TO THE EDITOR:
In our article “The Trust Model: A Different Feeding Paradigm for Managing Childhood Obesity,” we presented Ellyn Satter's trust model and offered an independent perspective on whether the model is feasible as an alternative to prevent or treat childhood obesity (1). We reviewed multiple factors that need to be considered if the trust model should be accepted as an alternative approach including maternal child feeding relationship, recognition of hunger and satiety cues among normal and overweight individuals, self regulation of food intake, portion size, parenting styles, and developmental stages. The trust model, which emphasizes a collaborative feeding dynamic between caregivers and children, is particularly salient at this time given (i) the high prevalence rates of obesity especially in very young children, (ii) the efficacy of current interventions for addressing childhood obesity (especially for long-term management) remain inconclusive, and (iii) some of the trust model's core components (e.g., avoiding restrictive feeding styles, eating meals together) are included within the expert committee obesity treatment guidelines (2). We concluded that the trust model is worthy of qualitative and quantitative research for preventing or treating childhood obesity. This recommendation was based on the lack of empirical research, outside of a few supportive correlational studies, investigating the trust model's tenets (1).
The trust model (Figure 1) emphasizes the division of feeding responsibility between caregivers and children and trust in children's ability to self-regulate food intake by eating in response to their hunger, appetite, and satiety cues within the context of regular eating patterns (i.e., structured meals and snacks) (1). The model de-emphasizes portion sizes, the food pyramid, calorie or carbohydrate counting, eliminating certain foods, or over-reliance on low-fat or low-calorie food options. Specifically, caregivers are responsible for selecting foods to present at meals and snacks, the timing for meals and snacks, choosing the place to eat, sitting and eating with children, and keeping the atmosphere pleasant. Children are responsible for what to eat and how much (or even whether) to eat from the food provided. Caregivers are also taught to plan and serve a balanced meal with protein, carbohydrates, fruits and/or vegetables, dairy/calcium, and fat. Food selection is emphasized within the scope of creating a variety of meals and snacks within the context of the family's abilities and preferences.
The premise of Kirschenbaum and Kelly's recommendation to “mistrust the trust model” was based on an inaccurate misinterpretation of the trust model (see their Table 1) (3). They stated that the core beliefs of the model include the premise that eating control is more important than activity control, that over-control or under-control of feeding is the primary cause of obesity among children, that overweight children do not have to deliberately restrict fat or calorie intake in order to lose weight and maintain weight loss, that weight control in professionally conducted treatment plans will backfire, and that obese children must learn to respond to internal cues in order to lose weight.
The trust model focuses primarily on building normal child feeding and growth patterns and not on overweight or obese children. Satter believes over-control and under-support of the feeding environment are at the core of nonorganic child weight and growth problems, not the “primary cause” of childhood obesity as stated by Kirschenbaum and Kelly (3). Nonorganic growth problems can appear in either underweight or overweight children. In fact, the trust model specifically addresses the picky eater, a subset of children that tend to be underweight or normal weight. In the trust model, there is an expectation placed on caregivers to provide a balanced meal, and they are taught about food choices and preparing a nutritious meal. Caregivers are not taught to restrict or count a specific amount of calories or fat grams. This mode of intervention has been used in a number of childhood obesity programs and studies that target lifestyle modification (4,5). Whether the caregiver can effectively assume these roles given the prevailing obesigenic environment or in response to their child's weight deserves further investigation.
Kirschenbaum and Kelly's interpretation of the model did not acknowledge that the trust model is implemented within an environmental context (3). Children's natural growth patterns, food choices and availability, the medical and psychosocial characteristics of the caregiver and the child, and physical activity are all part of the context for the trust model (Figure 1). We noted that the extant data show an inconsistent association in several of these contexts, e.g., between caregiver feeding behaviors and children's weight across age, gender, socioeconomic status, maternal characteristics (e.g., obesity), or within families. Thus we posited that these variables, in addition to ethnicity, culture, parental dieting history, parenting styles and eating behaviors need to further be examined in a testable model (1).
The relationship between internal regulation of hunger and satiety signals is an intriguing one, given that it is still poorly understood (1). In our perspective, we suggest that it is conceivable that the trust model's lack of dietary fat restriction may explain why it could be effective given that dietary fat intake has been recognized to some extent as a satiety signal (1). Kirschenbaum and Kelly in their interpretation use only a part of this statement and erroneously conclude that “the trust model believes limiting consumption of fat is not critical to successful weight loss” (flaw #4) (3). The trust model emphasis is on feeding dynamics and eating patterns, not obesity or weight loss. The trust model advocates for a balanced meal typical of lifestyle interventions not a macronutrient restrictive diet.
Most children live in the obesigenic environment. Indeed, according to Lowe (p. 49S, also acknowledged by Kirschenbaum and Kelly) (3), “[The] modern food-abundant environment may be particularly ‘toxic’ to those who are overweight.” Having structured meals and snacks and being able to recognize and respond to internal hunger and satiety cues as advocated by the trust model may be advantageous to children and enable them to resist eating when they are not physically hungry. Evidence suggests that young children do have an internal mechanism that helps them eat in accordance with their internal hunger and satiety cues (1). Laboratory experiments demonstrated that, even though their intake at each meal was highly variable, children's total daily energy intake was relatively constant (e.g., a high-calorie meal was followed by a low-calorie meal) (6).
Laboratory experiments have also shown that adults who restrict their food intake also overindulge in food when they perceive that their dietary rules have been broken or that they have eaten a forbidden food (7). Individuals who do not diet have two boundaries corresponding to hunger and satiety. When hungry, they will eat so as to escape the hunger zone and will stop eating when indifferent or slightly sated (8). The eating behavior of individuals who engage in food restriction is largely under the control of a third and unnatural diet boundary. When this diet boundary is breached, eating often becomes disinhibited and in defiance of the hunger and satiety boundaries (9). In the classic study performed by Ancel Keys and his colleagues, men who had no prior preoccupation with food were placed on a reduced calorie diet for 6 months. These men became extremely preoccupied with food, gained weight, and engaged in binge eating that persisted even after the diet was terminated (10). Finally, Kirschenbaum and Kelly (3) assert that Stice et al. have shown that dieters are not restrained eaters. However this is an inaccurate interpretation of the study. Stice et al. concluded that the existing scales may be invalid to measure dieting because of the lack of a negative correlation between restraint scales and food intake. Other researchers have noted that because disinhibited eating is often seen among restrained eaters in situations where there is perceived loss of control (9), it is not surprising that simple correlational analyses will find a negative link between restrained eating and dieting (11).
Kirschenbaum has advocated that all obese individuals including children and adolescents develop what he defines as a healthy obsession (12). This approach involves accepting the “tough goal” of eating as little fat as possible each day, writing down all food eaten, and “not seeking moderation” in anything related to food choice, weight, or physical activity (p. 8) Yet, studies on low-fat diets have not been conclusive nor have shown that it is more efficacious than other diets (13,14). Perhaps Kirschenbaum and Kelly's emphasis on the efficacy of low-fat diets or a healthy obsession reflects their experience with youth weight loss camps and boarding schools where the external environment is rigidly controlled with diets consisting of 7% daily fat intake (15).
Clearly, we need to be cautious of advocating highly restrictive eating behaviors for children.
Multiple studies have reported a positive relationship between restrictive feeding behaviors, dieting, and overweight status in children (1,16,17,18,19,20). Young children whose parents have restricted their food intake are more likely to eat in the absence of hunger and have a higher BMI (16). In a study of 2,516 adolescents followed over a 5-year period (1999–2004), a history of dieting (healthy and unhealthy) was a risk factor for overweight status, binge eating and extreme weight control even after adjusting for baseline outcomes, age, race or sociodemographic factors (17). Although only a minority of obesity intervention studies have reported a higher rise in eating disorders or binge eating, most studies did not use highly restrictive methods nor screen for these outcomes (5,21).
Kirschenbaum and Kelly (3) argued that we had an “error of omission” which involved excluding Stice's (1998) study (22) which found that “low dieters” and “moderate dieters” tended to gain weight over a 9-month period whereas the “extreme dieters” lost weight over this same period. Interestingly, this study also provides evidence against dieting. The study included a group of nondieters which reflects the nondieting philosophy advocated by the trust model. Nondieters had lower BMIs than dieters at the initial time of the study and 9-months later. Extreme dieting and caloric restriction surely will lead to weight loss, but can it be maintained beyond nine months? It is commonly known that ∼95% of those who lose weight will regain their weight within a few years (23). It is also conceivable that the low-to-moderate dieters in Stice's (1998) study were once extreme dieters that could not maintain rigid calorie and food restriction and thus moved into the low or moderate dieting group and gained weight. Indeed, Bacon et al. (24) randomly assigned obese female chronic dieters to either a nondieting group (focused on body acceptance, moderate activity, letting go of restrictive eating behaviors and replacing them with internally regulated eating) or a chronic dieting group (using the popular LEARN Program for Weight Control) for 24 weekly sessions. Attrition was high in the diet group (41%) compared to the nondieting group (8%) at the end of the intervention. Two years after the end of the intervention, the nondieting group participants maintained their weight whereas the dieting group did not sustain their initial weight loss.
Kirschenbaum and Kelly (3) also cited the work of Presnell and Stice (25) which found that women in a dieting condition lost more weight than a waitlist control condition over a 6-week period. However, 6 weeks is too brief of a period to measure the true effectiveness of dieting. In sum, it is erroneous to conclude that Stice's 1998 (ref. 22) and Presnell and Stice's 2003 (ref. 25) articles support extreme dieting over nondieting approaches for long-term weight control. In fact, the literature on dieting and weight loss, especially among adults, is so varied and inconclusive that it is possible to find studies that support or negate the efficacy of dieting. Therefore, we cannot prematurely conclude that dieting (consisting of low-fat diets or other means of restriction) is the best or only option for preventing and treating overweight children nor recommend research be conducted only in these areas. After all, the obesity epidemic has blossomed in spite of the popularity of low-fat diets.
Finally, most of the arguments put forth by Kirschenbaum and Kelly (3) overwhelming cite adult studies. As pediatric health-care providers, we must be acutely aware of the pitfalls of treating children or adolescents as little adults. In our perspective, we acknowledged the intersection between childhood developmental stages, parenting, environmental context and constructs of the trust model (1). For instance, we suggest younger children may be a subgroup where the division of responsibility may have the best outcomes. It is also probable that for specific populations, the trust model may not be applicable or certain elements of the trust model may need to be complemented or modified before it can be used for obesity intervention.
In conclusion, obesity is a heterogeneous condition that requires a heterogeneous solution and not a “one-size-fits-all” approach. This has been borne out by a recent study that found similar outcomes with different types of diets and concluded weight loss is largely determined by behavior modification and number of calories (14). Although the trust model does not categorically advocate for caloric restriction, we are well aware that its recommendations to decrease opportunities for grazing through structured meal and snack times, to limit intake to water between meals, to serve meals that are balanced, and to decrease opportunities for indiscriminate food intake in living rooms, bedrooms, playrooms all have the potential to decrease caloric intake. Thus, in our perspective, we presented a case for rigorous investigation into components of the trust model before it can be advocated for preventing or treating the overweight child.