CHAPTER 29 Obesity

EPIDEMIOLOGY AND DEFINITIONS

The prevalence of obesity in children has increased dramatically. Data from 2004 to 2006 indicate that 16.3% of American children 2 to 19 years of age are considered obese (body mass index [BMI] ≥95th percentile). The largest increases in the prevalence of obesity are seen in the most overweight classifications and in certain ethnic groups, such as African-American and Mexican-American children, of whom more than 30% are overweight.

Many obese children become obese adults. The risk of remaining obese increases with age and degree of obesity. Eleven-year-old children who are overweight are more than twice as likely to remain overweight at 15 years of age than are 7-year-old overweight children. The risk of becoming obese as a child and remaining obese as an adult is also influenced by family history. If one parent is obese, the odds ratio for the child to be obese in adulthood is 3, but if both parents are obese, the ratio increases to 10.

Obesity runs in families; this could be related to genetic influences or the influence of a common, shared environment. Eighty percent of the variance in weight for height or skin-fold thickness in adopted twin pairs may be explained on the basis of genetics. A strong relationship exists between the BMI of adoptees and that of their biologic parents; a weaker relationship exists between the BMI of adoptees and that of their adoptive parents. The association between obesity and television watching and dietary intake, the different rates of obesity observed in urban versus rural areas, and changes in obesity with seasons support the important influence of environment.

CLINICAL MANIFESTATIONS

Complications of obesity in children and adolescents can affect virtually every major organ system. The history and physical examination should screen for many potential complications noted among obese patients (Table 29-1) in addition to specific diseases associated with obesity (Table 29-2). Medical complications usually are related to the degree of obesity and usually decrease in severity or resolve with weight reduction.

TABLE 29-1 Complications of Obesity

Complication	Effects
Psychosocial	Peer discrimination, teasing, reduced college acceptance, isolation, reduced job promotion*
Growth	Advance bone age, increased height, early menarche
Central nervous system	Pseudotumor cerebri
Respiratory	Sleep apnea, pickwickian syndrome
Cardiovascular	Hypertension, cardiac hypertrophy, ischemic heart disease,* sudden death*
Orthopedic	Slipped capital femoral epiphysis, Blount disease
Metabolic	Insulin resistance, type 2 diabetes mellitus, hypertriglyceridemia, hypercholesterolemia, gout,* hepatic steatosis, polycystic ovary disease, cholelithiasis

* Complications unusual until adulthood.

TABLE 29-2 Diseases Associated with Childhood Obesity*

Syndrome	Manifestations
Alström syndrome	Hypogonadism, retinal degeneration, deafness, diabetes mellitus
Carpenter syndrome	Polydactyly, syndactyly, cranial synostosis, mental retardation
Cushing syndrome	Adrenal hyperplasia or pituitary tumor
Fröhlich syndrome	Hypothalamic tumor
Hyperinsulinism	Nesidioblastosis, pancreatic adenoma, hypoglycemia, Mauriac syndrome
Laurence-Moon-Bardet-Biedl syndrome	Retinal degeneration, syndactyly, hypogonadism, mental retardation; autosomal recessive
Muscular dystrophy	Late onset of obesity
Myelodysplasia	Spina bifida
Prader-Willi syndrome	Neonatal hypotonia, normal growth immediately after birth, small hands and feet, mental retardation, hypogonadism; some have partial deletion of chromosome 15
Pseudohypoparathyroidism	Variable hypocalcemia, cutaneous calcifications
Turner syndrome	Ovarian dysgenesis, lymphedema, web neck; XO chromosome

* These diseases represent <5% of cases of childhood obesity.

The diagnosis of obesity depends on the measurement of excess body fat. Actual measurement of body composition is not practical in most clinical situations. BMI is a convenient screening tool that correlates fairly strongly with body fatness in children and adults. BMI age-specific and gender-specific percentile curves (for 2- to 20-year-olds) allow an assessment of BMI percentile (available online at http://www.cdc.gov/growthcharts). Table 29-3 provides BMI interpretation guidelines. For children younger than 2 years of age, weight-for-length measurements greater than 95th percentile may indicate overweight and warrant further assessment. A BMI for age and gender above the 99th percentile is strongly associated with excessive body fat and is associated with multiple cardiovascular disease risk factors.

TABLE 29-3 Body Mass Index (BMI) Interpretation

BMI/Age percentile	Interpretation
<5th	Underweight
5–85th	Normal
85–95th	Overweight
≥95th	Obese
>99th	Severely obese

Page 110

ASSESSMENT

Early recognition of excessive rates of weight gain, overweight, or obesity in children is essential because family counseling and treatment interventions are more likely to be successful before obesity becomes severe. Routine evaluation at well-child visits should include the following:

1. Anthropometric data, including weight, height, and calculation of BMI. Data should be plotted on age-appropriate and gender-appropriate growth charts and assessed for weight gain trends and upward crossing of percentiles.

2. Dietary and physical activity history (Table 29-4). Assess patterns and potential targets for behavioral change.

3. Physical examination. Assess blood pressure, adiposity distribution (central versus generalized), markers of comorbidities (acanthosis nigricans, hirsutism, hepatomegaly, orthopedic abnormalities), and physical stigmata of genetic syndrome (Prader-Willi syndrome).

4. Laboratory studies. These are generally reserved for children who are obese (BMI >95th percentile), who have evidence of comorbidities or both. Useful laboratory tests may include a fasting lipid profile, fasting glucose levels, liver function tests, and thyroid function tests (if evidence of plateau in linear growth). Other studies should be guided by findings in the history and physical examination.

TABLE 29-4 Eating and Activity Habits for Overweight/Obesity Prevention and Treatment

DIET

Consume five or more servings of fruits and vegetables per day

Minimize consumption of sugar-sweetened beverages

Prepare more meals at home rather than purchasing restaurant food

Eat at table, as a family, at least five to six times per week

Consume a healthy breakfast every day

Allow child to self-regulate his or her meals and avoid overly restrictive feeding behaviors

ACTIVITY

Limit screen time (television, computer games/Internet, video games) to ≤2 hours per day (no TV for child <2 yr of age)

Be physically active ≥1 hour per day; engage in both unstructured and structured activities

TREATMENT

The approach to therapy and aggressiveness of treatment should be based on risk factors, including age, severity of overweight and obesity and comorbidities, and family history and support. The primary goal for all children with uncomplicated overweight is to achieve healthy eating and activity patterns. For children with a secondary complication, improvement of the complication is an important goal. Childhood and adolescent obesity treatment programs can lead to sustained weight loss and decreases in BMI when treatment focuses on behavioral changes and is family-centered. Concurrent changes in dietary and physical activity patterns are most likely to provide success.

Treatment recommendations by an Expert Committee include a systematic approach that promotes brief, office-based interventions for the greatest number of overweight and obese children, as well as a systematic intensification of efforts, tailored to the capacity of the clinical office, the motivation of the family, and the degree of obesity. The most aggressive therapy is considered only for those who have not responded to other interventions. The four levels or stages of treatment are described below.

Page 111

1. Prevention plus: The goal is improved BMI status. Problem areas identified by dietary and physical activity history should be provided (see Table 29-4), and emphasis should be placed on healthy eating and physical activity patterns. This is especially appropriate for preventing further weight gain and for overweight and mildly obese children. This stage of treatment can take place in the office setting.

2. Structured weight management: The approach may include planned diet, structured daily meals, and planned snacks; additional reduction in screen (computer/video game/television) time; planned, supervised activity; self-monitoring of behaviors, including logs; and planned reinforcement for achievement of targeted behavior change. This may be done in the primary care setting but generally requires a registered dietitian or a clinician who has specialized training. Monthly follow-up visits are recommended.

3. Comprehensive multidisciplinary intervention: This level of treatment increases the intensity of behavior change, frequency of visits, and the specialists involved. Programs at this level are presumed to be beyond the capacity of most primary care office settings. Typical components of a program include structured behavior modification, food monitoring, diet and physical activity goal setting, and contingency management. A multidisciplinary team with expertise in childhood obesity typically includes a behavior counselor, registered dietitian, exercise specialist, and primary care provider to monitor ongoing medical issues. Frequency of visits is typically weekly for 8 to 10 weeks, with subsequent monthly visits. Group visits and treatment programs, including commercial weight management programs, should be considered. The Weight Information Network, a service available through the National Institutes of Health, disseminates information on weight control programs (http://www.niddk.nih.gov//NutritionDocs.html).

4. Tertiary care intervention: This more intensive approach should be considered for severely obese children. Approaches include medications, very low calorie diets, and weight control surgery, in addition to the attainment of behavior changes to improve diet and activity patterns. This level of intervention also includes a multidisciplinary team with expertise in obesity and its comorbidities and takes place in a pediatric weight management center.

PREVENTION

Obesity is challenging to treat and can cause significant medical and psychosocial issues for young children and adolescents. Families need to be counseled on age-appropriate and healthy eating patterns beginning with the promotion of breastfeeding. For infants, transition to complementary and table foods and the importance of regularly scheduled meals and snacks, versus grazing behavior, should be emphasized. Age-appropriate portion sizes for meals and snacks should be encouraged. Children should be taught to recognize hunger and satiety cues, guided by reasonable portions and healthy food choices by parents. Children should never be forced to eat when they are not willing, and overemphasis of food as a reward should be avoided. The U.S. Department of Agriculture MyPyramid (http://www.mypyramid.gov) provides a good framework for a healthy diet, with an emphasis on whole grains, fruits, and vegetables and with age-appropriate portion sizes. After 2 years of age, most children should change from whole or 2% milk to skim milk, because other food sources provide adequate fat for growth and development.

The importance of physical activity should be emphasized. For some children, organized sports and school-based activities provide opportunities for vigorous activity and fun, whereas for others a focus on activities of daily living, such as increased walking, using stairs, and more active play may be better received. Time spent in sedentary behavior, such as television viewing and video/computer games, should be limited. Television in children’s rooms is associated with more television time and with higher rates of overweight, and the risks of this practice should be discussed with parents. Clinicians may need to help families identify alternatives to sedentary activities, especially for families with deterrents to activity, such as unsafe neighborhoods or lack of supervision after school.