The overweight and obesity epidemic among children and adolescents in the United States continues to worsen, with notable racial, ethnic, and socioeconomic disparities. Risk factors for pediatric obesity include genetics; environmental and neighborhood factors; increased intake of sugar-sweetened beverages (SSBs), fast-food, and processed snacks; decreased physical activity; shorter sleep duration; and increased personal, prenatal, or family stress. Pediatricians can help prevent obesity by measuring body mass index at least yearly and providing age- and development-appropriate anticipatory guidance to families. Public policies and environmental interventions aim to make it easier for children to make healthy nutrition and physical activity choices. Interventions focused on family habits and parenting strategies have also been successful at preventing or treating childhood obesity.
Key points
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Childhood obesity is a complex medical issue, representing the interplay of physical and environmental factors.
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The neuroendocrine control of weight includes multiple situations where genetic variation can influence a person’s weight status.
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The unhealthy evolution of food and activity environments has placed children at a higher risk for obesity and associated weight problems than they have ever been.
Introduction
The prevalence of obesity in the United States remains dangerously high, at nearly 10% among infants and toddlers, 17% of children and teens, and more than 30% of adults. Although the prevalence has stabilized somewhat over the past few years, rates of severe obesity have continued to climb, particularly in high-risk populations. Intervening during childhood is important due to the persistence of obesity into adulthood with associated increased morbidity and mortality. Comorbidities often affect children before they reach adulthood, requiring increased diligence in evaluating and treating these conditions and leading to increased health care expenditures. The personal and emotional face of childhood obesity is also serious: daily quality of life can be significantly worsened by obesity. The psychosocial complications of obesity include depression, body dissatisfaction, unhealthy weight control behaviors, stigmatization, and poor self-esteem.
Groups have advocated for the prevention of obesity for some time, yet efforts to advance preventative interventions may have been limited by the difficulties and expense of long-term studies of a complex problem and increasing focus on treatments. Despite the progress over the past 20 years, there is not a clear solution or one-size-fits-all approach. The body of literature on proved prevention interventions is not robust, although cross-sectional and associational studies have identified risk factors to address, and practical experience has provided a foundation on which to work with children and families. Childhood obesity is incredibly complex and reflects numerous systems that have an impact on a child’s health. Repetition of concepts can aid in approaching an issue as complex as childhood obesity; the ecological model of childhood obesity ( Fig. 1 ) provides a broad framework for understanding the mediators and moderators of childhood obesity. This overview highlights evidence-based factors on which clinicians can focus efforts to effectively prevent the development of childhood obesity. This article reviews both general and age-specific risk factors for pediatric obesity and discusses specific strategies for intervention at the level of the pediatrician, school, government, and family.
Introduction
The prevalence of obesity in the United States remains dangerously high, at nearly 10% among infants and toddlers, 17% of children and teens, and more than 30% of adults. Although the prevalence has stabilized somewhat over the past few years, rates of severe obesity have continued to climb, particularly in high-risk populations. Intervening during childhood is important due to the persistence of obesity into adulthood with associated increased morbidity and mortality. Comorbidities often affect children before they reach adulthood, requiring increased diligence in evaluating and treating these conditions and leading to increased health care expenditures. The personal and emotional face of childhood obesity is also serious: daily quality of life can be significantly worsened by obesity. The psychosocial complications of obesity include depression, body dissatisfaction, unhealthy weight control behaviors, stigmatization, and poor self-esteem.
Groups have advocated for the prevention of obesity for some time, yet efforts to advance preventative interventions may have been limited by the difficulties and expense of long-term studies of a complex problem and increasing focus on treatments. Despite the progress over the past 20 years, there is not a clear solution or one-size-fits-all approach. The body of literature on proved prevention interventions is not robust, although cross-sectional and associational studies have identified risk factors to address, and practical experience has provided a foundation on which to work with children and families. Childhood obesity is incredibly complex and reflects numerous systems that have an impact on a child’s health. Repetition of concepts can aid in approaching an issue as complex as childhood obesity; the ecological model of childhood obesity ( Fig. 1 ) provides a broad framework for understanding the mediators and moderators of childhood obesity. This overview highlights evidence-based factors on which clinicians can focus efforts to effectively prevent the development of childhood obesity. This article reviews both general and age-specific risk factors for pediatric obesity and discusses specific strategies for intervention at the level of the pediatrician, school, government, and family.
Risk factors
Genetic Risk Factors
Obesity is commonly known to run in families. The genetic contribution to this observation is difficult to discern, however, because families usually share not only genetic material but also environments and habits. Obesity in children correlates with obesity in their parents, and the level of obesity in children increases when both parents are obese as well as with increasing levels of obesity in the parents. It has been shown that parental overweight is the most significant risk factor for childhood overweight. Children’s food choices and eating behaviors are learned from parents at very young ages and influence eating behaviors as children get older.
Although a vast majority of cases of childhood obesity are exogenous, a small proportion may have endogenous causes. The following genetic disorders, both syndromic as well as monogenic in origin, predispose children to obesity:
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Syndromes: trisomy 21 syndrome; Prader-Willi syndrome; Albright hereditary osteodystrophy; Cohen syndrome; Bardet-Biedl syndrome; Alström syndrome; and Wilms tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR).
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Monogenic disorders: leptin deficiency, leptin receptor mutations, proopiomelanocortin deficiency, preproconvertase deficiency, and melanocortin 4 receptor mutations.
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Hormonal disorders: hypothyroidism, growth hormone deficiency, Cushing syndrome, hypothalamic obesity, polycystic ovary syndrome, and hyperprolactinemia.
Environmental/Societal Risk Factors
A child’s living environment, both in the home as well as in the community, can contribute to a higher risk of development of obesity:
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Living in lower-income, predominantly white, or non–mixed-race neighborhoods.
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Parents’ perceptions of the food and physical activity environments in their neighborhoods
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Difficulty getting to a main food store or difficulty purchasing fruits and vegetables there (food desert)
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Increased distance from parks
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Perceived danger of their neighborhood
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Food insecurity, although the evidence is mixed
Behavioral Risk Factors
Nutrition and diet
Although it might seem logical that increased total energy intake should be associated with a higher risk of childhood obesity, the evidence does not support this relationship. Similarly, the relationship between dietary fat intake and childhood obesity is not clearly established. A lower intake of dairy products or calcium is associated with childhood obesity, but the data regarding intake of fruits and vegetables are mixed and do not indicate a strong association with childhood weight status. Beverage choice may increase risk for childhood obesity: fruit juice, especially in large quantities ; SSBs ; and sodas are all positively associated with childhood obesity.
Some specific eating behaviors have been associated with childhood obesity. Skipping breakfast ; eating meals away from home, especially fast food ; quicker eating pace ; larger portion sizes ; and eating in the absence of hunger are all positively associated with childhood obesity. No consistent association has been identified with frequent snacking, whereas eating meals as a family is inversely associated with childhood obesity.
Although there can be conflicting evidence, or less-than-clear associations, clinicians can be confident in addressing intake of unhealthy foods, such as fast food, SSBs, high-fat proteins, and processed snacks, and encourage intake of healthy items, in particular fruits, vegetables, lean meats, and sugar-free beverages. Underneath the intake of these foods are the habits behind them, which clinicians should be cognizant of during an interaction: foods eaten away from home, eating in the absence of hunger, snacking, and family meals. Awareness of these issues can assist clinicians in working with families to prevent the development of unhealthy habits and build healthy ones to prevent excessive weight gain.
Physical activity
Overall, decreased physical activity among children is associated with obesity. Prospective studies objectively measuring physical activity have yielded inconsistent results; however, studies of either self-reported or parent-reported physical activity have demonstrated an inverse relationship between physical activity and both childhood and future adult obesity. An inverse relationship exists between some specific activity-related behaviors and childhood obesity, including sports team participation and active commuting to school.
Physical inactivity and sedentary behaviors are likely associated with childhood obesity, although the effect size may be small. Some prospective studies have found that more hours engaged in sedentary behavior, specifically watching TV or playing video games, was associated with an increased risk of becoming obese in the future ; however, other studies found no association between sedentary behavior and childhood obesity. Increased screen time, including television and electronic devices, is also associated with childhood obesity. Although increased sedentary time and decreased physical activity are both associated with childhood obesity, they may not be inversely proportional. Regardless, efforts to lower the former and increase the latter are key to preventing obesity development.
Sleep
Although there is less evidence regarding sleep, it seems that shorter sleep duration is associated with childhood obesity. Some prospective studies have borne out this association, both in the short term in young children and in the long term, persisting into adulthood. In combination with other positive household routines (eating as a family and limiting screen time), obtaining adequate sleep has a strong inverse relationship with obesity among preschool-aged children.
Stress
The short- and long-term effects of stress on the development of obesity are an emerging area for research. There are several types of stress that can affect a child: personal, parental, and family. Each of these can increase a child’s risk for obesity independently or in concert. Although the data are somewhat mixed, it is likely that there is a positive association between chronic stress and the risk of childhood obesity. This can manifest during childhood and may persist into adulthood. In many studies, parental stress is associated with obesity in children; this relationship is strengthened when a parent experiences stress from more than 1 source. Similarly, stress within the family is also associated with childhood obesity ( Box 1 ).
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Genetic syndromes, monogenic disorders, or hormonal disorders
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Living in neighborhoods that are lower income, predominantly non–mixed race, perceived as dangerous, or at an increased distance from parks and foods stores
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Increased intake of SSBs, fast food, and processed snacks
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Decreased physical activity
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Shorter sleep duration
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Increased personal, prenatal, or family stress
Developmental approach to obesity prevention
Many of the risk factors discussed previously, related to diet, physical and sedentary activity, and sleep, apply to children of many different ages. Other risk factors for pediatric obesity may apply at distinct development stages, offering specific opportunities for intervention by a primary care provider. These stage-specific risk factors have been identified as early as the prenatal period. Although obesity in either parent may increase a child’s risk, as discussed previously, a mother’s prepregnancy body mass index (BMI) and gestational weight gain have been directly associated with obesity in infancy and early childhood. Maintaining gestational weight gain within the Institute of Medicine (IOM) guidelines ( Table 1 ) is especially important for women who are overweight or obese at the time of conception and should be an important component of prenatal counseling. Both over- and undernutrition at this stage are thought to affect fetal programming and predispose to future obesity and metabolic disorders. One recent meta-analysis identified a moderate association between delivery via cesarean section and offspring obesity, with persistence of the association into adulthood. In addition, maternal exposure to tobacco and caffeine have both been associated with obesity at various points during gestation and throughout a child’s life.
| Nutrition | Physical Activity/Other | Specific Interventions | |
|---|---|---|---|
| Prenatal period |
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| Newborn–6 mo |
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| 6–12 mo |
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| 12–24 mo |
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| 24–48 mo |
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| 4–12 y |
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| 13–18 y |
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Additional risk factors become evident in infancy. High birth weight and rapid infant weight gain correlate with future childhood obesity, although they may be difficult to address specifically as modifiable risk factors. Many studies have attempted to determine optimal dietary intake during infancy, but the results are conflicting. Although many studies suggest that breastfeeding is protective against the development of obesity, others show no relationship. These differing results may be due to confounders present in the study; for example, it has been shown that lower protein content in infant formula is protective against obesity at 6 years, so studies on breastfeeding may differ based on the types of formula used by control infants. Results have also been mixed when assessing the effects of duration of breastfeeding. It has been suggested that it is an infant’s degree of self-regulation while breastfeeding rather than the composition of breast milk that may be protective, so that bottle-feeding either formula or pumped breast milk may be associated with increased risk.
Complementary foods represent another important dietary change during infancy, and both the timing of introduction and food selection may have an impact on future risk of obesity. Early introduction of solids (defined as ages <3–5 months depending on the study) may be associated with increased childhood overweight. Similarly, 1 systematic review concludes that higher intake of protein and energy during infancy can be associated with increased BMI, although other studies conclude that no specific complementary foods are associated with increased risk. Overall, the available evidence makes it difficult to establish firm guidelines for infants’ dietary intake.
Other exposures in infancy have also been investigated. Use of broad-spectrum antibiotics, especially with repeated exposures prior to 23 months of age, has a small but significant association with obesity in early childhood. Studies have yielded mixed results for family socioeconomic status, maternal parity, and maternal marital status. Finally, temperament traits identified as early as infancy, especially early negativity and lack of self-regulation, may predispose to later obesity.
Child temperament and parental feeding practices remain important predictors of obesity for toddlers and preschool-aged children. The concerning character traits are thought to be similar to those seen in infancy, in particular poor self-regulation and distress to limitations. Part of the mechanism of this association may reflect parental response to the child’s temperament, especially if parents initiate restrictive feeding practices given concerns over self-regulation or use emotional feeding habits, such as providing obesogenic foods to soothe a negative child. Children are typically weaned from the bottle as toddlers; the timing of this transition may affect obesity risk. At earlier ages (between 12 and 36 months), there is an association between current bottle use and obesity, but this was not seen at later ages (37–60 months). Furthermore, an intervention centered on bottle-weaning effectively reduced total caloric intake in children but did not change overweight status, so the degree to which prolonged bottle use contributes to obesity risk is unclear.
Although sedentary behavior and screen time are concerns for children of all ages, 1 systematic review suggests that preschool children are most amenable to interventions addressing this risk factor. Weight gain in this age group is known to be highly predictive of later obesity, with an earlier adiposity rebound (at <5 years old) associated with both BMI and adiposity at age 15 years. Therefore, this is an important age group to target as effective interventions are identified.
Most studies of obesity in school-aged children focus on interventions delivered within the school system (discussed later). Some research has shown, however, that children with overweight and obesity actually gain more weight during the summer months than during the school year, suggesting that interventions outside of school should also be investigated. The primary difference noted between the school year and summertime is in the level of physical activity. One intervention that has shown success in increasing physical activity in this age group, as well as adolescents, is exergaming, or use of electronic games designed to promote physical exercise. Although the video game experience makes activity more entertaining for children, use of exergames in several studies was found to increase energy expenditure and time spent on physical activity and to reduce waist circumference. These findings suggest that targeting known risk factors during the summer months may be especially important for obesity prevention at this age.
Use of technology for obesity prevention continues to be important in the adolescent age group. Technology-based interventions targeting both diet and exercise have been shown effective in this population, although there is wide variation among studies. Peer groups also take on increased importance during adolescence, and research has attempted to determine how this influences the risk of obesity. Peers are able to influence diet and activity levels in both positive and negative ways, so the inclusion of the peer group in interventions targeting adolescents is important.
Adolescence is a time of significant biological changes, notably puberty. Although there is a clear association between early puberty and obesity, it is difficult to determine cause and effect because prepubertal BMI influences the timing of puberty. Some studies have demonstrated an effect of early puberty on subsequent adiposity and fat distribution, but results have been mixed. Severe obesity in adolescence has been directly associated with poor health outcomes in adulthood, which makes prevention in this age group especially important. In addition, because they represent the next generation of parents, establishment of healthy lifestyle habits in the adolescent population has the potential to decrease the obesity risk of subsequent generations ( Box 2 ).
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Prenatal: appropriate gestational weight gain, no tobacco exposure
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Infancy: minimizing rapid weight gain, later introduction of solid foods, avoiding broad-spectrum antibiotics as possible
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Toddlers: encouraging self-regulation of feeding and lots of physical activity
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School-aged children: exergaming, use of technology-based interventions to improve nutrition and physical activity
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Adolescents: including peer groups in interventions
Role of the primary care provider
Primary care providers play a unique role in the prevention of obesity because they see the same patients and families, often from birth, on a regular basis ( Box 3 ). This gives them the opportunity to provide anticipatory guidance and counseling that can influence families’ nutrition and physical activity habits. As discussed previously, it is well established that there are strong familial links to obesity, both genetic and environmental. These influences do not dictate fate, however. By recognizing risk factors early in a child’s life, primary care providers can help families make positive changes that improve a child’s weight trajectory.
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Measure height and weight and calculate BMI at least annually, observe for trends such as a rapid increase in BMI
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Offer anticipatory guidance about nutrition and physical activity at every well child check
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Use motivational interviewing to help families to make healthier choices
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Advocate for children on a local and national level
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