively (wholesome, indulgent, sweet, heavy, rich) and negatively (processed) associate with expected appetitive sensations. Incorporation of sensory and packaging cues that elicit (or avoid, in the case of "processed") these attributes may aid in the creation of functional products to help manage appetite. Combining several intrinsic and extrinsic product modifications is likely necessary to meaningfully alter expected appetitive sensations.

The Modelled Population Obesity-Related Health Benefits of Reducing Consumption of Discretionary Foods in Australia

Over one third of Australians' daily energy intake is from discretionary foods and drinks. While many health promotion efforts seek to limit discretionary food intake, the population health impact of reductions in the consumption of different types of discretionary foods (e.g., sugar-sweetened beverages (SSBs), confectionery, sweet biscuits) has not been quantified. This study estimated the potential reductions in body weight, obesity-related disease incidence, and healthcare cost savings associated with consumption of one less serving per week of different discretionary foods. Reductions in the different types of discretionary food were modelled individually to estimate the impact on energy consumption and population body weight by 5-year age and sex groups. It was assumed that one serving of discretionary food each week was replaced with either a serving of fruit or popcorn, and a serving (375 mL) of SSBs was replaced with coffee, tea, or milk. Proportional multi-state multiple-cohort Markov modelling estimated likely resultant health adjusted life years (HALYs) gained and healthcare costs saved over the lifetime of the 2010 Australian population. A reduction of one serving of SSBs (375 mL) had the greatest potential impact in terms of weight reduction, particularly in ages 19-24 years (mean 0.31 kg, 95% UI: 0.23 kg to 0.37 kg) and overall healthcare cost savings of AUD 793.4 million (95% UI: 589.1 M to 976.1 M). A decrease of one serving of sweet biscuits had the second largest potential impact on weight change overall, with healthcare cost savings of $640.7 M (95% CI: $402.6 M to $885.8 M) and the largest potential weight reduction amongst those aged 75 years and over (mean 0.21 kg, 95% UI: 0.14 kg to 0.27 kg). The results demonstrate that small reductions in discretionary food consumption are likely to have substantial health benefits at the population level. Moreover, the study highlights that policy responses to improve population diets may need to be tailored to target different types of foods for different population groups.

Do children with a high level of eating motivation consume less when foods are partitioned?

Eating behaviors, especially the control of intake, are modulated by both internal and external factors. The objective of our study was to examine the effect of the interaction between eating motivation (as an internal factor) and food partition (as an external factor) on chocolate intake in children, with the hypothesis, based on the paradigm of motivated perception, that the effect of partition, i.e. reduced intake, is higher for children with a high level of eating motivation than for other children. A mixed model design was used in which 80 children aged 8-11 yrs. were offered, in their natural setting, two standardized afternoon snacks that included, among other things, 100 g of chocolate presented once as a whole (one bar) and once segmented (six pieces). The amount of chocolate eaten was weighed and compared between conditions (Bar vs Pieces). Children completed questionnaires in order to assess two of their eating motivational features (appetite arousal, chocolate specific appetite). Results indicated no effect of Partition: children ate the same quantity of chocolate in the two conditions (Bar or Pieces). Only chocolate specific appetite was associated with the amount of chocolate eaten, with children with a higher level eating more than other children (+13 g). Contrary to adults, children are not influenced by the "many is more effect". Methodological and developmental interpretations were suggested, linked to the size of the portion, the network of attention and the sensibility to the external cues underlying the control of intake.

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.

Discretionary intake among Australian adults: prevalence of intake, top food groups, time of consumption and its association with sociodemographic, lifestyle and adiposity measures

OBJECTIVE

To profile discretionary food and beverage (DF) consumption among Australian adults.

DESIGN

Cross-sectional analysis. Dietary and sociodemographic data were used to profile DF intake. Prevalence of DF consumption, DF servings (1 serving=600 kJ), nutrient contribution from DF and top DF food groups by self-reported eating occasions were determined. DF consumers (>0 g) were classified according to quartile of DF intake and general linear models adjusted for age and sex were used to determine associations.

SETTING

2011-12 National Nutrition and Physical Activity Survey (NNPAS).ParticipantsAdults aged ≥19 years (n 9341) who participated in the NNPAS 2011-12.

RESULTS

Most adults consumed DF (98 %) and over 60 % exceeded 3 DF servings/d, with a mean of 5·0 (se 0·0) DF servings/d. Cakes, muffins, scones, cake-type desserts contributed the most DF energy (8·4 %) of all food groups, followed by wines (8·1 %), pastries (8·0 %) and beers (6·1 %), with all these food groups consumed in large portions (2·3-3·0 DF servings). Lunch and dinner together contributed 45 % of total DF energy intake. High DF consumers had an average of 10 DF servings, and this group contained more younger adults, males, low socio-economic status, lower usual fruit intake and higher mean waist circumference, but not higher BMI.

CONCLUSIONS

A focus on DF consumed in large portions at lunch and dinner may help improve interventions aimed at reducing DF intake and addressing negative adiposity-related measures found in high DF consumers.

Right Sizing: Sensory-Based Product Design Is a Promising Strategy to Nudge Consumers toward Healthier Portions

Research has shown that people consume more food when offered larger portions, and that reducing exposure to large food portions and packages could decrease the average daily energy consumed. In this context, our aim is to develop strategies to promote healthier eating behaviors by reducing portion selection and intake. The present research investigates the impact of different visual attributes of foods on quantity perception and portion selection. In the first study, we tested whether modifying the shape of a familiar food influenced the ideal portion size in adults. In the second study, we assessed the impact of shape, number of units, size, and color variety on a perceived quantity for a familiar multiunit product in children. Participants (N₁ = 70 adults, N₂ = 62 children) completed different picture-based computer tasks. As hypothesized: (1) adults selected a smaller ideal portion size for an elongated product than for wider and thicker shapes, and (2) children’s perception of food quantity was primarily driven by number of pieces, with smaller effects of size and elongation. Perceived quantity was not influenced by color variety. These findings suggest that it may be possible to reduce the size of food portions without negatively impacting perceived quantity, and to provide opportunities to nudge consumers towards smaller portions while maintaining satisfaction.

Multisensory influence on eating behavior: Hedonic consumption

Research in obesity has traditionally focused on prevention strategies and treatments aimed at changing lifestyle habits. However, recent research suggests that eating behavior is a habit regulated not only by homeostatic mechanisms, but also by the hedonic pathway that controls appetite and satiety processes. Cognitive, emotional, social, economic, and cultural factors, as well as organoleptic properties of food, are basic aspects to consider in order to understand eating behavior and its impact on health. This review presents a multisensory integrative view of food at both the homeostatic and non-homeostatic levels. This information will be of scientific interest to determine behavior drivers leading to overeating and, thus, to propose effective measures, at both the individual and population levels, for the prevention of obesity and associated metabolic diseases.

Presenting a food in multiple smaller units increases expected satiety

Presentation of the same amount of a food in multiple smaller units (‘segmentation’) has been shown to reduce food intake and increase estimates of the amount of food consumed. However, this effect has been demonstrated for ad libitum food intake only. In the majority of cases, meals are not consumed ad libitum, but are pre-selected and consumed in their entirety, Expected satiety (ES; the anticipated capacity of a portion of food to relieve hunger between meals) is an excellent predictor of portion size selection. This study tested the hypothesis that segmentation increases ES. It was also hypothesised that perceived volume (PV) may account for the relationship between segmentation and ES. Sixty-eight participants made computer-based ES and PV judgments for equicaloric portions of three test foods (salted peanuts, spaghetti Bolognese, and chicken tikka masala), which were presented in either a single unit or as multiple smaller units (three or six units). Results revealed a consistent effect of segmentation on ES - foods presented in multiple smaller units were expected to deliver significantly greater satiety than when presented in a single unit (p < 0.005). Furthermore, results indicated that the effect of segmentation on ES was attributable to an increase in PV. ES plays an important role in determining the portion sizes that people select. Therefore, awareness of the effect of segmentation on ES may help to inform the design of foods that confer benefits for healthy weight maintenance.

Portion Size: Latest Developments and Interventions

PURPOSE OF REVIEW

The aim of this review is to provide an overview of (1) underlying mechanisms of the effect of portion size on energy intake, (2) external factors explaining the portion size effect and (3) interventions and measurements aimed at food portion size.

RECENT FINDINGS

Previous studies have shown that portion sizes have increased in recent decades. Many experimental studies have been conducted to unravel the mechanisms underlying the portion-size effect on food intake (e.g. the appropriateness mechanism, the 'unit bias' mechanism, the 'previous experience/expectation' mechanism, the 'visual cue' mechanism and the 'bite size' mechanism). In addition, external factors have been found to drive food portion selection and consumption (e.g. value for money, mindless eating, levels of awareness, estimation bias. Research on several interventions (ranging from 'providing information' to 'eliminating choice') have been conducted, but remain scarce, especially intervention studies in which portion size is a key focus in weight loss. Moreover, only three new instruments with respect to portion control behavior have been developed. There is considerable evidence for the portion-size effect on energy intake. However, the work on interventions targeting portion size and measurements for portion control behavior are limited. Moreover, from the literature it is not yet clear what type of interventions work best, for whom and in what context.

Portion-size preference as a function of individuals' body mass index

OBJECTIVE

Large portions of food are often blamed for rising rates of obesity. We tested the possibility that people who are heavier may tend to select or prefer larger portions than do people who are lighter.

METHODS

Participants (total N = 798) were asked to choose between a small and larger portion of pasta for a hypothetical meal (Studies 1, 2 and 4), to indicate their ideal portion from a range of portion-size options (Study 2), or to select their preferred portion size from each of 28 portion pairs (Study 3).

RESULTS

Across all studies, there were no significant differences between heavier and lighter participants in their portion-size selection (effect sizes ranged from d = -0.06 to 0.33). The pattern was the same regardless of whether we grouped participants as having a body mass index (BMI) <25 vs. ≥25, as having a BMI of <30 vs. ≥30, or treated BMI as a continuous predictor.

CONCLUSIONS

Given the lack of association between BMI and portion-size preference, we suggest that factors other than portion size, such as differences in meal frequency, food type, plate clearing or compensation at subsequent meals, may need to be considered in order to explain the increasing prevalence of obesity.

Discrete strategies to reduce intake of discretionary food choices: a scoping review

On a population level, dietary improvement strategies have had limited success in preventing the surge in overweight and obesity or reducing risk factors for chronic disease. While numerous multi-component studies have examined whole-of-diet strategies, and single component (i.e. discrete) dietary intervention strategies have targeted an increase in core foods (e.g. fruits, vegetables, dairy), there is a paucity of evidence on the effectiveness of dietary intervention strategies targeting a decrease in discretionary choices. The aim of this review was to identify dietary intervention strategies that are potentially relevant to reducing intake of discretionary choices in 2–65 year olds. A scoping review was carried out to map the literature on key discrete dietary intervention strategies that are potentially applicable to reducing discretionary choices, and to identify the targeted health/nutrition effects (e.g. improve nutrient intake, decrease sugar intake, and reduce body weight) of these strategies. Studies conducted in participants aged 2–65 years and published in English by July 20, 2015, were located through electronic searches including the Cochrane Library, Medline, Embase, CINAHL, and Scopus. Three thousand two hundred and eighty three studies were identified from the search, of which 44 met the selection criteria. The dietary intervention strategies included reformulation (n = 13), substitution (n = 5), restriction/elimination (n = 9), supplementation (n = 13), and nutrition education/messages (n = 4). The key findings of the review were: restricting portion size was consistently beneficial for reducing energy intake in the acute setting; reformulating foods from higher fat to lower fat could be useful to reduce saturated fat intake; substituting discretionary choices for high fibre snacks, fruit, or low/no-calorie beverages may be an effective strategy for reducing energy intake; supplementing nutrient dense foods such as nuts and wholegrain cereals supports an improved overall diet quality; and, a combination of permissive and restrictive nutrition messages may effectively modify behavior to reduce discretionary choices intake. Longer-term, well-controlled studies are required to assess the effectiveness of the identified dietary strategies as interventions to reduce discretionary choices intake.

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.

Sensory influences on food intake control: moving beyond palatability

The sensory experience of eating is an important determinant of food intake control, often attributed to the positive hedonic response associated with certain sensory cues. However, palatability is just one aspect of the sensory experience. Sensory cues based on a food's sight, smell, taste and texture are operational before, during and after an eating event. The focus of this review is to look beyond palatability and highlight recent advances in our understanding of how certain sensory characteristics can be used to promote better energy intake control. We consider the role of visual and odour cues in identifying food in the near environment, guiding food choice and memory for eating, and highlight the ways in which tastes and textures influence meal size and the development of satiety after consumption. Considering sensory characteristics as a functional feature of the foods and beverages we consume provides the opportunity for research to identify how sensory enhancements might be combined with energy reduction in otherwise palatable foods to optimize short-term energy intake regulation in the current food environment. Moving forward, the challenge for sensory nutritional science will be to assess the longer-term impact of these principles on weight management.

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.

Encouraging vegetable intake as a snack among children: the influence of portion and unit size

Objective

People eat more unhealthy foods when served more (portion size effect) and when the food is served in larger units (unit size effect). The present study aimed to examine whether these effects can be used for the good: to increase vegetable consumption among children.

Design

A 2×2 between-subjects experiment was conducted at two schools. Pupils were presented in class with cucumber that varied both in unit size (one piece v. pre-sliced) and portion size (one-third v. two-thirds of a cucumber). Children ate ad libitum during the morning break and filled in a survey.

Setting

Primary schools in the centre of the Netherlands.

Subjects

Primary-school pupils (n 255) aged 8–13 years.

Results

Children ate 54 % more cucumber when served a large compared with a smaller portion (difference of 49 g; P<0·001). Large units did not impact consumption (P=0·58), but were considered as less convenient to eat than small units (P=0·001).

Conclusions

Findings suggest that children’s vegetable intake can be improved by serving larger portions in smaller-sized pieces.

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.

Portion size and obesity

Portion size is a key environmental driver of energy intake, and larger-than-appropriate portion sizes could increase the risk of weight gain. Multiple acute, well-controlled laboratory studies, supported by data from free-living settings, demonstrated that portion size has a powerful and proportionate effect on the amount of food consumed. Of particular importance is that bouts of overeating associated with large portions are sustained and not followed by a compensatory reduction in energy intake. The positive effect of portion size on energy intake was demonstrated for different types of foods and beverages, and is particularly pronounced with energy-dense foods. The predisposition to overeat in response to large portions is pervasive and occurs regardless of demographic characteristics, such as socioeconomic status, age, body mass index, and sex. Secular trends toward greater availability of large portions, coupled with value-size pricing, effectively distorted consumption norms and perceptions of what is an appropriate amount to eat. Nevertheless, although a direct causal link between portion size and obesity remains to be established, advice to moderate portion sizes, especially of energy-dense foods, is presently the cornerstone of most weight management advice. Although many strategies have been proposed to counteract the deleterious effects of portion size, there are few data indicating which are likely to be acceptable in the medium- to long term. Further research is urgently needed to establish what types of interventions targeted at portion size are likely to be effective, in what settings, and among which target groups.

Inclusion of pork meat in the diets of young women reduces their intakes of energy-dense, nutrient-poor foods: results from a randomized controlled trial

Adherence of young women to dietary recommendations has been examined predominantly by surveys. This study aimed to determine the quality of women’s diets relative to the Australian Guide to Healthy Eating (AGHE); and to evaluate dietary changes during an intervention trial with pork meat or an iron supplement. A 12-week randomized trial was conducted in young women who were assigned to one of three groups. They maintained three, seven-day food diaries while continuing their routine diet (CG); taking an iron supplement (SG); or incorporating into their diets 500 g/week of pork (PG). Participants (n = 58) provided dietary information on 1218 diary-days. The serves consumed from the vegetable, fruit and dairy groups were lower (p < 0.001), and from the meat and alternatives group greater (p < 0.001) than the recommended serves. PG consumed significantly fewer (p < 0.001) serves of “extra” foods, and ate fruit more frequently (p < 0.001) than CG and SG. The participants’ dietary self-assessment showed poor agreement with the AGHE description of “serve”. The inclusion of pork in the diets of young women is associated with the reduced consumption of energy-dense nutrient-poor “extra” foods and increased frequency of fruit intake. The effect may be explained by diverse factors such as increased food knowledge, cooking skills and the effect of pork on satiety.

The portion size effect on food intake. An anchoring and adjustment process?

People consistently over-eat when served a large compared with a small (appropriate) portion of food. However, the mechanism underlying this so-called portion size effect is not well understood. We argue that the process of anchoring and adjustment naturally describes this effect, such that the size of a presented portion works as an anchor that strongly influences consumption. The classical anchoring and adjustment paradigm was applied to six hypothetical eating situations. Participants were asked to imagine being served either a small or a large portion of food (i.e., low and high anchor) and to indicate whether they would consume more or less than this amount. Then, they indicated how much they would eat. These estimates were compared with a no-anchor condition where participants did not imagine a specific portion size but only indicated how much they would eat. In addition, half of participants in the anchoring conditions received a discounting instruction stating that the portion size they had been asked to imagine was randomly selected and thus not informative for their consumption estimate. As expected, participants who imagined to be served larger portions estimated to consume significantly more food than participants in the no-anchor condition, and participants who imagined to be served smaller portions estimated to consume significantly less food than participants in the no-anchor condition. The discounting manipulation did not reduce this effect of the anchors. We suggest that the process of anchoring and adjustment may provide a useful framework to understand the portion size effect and we discuss implications of this perspective.

A review of visual cues associated with food on food acceptance and consumption

Several sensory cues affect food intake including appearance, taste, odor, texture, temperature, and flavor. Although taste is an important factor regulating food intake, in most cases, the first sensory contact with food is through the eyes. Few studies have examined the effects of the appearance of a food portion on food acceptance and consumption. The purpose of this review is to identify the various visual factors associated with food such as proximity, visibility, color, variety, portion size, height, shape, number, volume, and the surface area and their effects on food acceptance and consumption. We suggest some ways that visual cues can be used to increase fruit and vegetable intake in children and decrease excessive food intake in adults. In addition, we discuss the need for future studies that can further establish the relationship between several unexplored visual dimensions of food (specifically shape, number, size, and surface area) and food intake.

A brief mindfulness intervention reduces unhealthy eating when hungry, but not the portion size effect

OBJECTIVE

The present research examined the effects of a mindfulness-based intervention to foster healthy eating. Specifically, we tested whether a brief mindfulness manipulation can prevent the portion size effect, and reduce overeating on unhealthy snacks when hungry.

METHODS

110 undergraduate participants (MAge=20.9±2.3; MBMI=22.3±2.5) were served a small or a large portion of chocolate chip cookies after listening to an audio book or performing a mindfulness exercise (i.e., body scan). Current level of hunger was assessed unobtrusively on a visual analog scale before the eating situation.

MAIN OUTCOME MEASURE

Calorie intake from chocolate chip cookies.

RESULTS

When presented with a large compared to a small portion, participants consumed more cookies (+83kcal). This was not affected by the mindfulness intervention or by hunger. However, while control participants ate more unhealthy food when hungry than when not hungry (+67kcal), participants in the mindfulness condition did not (+1kcal).

CONCLUSIONS

Findings confirm the prevalence and robustness of the portion size effect and suggest that it may be independent from awareness of internal cues. Prevention strategies may benefit more from targeting awareness of the external environment. However, mindfulness-based interventions may be effective to reduce effects of hunger on unhealthy food consumption.

Behavioural strategies to control the amount of food selected and consumed

Several factors within the food environment may stimulate overconsumption. The present study aimed to (1) identify behavioural strategies to cope with this environment to control the amount of food consumed, (2) examine the feasibility and usefulness of the strategies, and (3) evaluate the association between the strategies and body mass index (BMI). After the literature was screened for evidence of factors that contribute to the consumption of large amounts of food, 32 behavioural strategies were identified to overcome these influences (study 1). Subjectively reported feasibility and usefulness of the 32 behavioural strategies in weight management were explored using a pretest post-test study (study 2: n = 52). Additionally, two cross-sectional questionnaire studies (study 3a: n = 120 and study 3b: n = 278) were conducted to evaluate the association between the 32 behavioural strategies and BMI. The strategies were subjectively reported as feasible and useful in weight management. Frequent use of strategies discriminated non-overweight from overweight individuals, but did not discriminate overweight from obese individuals. In conclusion, the findings provided preliminary evidence for the acceptability and validity of the strategies. The effectiveness of the strategies for controlling the amount consumed should be further investigated, especially in overweight and obese participants.

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.

"Split them!" smaller item sizes of cookies lead to a decrease in energy intake in children

OBJECTIVE

Examine the influence of altering the size of snack food (ie, small vs large cookies) on short-term energy intake.

METHODS

First- and sixth-graders (n = 77) participated in a between-subjects experimental design. All participants were offered the same gram weight of cookies during an afternoon tea at their school. For half of the participants, food was cut in 2 to make the small item size. Food intake (number of cookies, gram weight, and energy intake) was examined using ANOVA.

RESULTS

Decreasing the item size of food led to a decrease of 25% in gram weight intake, corresponding to 68 kcal. Appetitive ratings and subject and food characteristics had no moderating effect.

CONCLUSIONS AND IMPLICATIONS

Reducing the item size of food could prove a useful dietary prevention strategy based on decreased consumption, aimed at countering obesity-promoting eating behaviors favored by the easy availability of large food portions.

Sweet and salty. An assessment of the snacks and beverages sold in vending machines on US post-secondary institution campuses

This study assessed the nutritional quality of snacks and beverages sold in vending machines. The contents of snack and beverage vending machines in 78 buildings on 11 US post-secondary education campuses were surveyed. Of the 2607 snack machine slots surveyed, the most common snacks vended were salty snacks (e.g., chips, pretzels) and sweets (i.e., candy and candy bars). The 1650 beverage machine slots assessed contained twice as many sugar-sweetened beverages as non-calorie-containing beverages. Only two institutions sold both milk and 100% juice in vending machines. The portion of snacks and beverages sold averaged more than 200 cal. Neither snacks nor beverages were nutrient dense. The majority of snacks were low in fiber and high in calories and fat and almost half were high in sugar. Most beverages were high in calories and sugar. This study's findings suggest that vending machines provide limited healthful choices. Findings from benchmark assessments of components of the food environment, like the vending options reported here, can provide valuable input to campus administrators, health services, food service, and students who want to establish campus policies to promote healthful eating.