Childhood Obesity as a Chronic Disease: Title and subTitle BreakKeeping the Weight Off

Medical problems facing children are distinct in many ways from those of adults, and for this reason, their evaluation, management, and outcome assessment must be given special consideration. Decades ago, pediatric care focused on morbidities associated with acute infection or chronic illness lacking specific treatment, whereas, today, care of children must increasingly address the biological and social causes of chronic disease.¹ Childhood obesity has become a clear example of this new type of challenge, requiring that the full biopsychosocial context of a disease be considered in daily care of the patient.

Although pediatrics is distinct from its adult counterpart, potential management strategies for pediatric diseases can sometimes be adapted from the adult setting, and few medications find their way directly to children without some history in adult medicine. However, in the case of obesity, weight loss interventions in adults have generally yielded poor long-term outcomes,^{2 - 3} providing an unimpressive platform on which to develop pediatric-specific programs.

Moreover, children face additional challenges above and beyond those encountered by adults consistent with the variable, and often limited, success observed with many multifaceted interventions for childhood obesity.⁴ Excessively rapid weight gain early in life may be more refractory to intervention as it suggests the presence of especially adverse biological causes, psychosocial causes, or both. Although obesity is usually polygenic in origin, monogenic forms of obesity, such as defects in the receptor for melanocortin-4, are increasingly being recognized as causes for extreme obesity in young children.⁵ Increasing disparities in the prevalence of obesity in youth from racial or ethnic minorities continue to emerge,⁶ and food insecurity and poverty are clear risk factors for obesity in children.⁷ Other environmental influences beyond a child's control may make dietary and physical activity habits especially resistant to change. For example, branding of food and beverages has been shown to influence young children's taste perceptions,⁸ and exposure to food advertising promotes overconsumption.⁹ In addition, school lunches may be of substandard quality¹⁰ and the safety of the physical environment impacts levels of physical activity.¹¹ For older children and adolescents, lifestyle habits are strongly influenced by peers, with varying effects in boys and girls.¹² Given the array of issues that must be considered in the management of childhood obesity, strategies for successful behavior change recognize the importance of family support. Indeed, some obesity treatment strategies for younger children that target the parents as the exclusive agent of change have demonstrated better outcomes compared with conventional programs.¹³

Just as clinical pediatrics has unique features distinguishing it from adult medicine, pediatric research, and obesity research in particular, similarly requires special considerations. In adults, absolute measures of body mass index can be used to define obesity,¹⁴ whereas in children, changes in weight may be confounded by linear growth and puberty-related changes in body composition that differ between boys and girls. Therefore, body mass index relative to age and sex, in the form of percentiles or standardized z scores, are needed to define overweight and obesity in children.¹⁵ Assessing dietary adherence is also problematic in young children, limiting ability to correlate the outcomes of study interventions with behavioral changes. In addition to these methodological issues, research involving children presents ethical considerations that may affect study design, recruitment, and assessment of clinical end points.

The study by Wilfley and colleagues¹⁶ in this issue of JAMA contributes to the current understanding of childhood obesity management by tackling the important question of weight loss maintenance. Although the immediate effect of a maintenance intervention for childhood obesity has been previously evaluated,¹⁷ the longer-term residual effect of such an intervention has not been examined in a rigorous fashion. In this study, 150 overweight 7- to 12-year-old children with at least 1 overweight parent received a 5-month weight loss treatment program and were then randomized to a control group, a 4-month behavior skills maintenance group, or a 4-month social facilitation maintenance group. Consistent with the needs of a pediatric population, the investigators used body mass index z score as their outcome measure, used an intervention with a focus on the family, and considered how psychosocial factors modified outcomes. Not surprisingly, both active maintenance groups resulted in improved short-term efficacy at the end of the intervention compared with the control group. The novel finding is greater maintenance of weight loss persisting through an additional 20 months of follow-up, especially among children with few social problems who received social facilitation training. Nevertheless, the data provided a sobering message—despite a statistically significant effect of at least 1 of the active maintenance interventions over the longer term (with exclusion of outliers), the effects of all interventions diminished over time and even at their peak were small.

Are pediatric obesity interventions doomed to recapitulate the path of adult obesity interventions that have produced such disappointing long-term results? Anticipated growth in children, differentiating them from adults, fortunately provides an opportunity to treat less severe obesity in children by temporarily preventing or slowing the rate of weight gain, rather than obtaining absolute weight loss. However, as Wilfley et al¹⁶ note, these findings suggest that obesity treatment will likely require ongoing long-term maintenance therapy of some form to be optimally successful.

Further research to identify the most successful dietary and physical activity interventions could also augment the effects of the maintenance programs used in this study. For example, the authors used the traffic-light diet, which advocates reduction in fat consumption as its primary nutritional focus. However, the efficacy of dietary fat reduction has been questioned because prospective observational analyses do not show consistent associations between dietary fat and body weight, and because weight loss among interventional studies is not greater in lower- vs higher-fat diet groups.^{18 - 19} Given that few pediatric studies directly compare dietary treatments independent of other aspects of interventions,⁴ the question of which dietary approach is most efficacious in children remains unanswered. In addition, as the cohort in the study by Wilfley et al was predominantly white and middle class, study of other sociodemographic groups is warranted.

Improving outcomes for childhood obesity requires ongoing research to identify optimal dietary and lifestyle strategies, the behavioral interventions necessary to promote them, and their dose-response relationship in different clinical settings. Wilfley et al¹⁶ have provided a useful starting point. Ultimately, the environment in which these interventions are applied also must be considered. For greatest benefit, family-based approaches to obesity should be coupled with interventions in the school and in the community, while even broader efforts focus on the ways in which food marketing can be used to promote rather than jeopardize children's health.