Epidemiology

Obesity is a global public health problem, sparing only dramatically poor regions with chronic food scarcity such as sub-Saharan Africa and Haiti. As of 2005, more than 1.6 billion persons ≥15 yr old are overweight or obese (WHO).

In the USA, 30% of adults are obese, and an additional 35% of adults are overweight. In children, the prevalence of obesity increased 300% over approximately 40 years. The National Health and Nutrition Examination Survey (NHANES) IV, 1999-2002, found 31% of children older than 2 yr to be overweight or obese, and 16% of children and adolescents 6-19 years were in the obese range. Children’s risk varies by socioeconomic status, race, maternal education level, and gender. African-American adolescent girls and Mexican-American 6-12 yr old boys have higher rates of obesity compared to other groups. Childhood obesity is also increasingly common in some Native American groups. Across all racial groups, higher maternal education confers protection against childhood obesity.

Parental obesity correlates with a higher risk for obesity in their children. Prenatal factors including weight gain during pregnancy, high birth weight, and gestational diabetes are associated with increased risk for later obesity. Paradoxically, intrauterine growth restriction with early infant catch-up growth is associated with the development of central adiposity and cardiovascular risk.

Body Mass Index

Health care professionals define obesity or increased adiposity using the body mass index (BMI), which is an excellent proxy for more direct measurement of body fat. BMI = weight in kg/(height in meters)². Adults with a BMI ≥30 meet the criterion for obesity, and those with a BMI 25-30 fall in the overweight range. During childhood, levels of body fat change beginning with high adiposity during infancy. Body fat levels decrease for approximately 5.5 yr until the period called adiposity rebound, when body fat is typically at the lowest level. Adiposity then increases until early adulthood (Fig. 44-1). Consequently, obesity and overweight are defined using BMI percentiles; children >2 yr old with a BMI ≥95th percentile meet the criterion for obesity, and those with a BMI between the 85th and 95th percentiles fall in the overweight range. The terminology used for pediatric obesity previously was “overweight” and “risk for overweight.” This terminology has changed to improve consistency with the adult criteria and international definitions of pediatric obesity.

Etiology

Humans have the capacity to store energy in adipose tissue, allowing improved survival in times of famine. Simplistically, obesity results from an imbalance of caloric intake and energy expenditure. Even incremental but sustained caloric excess results in excess adiposity. Individual adiposity is the result of a complex interplay among genetically determined body habitus, appetite, nutritional intake, physical activity, and energy expenditure. Environmental factors determine levels of available food, preferences for types of foods, levels of physical activity, and preferences for types of activities.

Comorbidities

Complications of pediatric obesity occur during childhood and adolescence and persist into adulthood. An important reason to prevent and treat pediatric obesity is the increased risk for morbidity and mortality later in life. The Harvard Growth Study found that boys who were overweight during adolescence were twice as likely to die from cardiovascular disease as those who had normal weight. More immediate comorbidities include type 2 diabetes, hypertension, hyperlipidemia, and nonalcoholic fatty liver disease (Table 44-2). Insulin resistance increases with increasing adiposity and independently affects lipid metabolism and cardiovascular health. Nonalcoholic fatty liver disease occurs in 10-25% of obese adolescents and can progress to cirrhosis.

Table 44-2 OBESITY-ASSOCIATED COMORBIDITIES

DISEASE	POSSIBLE SYMPTOMS	LABORATORY CRITERIA
CARDIOVASCULAR
Dyslipidemia	HDL <40, LDL >130, total cholesterol >200	Fasting total cholesterol, HDL, LDL, triglycerides
Hypertension	SBP >95% for sex, age, height	Serial testing, urinalysis, electrolytes, blood urea nitrogen, creatinine
ENDOCRINE
Type 2 diabetes mellitus	Acanthosis nigrans, polyuria, polydipsia	Fasting blood glucose >110, hemoglobin, A1c, insulin level, C-peptide, oral glucose tolerance test
Metabolic syndrome	Central adiposity, insulin resistance, dyslipidemia, hypertension, glucose intolerance	Fasting glucose, LDL and HDL cholesterol
Polycystic ovary syndrome	Irregular menses, hirsutism, acne, insulin resistance, hyperandrogenemia	Pelvic ultrasound, free testosterone, LH, FSH
GASTROINTESTINAL
Gallbladder disease	Abdominal pain, vomiting, jaundice	Ultrasound
Nonalcoholic fatty liver disease (NAFLD)	Hepatomegaly, abdominal pain, dependent edema, ↑ transaminases Can progress to fibrosis, cirrhosis

AST, ALT, ultrasound, CT, or MRI NEUROLOGIC Pseudotumor cerebri Headaches, vision changes, papilledema Cerebrospinal fluid opening pressure, CT, MRI ORTHOPEDIC Blount disease (tibia vara) Severe bowing of tibia, knee pain, limp Knee x-rays Musculoskeletal problems Back pain, joint pain, frequent strains or sprains, limp, hip pain, groin pain, leg bowing X-rays Slipped capital femoral epiphysis Hip pain, knee pain, limp, decreased mobility of hip Hip x-rays PSYCHOLOGICAL Behavioral complications Anxiety, depression, low self-esteem, disordered eating, signs of depression, worsening school performance, social isolation, problems with bullying or being bullied Child Behavior Checklist, Children’s Depression Inventory, Peds QL, Eating Disorder Inventory 2, subjective ratings of stress and depression, Behavior Assessment System for Children, Pediatric Symptom Checklist PULMONARY Asthma Shortness of breath, wheezing, coughing, exercise intolerance Pulmonary function tests, peak flow Obstructive sleep apnea Snoring, apnea, restless sleep, behavioral problems Polysomnography, hypoxia, electrolytes (respiratory acidosis with metabolic alkalosis)

ALT, alanine aminotransferase; AST, aspartate aminotransferase; CT, computed tomography; FSH, follicle-stimulating hormone; HDL, high-density lipoprotein; LDL, low-density lipoprotein; LH, luteinizing hormone; MRI, magnetic resonance imaging; Peds QL, Pediatric Quality of Life Inventory.

In adults, the combination of central obesity, hypertension, glucose intolerance, and hyperlipidemia is the metabolic syndrome. Persons with the metabolic syndrome are at increased risk for cardiovascular morbidity and mortality. Experts do not uniformly agree that this symptom cluster in the pediatric age group has prognostic significance.

There is increasing evidence that obesity may be associated with chronic inflammation. Adiponectin, a peptide with anti-inflammatory properties, occurs in reduced levels in obese patients as compared to insulin-sensitive, lean persons. Low adiponectin levels correlate with elevated levels of free fatty acids and plasma triglycerides as well as a high BMI, and high adiponectin levels correlate with peripheral insulin sensitivity. Adipocytes secrete peptides and cytokines into the circulation, and pro-inflammatory peptides such interleukin (IL)-6 and tumor necrosis factor-α (TNF-α) occur in higher levels in obese patients. Specifically, IL-6 stimulates production of C-reactive protein (CRP) in the liver. CRP is a marker of inflammation and might link obesity, coronary disease, and subclinical inflammation.

Some complications of obesity are mechanical, including obstructive sleep apnea and orthopedic complications. Orthopedic complications include Blount disease and slipped femoral capital epiphysis (Chapters 669, 670.4).

Mental health problems can coexist with obesity, with the possibility of bidirectional effects. These associations are modified by gender, ethnicity, and socioeconomic status. Self-esteem may be lower in obese adolescent girls compared to nonobese peers. Some studies have found an association between obesity and adolescent depression. There is considerable interest in the co-occurrence of eating disorders and obesity.

Identification

Overweight and obese children are often identified as part of routine medical care, and the child and family may be unaware that the child has increased adiposity. They may be unhappy with the medical provider for raising this issue and respond with denial or apparent lack of concern. It is often necessary to begin by helping the family understand the importance of healthy weight for current and future health, especially because intervention requires considerable effort by the child and the family. Forging a good therapeutic relationship is important, because obesity intervention requires a chronic disease management approach. Successful resolution of this problem necessitates considerable family and child effort over an extended period in order to change eating and activity behaviors.

Evaluation

The evaluation of the overweight or obese child begins with examination of the growth chart for weight, height, and BMI trajectories; consideration of possible medical causes of obesity; and detailed exploration of family eating, nutritional, and activity patterns. A complete pediatric history is used to uncover comorbid disorders. The family history focuses on the adiposity of other family members and the family history of obesity-associated disorders. The physical examination adds data that can lead to important diagnoses. Laboratory testing is guided by the need to identify comorbid conditions.

Examination of the growth chart reveals the severity, duration, and timing of obesity onset. Children who are overweight (BMI in the 85th-95th percentile) are less likely to have developed comorbid conditions than those who are obese (BMI ≥95th percentile). Those with a BMI ≥99th percentile are even more likely to have coexisting medical problems. Once obesity severity is determined, the BMI trajectory is examined to elucidate when the child became obese. Several periods during childhood are considered sensitive periods or times of increased risk for developing obesity, including infancy, adiposity rebound (when body fat is lowest at approximately age 5.5 years), and adolescence. Severe obesity and obesity of long duration can require more intensive family intervention unless the family is highly motivated to make dietary and activity changes. An abrupt change in BMI might signal the onset of a medical problem or a period of family or personal stress for the child. Examination of the weight trajectory can further expand understanding of how the problem developed. A young child might exhibit high weight and high height, because linear growth can increase early in childhood if a child consumes excess energy. At some point, the weight percentile exceeds the height percentile and the child’s BMI climbs into the obese range. Another example is a child whose weight rapidly increases when she reduces her activity level and consumes more meals away from home. Examination of the height trajectory can reveal endocrine problems, which often occur with slowing of linear growth.

Consideration of possible medical causes of obesity is essential, even though endocrine and genetic causes are rare (see Table 44-1). Growth hormone deficiency, hypothyroidism, and Cushing syndrome are examples of endocrine disorders that can lead to obesity. In general, these disorders manifest with slow linear growth. Because children who consume excessive amounts of calories tend to experience accelerated linear growth, short stature warrants further evaluation. Genetic disorders associated with obesity can have coexisting dysmorphic features, cognitive impairment, vision and hearing abnormalities, or short stature. In some children with congenital disorders such as myelodysplasia or muscular dystrophy, lower levels of physical activity can lead to secondary obesity. Some medications can cause excessive appetite and hyperphagia, resulting in obesity. Atypical antipsychotic medications most commonly have this dramatic side effect. Rapid weight gain in a child or adolescent taking one of these medications might require a discontinuation of that medication. Poor linear growth and rapid changes in weight gain are indications for evaluation of possible medical causes.

Exploration of family eating and nutritional and activity patterns begins with a description of regular meal and snack times and family habits for walking, bicycle riding, active recreation, television, computer, and video-game time. It is useful to request a 24-hour dietary recall with special attention to intake of fruits, vegetables, and water, as well as high-calorie foods and high-carbohydrate beverages. When possible, evaluation by a nutritionist is extremely helpful. This information will form the basis for incremental changes in eating behavior, caloric intake, and physical activity during the intervention.

Initial assessment of the overweight or obese child includes a complete review of bodily systems focusing on the possibility of comorbid conditions (see Table 44-2). Developmental delay and visual and hearing impairment can be associated with genetic disorders. Difficulty sleeping, snoring, or daytime sleepiness suggests the possibility of sleep apnea. Abdominal pain might suggest nonalcoholic fatty liver disease. Symptoms of polyuria, nocturia, or polydipsia may be the result of type 2 diabetes. Hip or knee pain can be caused by secondary orthopedic problems, including Blount disease and slipped capital femoral epiphysis. Irregular menses may be associated with polycystic ovary syndrome. Acanthosis nigricans can suggest insulin resistance and type 2 diabetes (Fig. 44-3).

The family history begins with identifying other obese family members. Parental obesity is an important risk for child obesity. If all family members are obese, focusing the intervention on the entire family is reasonable. The child may be at increased risk for developing type 2 diabetes if a family history exists. Patients of African-American, Hispanic, or Native American heritage are also at increased risk for developing type 2 diabetes. Identification of a family history of hypertension, cardiovascular disease, or metabolic syndrome indicates increased risk for developing these obesity-associated conditions. If one helps the family to understand that childhood obesity increases risk for developing these chronic diseases, this educational intervention might serve as motivation to improve their nutrition and physical activity.

Physical examination should be thorough, focusing on possible comorbid conditions (see Table 44-2). Careful screening for hypertension using an appropriately sized blood pressure cuff is important. Systematic examination of the skin can reveal acanthosis nigricans, suggesting insulin resistance, or hirsutism, suggesting polycystic ovary syndrome. Tanner staging can reveal premature adrenarche secondary to advanced sexual maturation in overweight and obese girls.

Laboratory testing for fasting plasma glucose, triglycerides, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, and liver function tests are recommended as part of the initial evaluation for newly identified pediatric obesity (Table 44-3). Overweight children (BMI 85th-95th percentile) who have a family history of diabetes mellitus or signs of insulin resistance should also be evaluated with a fasting plasma glucose test. Other laboratory testing should be guided by history or physical examination findings.

Table 44-3 NORMAL LABORATORY VALUES FOR RECOMMENDED TESTS

LABORATORY TEST	NORMAL VALUE
Glucose	<110 mg/dL
Insulin	<15 mU/L
Hemoglobin A1c	<5.7%
AST 2-8 yr	<58 U/L
AST 9-15 yr	<46 U/L
AST 15-18 yr	<35 U/L
ALT	<35 U/L
Total cholesterol	<170 mg/dL
LDL	<110 mg/dL
HDL	<35 mg/dL
Triglycerides 2-15 yr	<100 mg/dL
Triglycerides 15-19 yr	<125 mg/dL

AST, aspartate aminotransferase; ALT, alanine aminotransferase; LDL, low-density lipoprotein; HDL, high-density lipoprotein.

From Children’s Hospital of Wisconsin: The NEW (nutrition, exercise and weight management) kids program (PDF file). www.chw.org/display/displayFile.asp?docid=33670&filename=/Groups/NEWKids/08_Referral_Form.pdf. Accessed February 2, 2011.

Intervention

Successful intervention for obesity is challenging and is best accomplished using multimodal approaches to accomplish substantial lifestyle change. In adults, long-term weight loss is uncommon despite the availability of a wide variety of diet plans, commercial products, and medications. Cognitive-behavioral therapy approaches to improve motivation have been promising. A combination of nutritional advice, exercise, and cognitive behavioral approaches usually work best. Bariatric surgery can accomplish considerable weight loss in adolescents. It is not yet clear whether these patients will maintain a healthy weight permanently, and long-term safety has yet to be established.

It is important to begin with clear recommendations about appropriate caloric intake for the obese child (Table 44-4). Working with a dietitian is very helpful. Meals should be based on fruits, vegetables, whole grains, lean meat, fish, and poultry. Prepared foods should be chosen for their nutritional value, with attention to calories and fat. Foods that provide excessive calories and low nutritional value should be reserved for infrequent treats. Because many obese children are consuming calories greatly in excess of their needs, it is often impossible to achieve an immediate reduction to the recommended daily calorie level. Instead, a gradual approach is recommended. A 10 yr old child who requires 2000 kcal/day and consumes 3500 kcal/day could reduce his typical daily intake by 280 kcal by forgoing two cans of high-carbohydrate beverage and drinking water instead. Although this dietary change will not result in weight loss, it will probably result in slightly slower weight gain. Once this change has been successfully incorporated, the child could make another change such as cutting out a snack, thereby eliminating an additional 300 kcal.

Weight-reduction diets in adults generally do not lead to sustained weight loss. Therefore, the focus should be on changes that can be maintained for life. Attention to eating patterns is helpful. Families should be encouraged to plan family meals, including breakfast. It is almost impossible for a child to make changes in nutritional intake and eating patterns if other family members do not make the same changes. Dietary needs also change developmentally, as adolescents require greatly increased calories during their growth spurts, and adults who lead inactive lives need fewer calories than active and growing children.

Psychological strategies are helpful. The “traffic light” diet groups foods into those that can be consumed without any limitations (green), in moderation (yellow), or reserved for infrequent treats (red) (Table 44-5). The concrete categories are very helpful to children and families. This approach can be adapted to any ethnic group or regional cuisine. Motivational interviewing, a strategy with proven efficacy for decreasing tobacco and substance use, shows promise for assisting patients in changing their nutritional patterns. This approach begins with assessing how ready the patient is to make important behavioral changes. The professional then engages the patient in developing a strategy to take the next step toward the ultimate goal of healthy nutritional intake. This method allows the professional to take the role of a coach, helping the child and family reach their goals. Other behavioral approaches include family rules about where food may be consumed—for example, “not in the bedroom.” Evidence-based strategies can be used to tailor interventions, given individual and environmental differences.

It is very difficult to achieve weight loss by increasing physical activity alone. Nonetheless, increasing fitness improves cardiovascular health even without weight loss. Therefore, increasing physical activity can decrease risk for cardiovascular disease, improve well-being, and contribute to weight loss. Increased physical activity can be accomplished by walking to school, engaging in physical activity during leisure time with family and friends, or enrolling in organized sports. Children are more likely to be active if their parents are active. Just as family meals are recommended, family physical activity is recommended.

Active pursuits can replace more sedentary activities. The American Academy of Pediatrics recommends that screen time be restricted to no more than 2 hr/day for children >2 yr old and that children <2 yr old not watch television. Television watching is often associated with eating, and many highly caloric food products are marketed directly to children during child-oriented television programs.

Pediatric providers should assist families to develop goals to change nutritional intake and physical activity. They can also provide the child and family with needed information. The family should not expect immediate lowering of BMI percentile related to behavioral changes but can instead count on a gradual decrease in the rate of BMI percentile increase until it stabilizes, followed by a gradual decrease in BMI percentile. Referral to multidisciplinary, comprehensive pediatric weight-management programs is ideal for obese children whenever possible. As part of a comprehensive program, adolescents may receive adjunctive pharmacologic therapy. In adults, the addition of antiobesity drugs to comprehensive lifestyle modification can produce more weight loss than lifestyle modification alone, with a BMI-lowering effect of 4%. Sibutramine, a norepinephrine and serotonin reuptake inhibitor, and Orlistat, an intestinal lipase inhibitor, is as effective as adjunctive therapy to behavior modification for weight loss in overweight adolescents (Table 44-6). The effect on long-term weight maintenance is not yet known. The pediatric provider also makes referrals to specialists to treat comorbid conditions, including type 2 diabetes, hypertension, nonalcoholic fatty liver disease, and orthopedic disorders.

Table 44-6 MEDICATIONS USED FOR WEIGHT LOSS IN ADULTS

DRUG	MECHANISM OF ACTION	SIDE EFFECTS
Sibutramine*†	Appetite suppressant: combined norepinephrine and serotonin reuptake inhibitor	Modest increases in heart rate and blood pressure, nervousness, insomnia
Phentermine*†	Appetite suppressant: sympathomimetic amine	Cardiovascular, gastrointestinal
Diethylpropion*†	Appetite suppressant: sympathomimetic amine	Palpitations, tachycardia, insomnia, gastrointestinal
Orlistat*	Lipase inhibitor: decreased absorption of fat	Diarrhea, flatulence, bloating, abdominal pain, dyspepsia
Bupropion	Appetite suppressant: mechanism unknown	Paresthesia, insomnia, central nervous system effects
Fluoxetine	Appetite suppressant: selective serotonin reuptake inhibitor	Agitation, nervousness, gastrointestinal
Sertraline	Appetite suppressant: selective serotonin reuptake inhibitor	Agitation, nervousness, gastrointestinal
Topiramate	Mechanism unknown	Paresthesia, changes in taste
Zonisamide	Mechanism unknown	Somnolence, dizziness, nausea

* Approved by the U.S. Food and Drug Administration for weight loss.

^† Drug Enforcement Administration schedule IV.

From Snow V, Barry P, Fitterman N, et al: Pharmacologic and surgical management of obesity in primary care: a clinical practice guideline from the American College of Physicians, Ann Intern Med 142:525–531, 2005.

In some cases, it is reasonable to refer adolescents for evaluation for bariatric surgery. The American Pediatric Surgical Association Guidelines recommends that surgery be considered only in children with complete or near-complete skeletal maturity, a BMI ≥40, and a medical complication resulting from obesity, after they have failed 6 mo of a multidisciplinary weight management program. Current surgical approaches include the Roux-en-Y and the adjustable gastric band.

Prevention

Prevention of child and adolescent obesity is essential for public health in the USA and most other countries (Tables 44-7 and 44-8). Efforts by pediatric providers can supplement national- and community-level public health programs. The National Institutes of Health (NIH) and Centers for Disease Control and Prevention (CDC) recommend a variety of initiatives to combat the current obesigenic environment, including promotion of breast-feeding, access to fruits and vegetables, walkable communities, and 60 min/day of activity for children. The USDA sponsors programs promoting 5.5 cups of fruits and vegetables per day. Incentives for the food industry to promote consumption of healthier foods should be considered. Marketing of unhealthy foods to children has begun to be regulated. We expect to see changes in federal food programs including commodity foods, the Women, Infant, and Children Supplemental Food Program (WIC), and school-lunch programs to meet the needs of today’s children.

The Ways to Enhance Children’s Activity and Nutrition (WE CAN) program is an example of a community-based child obesity prevention effort aimed at 8- to 12-year old children. This national program, designed for families and communities, focuses on three important behaviors: improved food choices, increased physical activity, and reduced screen time. Child health professionals can serve as leaders and topic experts for community programs. Speeches at schools, at community centers, and on local radio and television programs emphasize the importance of nutrition and physical activity for health.

Pediatric prevention efforts begin with careful monitoring of weight and BMI percentiles at health care maintenance visits. Attention to changes in BMI percentiles can alert the pediatric provider to increasing adiposity before the child becomes overweight or obese. All families should be counseled about healthy nutrition for their children because the current prevalence of overweight and obesity in adults is 65%. Therefore, approximately 2/3 of all children can be considered at risk for becoming overweight or obese at some time in their lives. Those who have an obese parent are at increased risk. Prevention efforts begin with promotion of exclusive breast-feeding for 6 mo and total breast-feeding for 12 mo. Introduction of infant foods at 6 months should focus on cereals, fruits, and vegetables. Lean meats, poultry, and fish may be introduced later in the 1st year of life. Parents should be specifically counseled to avoid introducing highly sugared beverages and foods in the 1st year of life. Instead, they should expose their infants and young children to a rich variety of fruits, vegetables, grains, lean meats, poultry, and fish to facilitate acceptance of a diverse and healthy diet. Parenting matters, and authoritative parents are more likely to have children with a healthy weight than those who are authoritarian or permissive. Families who eat regularly scheduled meals together are less likely to have overweight or obese children. Child health professionals are able to address a child’s nutritional status and to provide expertise in child growth and development.

Child health professionals can also promote physical activity during regular health care maintenance visits. Parents who spend some of their leisure time in physical activity promote healthy weight in their children. Beginning in infancy, parents should be cognizant of their child’s developmental capability and need for physical activity. Because television, computer, and video-game time can replace health-promoting physical activity, physicians should counsel parents to limit screen time for their children. Snacking during television watching should be discouraged. Parents can help their children to understand that television commercials intend to sell a product. Children can learn that their parents will help them by responsibly choosing healthy foods.