A 13-year-old Hispanic female is brought to her pediatrician with various concerns, including that her neck always appearing dirty no matter how much she washes and scrubs it. The pediatrician notes that the child has acanthosis nigricans of the neck and axillae along with obesity (Figure 194-1). The mother is obese and admits to having type 2 diabetes. A diet history reveals that the mother cooks traditional Mexican cuisine and the daughter is very fond of tortillas. She also loves to eat pizza, french fries, and other fast food. The girl is a good student but does not like to exercise or play sports. The pediatrician is concerned that the girl may have insulin resistance or type 2 diabetes so she plans to send the patient for screening labs including hemoglobin A1c and fasting blood sugar. She also recommends a healthier diet with less calories and increased physical activity. A referral to a nutritionist is offered.

Obesity in children is defined as a BMI greater than or equal to the age- and sex-specific 95th percentiles of the 2000 Centers for Disease Control (CDC) growth charts; a child is considered overweight at the 85^th to 95^th percentile.

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  Based on the National Health and Nutrition Examination Surveys (NHNS), 12.5 million children and adolescents (16.9%) are obese.¹ Slightly more boys (19.3%) were obese than girls (16.8%) of all included ages in the study. Since 1980, the prevalence of obesity in children has tripled.¹

  
  
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  The direct medical care costs (prescriptions, outpatient visits, and ER visits) for children aged 6 to 19 years for complications of obesity are 14.1 billion dollars annually.²

  
  
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  There is an overrepresentation of low-income children in the numbers of obese children, with 1 in 7 lowincome preschool children being obese.^3,4 The National Longitudinal Study of Adolescent Health showed that being obese (BMI > 95%) is highly associated with lower household income.⁴

  
  
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  Race and ethnicity are also associated with obesity, with high rates present in American Indian/Eskimo children.³ In the NHNS study (2007 to 2008), Hispanic boys, aged 2 to 19 years, were significantly more likely to be obese than non-Hispanic white males and non-Hispanic black girls aged 2 to 19 years were significantly more likely to be obese than non-Hispanic white girls.⁵

  
  
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  Interestingly, the effect of ethnicity appears to be mediated by income; Caucasian teenage girls from the lowest income quintile had relative risks for obesity of 2.72 compared to teens in the highest quintile.⁴

Obesity is a complex problem involving genetics, health behaviors (e.g., diet or exercise), environment, culture, and sometimes medical diseases (see differential diagnosis) or drugs (e.g., steroids or antidepressants). The simplest explanation of obesity is an imbalance between intake (calories eaten) and output (physical activity).

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  Genetics—Studies on twins, nontwin siblings, and adopted siblings show that the genetic component of obesity is somewhere between 40 to 70 percent. Researchers using Genome Wide Association Studies have identified 42 different genes likely associated with obesity.⁶ Most of these genes only make a small contribution to the overall elevation of BMI (around 0.17 kg/m²). The cumulative risk for developing obesity not only relies on the individuals genotype, but also on the environment and a wide variety of other factors.⁶

  
  
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  Diet—Many low-income families live in neighborhoods lacking supermarkets with fresh produce or healthy choices. Calorie dense “junk food” or fast food is more readily available and less expensive than healthier options. Daycares and schools are not regulated or monitored on their ability to provide healthy options for children. Exposure to sugary drinks and snack foods in school vending machines may lead to increased consumption of calorie dense foods.⁷ In addition, portion size is commonly much larger than what typical serving sizes for children should be. This leads to overeating and the expectation for increased food consumption at meals and snacks.

  
  
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  Television viewing—Sedentary TV viewing displaces physical play and exercise, and exposes children to targeted advertising.⁸ Authors of a recent study of 1,638 hours of television found 9000 food ads of which only 165 promoted fitness and good nutrition.⁹ TV viewing may lead to an increase in snacking behavior and interfere with normal sleep patterns; hours of TV watching predicts higher BMI in adulthood.⁸ In addition, having a bedroom TV set is an independent risk factor for obesity.⁸

  
  
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  Physical activity—School programs have limited the amount of time devoted to exercise, which falls well below the recommended 60 minutes per day for a child. Access to safe and appealing play areas, parks, and recreation facilities may be limited, especially in urban and rural areas.

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  Family history of obesity—In a retrospective cohort study of 854 children, children aged 1 to 2 year olds with non-obese parents had an 8 percent chance of being obese adults while children aged 10 to 14 years with one obese parent had a 79 percent chance of being obese as adults.¹⁰

  
  
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  Diet—High calorie, low in fruits and vegetables, high number of snack foods, and fast food consumption.

  
  
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  Low levels of physical activity.

  
  
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  Mother with gestational diabetes.

  
  
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  Small-for-gestational-age at birth.

  
  
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  Stressors—Investigators in the Fragile Families and Child Well Being Study found that cumulative social stressors between the ages of 1 to 3 years were associated with increased odds of early onset obesity among girls.¹¹ The greater the number of stressors at one time predicted a greater risk for obesity at the age of 5 years.

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  Body mass index (BMI) is calculated by taking the child’s weight in kilograms divided by the standing height in m². That number is highly variable over the child’s growing years, and should be charted on the 2000 CDC growth chart for BMI to determine if the child is normal (<85^th percentile), overweight (85 to 94^th percentile), or obese (>95^th percentile). As the child’s age gets closer to 19 years, the adult definition for obesity of 30 kg/m² can be utilized. The 2007 expert committee of the American Academy of Pediatrics (AAP) on Child and Adolescent Obesity proposed a new category of severe obesity, defined as BMI of 30 to 32 kg/m² for 10 to 12 year olds and >34 kg/m² for 14 to 16 year olds.¹²

  
  
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  Children grow very rapidly in the first 24 months and standards for BMI are not available for children <2 years of age. The BMI as a percentage usually peaks in the first 8 months and then falls to a nadir at around age 6 years. By around 8 years of age, most children are at the percentile that they will follow into adolescence. In general, the earlier a child reaches their nadir, the more likely the child will have an elevated BMI later.

  
  
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  In adults, increased waist circumference (WC) confers additional morbidity risk for those who have elevated weight. For children, WC and skin fold measurement are not valid indicators of risk or predictors for obesity and are not followed routinely.

Clinical Features

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  Obese children (Figure 194-1) are more likely to have hypertension (2.9 times higher), high cholesterol (2.1 times higher), insulin resistance, and type 2 diabetes mellitus (2.9 times higher).

  
  
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  Obese children have a higher incidence of increased severity asthma and may suffer from sleep apnea.

  
  
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  There is an increased prevalence of non-alcoholic fatty liver disease (NAFLD) and gastro esophageal reflux among obese children.

  
  
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  Acanthosis nigricans is a skin condition that is commonly present in obese children (Figures 194-1 and 194-2; see Chapter 190, Acanthosis Nigricans).

  
  
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  Obese children can also develop striae (Figure 194-3).

  
  
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  Obese boys are more likely to have pseudogynecomastia (Figures 194-4 and 194-5). This appears similar to gynecomastia but this is not real breast development just increased adipose tissue.

  
  
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  Slipped capital femoral epiphysis, joint problems, and muscle strain/pain often limit obese children’s ability to exercise.

  
  
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  It is common for obese children to experience depression, low self-esteem, discrimination, and bullying.