Development of Eating Behaviors Among Children and Adolescents

Food Preferences: Predispositions to Prefer Energy-dense Foods

Although repeated exposure can enhance liking for a wide variety of new foods, other learning mechanisms favor development of preferences for energy-dense foods. There is no evidence that children have an innate, unlearned preference for high-fat or high-energy foods (see Birch³⁰ for a discussion of this point). Children are predisposed to learn to prefer energy-dense foods over energy-dilute foods by learning to associate the flavors of these foods with the positive physiologic consequences that result from eating energy-dense foods, especially when they are hungry. Although limited, the findings from research with young children^50-53 are consistent with extensive data in the literature on conditioned preferences for energy-dense foods in animals.⁵⁴

In particular, repeated experience with foods high in energy can enhance children's preferences for those foods via associative conditioning. In this form of learning, flavors in foods become associated with satiation cues involved in digestion and absorption of high-energy foods.^52-54 These learned associations can produce flavor preferences that may mediate the relationship between children's exposure to and liking of high-energy foods. In addition, the physiologic consequences of consuming high-energy high-density foods may enhance the effects of repeated exposure on liking. The physiologic conditioning of flavor preferences for foods high in energy density may have the greatest effect on children's liking of energy-dense foods among families in which those foods are most available and accessible. To date, there has been no research exploring whether children's ability to learn preferences for foods high in fat might differ for children in obese and normal-weight families. Genetic differences could shape phenotypic differences in how readily children learn preferences for high-fat foods. Among adults, there are differences between obese and normal-weight individuals in their preferences for fat and for mixtures of sugar and fat,^55,56and this suggests a mechanism that could be involved in the etiology of these differences.

The Social Context of Eating: Effects on Children's Preferences

For children, eating typically is a social occasion, and other eaters, including parents, other adults, peers, and siblings, as well as children's observations of others' eating behavior, influence the development of their own preferences and eating behaviors. The social context in which children's eating patterns develop becomes important because the eating behavior of people in that environment serves as a model for the developing child. Models can have powerful effects on food selection, especially when the model is similar to the observer^57,58 or is seen as particularly powerful,⁵⁹ as in the case of older peers. Findings suggest that day care could provide opportunities for expanding the availability and accessibility of foods and for fostering preferences for foods by modeling effects. Birch⁵⁷ found that when preschool children were given opportunities during meals to observe other children choosing and eating vegetables that the observing child did not like, preferences for and intake of the disliked vegetables were increased.

Modeling appears to play an important role in establishing preferences for inherently unpalatable substances. Rozin and Schiller⁶⁰demonstrated the powerful role of social influences in the development of preferences for chili peppers, a flavor that is aversive to animals and to many humans. Rozin and Kennel⁶¹ reported that although a variety of established learning protocols failed to facilitate preference for chili peppers among nonhuman primates, increased preference for chili-flavored crackers resulted after the monkeys observed their keepers eating the crackers. Rozin and colleagues⁶⁰ reported a similar phenomenon among humans in Mexican families, in which the older members modeled eating chili-flavored foods for young children, which facilitated children's acceptance of hot foods.

Children's food preferences may be shaped by observing food selection patterns and eating behavior of their parents. For instance, Harper and Sanders⁶² observed that toddlers put foods in their mouths more readily when they were following the example of their mothers relative to the same modeling behavior by a stranger. Especially in families in which obesity, dieting, and weight control are salient issues, children's eating may be influenced by parents' eating, dietary restraint, and disinhibition.⁶³ Models also may play a role in the emergence of dieting behaviors in childhood and adolescence. Pike and Rodin⁶⁴ reported that dieting daughters are likely to have dieting mothers and that parents who report dietary disinhibition and problems in controlling their own eating are likely to have daughters who show similar patterns,⁶⁵ which suggests a role for modeling in these familial patterns.

Effects of Television on Children's Food Preferences and Food Selection

Television is a pervasive purveyor of culture, providing children with a wide array of models and messages about eating that can influence children's food preferences and food selection as well as their activity patterns. However, despite the central role of television as a purveyor of American culture, surprisingly few studies have investigated the effect of television on children's food preferences, intake, and adiposity. Although there do not appear to be dramatic changes in watching television by children during the period of increased prevalence of childhood obesity, the largest share of advertisements during children's programming is for food products.⁶⁶ In 1987, in a content analysis of food advertisements that were on television during a 12-hour period, Cotugna⁶⁷ observed that 80% of advertisements showed foods with low nutritional value, including breakfast cereals high in simple sugars and snack foods high in sugar, fat, and salt. A number of investigations have revealed that children's requests for foods were related to the frequency with which children saw the foods advertised on television.^68,69 Goldberg et al⁷⁰ observed that children who were exposed to advertisements selected more sugared foods than children who had not viewed any advertisements. Thus, repeated exposure to food advertisements for particular types of foods may foster children's preferences for energy-dense, nutrient-poor foods. We know even less about how the depiction of eating, dieting, and exercise patterns may influence children's food intake and activity patterns.

Child-feeding Practices, Children's Food Preferences, and Food Selection

Parents shape their children's eating environments in a variety of ways: through the choice of an infant feeding method, by the foods they make available and accessible, by direct modeling influences, by the extent of media exposure in the home, and by way they interact with children in the eating context. Parents believe that their feeding practices can exert a major influence on children's food preferences and on developing control of children's food intake,⁷¹ although recent research indicates that the influence is not necessarily in the ways that parents intend.⁷² The pervasive messages directed at ways that nutrition can improve health and appearance have created an increasingly complex eating environment in which parents attempt to foster healthy eating behaviors in their children. For example, the messages of the dietary guidelines convey the importance of consuming certain types of foods and limiting the consumption of others.²³ The means by which parents attempt to shape children's eating toward nutritionally desirable dietary outcomes can have unintended consequences for children's eating behavior. Parents' practices may be especially controlling and may have particularly negative effects on children when there is heightened concern that the child may be at risk for obesity.⁷³

Although current guidelines attempt to convey the importance of variety and moderation, these nutritional guidelines are cognitively complex. Rozin et al,⁷⁴ in a study of adults' understanding of nutritional concepts, concluded that even well-educated adults engaged in categorical thinking, ie, grouping foods as either “good” or “bad,” and a monotonic mind belief that something that is harmful in large quantities (such as dietary fat) is also harmful at low levels. Nutritional messages interpreted with such categorical thinking may result in parental attempts to restrict children's intake of “bad” foods and encourage the intake of “good” foods.

Parental Control to Encourage or Limit Children's Eating

Child-feeding practices that control what and how much children eat also can affect their food preferences. Child-feeding strategies that encourage children to consume a particular food increase children's dislike for that food.^75-77 Many of the foods that parents encourage children to consume are the fruits and vegetables they would like to see consumed with greater frequency and in greater quantities. Hertzler⁷⁸ noted that parents' feedback to children about eating vegetables was associated with children's preferences for fewer vegetables.

In carrying out what one clinician described as “good food intentions,” parents frequently may limit their children's consumption of “bad” but palatable foods by withholding these foods as punishment.^79,80 In a recent study assessing parental opinions on the efficacy of using various practices to modify their children's food preferences, 40% of parents spontaneously reported the belief that restricting or forbidding the consumption of a particular food would decrease their child's preference for that food,⁸¹ a prediction opposite research findings. Contrary to these parental beliefs, restricting children's access to foods does not produce food dislikes for the restricted food; instead, such practices enhance liking and can increase intake. Birch et al⁸² found that children's preferences for foods increased after the foods were used as rewards for performing a nonfood-related task; limiting the availability of the reward food promoted children's liking of those foods. Again, these restricted foods are typically “bad” foods, those palatable foods that are high in sugar, fat, and energy and that we would like to see consumed in smaller amounts and on fewer occasions. Restricting children's access to foods actually may promote their overconsumption of those foods. Fisher and Birch⁶ found that maternal restriction of children's access to snack foods was related to girls' (but not to boys') consumption of those same foods in an unrestricted setting.

Creating dietary habits that include moderation and limited consumption of dietary fat and sugar constitutes a desirable objective of child-feeding. However, the limited evidence on the effects of these practices on children's preferences suggests that restricting children's consumption of “bad” foods and encouraging consumption of “good” foods does not provide a means of achieving these dietary goals. From a developmental perspective, this type of feeding practice may send mixed messages to children, because these same forbidden foods are offered in positive social contexts such as parties, dinners out, and holiday celebrations, and are restricted in others. Finally, restricting access to some foods and encouraging consumption of others may well foster children's categorical thinking about “good” and “bad” foods. In a study that involved focus groups of kindergarten children, Murphy et al⁸³ concluded that children tended to indicate preference for fatty and sugary foods but that they also identified those foods as being high in fat and “not good for you.” However, just to show that the implications for intervention are not simple, the work by Smith and Epstein⁸⁴ confirmed that limiting the availability of a preferred food also may enhance children's desire to obtain a less preferred food when both types are present.

Parental Control and Children's Self-regulation of Food Intake

In addition to influencing which foods children prefer and select, controlling child-feeding practices may affect children's ability to regulate energy intake and the amount of food consumed. As indicated above, a very early decision parents make is choosing whether to formula-feed or breastfeed their infant. In the United States, formula-fed infants show more rapid growth than breastfed infants, and these differences are of sufficient magnitude that some experts have suggested that different growth norms should be used for breastfed and bottle-fed infants. Fomon⁸⁵ speculates that the differences in infant growth may be attributable to differences in intake, with the greater intakes by formula-fed infants resulting from overfeeding as a result of heightened maternal control over the infant's intake. In the case of the formula-fed infant, the mother can see how much formula remains in the bottle and she may be inclined to take control of how much the infant eats, encouraging the infant to finish the bottle. In contrast, the breastfed infant may have more control over the size of the feed because this feedback is not available to the mother.

Clearly, maternal feeding practices can influence infant intake. In a series of experiments to investigate whether the energy density of formula influenced infants' intake, Fomon and colleagues varied the energy density of formulas infants were consuming and demonstrated that in the absence of maternal control, infants 6 weeks old adjusted their volume of formula intake, consuming more of energy-dilute than of concentrated formulas, so that total energy intake did not differ across the conditions.⁸⁵ Fomon's research suggests that when given the opportunity, infants are capable of being responsive to the energy density of formula and adjusting intake accordingly; however, maternal control can override the infant's regulatory ability. There is some evidence for a parallel relationship between parental control and children's ability to regulate intake during early childhood. Although many children continue to be sensitive to internal signals arising from the energy density of the diet in controlling their food intake, child-feeding practices that encourage or restrict children's consumption of foods may decrease the extent to which children use internal signals of hunger and satiety as a basis for adjusting energy intake. To investigate children's responsiveness to energy density, we have conducted research examining children's intake within individual meals by using two-course preloading protocols as well as by examining children's intake across meals by using 24-hour self-selected energy intakes.

To determine whether they could adjust intake in response to the energy density of foods within meals, we had children consume a fixed amount of a first course that varied in energy density, by manipulating fat or carbohydrate content, and looked at effects on children's self-selected food intake in a second course. We predicted that if children were responsive to the energy density of the first course, they would eat less in the self-selected second course after the high-energy than after the low-energy first course. Across a series of experiments, findings confirmed this prediction,^50-53,86,87 providing evidence that children can regulate their intake based on feedback arising from the energy content of foods just consumed. Subsequent research extended our findings to reveal that children's responsiveness to energy density can affect their food intake not only within a meal but also across a series of meals, influencing their 24-hour energy intake. Children showed adjustments in energy intake across successive meals in a manner similar to the adjustments in energy intake observed within meals. These adjustments resulted in relatively consistent coefficients of variation for 24-hour energy intake, which averaged ∼10%, compared with the much higher coefficients of variation of ∼40% for energy intake at individual meals.^88,89 Children also adjusted their intake to compensate for reduced energy density of meals produced when we substituted olestra for dietary fat, indicating that at least when energy density is reduced, children are responsive to and adjust intake for the energy dilution. Whether children's ability to adjust their food intake in response to energy density is impaired when diets are very high in fat remains an unanswered question.

With respect to whether child-feeding practices can alter children's responsiveness to energy density, our initial findings revealed that children's responsiveness to energy density was diminished when adults used control strategies that focused children on external cues to encourage consumption. We explored children's ability to adjust food intake in response to differences in energy density in two different child-feeding contexts. In one condition, child-feeding practices focused on internal cues of hunger and satiety as controls of food intake. In this condition, children showed clear evidence of adjusting their intake in response to the energy-density differences in the first course. In the other condition, child-feeding practices included rewarding children for cleaning their plates and a focus on external cues to control eating, such as the amount of food remaining on the plate. In the latter condition, all evidence of responsiveness to the energy content of the foods disappeared, and children's intake was significantly increased by rewarding them for eating.⁸⁶These findings suggested a powerful role for child-feeding practices in shaping how much children eat and the extent to which children are responsive to the energy density of the diet in controlling their food intake. Other evidence on this issue comes from observations of family meal times by Klesges et al.⁹⁰ They found that parental prompts to eat were positively associated with time spent eating and degree of overweight in children. Interestingly, in an examination of the sequencing of parental prompts to eat, Klesges and colleagues⁹¹ observed that prompts to eat were preceded by food refusals by the child and followed by the child eating. These findings suggest that parental prompts to eat may act to oppose children's own attempts to control the amount consumed and promote consumption within a meal.

Factors Influencing Child-feeding Practices: Gender, Adiposity, and Eating Style

Although the potential of nutritional messages to promote restrictive child-feeding practices exists on a societal level, eating-related issues within families also determine parental use of controlling feeding practices. In discussing children's obesity proneness, Costanzo and Woody⁷³ assert that parents impose behavioral control in domains of their children's development when 1) the parents have problems regulating their own behavior, 2) the child is perceived to be at risk for developing problematic behavior, and 3) the child demonstrates a lack of self-regulatory behavior. These authors use obesity proneness as an example and contend that the use of controlling parenting styles impedes children's ability to develop self-regulatory behavior, thereby promoting the problems they attempt to avoid.

Subsequent research by Johnson and Birch⁷² confirmed the links among child-feeding practices and children's responsiveness to energy density. Children's compensation for energy density in our standard two-course-meal protocol was used as a measure of individual differences in regulation of energy intake. Parents who reported using a high degree of control over what and how much their children ate had children who showed relatively little evidence of energy regulation; a high degree of parental control was associated with low self-control in children. For girls, energy regulation was related to their adiposity, with thinner girls regulating energy intake more precisely than heavier ones. In addition, for girls, but not for boys, parental control was linked to the girls' adiposity, with parents using more control with heavier girls. Parental control also was linked to the parents' dieting and weight history. Mothers who were more restrained used more control and had daughters (but not so for mothers with sons) who showed little evidence of energy regulation. These early gender differences may be precursors of later gender differences in problems of energy balance, in which the prevalence of eating problems is much higher among women. These findings are limited to middle-class white families; we have no data on whether such relationships exist among other racial, ethnic, or socioeconomic groups. One area for future research is to determine whether racial and socioeconomic differences in the prevalence of obesity in children (reported by Troiano and Flegal)¹ may be mediated in part by racial and socioeconomic differences in parenting practices.

Fisher and Birch⁶⁵ found that young children's weight for height predicted the degree to which mothers reported restricting their child's intake of snack foods. For girls, the parents' dieting and restrictive eating predicted the level of maternal restriction. The cross-sectional nature of the data cannot address the causal direction of the relationships observed, but the results suggest that controlling child-feeding practices adversely affects children's ability to self-regulate food intake and hence their adiposity, although it is possible that parents of heavier children are more controlling. We are obtaining longitudinal data on this question.

The child's eating style also may elicit parental concern and control and influence the extent to which the parent sees the child as at risk for obesity and eating problems. Stunkard and Kaplan⁹²reported that the obese ate at a faster rate than normal individuals. Comparisons of obese and normal children have yielded similar results. Drabman et al⁹³ reported that obese preschoolers ate at a faster rate, taking more bites, and chewing each bite fewer times. Marston and colleagues⁹⁴ reported similar patterns of results for school children. Recently, Barkeling et al⁹⁵compared eating behaviors of obese and normal-weight 11-year-olds. Obese children ate faster and failed to show the normal pattern of slowing down the rate of eating toward the end of the meal; the authors suggest that this pattern could reflect an impaired satiety signal or an impaired response to such signals. Evidence for links between eating style and adiposity appears even during infancy. Agras et al³⁹ found that infants with more rapid suckling during feedings at 2 and 4 weeks had greater intakes and that this sucking pattern was associated with greater skinfolds and BMI at 1 and 2 years of age. Stunkard and colleagues' recent research (unpublished observations) on genetic and environmental factors predicting infant weight gain also has shown sucking rate to be a predictor of later weight. One potentially productive area of research would investigate the extent to which children's different eating behaviors elicit different child-feeding practices.

In summary, controlling child-feeding practices can have negative and unintended effects on children's food preferences and the developing controls of food intake. It is likely that such practices foster rather than prevent the development of childhood obesity and eating problems, although additional research is needed to confirm this point. Satter^96,97 has discussed an alternative to such controlling child-feeding practices based on her extensive clinical work. She suggests a division of responsibility between parent and child; it is the parents' responsibility to supply the child with a healthful array of foods and a supportive eating context, and it is the child's responsibility to decide when and how much to eat.

Emergence of Dieting to Control Weight

By middle childhood, even before the fat deposition that occurs in girls at puberty, gender differences in weight concerns and dieting prevalence apparent in adulthood already are emerging.⁹⁸ Societal values equating physical attractiveness and thinness with femininity foster the pervasive trend of dieting among most young women, many of whom do not need to lose weight. By the age of 7, children identify overweight silhouette drawings as being less attractive, having fewer friends, and being less smart than their thin counterparts. Even before puberty, girls report a heightened sense of body dissatisfaction and a desire to be thinner, with dieting behaviors reported among children as young as 9 years of age.⁹⁹ Serdula et al¹⁰⁰ reported that 44% of high school girls were dieting. Although the nature of dieting behaviors in young girls is not well characterized, the potential adverse consequences of dieting on physical growth and well-being must be addressed.

Early dieting itself may constitute a risk behavior for the development of obesity. Dietary restriction involving cognitive restriction of food intake involves explicit denial of hunger cues and includes stopping eating while still hungry and skipping meals. Dietary restriction has been associated with overeating in adolescents¹⁰¹ and adults.¹⁰² Westenhoefer and colleagues¹⁰² have suggested that restrained eating may give rise to eating binges through the weakening of satiety cues and the heightened attractiveness of food in restrained eaters. Dieting may be iatrogenic, producing the very outcome it is used to avoid. Dieting, with its self-imposed restriction, has certain parallels to controlling child-feeding practices restricting children's intake. Dietary restraint, or the intent to restrict food intake cognitively, has been associated with a number of adverse psychosocial outcomes. In a study of adolescent girls, Killen¹⁰³ found that restrained eaters exhibited high levels of worthlessness, body dissatisfaction, fear of weight gain, and disaffect, and they were heavier and were more physically developed than unrestrained girls. Similarly, Rosen et al¹⁰⁴ found that adolescents' restraint scores were positively associated with depression, body dissatisfaction, social anxiety, and weight status. This all suggests that attempts designed to reduce the prevalence of childhood obesity must consider the potential costs of approaches that may increase the prevalence of early dietary restriction.