Effects of age on children's intake of large and self-selected food portions

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.

A systematic review of the relationship between portion size and indexes of adiposity in children

Research suggests that larger food portion sizes (PS) during a meal or snack increase daily energy intake in children. However, it remains unclear whether this 'PS effect' would lead to a sustained increase in consumption and affect body adiposity. This systematic review assesses the evidence for a relationship between served, consumed, and preferred PS (food or drink size in grams or kcal) and indexes of adiposity (e.g., BMI percentile, BMI z-scores) in children (< 19 years). A total of 17 articles were identified using six electronic databases (PsycINFO, MEDLINE, EMBASE, Web of Science, Cochrane Library, and ProQuest Dissertations & Theses Global). Articles were screened independently by 2 researchers; 21 studies were included (15 cross-sectional, 2 experimental, 1 case study, 1 longitudinal, and two interventions). A narrative review was conducted due to high levels of heterogeneity. Cross-sectional and experimental studies (n = 13) reported positive associations between PS and adiposity, but results differed according to the sex/gender of the participants and food type. Interventions (n = 2) showed that portion size reduction may be effective in reducing child adiposity. Due to the limited evidence on the causality and direction of the effect, and over-reliance on cross-sectional studies, more evidence on the longer-term impact of PS on indexes of body adiposity is required.

Child eating behaviors are consistently linked to intake across meals that vary in portion size

Prior studies evaluating a single meal in children characterized an "obesogenic" style of eating marked by larger bites and faster eating. It is unclear if this style is consistent across portion sizes within children so we examined eating behaviors in 91 children (7-8 years, 45 F) without obesity (BMI<90th percentile). Children consumed 4 ad libitum meals in the laboratory consisting of chicken nuggets, macaroni, grapes, and broccoli that varied in portion size (100%, 133%, 166%, 200%) with a maximum of 30 min allotted per meal. Anthropometrics were assessed using age and sex adjusted body mass index (BMI) percentile and dual energy x-ray absorptiometry. Bites, sips, active eating time, and meal duration were coded from meal videos; bite size (kcal and g/bite), proportion of active eating (active eating time/meal duration), and eating rate (kcal and g/meal duration) were computed. Intraclass correlation coefficients (ICC) showed that most eating behaviors were moderately consistent across portions (>0.50). The consistency of associations between eating behaviors and total meal intake and adiposity were assessed with general linear models adjusted for food liking, pre-meal fullness, age, and sex. Across all portions, more bites, faster eating rate, and longer meal duration were associated with greater intake. While higher BMI percentile was associated with faster eating rates across all meals, greater fat mass index was only associated with faster eating at meals with portions typical for children (i.e., 100% and 133%). In a primarily healthy weight sample, an 'obesogenic' style of eating was a consistent predictor of greater intake across meals that varied in portion size. The consistent relationship of these behaviors with intake makes them promising targets to reduce overconsumption.

'You just eyeball it': Parent and nursery staff perceptions and influences on child portion size: A reflexive thematic analysis

Background: Childhood obesity is one of the most serious public health epidemics of the 21st century. Observational studies report that increases in portion size (PS) have occurred in parallel with levels of obesity. Increased PSs of high-energy-dense foods can promote overeating, and without compensatory behaviours, can contribute to childhood obesity. Caregivers make decisions about PSs for children in the home and nursery environment, thus are gatekeepers to child food intake. Understanding caregiver PS decisions can aid in the best practice of PS provision to young children. The aim of this study was to explore parent and nursery staff influences on child PS selection and their suggestions for useful tools/strategies in PS decisions. Methods: A qualitative design was employed using focus group discussions (FGDs) with parents and nursery staff of children aged 3-5 years. FGDs were employed given their ability to generate rich data, as well as permit the exploration of collective perceptions, attitudes, behaviours and experiences. Data were analysed using an inductive, semantic approach to reflexive thematic analysis. Results: Four FGDs were conducted: two with parents (n = 13), two with nursery staff (n = 17). Four overarching themes were derived: (i) awareness of PS guidelines; (ii) control over PS; (iii) social influences on children's eating behaviours; (iv) child-specific, social and external factors influencing parent and nursery staff PS decisions. Additionally, participants discussed tools/strategies they believe would be useful in PS decisions. Conclusion: Data from the themes suggest that caregiver control, social, child-specific and external factors are more influential than PS guidelines in both parent and nursery staff PS decisions for young children aged 3-5 years. These findings can inform future childhood obesity prevention initiatives focussed on improving parent and nursery staff provision/use of age-appropriate PSs.

Child food portion sizes in the home environment: how do parents decide?

The consumption of larger portion sizes (PS) of food has been implicated in the increased prevalence of childhood obesity. The home is usually the first place children learn about food, however, little is known about how parents determine child PS in the home environment. This narrative review aimed to explore parental beliefs, decisions, strategies and barriers to the provision of appropriate food PS for children in the home environment. Results indicate that parental decisions on child food PS are based on the amounts they serve themselves, personal intuition and knowledge of child appetite. Owing to the habitual nature of food provision, parental decisions on child PS may be taken without conscious thought and/or could be part of a complex decision-making process influenced by several interlinked factors, including parental childhood mealtime experiences, other family members and child weight status. Strategies to determine child-appropriate PS include modelling the desired PS behaviour, use of unit-based food packaging and PS estimation aids, and providing the child with a degree of autonomy to rely on their own appetite cues. A lack of knowledge/awareness of PS guidance is a key barrier identified by parents to the provision of age-appropriate PS, warranting the inclusion of salient child-appropriate PS guidance within national dietary recommendations. Further home-based interventions to improve the provision of appropriate child PS are required, leveraged on parental strategies already in use, as outlined in this review.

Food Properties and Individual Characteristics Influence Children's Intake Across Multiple Days of Weighed Assessments in Childcare Programs

BACKGROUND

Because children often consume substantial proportions of their diets in childcare programs, it is critical to determine what they eat when served menus meeting dietary recommendations and how intake is related to individual characteristics.

OBJECTIVES

Using weighed assessments, we characterized children's consumption across 15 daily menus and investigated the relationship between properties of the food consumed and child characteristics.

METHODS

In 3 crossover trials in childcare centers that followed dietary guidelines, we provided and weighed all meals and snacks for 5 consecutive days. For this descriptive secondary analysis, we characterized primary outcomes (daily food weight, energy density, and energy intake) by including the most typical set of menus from each trial, yielding 603 daily intakes for 128 preschool children (15% with overweight or obesity). Physical activity was measured by accelerometry during childcare sessions. Children's appetitive traits were assessed by parental questionnaires.

RESULTS

Both food properties and child characteristics were related to daily intake. More food was consumed from menus with greater food weight, and the energy density of consumed food was greater from menus with higher energy density (both P < 0.0001); these menu differences resulted in greater energy intake (P = 0.009). Children with overweight and obesity had greater energy intake as a proportion of requirements than did children with healthy weight (113 ± 6% versus 101 ± 2%; P = 0.039). Vegetable intake was 39 ± 2% of the recommended amounts and boys had lower consumption than girls (P = 0.004). Children with appetitive traits of lower satiety responsiveness or higher food responsiveness had greater daily energy intake (both P < 0.003).

CONCLUSIONS

Weighed intakes showed that when children were served daily menus with substantial portions of foods that met dietary recommendations, they selectively consumed higher-energy-dense items and ate few vegetables. A particular concern was that children with overweight ate amounts that exceeded their energy needs. The trials were registered at clinicaltrials.gov (NCT02963987, NCT03010501, NCT03242863).

Effect of food portion on masticatory parameters in 8- to 10-year-old children

The objective of this study was to explore differences in bite size and the amount of intraoral processing of four different foods between a reference and a double portion in 8- to 10-year-old children and, also to explore if there were differences depending on the child's weight status. The study was undertaken in 8- to 10-year-old children (n = 89). Body mass index was determined, and weight status was established based on Centers for Disease Control and Prevention(CDC) guidelines. A reference (half a banana, half a large peeled carrot, a slice of loaf cake, and half a salami stick), and a double portion of each food were offered to children in a randomized order in two different sessions. Three consecutive bites were taken and averaged. Variables in this study were bite size (g), number of cycles until swallowing, sequence duration as well as cycles/g. Comparisons were performed with Mann-Whitney, Kruskal-Wallis, and Wilcoxon tests, regressions and correlations were run. Bite size was ≈13% larger with the double portion (p ≤ .05 for salami, banana, and loaf cake). Cycles/g decreased for all foods with the double portion, although only significantly for banana and loaf cake. Normal and obese children had larger bite sizes (p ≤ .05) of banana than overweight children, while only obese had larger bites of loaf cake with the double portion. In conclusion, the bite size of foods in 8- to 10-year-old children increases (13%) when the portion size is doubled and the larger bite size leads to fewer cycles/g (8%). These effects differ among foods. These parameters do not depend on weight status.

Children's Portion Selection Is Predicted by Food Liking and Is Related to Intake in Response to Increased Portions

BACKGROUND

When children choose amounts of food to eat, it is unclear what influences the portions they select and whether their selections are related to the amounts they consume.

OBJECTIVES

Using a computer survey, we investigated the effect of food liking on portion selection in middle childhood and examined how children's selections were related to measured intake at meals in which portions of all foods were varied across 4 test days.

METHODS

Fifty-one children aged 7-10 y completed a computer survey of 20 common foods with a range of energy density. For each food, the survey presented sliding scales with 5 images varying in portion size and children indicated their liking and the amount they would eat at a specified meal or snack. On 4 test days in a randomized crossover design, children were served a meal of 6 foods from the survey with portions of 100%, 133%, 167%, or 200% of baseline amounts. Data were analyzed using random coefficients models.

RESULTS

Across the 20 foods used in the survey, portion selection ratings were predicted by food liking ratings (P < 0.0001). After accounting for liking, portion selection ratings did not vary by food energy density (P = 0.50). At the meals, intake of all 6 foods increased when larger portions were served (P = 0.002). Furthermore, the selected portion of a food on the survey was positively related both to intake of that food at the 100%-portion meal (P = 0.014) and to increased intake as larger portions were served (P < 0.0001).

CONCLUSIONS

Children aged 7-10 y were able to use a computer survey to choose food portions that predicted their measured intake in response to increased portions. The relation of liking to selection and intake indicates that to promote children's consumption of larger portions of low-energy-dense foods such as fruits and vegetables, these foods must be well liked by the children. This trial was registered at clinicaltrials.gov as NCT02759523.

Child meal microstructure and eating behaviors: A systematic review

Observational coding of children's eating behaviors and meal microstructure (e.g., bites, chews) provides an opportunity to assess complex eating styles that may relate to individual differences in energy intake and weight status. Across studies, however, similar terms are often defined differently, which complicates the interpretation and replication of coding protocols. Therefore, this study aimed to compile methods of coding meal microstructure in children. To limit bias and ensure a comprehensive review, a systematic search was conducted in January 2021 across three databases (PubMed, PsychInfo, Web of Science) resulting in 46 studies that coded at least one meal-related behavior in healthy children (i.e., no medical/psychological disorders) who were able to self-feed (i.e., no spoon-, breast-, or bottle-feeding). While the majority of studies had good interrater reliability, the details reported about study foods and the clarity of the definitions used for behavioral coding varied considerably. In addition to reported microstructure behaviors, a non-exhaustive review of individual differences was included. While few studies reported individual differences related to age and sex, there was a larger literature related to weight status that provided evidence for an 'obesogenic' style of eating characterized by larger Bites, faster Eating and Bite Rates, and shorter Meal Durations. However, some studies may not have been optimally designed or powered to detect individual differences because they did not set out a priori to examine them. Based on this systematic review, best practices for the field are recommended and include reporting more details about foods served and coded eating behaviors to improve reproducibility. These suggestions will improve the ability to examine patterns of individual differences across studies, which may help identify novel targets for intervention.

Where and when are portion sizes larger in young children? An analysis of eating occasion size among 1·5-5-year-olds in the UK National Diet and Nutrition Survey (2008-2017)

OBJECTIVE

To identify eating occasion-level and individual-level factors associated with the consumption of larger portions in young children and estimate their relative importance.

DESIGN

Cross-sectional.

SETTING

Data from parent-reported 4-d food diaries in the UK National Diet and Nutrition Survey (2008-2017) were analysed. Multilevel models explored variation in eating occasion size (kJ) within (n 48 419 occasions) and between children (n 1962) for all eating occasions. Eating contexts: location, eating companion, watching TV, and sitting at a table and individual characteristics: age, gender, ethnicity and parental socio-economic status were explored as potential correlates of eating occasion size.

PARTICIPANTS

Children aged 1·5-5 years.

RESULTS

Median eating occasion size was 657 kJ (IQR 356, 1117). Eating occasion size variation was primarily attributed (90 %) to differences between eating occasions. Most (73 %) eating occasions were consumed at home. In adjusted models, eating occasions in eateries were 377 kJ larger than at home. Eating occasions sitting at a table, v. not, were 197 kJ larger. Eating in childcare, with additional family members and friends, and whilst watching TV were other eating contexts associated with slightly larger eating occasion sizes.

CONCLUSIONS

Eating contexts that vary from one eating occasion to another are more important than demographic characteristics that vary between children in explaining variation in consumed portion sizes in young children. Strategies to promote consumption of age-appropriate portion sizes in young children should be developed, especially in the home environment, in eating contexts such as sitting at the table, eating with others and watching TV.

Relationship between chewing features and body mass index in young adolescents

BACKGROUND

Behavioural aspects of chewing may influence food intake, nutritional status and in turn body weight.

OBJECTIVES

The current study aimed to study chewing features in adolescents as they naturally occur in home-based settings, and to test for a possible association with weight status.

METHODS

Forty-two adolescents (15.3 ± 1.3 years) were recruited (21 with healthy-weight/21 with overweight). Using a smartphone-assisted wearable electromyographic device, the chewing features of each participant were assessed over one evening, including the evening meal, in their natural home setting.

RESULTS

The mean (±SD) for chewing pace was 1.53 ± 0.22 Hz, chewing power 30.1% ± 4.8%, number of chewing episodes 63.1 ± 36.7 and chewing time 11.0 ± 7.7 minutes. The chewing pace of the group with overweight was slower than that of healthy weight (-0.20 Hz; 95% CI, -0.06 to -0.33; P = .005) while their chewing time was shorter (-4.9 minutes; 95% CI, 0.2-9.7; P = .044). A significant negative correlation was observed between BMI z-score and chewing pace (R = -.41; P = .007), and between BMI z-score and chewing time (R = -0.32; P = .039).

CONCLUSION

The current study suggests that adolescents who are overweight eat at a slower pace for a shorter period of time than their counterparts who are a healthy weight. This unexpected finding based on objective data appears to conflict with existing questionnaire findings but provides impetus for further work testing the effectiveness of changing eating behaviour as a weight-management intervention in youth.

Home packed food for nursery children in United Arab Emirates provides suboptimal quality

BACKGROUND: Early childhood nutrition is associated with health outcomes later in life, hence developing health promoting habits from an early age is imperative. OBJECTIVE: The aim of this study was to assess the nutritional adequacy of home-packed food brought to the nurseries by attending children. METHODS: In a cross sectional study conducted in 7 nurseries in Abu Dhabi, United Arab Emirates 315 food-boxes were assessed through detailed food observations at the nurseries prior to mealtimes. The food content was evaluated using the Alberta Guidelines for nursery food, Canada. RESULTS: Most food boxes contained refined grains (77.5%), fruits (74.6%), sweet/full fat dairy products (77.5%), discretionary-calorie-food-items (70.6%). Emirati children were offered sweetened drinks significantly more (p < 0.001). Non-dairy protein sources, vegetables, low-fat-natural-dairy products were offered to 45.4%, 44.1% and 3.9% of children, respectively. Overall, 70.2% of the food-boxes contained not-recommended food and 63.1% of the children were served a very poor food combination. CONCLUSIONS: Despite frequent inclusion of recommended food, many food boxes were nutritionally inadequate due to their low content of whole grains, low-fat dairy products, vegetables and animal proteins and high content of sweet food and drinks. The inadequate dietary patterns necessitate developing nutrition guidelines for nurseries in Abu Dhabi.

Short-Term Effects of an Obesity Prevention Program Among Low-Income Hispanic Families With Preschoolers

OBJECTIVE

To assess the short-term effects of an obesity prevention program promoting eating self-regulation and healthy food preferences in low-income Hispanic children.

DESIGN

Randomized controlled trial with pretest, posttest, and 6- and 12-month assessments.

SETTING AND PARTICIPANTS

Head Start and similar early learning institutions in Houston, TX, and Pasco, WA. A total of 255 families with preschoolers randomized into prevention (n = 136) and control (n = 119) groups.

INTERVENTION

Multicomponent family-based prevention program. Fourteen waves lasted 7 weeks each with 8-10 mother-child dyads in each group.

MAIN OUTCOME MEASURES

Parent assessments included feeding practices, styles, and knowledge. Child assessments included child eating self-regulation, willingness to try new foods, and parent report of child fruit and vegetable preferences. Parent and child heights and weights were measured.

ANALYSIS

Multilevel analyses were employed to consider the nested nature of the data: time points within families within waves.

RESULTS

The program had predicted effects on parental feeding practices, styles, and knowledge in the pre- to post-comparisons. Effects on child eating behavior were minimal; only the number of different vegetables tried showed significant pre-post differences.

CONCLUSIONS AND IMPLICATIONS

Short-term effects of this prevention program highlight the importance of family-focused feeding approaches to combating child overweight and obesity.

Food choices: concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

Snack foods-typically high in salt, sugar, fat and/or energy-are likely important to the obesity epidemic. In the context of a population-based health assessment involving parent-child dyads at child age 11-12 years, we report cross-generational concordance in intake at a controlled snack food observation.

DESIGN

Cross-sectional study (Child Health CheckPoint), nested within the Longitudinal Study of Australian Children.

SETTING

Assessment centres in seven Australian cities, February 2015-March 2016.

PARTICIPANTS

Of all participating CheckPoint families (n=1874), 1299 children (50.3% girls) and 1274 parents (85.9% mothers) with snack data were included. Survey weights and methods were applied to account for the clustered multistage sample design.

OUTCOME MEASURES

Partway through the 3.5-hour assessment, parents and children attended Food Stop separately for a timed 15 min 'snack break'. One of four standardised box size/content combinations was randomly provided to all participants on any given day. Total food mass, energy, nutrients and sodium consumed was measured to the nearest 1 g. Pearson's correlation coefficients and adjusted multivariable linear regression models assessed parent-child concordance in each variable.

RESULTS

Children consumed less grams (151 g [SD 80] vs 165 g [SD 79]) but more energy (1393 kJ [SD 537] vs 1290 kJ [SD 658]) than parents. Parent-child concordance coefficients were small, ranging from 0.07 for sodium intake to 0.17 for carbohydrate intake. Compared with children with parents' energy intake on the 10th centile, children whose parents were on the 90th centile ate on average 227 kJ more. If extrapolated to one similar unsupervised snack on a daily basis, this equates to an additional 83 050 kJ per year, which could have a cumulative impact on additional body fat.

CONCLUSIONS

Although modest at an individual level, this measured parent-child concordance in unsupervised daily snack situations could account for substantial annual population differences in energy, fat and sodium intake for children aged 11-12 years.

TRIAL REGISTRATION NUMBER

ISRCTN12538380.

Portion size has sustained effects over 5 days in preschool children: a randomized trial

BACKGROUND

Although short-term studies have found that serving larger portions of food increases intake in preschool children, it is unknown whether this portion size effect persists over a longer period or whether energy intake is moderated through self-regulation.

OBJECTIVES

We tested whether the portion size effect is sustained in preschool children across 5 consecutive days, a period thought to be sufficient for regulatory systems to respond to the overconsumption of energy.

METHODS

With the use of a crossover design, over 2 periods we served the same 5 daily menus to 46 children aged 3-5 y in their childcare centers. In 1 period, all foods and milk were served in baseline portions, and in the other period, all portions were increased by 50%. The served items were weighed to determine intake.

RESULTS

Increasing the portion size of all foods and milk by 50% increased daily consumption: weighed intake increased by a mean ± SEM of 143 ± 21 g/d (16%) and energy intake increased by 167 ± 22 kcal/d (18%; both P < 0.0001). The trajectories of intake by weight and energy across the 5-day period were linear and the slopes did not differ between portion conditions (both P > 0.13), indicating that there were sustained increases in intake from larger portions without compensatory changes over time. Children differed in their response to increased portions: those with higher weight status, lower ratings for satiety responsiveness, or higher ratings for food responsiveness had greater increases in intake from larger portions (all P < 0.03).

CONCLUSIONS

This demonstration that preschool children failed to adjust their intake during prolonged exposure to larger portions challenges the suggestion that their self-regulatory behavior is sufficient to counter perturbations in energy intake. Furthermore, overconsumption from large portions may play a role in the development of overweight and obesity, as the magnitude of the effect was greater in children of higher weight status. This trial was registered at www.clinicaltrials.gov as NCT02963987.

Associations between inhibitory control, eating behaviours and adiposity in 6-year-old children

Background

Lower inhibitory control has been associated with obesity. One prediction is that lower inhibitory control underlies eating behaviours that promote increased energy intakes. This study examined the relationships between children’s inhibitory control measured using the Stop Signal Task (SST), body composition and eating behaviours, which included self-served portion size, number of servings, eating rate, and energy intake at lunch and in an eating in the absence of hunger (EAH) task.

Methods

The sample included 255 six year old children from an Asian cohort. Stop-signal reaction time (SSRT) was used as an index of inhibitory control. Children participated in a recorded self-served lunchtime meal, followed by the EAH task where they were exposed to energy-dense snacks. Behavioural coding of oral processing was used to estimate eating rates (g/min). BMI, waist circumference and skinfolds were used as indices of adiposity.

Results

Children with lower inhibitory control tended to self-serve larger food portions (p=0.054), had multiple food servings (p=0.006) and significantly faster eating rates (p=0.041). Inhibitory control did not predict energy intake at lunch (p=0.17) or during the EAH task (p=0.45), and was unrelated to measures of adiposity (p>0.32). Twenty percent of the children in the sample had problems focusing on the SST and were described as ‘restless’. Post-hoc analysis revealed that these children had lower inhibitory control (p<0.001) and consumed more energy during the EAH task (p=0.01), but did not differ in any other key outcomes from the rest of the sample (p>0.1).

Conclusions

Children with lower inhibitory control showed a trend to select larger food portions, had multiple food servings and faster eating rates, but were equally as responsive to snacks served in the absence of hunger as children with better inhibitory control. Inhibitory control may impact a number of eating behaviours, not limited to energy-dense snacks.

Potential moderators of the portion size effect

AIM

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

SUMMARY OF FINDINGS

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

CONCLUSIONS

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

The effect of food type on the portion size effect in children aged 2-12 years: A systematic review and meta-analysis

Visual cues such as plate size, amount of food served and packaging are known to influence the effects of portion size on food intake. Unit bias is a well characterised heuristic and helps to determine consumption norms. In an obesogenic environment where large portions are common place, the unit or segmentation bias may be overridden promoting overconsumption of both amorphous or unit foods. The aim of this review was to investigate the impact of offering unit or amorphous food on the portion size effect (PSE) in children aged 2-12 years. A systematic search for literature was conducted in Medline, PsycInfo and Web of Science in February 2018. A total of 1197 papers were retrieved following the searches. Twenty-one papers were included in the systematic review, of which 15 provided requisite statistical information for inclusion in a random effects meta-analysis. Increasing children's food portion size by 51-100% led to a significant increase in intake (SMD = 0.47, 95% CI: 0.39-0.55). There was no evidence to suggest that increases in consumption were related to food type (p = 0.33), child age (p = 0.47) or initial portion size served (p=0.14). Residual heterogeneity was not significant (p=0.24). The PSE was demonstrated in children aged 2-12 years when offered both unit and amorphous food items. The effect was not restricted by food type, child age or influenced by initial portion size served. Of the studies included in the meta-analysis between study heterogeneity was low suggesting minimal variation in treatment effects between studies, however, more research is required to understand the mechanisms of the PSE in preschool children. Future research should determine feasible methods to downsize portion sizes served to children.

Increased brain and behavioural susceptibility to portion size in children with loss of control eating

BACKGROUND

Portion size influences intake (i.e. the portion size effect [PSE]), yet determinants of susceptibility to the PSE are unclear.

OBJECTIVE

We tested whether children who reported an episode of loss of control (LOC) eating over the last 3 months would be more susceptible to the PSE and would show differential brain responses to food cues compared with children with no-LOC.

METHODS

Across five sessions, children (n = 47; 7-10 years) consumed four test meals at 100%, 133%, 167% and 200% conditions for portion size and completed a functional magnetic resonance imaging scan while viewing pictures of foods varied by portion size and energy density (ED). Incidence of LOC over the past 3 months was self-reported. Random coefficient models were tested for differences in the shape of the PSE curve by LOC status. A whole-brain analysis was conducted to determine response to food cues during the functional magnetic resonance imaging.

RESULTS

Reported LOC (n = 13) compared with no-LOC (n = 34) was associated with increased susceptibility to the PSE, as evidenced by a positive association with the linear slope (P < 0.005), and negative association with the quadratic slope (P < 0.05) of the intake curve. Children who reported LOC compared with no-LOC showed increased activation in the left cerebellum to small relative to large portions (P < 0.01) and right cerebellum to High-ED relative to Low-ED food cues (P < 0.01).

CONCLUSION

Children who reported LOC were more susceptible to the PSE and showed alterations in food-cue processing in the cerebellum, a hindbrain region implicated in satiety signalling.

Eating in the absence of hunger: Stability over time and associations with eating behaviours and body composition in children

BACKGROUND/OBJECTIVES

Eating in the absence of hunger (EAH) has been linked to obesity in adults and children. This study examined the stability of EAH in children between 4.5 and 6 years old, and associations with energy intake and portion selection, as well as cross-sectional and prospective associations with body composition.

METHODS

The participants were 158 boys and girls from the Growing Up in Singapore Towards healthy Outcomes cohort. At ages 4.5 and 6 years old children were provided lunch ad libitum, and immediately afterwards were exposed to palatable snacks to measure energy intake in the absence of hunger. At age 6 children completed an additional computer-based task to measure ideal portion size, where they selected pictures of the portions they would like to eat across eight foods. Measures of anthropometry (height/weight/skinfolds) were collected at both ages.

RESULTS

Children who consumed energy during the EAH task at age 4.5 years were 3 times more likely to also do so at age 6 years. Children with high EAH intakes at age 4.5 years had high EAH intakes at age 6, highlighting stability of this behaviour over time. Energy consumed at lunch was unrelated to energy consumed during the EAH task, but children who ate in the absence of hunger cumulatively consumed more energy over lunch and the EAH task. Children who showed EAH tended to select larger ideal portions of foods during the computer task. EAH was not associated with measures of body composition.

CONCLUSIONS

EAH is a stable behavioural risk factor for increased energy intake, but was not associated with body composition in this cohort. The majority of children ate in the absence of hunger, suggesting that interventions aimed at reducing responsiveness to external food cues could help to reduce energy intakes. Trial Registry Number: NCT01174875; https://clinicaltrials.gov/.

Friday Night Is Pizza Night: A Comparison of Children's Dietary Intake and Maternal Perceptions and Feeding Goals on Weekdays and Weekends

Childhood obesity is a serious issue in the U.S. While obesity is the result of a multitude of factors, a great deal of research has focused on children's dietary intake. While children's eating patterns vary throughout the week, not much else is known about weekday-weekend differences. Therefore, the current study examined differences in the frequency and portion size of school-age children's consumption of common foods and beverages, as well as mothers' perceptions of those items and their child feeding goals, on weekdays and weekends. A total of 192 mothers of children aged 7 to 11 were recruited through Amazon's Mechanical Turk. Results showed a consistent pattern of more frequent consumption and larger portions of unhealthy foods and beverages on weekends. This aligned with mothers' perceptions of those foods and beverages as weekend items, as well as their feeding goals of health and price being less important on weekends. It is quite possible that weekends are viewed as having less structure and facilitate schedules that allow children to consume more meals away from home. These findings shed light on additional risk factors in children's eating patterns and highlight the serious implications that day of the week can have on childhood obesity.

Brain response to food cues varying in portion size is associated with individual differences in the portion size effect in children

Large portions promote intake of energy dense foods (i.e., the portion size effect--PSE), but the neurobiological drivers of this effect are not known. We tested the association between blood oxygen level dependent (BOLD) brain response to food images varied by portion size (PS) and energy density (ED) and children's intake at test-meals of high- and low-ED foods served at varying portions. Children (N = 47; age 7-10 years) participated in a within-subjects, crossover study consisting of 4 meals of increasing PS of high- and low-ED foods and 1 fMRI to evaluate food images at 2 levels of PS (Large, Small) and 2 levels of ED (High, Low). Contrast values between PS conditions (e.g., Large PS - Small PS) were calculated from BOLD signal in brain regions implicated in cognitive control and reward and input as covariates in mixed models to determine if they moderated the PSE curve. Results showed a significant effect of PS on intake. Responses to Large relative to Small PS in brain regions implicated in salience (e.g., ventromedial prefrontal cortex and orbitofrontal cortex) were positively associated with the linear slope (i.e., increase in intake from baseline) of the PSE curve, but negatively associated with the quadratic coefficient for the total meal. Responses to Large PS High ED relative to Small PS High ED cues in regions associated with cognitive control (e.g., dorsolateral prefrontal cortex) were negatively associated with the linear slope of the PSE curve for high-ED foods. Brain responses to PS cues were associated with individual differences in children's susceptibility to overeating from large portions. Responses in food salience regions positively associated with PSE susceptibility while activation in control regions negatively associated with PSE susceptibility.

A Pilot Intervention Designed to Address Behavioral Factors That Place Overweight/Obese Young Children at Risk for Later-Life Obesity

The purpose of this pilot randomized controlled trial (RCT) was to intervene with parents of overweight/obese 4- to 8-year-old children to improve child internalizing and externalizing behaviors. Parent-child dyads ( N = 60) were randomly assigned to treatment or comparison conditions. Parents attended four intervention sessions at their child's primary health care office over 3 months. Child behaviors were assessed at 0, 3, 6, and 12 months post intervention. Parental beliefs in their skills/abilities increased in the experimental group parents, but there was no statistical difference between groups at any time. Child externalizing behaviors significantly decreased from baseline to postintervention for both groups ( F = 3.26, p = .020). Post hoc model testing suggests that this change was more pronounced in the intervention group ( F = 0.56, p = .692). Child somatic symptoms significantly decreased over time ( F = 4.55, p = .004), and there were group differences in child depressive behaviors ( F = 6.19, p = .020). These findings suggest that a parent-focused intervention program demonstrated positive preliminary effects on children's behaviors.

Meal size is a critical driver of weight gain in early childhood

Larger serving sizes and more frequent eating episodes have been implicated in the rising prevalence of obesity at a population level. This study examines the relative contributions of meal size and frequency to weight gain in a large sample of British children. Using 3-day diet diaries from 1939 children aged 21 months from the Gemini twin cohort, we assessed prospective associations between meal size, meal frequency and weight gain from two to five years. Separate longitudinal analyses demonstrated that every 10 kcal increase in meal size was associated with 1.5 g/wk or 4% (p = 0.005) faster growth rate, while meal frequency was not independently associated with growth (β = 0.3 g/wk p = 0.20). Including both meal parameters in the model strengthened associations (meal size: β = 2.6 g/wk, p < 0.001; meal frequency: β = 1.0 g/wk, p = 0.001). Taken together, the implication is that meal size promotes faster growth regardless of frequency, but meal frequency has a significant effect only if meal size is assumed to be held constant. Clearer advice on meal size and frequency, especially advice on appropriate meal size, may help prevent excess weight gain.

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.

Are Mealtime Best Practice Guidelines for Child Care Centers Associated with Energy, Vegetable, and Fruit Intake?

BACKGROUND

Mealtime best practices for obesity prevention in child care have been developed from experimental studies and expert opinion. Our objective was to describe adherence to best practices in child care centers and to evaluate the association between mealtime practices and children's dietary intake.

METHODS

We conducted an observational study of 349 preschoolers, ages 36 to 72 months, from 30 child care centers in Cincinnati, Ohio (November 2009 to January 2011). Trained observers recorded providers' behaviors related to six mealtime best practice recommendations and documented children's intake (n = 60 group lunches). General linear mixed models were used to evaluate the association between practice use and children's total energy (caloric consumption) and fruit and vegetable consumption.

RESULTS

Adherence to individual mealtime best practices was variable (0%-77%). Staff sitting with children at lunch was associated with lower energy intake and higher vegetable intake. Staff eating some of the same foods was associated with higher energy intake and higher vegetable intake. Staff encouraging children to try new/less-favorite foods more than once was associated with lower fruit intake. Staff having general conversations with children (not addressed in recommendations) was associated with lower vegetable intake. Family-style meal service, staff talking about healthy foods, and staff helping children assess hunger before seconds were not significantly associated with intake.

CONCLUSIONS

Few mealtime best practices were associated with dietary intake. Given the number of meals children consume in child care and the prevalence of childhood obesity, efforts to identify mealtime practices that improve children's dietary intake are crucial for obesity prevention.

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.

Increasing portion sizes of fruits and vegetables in an elementary school lunch program can increase fruit and vegetable consumption

Increasing portion size can increase children's consumption of food. The goal of this study was to determine whether increasing the portion sizes of fruits and vegetables in an elementary school cafeteria environment would increase children's consumption of them. We measured each child's consumption of the fruit and vegetables served in a cafeteria line on a control day (normal cafeteria procedures) and on two intervention days. When we increased the portion size of 3 of the 4 fruits and vegetables by about 50%, children who took those foods increased their consumption of them. Although this was an effective strategy for increasing fruit and vegetable consumption among students who took those foods, many children chose not to take any fruits or vegetables. Further efforts are needed to increase children's selection and consumption of fruits and vegetables in an environment of competing foods of higher palatability.

Individual differences in susceptibility to large portion sizes among obese and normal-weight children

OBJECTIVE

Determine the association of children's susceptibility to large food portion sizes with appetite regulation and obesity.

METHODS

Normal-weight and obese non-Hispanic black children (n = 100) aged 5-6 years were observed in four dinner conditions of varying portion size; portions of all foods (except milk) offered were: 100% (677 kcal), 150% (1015 kcal), 200% (1353 kcal), or 250% (1691 kcal) of those in the reference condition (100%). Condition order was randomly assigned to 2-4 children who ate together at each meal. Child height and weight were measured and caregiver reports of child appetite were obtained. Hierarchical growth curve models were used to estimate associations of meal energy intake with portion size condition, child weight status, and appetite regulation traits, controlling for demographics.

RESULTS

Total energy intake increased across conditions of increasing food portion size (P < 0.001). The effect of portion size condition on total energy intake varied with food responsiveness (P = 0.05) and satiety responsiveness (P < 0.05), but not weight status (P = 0.682). Children with lower satiety responsiveness and greater food responsiveness showed greater increases in meal energy across conditions.

CONCLUSIONS

Children with poorer appetite regulation may be more vulnerable to obesogenic dietary environments offering large food portions than other children.

Longitudinal relations between observed parenting behaviors and dietary quality of meals from ages 2 to 5

OBJECTIVES

Parents influence a child's diet by modeling food choices, selecting the food they make available, and controlling the child's intake. Few studies have examined the covariation between parent's behavior management practices and their guidance and support for a young child's nutritional environment in early childhood. We hypothesized that parents' positive behavior support (PBS), characterized as skillful behavior management and proactive structuring of children's activities, would predict dietary quality over the course of early childhood (age 2 to 5 years), a critical period for the development of a dietary lifestyle.

METHODS

Participants included 731 culturally diverse, low-income families in a randomized, controlled trial of the Family Check-Up. Families participated in a yearly home visit videotaped assessment PBS and dietary quality of meals parents served to their children were assessed by coding videotapes of structured parent-child interactions. A cross-lagged panel model was used to evaluate the longitudinal relation between PBS and the dietary quality of meals served during a meal preparation task.

RESULTS

Analyses revealed that PBS repeatedly predicted meals' dietary quality the following year: age 2-3 (β = .30), age 3-4 (β = 0.14), age 4-5 (β = 0.37). Dietary quality significantly predicted PBS 1 year later: age 3-4 (β = 0.16), age 4-5 (β = 0.14). As expected, the relative strength of the relationship from PBS to dietary quality was significantly stronger than the reverse, from dietary quality to PBS.

CONCLUSIONS

Positive behavior management and proactive parenting practices are an important foundation for establishing a healthy nutritional environment for young children. These findings suggest that family-centered prevention interventions for pediatric obesity may benefit from targeting PBS in service of promoting better dietary quality.

Getting my child to eat the right amount. Mothers' considerations when deciding how much food to offer their child at a meal

Feeding young children successfully requires parenting skills, trust that children will eat, and nutrition and child development knowledge to ensure that foods and the amounts offered are developmentally appropriate. Mothers are often responsible for determining how much food is offered to their children; however, the influences on mothers' decisions regarding how much to offer their children--their motivations, goals for feeding and child consumption--have not been investigated. Study aims included gathering qualitative data regarding mothers' decisional processes related to preparing a dinner meal plate for her preschooler. Low income mothers (n = 15 African American and n = 15 Latina mothers) were recruited from preschools in the Denver, CO metropolitan area to participate in semi-structured interviews. Mothers prepared a plate for their preschooler and were asked about influences on their decisions about portion sizes and their expectations for children's eating. Data were coded by 2 independent coders using a consensus coding process and analyzed by investigators. Three themes emerged: (1) portion sizes differ for children who are "good" eaters and "picky" eaters; (2) mothers know the "right amounts" to serve their child; and (3) mothers have emotional investments in their children's eating. Some influencing factors were child-centered (e.g. child's likes and dislikes, "picky" and "good" eaters, and foods previously eaten in the day) and some related to adult expectations and concerns (nutrient content and waste). Interventions focusing on portion size may be more effective if tailored to the mothers' perceptions regarding her child's eating characteristics.

Environmental strategies for portion control in children

Evidence from laboratory and field studies indicates that large portions lead to greater food and energy intake relative to small portions. However, most children and adults demonstrate limited abilities to estimate and control the amounts of food they serve and consume. Five potential environmental strategies appear promising for improving portion control in children: (1) using tall, thin, and small volume glasses and mugs, (2) using smaller diameter and volume plates, bowls and serving utensils, (3) using plates with rims, (4) reducing total television and other screen watching and (5) reducing or eliminating eating while watching television and/or other screens. Further experimental research in real world settings is needed to test these interventions as strategies for portion control and their roles in prevention and treatment of obesity.

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.

Variability in children's eating response to portion size. A biobehavioral perspective

The portion size of foods and beverages offered at meals has been shown to significantly affect human food intake. While portion size effects appear to be fairly robust across studies in adults, findings from studies in children are generally more variable and do not reliably predict a significant portion size effect. Eating behaviors are still forming at a young age and individual differences in children's response to portion size will depend upon genetic predisposition interacting with the child's environment. The aim of this review is to present and discuss evidence that innate controls of appetite and eating, which involve genes that encode key hormones and neuropeptides implicated in processes of satiety and satiation, may differentially affect meal size. We also present evidence that children's response to portion size is learned and this is in turn shaped by upbringing, the early family and home environment. The review will conclude with a conceptual model that illustrates how biological and environmental factors may interact to shape child eating traits including a behavioral susceptibility to overeating when large portion sizes are available.