The portion size effect and overconsumption - towards downsizing solutions for children and adolescents

A Multi-Level Approach to Childhood Obesity Prevention and Management: Lessons from Japan and the United States

BACKGROUND

Childhood obesity is a pressing global public health challenge, marked by significant disparities in prevalence and management across countries. Japan and the United States offer contrasting approaches to addressing this issue, presenting a valuable opportunity for comparative analysis.

OBJECTIVE

This review examines the effectiveness of public health policies, cultural dietary habits, and lifestyle factors in combating childhood obesity in Japan and the United States. It aims to identify actionable insights to inform global strategies for obesity prevention.

RESULTS

Japan exhibits one of the lowest childhood obesity rates globally, attributed to prevention-focused policies such as the food education program, stringent school lunch standards, and culturally ingrained healthy eating practices. These efforts are complemented by active lifestyle promotion through urban planning and school-based physical education programs. In contrast, the United States faces higher obesity rates due to systemic challenges, including socioeconomic disparities, reliance on processed foods, sedentary lifestyles, and inconsistent implementation of federal programs like the National School Lunch Program (NSLP) and Supplemental Nutrition Assistance Program Education (SNAP-Ed).

CONCLUSIONS

This review highlights Japan's success in aligning public health initiatives with cultural norms to achieve sustainable outcomes. In the United States, systemic barriers and cultural disconnects hinder obesity prevention efforts. Recommendations include adopting integrated, prevention-focused policies, addressing socioeconomic inequities, redesigning urban environments to promote active living, and fostering global collaboration. This comparative analysis underscores the importance of culturally tailored, multidimensional strategies for addressing childhood obesity and improving public health outcomes worldwide.

Utilising online paradigms to explore the effect of boredom and sadness on children's snack choice: The role of parental feeding practices and child temperament

Emotional eating (EE) is defined as eating in response to negative emotions (e.g., sadness and boredom). Child temperament and parental feeding practices are predictive of child EE and may interact to shape child EE. Previous research has demonstrated that children eat more when they are experiencing sadness, however, boredom-EE (despite how common boredom is in children) has yet to be explored experimentally using remote methodologies. The current study explores whether feeding practices and child temperament interact with mood to predict children's snack selection in an online hypothetical food choice task. Using online experimental methods, children aged 6-9-years (N = 347) were randomised to watch a mood-inducing video clip (control, sadness, or boredom). Children completed a hypothetical food choice task from images of four snacks in varying portion sizes. The kilocalories in children's online snack choices were measured. Parents reported their feeding practices and child's temperament. Results indicated that the online paradigm successfully induced feelings of boredom and sadness, but these induced feelings of boredom and sadness did not significantly shape children's online food selection. Parental reports of use of restriction for health reasons (F = 8.64, p = .004, n2 = 0.25) and children's negative emotionality (F = 6.81, p = .009, n2 = 0.020) were significantly related to greater total kilocalorie selection by children. Three-way ANCOVAs found no evidence of any three-way interactions between temperament, feeding practices, and mood in predicting children's online snack food selection. These findings suggest that children's hypothetical snack food selection may be shaped by non-responsive feeding practices and child temperament. This study's findings also highlight different methods that can be successfully used to stimulate emotional experiences in children by using novel online paradigms, and also discusses the challenges around using online methods to measure children's intended food choice.

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.

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.

Examination of dietary intake of UK preschool children by varying carers: evidence from the 2008-2016 UK National Diet and Nutrition Survey

Early years caregivers can play a key role in young children's eating and the prevention of childhood obesity. The UK National Diet and Nutrition Survey (NDNS) is a large representative survey collecting detailed food and nutrition consumption data. Using these data, the aim of this study was to investigate the relationship between dietary intake of preschool children in the UK aged 2 to 4 years and accompanying adult/s. Nutrition consumption data from 1218 preschool children from years 1 to 8 of the 2008-2016 NDNS were accessed. Dietary data were captured using 3 or 4 day estimated food diaries. Regression analyses revealed significant differences in consumption when children were not accompanied by their parents. Compared with when children were with parents, children consumed significantly more energy dense meals (0·32 kJ/g, 95% CI 0·1-0·6 kJ/g), energy (62 kJ/g, (95% CI 27-97 kJ)) Na (19 mg, (95 % CI 6, 32)), added sugars (0·6 g, (95 % CI 0·1, 1·1)), vegetables (3 g, (95 % CI 1, 4)), total grams (12 g, (95 % CI 3, 21)) and saturated fat (0·2 g, (95 % CI 0·1, 0·4)) per eating occasion when accompanied by wider family. When children were accompanied by a formal childcare provider, they consumed significantly lower energy dense meals (-0·9 kJ/g, (95% CI -1·4 - -0·3 kJ/g)), less added sugars (-1·6 g, (95 % CI -2·4, -0·8)) and more fruit (12 g, (95 % CI 3, 21)) per eating occasion than when they were with their parents. The results demonstrate that non-parental caregivers might be an important target to promote healthy eating in young children. Further research is needed to establish which caregivers would benefit most.

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

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

How Do French Parents Determine Portion Sizes for Their Pre-Schooler? A Qualitative Exploration of the Parent-Child Division of Responsibility and Influencing Factors

Large portion sizes can make children overeat, alter their self-regulation abilities and induce weight gain. However, little is known about how parents determine portion sizes for their children. Using semi-structured interviews with 5 fathers and 32 mothers of pre-schoolers, this study examined French parents' food portioning practices. The division of responsibility between parent and child in deciding portion sizes was explored, as well as the influencing factors and possible sources of information. Parents described a wide range of practices. For most, determining portion sizes is an intuitive action that depends on habits and mainly arises from experiences with feeding their child and his/her appetitive traits. Few parents grant autonomy to their child for portioning and serving food, especially for the first serving. Many influencing factors were identified, including child-related (e.g., appetite, food preferences), parent-related (e.g., avoiding food waste), and external factors (e.g., influence of siblings, French food culture). Most parents do not search for information/recommendations to guide their practices. Stimulating optimal self-regulation of eating in children is important and parents can play a crucial role in this. This study identified barriers and facilitators to guide parents in providing appropriate portion sizes and help include children in this decision process.

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

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

Food Waste and Nutrition Quality in the Context of Public Health: A Scoping Review

Food waste and nutrition are intrinsically linked in terms of environmental health and public health. Despite this, it is unknown whether these topics have been previously synthesized into a review. The aim was to identify the interdisciplinary parameters that exist in public health and nutrition literature in terms of food waste and plastic waste associated with food, and to identify how these parameters currently contribute to food sustainability messaging and interventions. A rapid scoping review was conducted. Data were mapped into concepts and synthesized in a narrative review. Four main concepts were identified: (1) food waste and diet quality, nutrient losses, and environmental health, (2) food waste reduction interventions and diet quality, (3) food banks/pantries and diet/nutritional quality, and (4) food and plastic waste messaging in nutrition or dietary guidelines. Food waste is associated with nutrient wastage, and interventions to reduce food waste can successfully address food sustainability and nutrition quality. Food redistribution systems do not currently address access to sustainably sourced foods that are also nutrient-dense for lower-income communities. Opportunities for future research and practice include aligning food waste, plastic waste, and nutrition priorities together and developing better food redistribution systems to limit wastage of high-quality foods.

When do children learn how to select a portion size?

The reduction of portion sizes supports weight-loss. This study looks at whether children have a conceptual understanding of portion size, by studying their ability to manually serve a portion size that corresponds to what they eat. In a clinical setting, discussion around portion size is subjective thus a computerised portion size tool is also trialled, with the portion sizes chosen on the screen being compared to amounts served manually. Children (n = 76) age 5-6, 7-8 and 10-11 were asked to rate their hunger (VAS scale), liking (VAS scale) and 'ideal portion size for lunch' of eight interactive meal images using a computerised portion size tool. Children then manually self-served and consumed a portion of pasta. Plates were weighed to allow for the calculation of calories served and eaten. A positive correlation was found between manually served food portions and the amount eaten (r = 0.53, 95%CI [0.34, 0.82, P < .001), indicating that many children were able to anticipate their likely food intake prior to meal onset. A regression model demonstrates that age contributes to 9.4% of the variance in portion size accuracy (t(68) = -2.3, p = .02). There was no relationship between portion size and either hunger or liking. The portion sizes chosen on the computer at lunchtime correlated to the amount manually served overall (r = .34, 95%CI [0.07, 0.55], p < .01), but not in 5-6-year-old children. Manual portion-size selection can be observed in five-year olds and from age seven, children's 'virtual' responses correlate with their manual portion selections. The application of the computerised portion-size tool requires further development but offers considerable potential.

The Role of Snack Choices, Body Weight Stereotypes and Smoking Behavior in Assessing Risk Factors for Adolescent Overweight and Obesity

This study investigated the relationship of behavioral factors, such as snack choices, obesity stereotypes and smoking with adolescents’ body weight. Individual-level data for 1254 Greek youths were selected via a formal questionnaire. Snack choices seem to be gender specific with girls showing a stronger preference for healthier snacks. Frequent consumption of high-calorie and more filling snacks was found to increase Body Mass Index (BMI) in both genders. Fruit/vegetable snacks were associated with lower body weight in females, whereas cereal/nut snacks had a negative influence in males’ BMI. The majority of participants expressed anti-fat attitudes and more boys than girls assigned positive attributes to lean peers. The endorsement of the thin-ideal was positively associated with the BMI of both adolescent boys and girls. This study also revealed that neglecting potential endogeneity issues can lead to biased estimates of smoking. Gender may be a crucial moderator of smoking–BMI relationships. Male smokers presented a higher obesity risk, whereas female smokers were more likely to be underweight. Nutrition professionals should pay attention to increase the acceptance of healthy snack options. Gender differences in the influence of weight stereotypes and smoking on BMI should be considered in order to enhance the efficacy of obesity prevention interventions.

Analysing Credibility of UK Social Media Influencers' Weight-Management Blogs: A Pilot Study

Social media influencers (SMI) are individuals with large follower engagement, who can shape the thoughts and dietary behaviours of their audience. Concerns exist surrounding the spread of dietary misinformation by SMI, which may impact negatively on public health, yet no standards currently exist to assess the credibility of their information. This study aimed to evaluate the credibility of key SMI weight management (WM) blogs (n = 9), piloting a pre-prepared credibility checklist. SMI were included if they had a blue-tick verification on ≥2 social media (SM) and an active WM blog. A sample of blog posts were systematically evaluated against thirteen credibility indicators under four themes: ‘transparency’, ‘use of other resources’, ‘trustworthiness and adherence to nutritional criteria’ and ‘bias’. Indicators were yes/no questions to determine an overall credibility percentage for each SMI. The ten most recent meal recipes from each blog were evaluated against Public Health England’s (PHE) calorie targets and the UK ‘traffic light’ food labelling scheme to assess nutritional quality. Percentages ranged from 23–85%, the highest gained by a Registered Nutritionist. SMI blogs may not be credible as WM resources. Given the popularity and impact of SM in the context of overweight, obesity and WM, this study may inform the methodological approach for future research.

A systematic review of recall errors associated with portion size estimation aids in children

To reduce errors in portion size estimation, a number of aids have been developed and tested. This systematic review synthesizes what is known about error associated with use of different portion size estimation aids (PSEAs) within self-reported dietary recall studies in children (aged ≤18 years). Eight electronic databases were searched using relevant keywords. From 8184 records identified and screened, 327 full texts were retrieved, with 10 records representing 9 studies meeting inclusion criteria. Studies using proxy reporting were excluded. Thirteen PSEAs were identified. To facilitate comparisons between different types of aids they were categorized into 'physical 2-dimensional (2D)', 'digital 2D' and '3-dimensional' PSEAs. Seven were physical 2D (e.g. food atlas), two were digital 2D (i.e. computer-based), and four were 3D (e.g. modelling clay, household items). Comparisons of PSEAs within studies found the smallest estimation errors for digital 2D and largest for 3D aids. Errors in relation to food type were varied, with portions of amorphous foods overestimated in multiple studies. No effects for recall interval time or sex were identified. One study reported a significant improvement in estimation error with increasing age. Across studies, large variations in study design and reporting of estimation error hindered the synthesis of evidence regarding the influence of different types of PSEAs on accuracy. While a definitive conclusion about the most accurate PSEA could not be drawn, a check-list to guide future PSEA development and testing has been proposed in the current review. This will assist comparability with future studies of PSEAs for children facilitate development of more accurate PSEAs in the future.

Snack Portion Sizes for Preschool Children Are Predicted by Caregiver Portion Size, Caregiver Feeding Practices and Children's Eating Traits

Caregivers are mostly responsible for the foods young children consume; however, it is unknown how caregivers determine what portion sizes to serve. This study examined factors which predict smaller or larger than recommended snack portion sizes in an online survey. Caregivers of children aged 2 to 4 years were presented with 10 snack images, each photographed in six portion sizes. Caregivers (n = 659) selected the portion they would usually serve themselves and their child for an afternoon snack. Information on child eating traits, parental feeding practices and demographics were provided by caregivers. Most caregivers selected portions in line with recommended amounts for preschool children, demonstrating their ability to match portion sizes to their child's energy requirements. However, 16% of caregivers selected smaller than recommended low energy-dense (LED, e.g., fruits and vegetables) snacks for their child which was associated with smaller caregiver's own portion size, reduced child food liking and increased satiety responsiveness. In contrast, 28% of caregivers selected larger than recommended amounts of high energy-dense (HED, e.g., cookies, crisps) snacks for their child which were associated with larger caregiver's own portion size, greater frequency of consumption, higher child body mass index (BMI), greater pressure to eat and lower child food liking. These findings suggest that most caregivers in this study select portions adjusted to suit their child's age and stage of development. Future interventions could provide support to caregivers regarding the energy and nutrient density of foods given the relatively small portion sizes of LED and large portions of HED snacks offered to some children.

Determinants of Portion Size in Children and Adolescents: Insights from the UK National Diet and Nutrition Survey Rolling Programme (2008-2016)

Large portion sizes have been identified as contributing to overweight and obesity, particularly in children and adolescents. This study examined predictors of portion sizes of high energy snack foods eaten by children aged 1.5–18 years. Specifically, we examined whether portion sizes were adjusted for age, and what external features of the environment might be linked to large portion sizes. Portion sizes were derived from four-day food diaries that form the UK National Diet and Nutrition Survey. Diaries from 5942 children were examined and multilevel models were used to discover whether age, gender, location, time of day, household income, and watching TV while eating predicted portion sizes of savoury snacks, chocolate, confectionery and biscuits. Portion sizes of all the target foods were predicted by age. Boys had larger portions, and portion sizes were larger when target foods were consumed later in the day. Portion sizes were larger outside the home, for example in leisure venues, but the target foods were eaten more frequently in the home. As dietary patterns change to include more snack intake outside the home, these locations could be an important space to target for interventions for portion control.

The effectiveness of a social media intervention for reducing portion sizes in young adults and adolescents

Objective

Adolescents and young adults select larger portions of energy-dense food than recommended. The majority of young people have a social media profile, and peer influence on social media may moderate the size of portions selected.

Methods

Two pilot interventions examined whether exposure to images of peers’ portions of high-energy-dense (HED) snacks and sugar-sweetened beverages (SSBs) on social media (Instagram) would influence reported desired portions selected on a survey. Confederate peers posted ‘their’ portions of HED snacks and SSBs on Instagram. At baseline and intervention end participants completed surveys that assessed desired portion sizes.

Results

In intervention 1, undergraduate students (n = 20, mean age=19.0 years, SD=0.65) participated in a two-week intervention in a within-subjects design. Participants reported smaller desired portions of HED snacks and SSBs following the intervention, and smaller desired portions of HED snacks for their peers. In intervention 2, adolescents (n = 44, mean age = 14.4 years, SD = 1.06) participated in a four-week intervention (n = 23) or control condition (n = 21) in a between-subjects design. Intervention 2 did not influence adolescents to reduce their reported desired portion sizes of HED snacks or SSBs relative to control.

Conclusions

These preliminary studies demonstrated that social media is a feasible way to communicate with young people. However, while the intervention influenced young adults’ reported desired portions and social norms regarding their peers’ portions, no significant impact on desired reported portion sizes was found for HED snacks and SSBs in adolescents. Desired portion sizes of some foods and beverages may be resistant to change via a social media intervention in this age group.

Using pictorial nudges of fruit and vegetables on tableware to increase children's fruit and vegetable consumption

Children's fruit and vegetable consumption is lower than recommended. Increasing consumption is important for children's health. Nudges influence children's eating behaviour, but less is known about the influence of a pictorial nudge on tableware on children's fruit and vegetable consumption. Two studies examined this. Study 1 examined whether a pictorial fruit nudge (a grape image) on a plate influenced children's fruit (grape) consumption relative to a control condition (no image). In a between-subjects design, children (n = 63, Mean age = 8.9 years, SD = 1.41, 38 females, 25 males, 73% had a healthy-weight) were randomly assigned to one of two conditions (fruit nudge vs. control). Study 2 examined the influence of a large portion pictorial nudge (a large portion carrot image) vs. a small portion pictorial nudge (a small portion carrot image) vs. control (no nudge) on children's vegetable (carrot) consumption. In a between-subjects design, children (n = 59, Mean age = 8.57 years, SD = 2.13, 31 females, 28 males, 85% had a healthy-weight) were randomly assigned to a condition. In Study 1 children consumed significantly more fruit in the pictorial nudge condition than the control condition. In Study 2 children ate significantly more vegetables in the large portion pictorial nudge condition than the other two conditions. The small portion pictorial nudge did not affect children's vegetable consumption relative to control. The results indicate that pictorial nudges on tableware influence children's fruit and vegetable consumption, and the portion size of this type of nudge may be key to whether it influences children's eating behaviour.