What is the etiology, epidemiology, pathophysiology, presentation, diagnosis, treatment, prognosis, prevention, and patient education for childhood obesity in individuals under 18?

Childhood Obesity: Comprehensive Clinical Overview

Etiology and Epidemiology

Overall Prevalence

Currently, approximately 17-21% of children aged 2-19 years in the United States have obesity (BMI ≥95th percentile), with severe obesity (BMI ≥120% of 95th percentile or ≥35 kg/m²) affecting 4-6% of this population. 1, 2

• Using the BMI ≥99th percentile cutoff, prevalence is approximately 4% across age groups 2-19 years 1
• When applying BMI ≥120% of 95th percentile criteria, prevalence ranges from 4.6% (NHANES 1999-2006) to 6.4% (California health plan 2007-2008) 1
• Approximately 1.3% of adolescents aged 12-19 years have BMI ≥40 kg/m² 1

Age-Specific Patterns

• Preschoolers (2-5 years): 2.2-4.7% prevalence of severe obesity depending on definition used 1
• School-age children (6-11 years): 4.0-7.4% prevalence 1
• Adolescents (12-19 years): 3.4-7.7% prevalence, with higher rates in older adolescents 1

Racial and Ethnic Disparities

Hispanic and non-Hispanic Black youth consistently demonstrate higher prevalence rates across all definitions of obesity. 1

• Hispanic youth: 5.2-7.9% prevalence of severe obesity 1
• Non-Hispanic Black youth: 5.8-8.7% prevalence 1
• Non-Hispanic White youth: 3.1-3.8% prevalence 1
• Among middle school students, Black girls show 8.7% prevalence compared to 4.1% in White girls 1

Socioeconomic Factors

• Children with poverty-income ratio (PIR) <1 have 4.3% prevalence of severe obesity 1
• Those with PIR >3 have 2.5% prevalence 1
• For extreme obesity (BMI ≥40 kg/m²), prevalence is 2.0% in lowest income groups versus 0.8% in highest 1

Etiological Factors

Childhood obesity results from an energy imbalance where excess caloric intake exceeds caloric expenditure, influenced by biological, developmental, environmental, behavioral, and genetic factors. 3

• Adiposity rebound (AR) in early childhood serves as a critical risk factor for obesity in adolescence and adulthood 3
• Lifestyle changes over recent decades have led to decreased physical activity and increased consumption of calorie-dense foods 4
• Genetic, metabolic, environmental, and social determinants contribute to the multifactorial etiology 5

Pathophysiology

Obesity represents a complex, chronic disease involving dysregulation of energy homeostasis with progressive potential for end-organ damage. 5

• Excess adipose tissue accumulation leads to insulin resistance as a primary metabolic derangement 2
• Adiposity triggers inflammatory cascades that contribute to cardiovascular and metabolic complications 3
• The condition involves alterations in metabolism, hormonal regulation, and cellular function beyond simple energy storage 5

Clinical Presentation

Diagnostic Criteria

Obesity in children is defined as BMI ≥95th percentile for age and sex, while severe obesity is defined as BMI ≥120% of the 95th percentile or absolute BMI ≥35 kg/m², whichever is lower. 5, 1

• Overweight is defined as BMI between 85th-94th percentiles 1
• BMI percentiles must be calculated using age- and sex-specific growth charts because BMI distribution changes throughout childhood 1
• Electronic health record programs can automatically calculate and plot BMI percentiles 1

Associated Comorbidities

Children with obesity present with multiple serious comorbidities that were previously seen primarily in adults. 3, 6

Cardiovascular Risk Factors

• Hypertension: Blood pressure should be compared with norms for gender, age, and height published by the National Heart, Lung and Blood Institute 1
• Dyslipidemia: Screen starting at age 2 years if obesity is present, with abnormal values confirmed 2 weeks to 3 months after initial screen 1

Metabolic Complications

• Type 2 Diabetes Mellitus: Screen with fasting glucose starting at age 10 years for children with obesity and 2 other diabetes risk factors 1
• Insulin resistance develops as a primary metabolic consequence 2
• Metabolic syndrome clustering occurs more frequently in severe obesity 7

Hepatic Disease

• Non-alcoholic Fatty Liver Disease (NAFLD): Prevalence of 9% among all children, with significantly higher risk in obese children 1
• Screen children with obesity aged 9-11 years for NAFLD, coincident with lipid and diabetes screening 1
• Screening in younger children may be appropriate when risk is high 1

Respiratory Complications

• Obstructive Sleep Apnea (OSA): Severe obesity significantly increases OSA risk compared to less extreme obesity 8
• A STOP-BANG score of 3 in severely obese adolescents indicates intermediate risk and warrants polysomnography 8

Orthopedic Problems

• Musculoskeletal complications are common in obese children 1, 2

Psychosocial Issues

Children and adolescents with obesity face significant mental health risks including depression, poor self-esteem, and bullying regardless of demographics or social standing. 1

• Psychosocial disturbances and impaired quality of life are prevalent 6
• Risk of developing eating disorders (Bulimia Nervosa, Binge-Eating Disorder, Night Eating Syndrome, or Anorexia Nervosa) when attempting dietary restriction 3

Diagnosis

Clinical Assessment

Assessment begins with accurate BMI calculation using age- and sex-specific percentiles, followed by systematic evaluation for comorbidities. 1

• Calculate BMI and plot on CDC growth charts (available at cdc.gov/growthcharts/cdc_charts.htm) 1
• Measure blood pressure and compare to age-, sex-, and height-specific norms 1

Laboratory Screening

All children with obesity require comprehensive metabolic screening starting at specific age thresholds. 1

• Lipid panel: Begin at age 2 years if obesity is present 1
• Fasting glucose: Begin at age 10 years for children with obesity plus 2 additional diabetes risk factors 1
• NAFLD screening: Begin at ages 9-11 years, coincident with lipid and diabetes screening 1

Sleep Evaluation

• Polysomnography remains the gold standard for OSA diagnosis in high-risk patients 8
• Home sleep apnea testing may be considered if in-laboratory polysomnography is not readily available 8
• STOP-BANG questionnaire has high sensitivity but low specificity and was primarily validated in middle-aged males, limiting accuracy in adolescent females 8

Psychosocial Assessment

• Screen for depression, self-esteem issues, and history of bullying 1
• Evaluate for eating disorder behaviors 3

Treatment

Behavioral Interventions (First-Line)

Multicomponent lifestyle modification therapy addressing diet, physical activity, and behavior change strategies represents first-line treatment, requiring at least 25-75 hours of contact over 6 months to achieve modest BMI reductions of approximately 3%. 1, 2

Dietary Recommendations

• MyPlate method serves as the core approach for the entire family, incorporating low added sugar, moderate balanced fats, adequate dairy, appropriate whole grains, proteins, fruits and vegetables, and appropriate portion sizes 1
• Eliminate sugar-sweetened beverages, which can lead to marked reductions in daily caloric intake and improve weight in the short term 1
• Avoid highly restrictive diets in preadolescents as rapid weight loss can delay linear growth 1

Physical Activity

• All children should engage in 60 minutes of moderate to vigorous activity daily 1
• Unstructured play provides effective activity opportunities 1

Family Involvement

Parent involvement in weight management programs, especially when focusing on both parent and child weight, significantly improves success. 1

• Parents control the food and electronic "screen" environment, particularly for younger children 1
• Parents must be motivated and have time and resources for program participation 1

Treatment Outcomes and Limitations

Lifestyle modification therapy alone produces modest, non-durable results in severe obesity, with benefits typically disappearing within 1 year after intervention ends. 1

• In one study, children in intensive intervention decreased percent overweight by 7.6% versus 0.7% in usual care at 6 months, but differences disappeared by 18 months 1
• Mean BMI z-score returned to baseline in those with severe obesity who completed 12-month intervention 1
• Younger children (aged 6-9 years) with severe obesity fare better than adolescents (aged 14-16 years), with only 2% of severely obese adolescents achieving BMI standard deviation score reduction ≥0.5 at 3 years 1
• Outcomes improve when lifestyle modification therapy is instituted early in childhood 1

Pharmacotherapy

Newer antiobesity medications combined with lifestyle modification can reduce mean BMI by approximately 5-17% at 1 year, with severe adverse events being rare. 2

GLP-1 Agonists

• Liraglutide and semaglutide have demonstrated success in effective weight loss in obese adolescents and pediatric patients 3
• These medications show emerging efficacy from interventional drug trials 3

Phentermine/Topiramate

• Combination therapy achieves significant BMI reductions when added to lifestyle modification 2

Metformin

• Evaluated for weight loss in numerous pediatric studies but lacks FDA approval for this indication in children and adolescents 1
• Available as shorter-acting twice-daily tablet or extended-release once-daily formulation 1
• Most studies show modest reductions in body weight and/or BMI, though many did not specify weight change as primary endpoint 1
• Only 3 randomized controlled trials identified BMI change as primary efficacy endpoint 1

Important Limitation

• Limited data exists on efficacy and safety of most weight-loss medications in children and adolescents 3

Metabolic and Bariatric Surgery

Surgery represents the most effective intervention for adolescents with severe obesity (BMI ≥120% of 95th percentile), achieving approximately 30% BMI reduction at 1 year. 2

• Approximately 6% of US adolescents are severely obese and may be candidates for bariatric surgery 3
• Roux-en-Y gastric bypass and vertical sleeve gastrectomy are the primary procedures 2
• Minor perioperative complications occur in approximately 15% of patients 2
• Major complications (reoperation, hospital readmission for dehydration) occur in approximately 8% of patients 2

Alternative Approaches

• Inpatient therapy (diet, physical activity, psychosocial support) shows relatively large BMI reductions but has limited clinical relevance due to few existing programs and limited access 1
• Meal replacement programs have been assessed with variable results 1

Prognosis

Obese children are highly likely to continue obesity into adulthood, with tracking of adiposity being extremely strong, particularly in those with severe obesity. 1

• Obesity during adolescence is associated with increased risk of mortality from cardiovascular disease and type 2 diabetes in adulthood 2
• Children with severe obesity face markedly worse healthcare outcomes and heightened levels of risk 1
• Most treatment programs lead to brief weight loss followed by rapid re-accumulation after therapy termination 6
• Long-term durability of all obesity treatments requires future research 2

Prevention

Prevention represents the key strategy for controlling childhood obesity, as established obesity is often refractory to treatment. 6, 9

Primary Prevention

• Educate children and families from a young age through adulthood 9
• Encourage appropriate diet and exercise habits early 9
• Promote healthy diet, regular physical activity, and lifestyle modification 6
• Parents should engage in school and community programs that improve children's nutritional status and physical activity 6

Secondary Prevention

• Target interventions to lessen effects of existing childhood obesity 9
• Prevent continuation of unhealthy habits and obesity into adulthood 9
• Combination of primary and secondary prevention is necessary for best results 9

Patient and Family Education

Parents play a major role in adapting children to a healthy environment and must be actively involved in all aspects of obesity management. 4

• Assess nutritional adequacy of what the child consumes versus recommended diet 4
• Encourage inclusion of any form of physical activity in daily routine 4
• Address the reality that overweight children struggle with physical exercise and require support 4
• Educate families that obesity is a complex, chronic disease requiring ongoing medical attention 5
• Emphasize that prevention is more effective than treatment once obesity is established 6, 9