As the need for broad measures to address the pediatric obesity epidemic has been recognized, significant attention has been focused on ways to prevent weight problems among children.

Although genetics may play a substantial role in many cases of obesity, much can be done in the way of prevention by changing individual behaviors (e.g., diet and exercise) (American Academy of Pediatrics Committee on Nutrition, 2003). Prevention programs may target obesigenic behaviors and aim to facilitate lifelong healthy habits. To date, a majority of such programs have been offered in school settings with the goals of increasing children’s physical activity, decreasing sedentary behavior, and improving dietary habits. These efforts have had mixed results.

Beyond more individualistic prevention approaches, prevention efforts are emerging in broader socioecological contexts.  Most notable are the recent changes in the public policy and corporate policy arenas that have led to changes in some school breakfast and lunch menus as well as changes in marketing strategies vis-à-vis processed food and fast-food products.  These larger contexts of change may reflect a cultural shift toward healthier behaviors spurred on by increasing awareness of the health risks associated with overweight and obesity.

Whether these changes will result in a reversal of current trends in pediatric overweight is not known. Given the scope of the current problem, preventionists will be challenged to be forward-thinking in developing efforts to overcome obstacles to optimal health.  Historically,  prevention efforts in the United States have often been neglected in favor of later treatment; however, the current epidemic will require a substantial shift toward preventative efforts (American Academy of Pediatrics Committee on Nutrition, 2003).

Prevention is one of the hallmarks of pediatric practice and includes such diverse activities as newborn screenings, immunizations, and promotion of car safety seats and bicycle helmets. Documented trends in increasing prevalence of overweight and inactivity mean that pediatricians must focus preventive efforts on childhood obesity, with its associated comorbid conditions in childhood and likelihood of persistence into adulthood. These trends pose an unprecedented burden in terms of children’s health as well as present and future health care costs. A number of statements have been published that address the scope of the problem and treatment strategies.

The intent of this statement is to propose strategies to foster prevention and early identification of overweight and obesity in children. Evidence to support the recommendations for prevention is presented when available, but unfortunately, too few studies on prevention have been performed. The enormity of the epidemic, however, necessitates this call to action for pediatricians using the best information available.

RISK FACTORS
Development of effective prevention strategies mandates that physicians recognize populations and individuals at risk. Interactions between genetic, biological, psychologic, sociocultural, and environmental factors clearly are evident in childhood obesity. Elucidation of hormonal and neurochemical mechanisms that promote the energy imbalance that generates obesity has come from molecular genetics and neurochemistry. Knowledge of the genetic basis of differences in the complex of hormones and neurotransmitters (including growth hormone, leptin, ghrelin, neuropeptide Y, melanocortin, and others) that are responsible for regulating satiety, hunger, lipogenesis, and lipolysis as well as growth and reproductive development will eventually refine our understanding of risk of childhood overweight and obesity and may lead to more effective therapies.

Genetic conditions known to be associated with propensity for obesity include Prader-Willi syndrome, Bardet-Biedl syndrome, and Cohen syndrome. In these conditions, early diagnosis allows collaboration with subspecialists, such as geneticists, endocrinologists, behavioralists, and nutritionists, to optimize growth and development while promoting healthy eating and activity patterns from a young age. For example, data suggest that growth hormone may improve some of the signs of Prader-Willi syndrome.

It has long been recognized that obesity “runs in families”—high birth weight, maternal diabetes, and obesity in family members all are factors—but there are likely to be multiple genes and a strong interaction between genetics and environment that influence the degree of adiposity. For young children, if 1 parent is obese, the odds ratio is approximately 3 for obesity in adulthood, but if both parents are obese, the odds ratio increases to more than 10. Before 3 years of age, parental obesity is a stronger predictor of obesity in adulthood than the child’s weight status. Such observations have important implications for recognition of risk and routine anticipatory guidance that is directed toward healthy eating and activity patterns in families.

There are critical periods of development for excessive weight gain. Extent and duration of breastfeeding have been found to be inversely associated with risk of obesity in later childhood, possibly mediated by physiologic factors in human milk as well as by the feeding and parenting patterns associated with nursing. Investigations of dietary factors in infancy, such as high protein intake or the timing of introduction of complementary foods, have not consistently revealed effects on childhood obesity. It has been known for decades that adolescence is another critical period for development of obesity. The normal tendency during early puberty for insulin resistance may be a natural cofactor for excessive weight gain as well as various comorbidities of obesity. Early menarche is clearly associated with degree of overweight, with a twofold increase in rate of early menarche associated with BMI greater than the 85th percentile. The risk of obesity persisting into adulthood is higher among obese adolescents than among younger children. The roles of leptin, adiponectin, ghrelin, fat mass, and puberty on development of adolescent obesity are being actively investigated. Data suggest that adolescents who engage in high-risk behaviors, such as smoking, ethanol use, and early sexual experimentation also may be at greater risk of poor dietary and exercise habits.

Environmental risk factors for overweight and obesity, including family and parental dynamics, are numerous and complicated. Although clinical interventions cannot change these factors directly, they can influence patients’ adaptations to them, and the physician can advocate for change at the community level. Food insecurity may contribute to the inverse relation of obesity prevalence with socioeconomic status, but the relationship is a complex one. Other barriers low-income families may face are lack of safe places for physical activity and lack of consistent access to healthful food choices, particularly fruits and vegetables. Low cognitive stimulation in the home, low socioeconomic status, and maternal obesity all predict development of obesity. In research settings, there is accumulating evidence for the detrimental effects of overcontrolling parental behavior on children’s ability to self-regulate energy intake. For example, maternal-child feeding practices, maternal perception of daughter’s risk of overweight, maternal restraint, verbal prompting to eat at mealtime, attentiveness to noneating behavior, and close parental monitoring all may promote undesired consequences for children’s eating behaviors. Parental food choices influence child food preferences, and degree of parental adiposity is a marker for children’s fat preferences. Children and adolescents of lower socioeconomic status have been reported to be less likely to eat fruits and vegetables and to have a higher intake of total and saturated fat. Absence of family meals is associated with lower fruit and vegetable consumption as well as consumption of more fried food and carbonated beverages. Although our understanding of the development of eating behaviors is improving, there are not yet good trials to demonstrate effective translation of this knowledge base into clinical practices to prevent obesity. At a minimum, however, pediatricians need to proactively discuss and promote healthy eating behaviors for children at an early age and empower parents to promote children’s ability to self-regulate energy intake while providing appropriate structure and boundaries around eating.

Widespread and profound societal changes during the last several decades have affected child rearing, which in turn has affected childhood patterns of physical activity as well as diet. National survey data indicate that children are currently less active than they have been in previous surveys. Leisure activity is increasingly sedentary, with wide availability of entertainment such as television, videos, and computer games. In addition, with increasing urbanization, there has been a decrease in frequency and duration of physical activities of daily living for children, such as walking to school and doing household chores. Changes in availability and requirements of school physical education programs have also generally decreased children’s routine physical activity, with the possible exception of children specifically enrolled in athletic programs. All these factors play a potential part in the epidemic of overweight.

National survey data indicate that 20% of US children 8 to 16 years of age reported 2 or fewer bouts of vigorous physical activity per week, and more than 25% watched at least 4 hours of television per day. Children who watched 4 or more hours of television per day had significantly greater BMI, compared with those watching fewer than 2 hours per day. Furthermore, having a television in the bedroom has been reported to be a strong predictor of being overweight, even in preschool-aged children. Some cross-sectional data have found significant correlation between obesity prevalence and television viewing, but others have not. The results of a randomized trial to decrease television viewing for school-aged children has provided the strongest evidence to support the role of limiting television in prevention of obesity. In this study, decreasing “media use” without specifically promoting more active behaviors in the intervention group resulted in a significantly lower increase in BMI at the 1-year follow-up, compared with the control group. Additional support for the importance of decreasing television viewing comes from controlled investigations that demonstrated that obese children who were reinforced for decreasing sedentary activity (and following an energy-restricted diet) had significantly greater weight loss than those who were reinforced for increasing physical activity. These findings have important implications for anticipatory guidance and provide additional support for recommendations to limit television exposure for young children.

REFERENCES

Elissa Jelalian, Ph.D.
Warren Alpert Medical School of Brown   University
Providence, RI USA
Elissa_Jelalian {at}brown.edu