CHAPTER 155

Childhood Obesity

H. Mollie Greves Grow, MD, MPH, FAAP

Childhood obesity is of significant concern because children with overweight are more likely to have overweight as adults and are at increased risk for multiple chronic conditions. Additionally, having obesity carries a psychosocial toll for affected adults and children, because it remains among the most stigmatized conditions. Children with obesity are often shunned by peers at school, feel isolated, and have fewer friends, whereas adolescents with obesity complete less schooling, go on to have lower household incomes, and are more likely to live in poverty than their counterparts without obesity. The primary care physician is usually the first (and often only) resource available to help patients and their families in screening, diagnosing, discussing, and managing childhood obesity.

Defining obesity presents certain challenges. Ideally, a measure of obesity would correlate with adiposity and predict morbidity and mortality. Body mass index (BMI) (weight in kilograms divided by height in meters squared) is the best and most widely used surrogate measure for obesity but does not completely correlate with adiposity for all individuals. Standards for adults have established a BMI of 25 or greater as overweight and 30 or greater as obese, based on increased risk of morbidity and mortality above these levels. Although BMI currently is the preferred method for assessing degree of obesity in children, other criteria are also used (Box 155.1). Experts classify children at the 85th to 95th percentile of BMI for age as having overweight and those greater than the 95th percentile of BMI for age as having obesity. Because BMI is not a direct measure of adiposity, it is important to recognize that not all children who meet the BMI criteria for overweight and obesity will have adverse health effects of their weight status. A helpful general rule is that the higher the

BMI rises above the 95th percentile, the greater likelihood of adverse health effects. For BMI greater than the 99th percentile, which is associated with the most comorbidities, often a switch is made to using a BMI number, as for adults, or alternatively, the percentage above the 95th percentile. The BMI changes as children age because of changes in their proportion of bone mass and lean-to-fat tissue composition. After approximately 1 year of age, BMI-for-age values begin to decline and continue to do so during the preschool years until the BMI reaches a minimum at approximately 5 to 6 years of age, before rising throughout the remainder of childhood, into adolescence and adulthood. This phenomenon of increasing BMI after the nadir in the preschool years is referred to as adiposity rebound. Early adiposity rebound (age <4.8 years) is a predictor of later obesity and can be used clinically to identify children at risk.

Epidemiology

The prevalence of obesity is on the rise globally, especially in developed countries. Between 1980 and 2000, the percentage of overweight children and adolescents in the United States tripled, reaching 17.1% in 2003 to 2004. Since then, no significant increases have been seen overall among the US youth population, except for increases in the highest BMI group (>97th percentile). Severe obesity affects 4.5 million U.S. children and adolescents. Hispanic, black, and Native American individuals are disproportionately affected. People with lower education and those in poverty are at highest risk. Prevention and treatment of obesity is important to avoid health risks that affect the individual and are costly to society as a whole. In the United States, the overall spending associated with overweight and obesity was $93 billion in 2002 dollars, one-half of which was publicly financed through Medicare or Medicaid.

Clinical Presentation

The child with obesity usually presents to the physician in 1 of 2 ways. The parent(s)/guardian(s) or the child may come in concerned that the child has overweight (as in the case study). The physician must then consider the growth parameters and BMI for age to make an appropriate determination of the child’s overweight status. The more common presentation is the parent who does not recognize that the child has overweight and who may believe that being big is a sign of health. The lack of awareness of the child’s risk may particularly affect a parent during the time of the adiposity nadir (ie, the preschool and early school-age years when children are most lean), when early intervention to improve energy balance might yield the most benefit. Measurement of the child’s height and weight and determination of BMI for age is important at all ages to identify the child who has overweight or obesity or is gaining weight more rapidly than expected; it is especially critical during early childhood when outward appearances may be most unreliable. Seeing change in percentiles is particularly helpful to differentiate children who may be healthy and grow steadily along a higher BMI curve, such as those 5% at the 95th percentile who are naturally in the high BMI range and are not adversely affected in their overall health.

Pathophysiology

Understanding of the pathophysiology of obesity continues to evolve. Certain neurohormones affect appetite, satiety, and the balance between fat storage and energy production. Ultimately, obesity results when energy intake exceeds expenditure. Historically, the storage of excess calories was an advantage to our ancestors who faced intermittent food shortage; however, this predisposition to store excess calories has contributed to increasing rates of obesity in our current setting in which the environment provides ubiquitous highly palatable, high-calorie, convenient foods and limited opportunities for physical activity.

It is known from studies of twins and family networks that susceptibility to obesity is influenced substantially by genetics; however, the magnitude of recent increases in obesity rates is suggestive of an interaction between genetic susceptibility and an obesogenic environment that facilitates unhealthy behaviors. National surveys indicate that individuals in the United States are consuming more calories now than they were decades ago. This trend is most related to increasingly widespread and easily available calorically dense foods in larger portions than ever before. A smaller but also important contribution of the population weight gain comes from less physical activity and more sedentary lifestyles. The reasons for this are myriad and include changes in transportation patterns, shifts in the workforce to jobs that involve less manual labor, and automation of household work. Children in particular have fewer opportunities for activity because of safety concerns; work habits of parents; the availability of television, computers, tablets, and smartphones; and reduced availability of physical education in school and after-school programs.

Differential Diagnosis

Most children who present to a physician with excess weight have primary obesity resulting from genetic susceptibility combined with an imbalance of caloric intake and activity levels. Only a small proportion of children have another cause, such as hypothyroidism, although many parents or guardians may initially inquire about another etiology. A thorough history, including review of systems, physical examination, and evaluation of growth parameters, helps confirm primary obesity in most cases. Whereas the child with primary obesity tends to have normal or increased height for age, the child with another etiology, such as hypothyroidism, typically is shorter than normal or has a delayed rate of linear growth. Certain genetic syndromes, such as Prader-Willi syndrome, pseudohypo-parathyroidism, Bardet-Biedl syndrome, and Laurence-Moon syndrome, are associated with obesity. However, a child with any of these syndromes has other findings, such as developmental delay, dysmorphic features, and short stature, that are usually identifiable during the physical examination. Although initially another medical cause of weight gain may be lacking, evidence exists that weight gain can be exacerbated by an acquired diagnosis, such as sleep apnea, that manifests as a complication of obesity.

Evaluation

History

The history should include the age of the child, parental weight, and lifestyle information (Box 155.2). Knowledge of a child’s birth weight and gestational age may be helpful. Term neonates weighing more than 4 kg (9 lb) are at increased risk of obesity. Preterm status is also a risk factor for subsequent obesity, possibly related to early metabolic effects of rapid catch-up weight gain after birth. Exclusive formula feeding may be a risk factor for obesity. A diet history, such as the 24-hour recall method or, alternatively, use of screening questions filled out by the parent or guardian in the waiting room, can be helpful to understand the dietary factors contributing to the child’s overweight status, as well as to identify areas for potential change. Additionally, a history of signs or symptoms of complications of obesity should be elicited. For example, a teenager may complain of hip or knee pain suggestive of slipped capital femoral epiphysis (SCFE). The child may have a history of snoring, or apneic pauses followed by gasping for breath during sleep, and daytime sleepiness indicating obstructive sleep apnea (OSA). A history of irregular menstrual periods is useful in evaluation for polycystic ovary syndrome. A mental health history, including depression and anxiety symptoms, disordered eating, and history of bullying, is important to obtain. The family history, especially information on familial obesity, diabetes, hypertension, and early cardiac death, offers clues to the risk of obesity complications. Finally, a social history, including family social stressors, substance use, poverty, and food insecurity, is important to gauge the child’s risks and the family’s need for support to address obesity concerns.

Stay updated, free articles. Join our Telegram channel

Join