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1 From the US Department of Agriculture Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston (JOF), and the Departments of Nutritional Sciences (BJR and LLB), Biobehavioral Health (BJR), and Human Development and Family Studies (LLB), The Pennsylvania State University, University Park.
2 Supported by USDA grant NRI 00001322. 3 Address reprint requests to JO Fisher, USDA Children’s Nutrition Research Center, Baylor College of Medicine, 1100 Bates Street, Houston, TX 77030. E-mail: jfisher{at}bcm.tmc.edu.
ABSTRACT
Background: Whether large portion sizes affect children’s eating behavior has rarely been studied.
Objectives: Our objectives were 1) to determine the effects of repeated exposure to a large portion of an entrée on preschool-aged children’s awareness of portion size, self-selected portion size, and food intake and 2) to evaluate associations of children’s responsiveness to portion size with weight status and overeating.
Design: Energy intake, bite size, and comments about portion size were evaluated among 30 children at 2 series of lunches in which either an age-appropriate portion or a large portion of an entrée was served. On separate occasions, the children’s self-served portions, weight, height, and tendency to overeat were assessed.
Results: Doubling an age-appropriate portion of an entrée increased entrée and total energy intakes at lunch by 25% and 15%, respectively. Changes were attributable to increases in the average size of the children’s bites of the entrée without compensatory decreases in the intake of other foods served at the meal. These increases were seen even though observational data indicated that the children were largely unaware of changes in portion size. Greater responsiveness to portion size was associated with higher levels of overeating. The children consumed 25% less of the entrée when allowed to serve themselves than when served a large entrée portion.
Conclusions: Large entrée portions may constitute an "obesigenic" environmental influence for preschool-aged children by producing excessive intake at meals. Children with satiety deficits may be most susceptible to large portions. Allowing children to select their own portion size may circumvent the effects of exposure to large portions on children’s eating.
Key Words: Portion size • children’s eating behavior • food intake • preschool-aged children
INTRODUCTION
Rapid increases in childhood overweight since the mid-1970s cannot be explained by genetic factors alone, suggesting that overweight is expressed when genetically susceptible children are placed in environments that promote obesity-favoring behaviors (1). Obesigenic eating environments are thought to offer convenient access to large portion sizes of inexpensive, palatable, energy-dense foods (2–5). There is concern that portion sizes have become excessively large in recent years, particularly for foods that are consumed outside the home (2–5, 6). A recent report indicates that restaurant portions may offer close to the recommended daily number of food group servings in a single entrée (7). Because the average US family spends 1 of every 3 food dollars on foods and beverages consumed away from the home (7), many children have extensive exposure to large portions.
The extent to which serving children excessive food portions affects children’s energy intake and body weight has rarely been studied. To date, only one study experimentally evaluated the effects of increasing portion size on food intake in children. Rolls et al (8) served preschool-aged children small, medium, or large portions of a main course entrée at 3 different lunches. Children aged 4–6 y had increased entrée and lunch intakes across conditions of increasing entrée portion size. Intakes among 2–3-y-old children, however, did not vary across those conditions. These findings provided initial evidence that increases in portion size stimulate young children’s food intake, and this effect is apparent by the time children reach preschool. These findings raise the questions of whether these effects are transient or persist with repeated exposure and why developmental differences in responsiveness to large portions may exist.
This research was designed to extend the previous investigation (8) by determining the effects of repeated exposure to a large portion of an entrée on preschool-aged children’s bite frequency, bite size, and energy intake at a series of lunches. The children’s comments about portion size and the children’s self-served portions were also evaluated to understand the extent to which any effects on the children’s food intake may be reflected in changes in their self-selection or awareness of portion size. We hypothesized that repeated exposure to large portions would result in consistent increases in intake at meals, particularly among older children, and would be accompanied by increases in awareness of portion size and in self-served portion size. A final and more exploratory aim was to evaluate relations between children’s weight, overeating, and susceptibility to large portions. Because individual differences in the ability to regulate energy intake are associated with weight among preschool-aged children (9–12), we hypothesized that heavier children who had deficits in satiety would have the greatest tendency to eat more when served large portions.
SUBJECTS AND METHODS
Design
A within-subjects crossover design was used to evaluate the effects of repeated exposure to a large portion of an entrée on children’s eating. To provide uniform initial exposure to the reference portion size of the entrée, all children received an age-appropriate portion of the entrée once a week at lunch for 4 wk before the study. Subsequently, all children received both the reference portion and the large portion of the entrée. As shown in the experimental timeline (Table 1), each portion size was served during a series of 4 lunches, and the 2 series were separated by 2 wk. During the reference-portion series of lunches, children received an age-appropriate portion of the entrée at a standard lunch. During the large-portion series of lunches, the portion size of the entrée was doubled. The order in which the children received the reference and large portions was balanced for age and sex. A single lunch menu was used throughout the experiment and differed only in the portion size of the main entrée. Weighed-food intake data were obtained at each lunch. Bite size and frequency were measured at one-half of the sessions, and comments about portion size were recorded at the remaining sessions. Children’s self-served portions of the main entrée were assessed at 2 lunches after each of the 2 series. Separate sessions were used to obtain weight and height measures and a measure of the children’s eating behavior in the absence of hunger.
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TABLE 1 . Experimental timeline1
Participants
As in the study by Rolls et al (8), the participants in the present study were preschool children attending full-day daycare programs at The Pennsylvania State University, University Park. Thirty-six children in 2 separate classrooms were screened for inclusion in the study. One family refused to participate. Data were obtained from 35 children (17 boys and 18 girls; 1 African American, 4 Asians, 28 non-Hispanic whites, and 2 Hispanics) with a mean (± SD) age of 4.0 ± 0.5 y (range: 2.9–5.1 y). Parents tended to be highly educated and currently employed: 81% of mothers and 90% of fathers reported having a 4-y university degree, and 84% of mothers and 90% of fathers reported current employment. Most of the families (68%) reported combined family incomes of > $50 000. Parents provided written consent for their own and their child’s participation. All procedures were reviewed and approved by The Pennsylvania State University Institutional Review Board.
Data are reported for 30 of the 35 children; the data from 5 children were excluded from analyses because their mean intake of the main entrée was < 10 g across the 4 lunches in which the reference portion was served. The children whose data were excluded were not significantly different from all others in terms of age (P = 0.74) or body mass index (BMI)–for–age z score (P = 0.44). Missing data or children identified as outliers (> 2 SDs) are reflected in the sample size for each change variable.
Measures and procedures
Entrée and total energy intakes at reference-portion and large-portion lunches
The children’s entrée and total energy intakes at lunch were measured during both the reference-portion and the large-portion series of lunches. Each of 2 daycare classrooms was seen as a group at the Pennsylvania State University Children’s Eating Laboratory during regularly scheduled lunches. Each table seated 4–5 children. Seating assignments were based on age group and entrée portion size so that all children at a given table received the same portion size of the main entrée at a given lunch. To decrease visual comparisons of portion size by children receiving different portion sizes, a portable room divider was used to separate the tables. Each child received a tray containing a plate with the main entrée and separate containers with generous portions of items from the standard menu (see Experimental Menu for details). Each lunch session began after the children were given a description of each of the foods on the single menu. The children were instructed not to share any foods, to eat as much or as little as they desired, and to remain seated for the duration of the lunch period. They were given 15 min to eat lunch, with a reminder at 5 min remaining. Spilled and dropped foods were collected and added to the postconsumption weight of that food. Entrée and lunch intakes were measured by using weighed-food intake data. Data were not collected on holidays or on any other day that involved scheduled celebrations with food (ie, Halloween and Thanksgiving dinner).
Behavioral observations of children’s comments about portion size
The children’s comments about portion size during the lunches were recorded at one-half of both the reference-portion and the large-portion lunch sessions. A staff member sat with each table of 4–5 children. The frequency of any evaluative comments regarding the size of the main entrée as being "small," "okay," or "big" was tallied. Coders were trained by using written descriptions and examples of comments to be coded in each category. Any questionable comment was recorded verbatim and coded at the end of the session. Coders were instructed not to encourage interaction with the children during the lunch sessions and to provide minimal answers to all questions asked by the children. To familiarize the children to the presence of a coder at the table, the staff member sat with each table of children during the 4 lunch sessions used to familiarize the children with the reference portion of the entrée before the study.
Behavioral observations of children’s bite size and frequency
The total number of bites of entrée taken was recorded by the behavioral coder at the remaining one-half of both the reference-portion and the large-portion lunch sessions. Interrater agreement was assessed for each table of children during random 5-min periods at each lunch. The agreement for observations of total bite frequency was 81% for observations made during the reference-portion lunches and 75% for observations made during the large-portion lunches. Bite frequency was calculated as the sum of all bites of entrée during the 15-min period. Average bite size for each child was calculated as the total grams of entrée consumed divided by the total number of bites of entrée taken.
Children’s self-served portion size of the main entrée
The sizes of the children’s self-served portions of the main entrée were measured at 2 lunches after both the reference-portion and the large-portion lunch series (see Table 1). Children were seen as a classroom, and the same seating assignments were used as were used during the reference-portion and large-portion lunch series. Two practice sessions were conducted before the beginning of the study to familiarize the children with the procedure and reduce novelty effects on self-selection behavior. At self-served lunch sessions, a preweighed serving bowl containing the large portion size (250 g for the younger children and 350 g for the older children) of the main entrée was placed adjacent to each child’s plate. Children were given 15 min to eat lunch and were instructed to serve themselves as much or as little as they desired. The children were given a 30-mL (0.125-cup) metal serving spoon with which to serve themselves. All of the other foods that were served were preweighed standard portions from the menu described below. The children’s self-served portion size was calculated as the difference in the weight of the serving bowl before and after the lunch. The children’s entrée intake and total lunch intake were also measured at these self-serve sessions.
Experimental menu
Macaroni and cheese (Kraft Inc, Glenview, IL) with an energy density of 15.5 kJ/g (3.7 kcal/g) was served as the main entrée throughout the study. Determination of the portion size for the reference-portion and large-portion entrées was based on the manipulations used by Rolls et al (8) in conjunction with data on macaroni and cheese consumption from the Continuing Survey of Food Intakes by Individuals, 1994–1996 (13). In the present study, the reference portion was 125 g for the younger children [< 4 y of age; n = 11; mean (± SD) age: 3.5 ± 1.1 y] and 175 g for the older children ( 4 y of age; n = 18; mean age: 4.3 ± 1.0 y). These portion sizes were within 25 g of the mean intake (159 g) of 2–5-y-old children in data from the Continuing Survey of Food Intakes by Individuals (13). The size of the large portions was double that of the reference portions (250 g for the younger children and 350 g for the older children); the size of the large portions was close to the 90th percentile of the data for 2–5-y-olds from the Continuing Survey of Food Intakes by Individuals and was in between the medium and large portion sizes used in the study by Rolls et al (8).
Other foods of the standard menu were milk (297 mL), applesauce (113 g), carrots (65 g), and sugar cookies (32 g). The total energy offered at the experimental lunch sessions was ample: 3341 kJ (798 kcal) and 5263 kJ (1257 kcal) for the younger and the older children, respectively, when the reference portions were served and 4111 kJ (982 kcal) and 6795 kJ (1623 kcal) for the younger and the older children, respectively, when the large portions were served. All foods were weighed before and after the lunch to calculate gram intakes. Manufacturers’ information was used to estimate energy density and calculate energy intakes.
Food preference and familiarity data were obtained for 29 of the 30 children. Among those 29 children, 27 reported that they had previously eaten the entrée, and 26 gave taste ratings for the entrée of either "yummy" or "just okay." Most of the children reported having previously eaten the other menu foods (carrots: 27 of 29; applesauce: 24 of 28; sugar cookies: 21 of 28) and rated the other menu foods as tasting either "yummy" or "just okay" (carrots: 22 of 28; applesauce: 25 of 28; sugar cookies: 27 of 29).
Other measures
Children’s eating in the absence of hunger
The free access protocol was used to obtain a behavioral measure of children’s overeating or eating in the absence of hunger. The children were interviewed individually immediately after one of the reference-portion lunches. A subjective measure of hunger was obtained from each child; children who indicated that they were "hungry" after lunch were not included in the analyses. Next, each child was given the opportunity to taste small samples of 10 sweet and savory snack foods that differed in fat and energy content and in sensory properties. The child was then provided various toys and a large tray containing generous portions of the same 10 snack foods: popcorn (15 g), potato chips (58 g), pretzels (39 g), nuts (44 g), fig bars (51 g), chocolate chip cookies (66 g), fruit-chew candy (66 g), chocolate bars (66 g), ice cream (168 g), and frozen yogurt (168 g). Next, the child was left alone for 10 min with the instruction that he or she could play with the toys or eat any of the foods while the experimenter did some work in the adjacent room. Eating in the absence of hunger was quantified as total energy intake during the 10-min period. This behavioral measure predicted weight status across a 2-y period in young girls and was shown to have intraindividual stability (12) and was positively associated with mothers’ own overeating (14) and with parents’ reports of restrictive child-feeding practices (10–12). Three children declined to participate in this procedure. Three additional children were not included in the analysis: one child cried during the 10-min period, one indicated feeling hungry before the session, and one did not follow the instructions given by the experimenter.
Children’s weight status
Height and weight measurements were obtained by a trained staff member following procedures described by Lohman et al (15). Height was measured in triplicate to the nearest 0.1 cm. Weight was measured in triplicate to the nearest 0.1 kg. Growth charts from the Centers for Disease Control and Prevention were used to calculate age- and sex-specific BMI z scores for each child (16). Of the 30 children whose data were used in the analysis, 28 consented to provide height and weight data.
Statistical analyses
Statistical analyses were performed by using SAS version 8.0 (SAS Institute Inc, Cary, NC). In cases in which the child was absent or ill, the child’s mean intake value for that portion size (ie, reference or large) was assigned for the missing value; in all but one case, the children missed 1 of the 4 lunches for either portion size. Data from the 4 lunches before the study (in which the reference portion was served) were used to replace missing data for one child who missed every lunch in the reference-portion series. Descriptive statistics were generated for all variables of interest; measures of central tendency are reported as means ± SEMs. Repeated-measures analysis of variance was used to evaluate time-related trends for entrée and total energy intakes within each portion-size series. Paired t tests were used to assess changes from the reference-portion lunches to the large-portion lunches in the following dependent variables: entrée intake, total energy intake at lunch, bite size and frequency, comments about portion size, and self-served portion size. Each child served as his or her own control: behavior at the large-portion lunches was expressed relative to the behavior at the reference-portion lunches. Analysis of covariance was performed to evaluate portion assignment order, sex, and age as potential covariates of changes in the dependent variables. As in the study by Rolls et al (8), age was expressed as a categorical variable (younger = 3–4 y; older = 4–5 y); analyses including age as a continuous variable are presented only when the results differed from those in which age was included as a categorical variable. Correlations were used to determine the extent to which each dependent variable measuring the children’s response to repeated exposure to large portions was associated with weight and eating in the absence of hunger.
RESULTS
Entrée and lunch intakes at reference-portion and large-portion lunches
For both the reference-portion and the large-portion lunches, there were no significant time-related trends across the 4 lunch sessions in either entrée intake [P = 0.11 (n = 30) and P = 0.21 (n = 30), respectively] or lunch intake [P = 0.12 (n = 30) and P = 0.24 (n = 30), respectively]. Because there were no significant time-related trends, entrée and lunch intakes were averaged across each of the 4 lunch sessions (Figure 1). Doubling the portion size of the entrée (ie, comparing the reference portion with the large portion) increased the children’s entrée and total energy intakes by 25 ± 7% (P 0.001; n = 29) and 15 ± 5% (P 0.01; n = 29), respectively.
FIGURE 1. . Mean (± SEM) entrée () and total energy () intakes of the preschool-aged children (n = 29) during the reference-portion and the large-portion lunches. **Significantly higher than reference, P < 0.01.
Increases in entrée intake were not significantly related to sex (P = 0.80; n = 29), age (P = 0.20; n = 29), or the order in which the 2 portion sizes were served (P = 0.92; n = 29). Increases in total energy intake at lunch were not significantly related to sex (P = 0.78; n = 29), age expressed as a categorical variable (P = 0.10; n = 29), or the order in which the 2 portion sizes were served (P = 0.24; n = 29) but were positively associated with age expressed as a continuous variable (R2 = 0.17, P < 0.05).
Mean lunch intakes at the reference-portion and large-portion lunches (2275 ± 109.0 and 2603 ± 155 kJ, respectively) represented 34% and 38%, respectively, of average daily energy allowances based on age and weight (17). Neither the size of the reference entrée nor the total energy offered at the reference-portion lunches limited the children’s intake during the reference-portion lunches: on average, only 67 ± 4% of the reference-portion entrée and 52 ± 3% of the total energy offered at lunch were consumed during the reference-portion lunches, and only 2 of the 29 children, both of whom were in the older age group, consumed an average of > 95% of the entrée during the reference-portion lunches. On average, the children consumed 48 ± 4% of the nonentrée foods offered; there were no significant differences in the children’s intake of nonentrée foods between the reference-portion and the large-portion lunches (697 ± 62 and 681 ± 60 kJ, respectively; P = 0.91; n = 28).
Bite size and frequency at reference-portion and large-portion lunches
There were no significant differences between the reference-portion and the large-portion lunches in the total number of bites taken (18 ± 1 compared with 17 ± 1 bites, respectively; P = 0.73; n = 26). Changes in bite frequency from the reference-portion lunches did not vary as a function of sex (P = 0.27; n = 26), age (P = 0.11; n = 26), or the order in which the 2 portion sizes were served (P = 0.45; n = 26).
In contrast, the average bite size was 0.5 g (12 ± 5%) higher during the large-portion lunches than during the reference-portion lunches (7.1 ± 0.4 compared with 6.6 ± 0.4 g/bite; P < 0.05; n = 29). Changes in bite size from the reference-portion lunches did not vary as a function of sex (P = 0.43; n = 29) or age (P = 0.11; n = 29). The children who consumed the reference-portion lunches before consuming the large-portion lunches had significantly greater increases in average bite size than did those who consumed the lunches in the opposite order (P < 0.05; n = 29).
Comments about portion size at reference-portion and large-portion lunches
The children’s comments about portion size were measured to determine the extent to which any changes in intake might reflect changes in awareness of portion size. Few comments were made regarding portion size throughout the experiment. During 2 reference-portion lunches and 2 large-portion lunches at which behavioral observations were made, none of the children described the portion sizes as "small" or "okay." The reference portion size was described as being "big" by 1 child during a reference-portion lunch, and the large portion size was described as being "big" by 6 children during the large-portion lunches.
Children’s self-served portion sizes
Self-selected portion sizes were measured after both the reference-portion and the large-portion series of lunches to determine the extent to which increases in intake related to portion size were accompanied by changes in the children’s own self-selected portion sizes. The children’s average self-served portion size of the entrée at 2 lunches after the large-portion series of lunches was not significantly different (P = 0.37; n = 29) from their average self-served portion size of the entrée at 2 lunches after the reference-portion series of lunches (146 ± 14 and 151 ± 14 g, respectively). Age (P = 0.48; n = 29), sex (P = 0.54; n = 29), and the order in which the 2 portion sizes were served (P = 0.49; n = 29) did not predict changes in the children’s self-served portion sizes. Similarly, there were no significant differences (P = 0.3; n = 29) in entrée intake between the 2 lunches after the reference-portion series of lunches (100 ± 9 g) and those after the large-portion series of lunches (102 ± 9 g). In addition, changes in entrée intake at the self-serve lunches did not vary by sex (F = 0.8, df = 28, P = 0.37), age (F = 2.2, df = 28, P = 0.15), or the order in which the 2 portion sizes were served (P = 0.10; n = 29).
As shown in Figure 2, the children’s average self-served portion size did not differ significantly from the size of the reference portion: the younger children served themselves 115 ± 12 g and were served a 125-g reference portion, and the older children served themselves 165 ± 18 g and were served a 175-g reference portion. The children’s average entrée intake at the self-selection lunches was compared with that at the reference-portion and the large-portion lunches. Although the container from which the children served themselves contained exactly the same amount of the entrée as was served to them on a plate at the large-portion lunches, the children consumed 24 ± 8% more (P 0.01; n = 28) when served the large portion than when serving themselves. In contrast, the children’s entrée intake at the self-selection lunches did not differ significantly from that at the reference-portion lunches (P < 0.60; n = 29). After age and weight were controlled for, the children’s self-served portions of the entrée were highly related to their intake, explaining 58% of the variance in entrée consumption (standardized ß = 0.76, P < 0.0001).
FIGURE 2. . Mean (± SEM) entrée portion sizes that were served to () or selected by () the preschool-aged children (n = 28) and consumed by () them at lunches in which the children either selected their own portion size or were served a reference portion or a large portion. **Significantly higher than self-selected, P < 0.01.
Associations of children’s responses to portion size with weight and eating in the absence of hunger
Changes in the children’s entrée intake with exposure to the large portion ranged from a 44% decrease to a 109% increase in intake; the upper quartile of the sample had increases of 45%. Increases in the children’s entrée intake, total energy intake at lunch, bite size, and self-served portion size with exposure to large portions were not correlated with the children’s BMI-for-age z scores (Table 2). Mean bite size, however, was positively related to BMI-for-age z score: the heavier children tended to take larger bites. On average, the children consumed 270 ± 49 kJ (n = 23) in the absence of hunger during a 10-min period in which they were provided with large portions of palatable, energy-dense foods. As shown in Table 2, the children who had higher intakes in the absence of hunger had greater increases in entrée intake and showed a trend toward greater increases in total energy intake at lunch with exposure to the large portion size.
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TABLE 2 . Correlations of the children’s responses to portion size with eating in the absence of hunger and weight status1
DISCUSSION
Although evidence exists that young children have the ability to regulate energy intake within meals (9, 18, 19) and over the course of the day (20, 21), children’s ability to self-regulate energy intake is continually subject to modification by factors within the environment in which eating occurs (22). The findings of this research indicate that large portions may constitute an obesigenic influence on young children’s eating by promoting intake at meals. In the present study, doubling the size of the entrée increased entrée and total energy intakes at lunch 25% and 15%, respectively. The finding that the children’s intake was not limited by the total energy provided at the reference-portion lunches indicates that the children’s intake at the large-portion lunches was in excess of normal consumption.
An effect of large portions on intake at meals is consistent with the results observed among older preschool-aged children in the study by Rolls et al (8), as well as with the results of a few studies in adults (23–25). In particular, doubling the portion size of a dinner entrée increased entrée intake among adults by 30% (26). The results of the present study extend the results of previous research with preschool-aged children (8) by showing that increases in children’s intakes are both immediate and consistent over time with repeated exposure to large portions. Furthermore, the findings of the present study indicate that elevations in intake are attributable to increases in the average size of children’s bites of an entrée without compensatory decreases in the intake of other foods at the meal. Additional studies are needed to determine the extent to which portion size–related increases in young children’s intake at individual meals are sustained across subsequent meals and have the potential to promote positive energy balance.
In the present study, few children made comments about portion size, and the children’s self-selected portions of the entrée did not change with repeated exposure to large portions. It is possible that changes in portion size may have been visually difficult to discern because of the use of an amorphous entrée (27). In any case, these findings indicate that increases in children’s entrée bite size and intake occurred without appreciable awareness of changes in portion size. A recent survey by the American Institute for Cancer Research (28) found that less than one-third of 1003 adults surveyed believe that portion sizes at restaurants have increased over the past 30 y. Furthermore, adults tend to view the portion size they typically consume as being a "medium" portion, regardless of its actual size (29). The visual-cognitive mechanisms through which large portions stimulate intake have not been identified. It is possible that naive visual cues regarding the amount of food on the plate provide a subtle anchor for determining how much food is brought to the mouth at any time. This perspective is consistent with the results of a study in adults that showed that the selected portion size of various foods increased with the size of the box in which those foods were contained (30).
Although unchanged by exposure to large portions in the present study, the children’s own self-selected portions were closely tied to their entrée intake and were consistently smaller than those served to them at the large-portion lunches. Furthermore, the children consumed 25% more of the entrée when the large portion was presented on their plates than they did when the large portion was presented in a serving bowl from which they could self-select their own portion. These findings indicate that self-served portions may play an important role in circumventing children’s exposure to excessive portion sizes and the consequent effects on intake. Morris et al (26) found no effects of serving method on the amount of a dinner entrée consumed by adults. How young children establish typical or customary self-served portion sizes is unknown. In a recent survey of adults, 40% failed to report that hunger was an important factor in determining their portion size, and between one-quarter and one-third of those surveyed reported that habitual portions and the amount served to them were influential factors (28). Research is needed to understand the factors that shape children’s habitual portions, such as whether food is typically served by the parent or the child.
The findings of the present study provide evidence that the intake-enhancing effects of exposure to large portions are apparent by 3 y of age. In contrast with the results of the study by Rolls et al (8), portion size effects on entrée intake were observed for both the younger and the older preschool-aged children in the present study. Consistent with the results of previous research, however, the older children showed larger increases in total energy intake at lunch than did the younger children, suggesting that the effects on total energy intake at meals are more pronounced as children transition through the preschool period. Furthermore, because several of the age effects were of borderline significance, it is possible that other age effects were present but not detected. Although the sample sizes were similar across studies, the portion size manipulation used in the present study was smaller than that used by Rolls et al (8). Equally plausible and perhaps more important is the possibility that the magnitude of developmental differences in children’s responsiveness to portion size may become more pronounced with increasing age and exposure to environmental influence. Because the average age of the younger and the older preschool children in the present study differed by < 1 y, additional research is needed to evaluate developmental differences in children’s responses to large portions.
The results of the present study provide preliminary evidence that individual differences in children’s susceptibility to large portions may reflect a general insensitivity to fullness cues. In this study, greater increases in entrée intake and a nonsignificant trend for greater increases in total energy intake at lunch occurred among the children who had greater intakes in the absence of hunger. This finding indicates that children who exhibit weak satiety responses by eating in the absence of hunger may also have insufficient satiation cues or the behavioral inclination to ignore those cues when exposed to large portions. The implications of these individual differences for overweight among children, however, are unclear; responsiveness to large portions was not associated with children’s weight status. Observational studies, however, showed that girls who eat greater amounts when exposed to large portions of energy-dense foods in the absence of hunger tend to be heavier (10–12). Similarly, overweight adults ate more when presented with 3 sandwiches than when presented with 1, whereas normal-weight adults ate the same amount in both cases (31). Larger samples are needed to confirm these results and to adequately evaluate the extent to which individual differences in susceptibility to portion size confer an increased risk of overweight.
In conclusion, the present study shows that repeated exposure to a large portion size results in consistent increases in preschool-aged children’s bite size and entrée intake at a meal. These changes occurred without observable awareness of increasing portion size or compensatory decreases in the intake of other foods at the meal. The observation that the children who ate more when served large portions also tended to have greater intakes in the absence of hunger suggests that children who show poor satiety responses may also have a greater behavioral susceptibility to this environmental cue than do other children. Finally, these data provide initial evidence that allowing children to self-select portion sizes can affect the amount consumed and may play an important role in reducing the effects of exposure to large portion sizes on children’s intake. Previous studies showed that restrictive child-feeding strategies are associated with overeating and overweight in young children (10–12). At the other end of the continuum, however, the risk of overweight has been associated with neglectful family environments during childhood (32) and with a lack of maternal knowledge of their children’s consumption of sweets (33). Whether offering children large portion sizes is indicative of a broader and more problematic approach to child feeding is unknown and is beyond the scope of the current investigation. At a minimum, however, these results suggest that portion size has effects on children’s energy intake that could promote childhood overweight; parental monitoring is important to avoid routine exposure to large portions that far exceed children’s energy needs. Suggested intervention strategies include providing parents with information on appropriate serving sizes for children and with guidance regarding feeding practices that support adequate self-regulation of intake by children, including teaching children to choose appropriate portions in the context of excessive serving sizes.
ACKNOWLEDGMENTS
We thank Issa Zakeri and Su Jau for their assistance in conducting statistical analyses; Tanja Cutting, Kirsten Davison, Lori Francis, Amy Galloway, Theresa Jenkins, and Shelly Mannino for their assistance in data collection; and the teachers and families at the Pennsylvania State University Child Development Laboratory for their participation in and support of this research.
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