DESCRIPTION

Excess adiposity correlates closely with increased health risk for multiple medical and psychological disorders. Body mass index (BMI) is an easily obtained clinical measure to assess for increased body fat and concomitant health risks. BMI is calculated as weight in kilograms divided by height in meters squared. In children, age- and sex-specific percentiles define obesity.

• Children ≥2 years of age
  • BMI ≥85th to <95th percentile: overweight
  • BMI ≥95th percentile to <120% of the 95th percentile: class I obesity
  • BMI ≥120% of the 95th percentile or BMI ≥35: class II obesity
  • BMI ≥140% of the 95th percentile or BMI ≥40: class III obesity
• Children <2 years of age
  • Weight-for-length ≥95% for age and sex: overweight
  • Note: BMI reference standards are not available for children <2 years of age.

EPIDEMIOLOGY

Obesity prevalence based on National Health and Nutrition Examination Survey (NHANES), 2017 to 2020 data:

• Overall (children 2 to 19 years of age): 19.7%
• By age
  • 2–5 years of age: 12.7%
  • 6–11 years of age: 20.7%
  • 12–19 years of age: 22.2%
• By sex
  • Boys: 20.9%
  • Girls: 18.5%
• By race and hispanic origin
  • Hispanic children: 26.2%
  • Non-Hispanic Black children: 24.8%
  • Non-Hispanic White children: 16.6%
  • Non-Hispanic Asian children: 9.0%

RISK FACTORS

Obesity is most often a multifactorial condition with several risk factors. In addition to environmental factors such as limited access to healthful and affordable food options or exercise opportunities, risk factors include the following:

• Parental obesity
• Gestational factors
  • Maternal obesity during pregnancy
  • Maternal gestational diabetes
  • Maternal preeclampsia
  • Maternal smoking during pregnancy
  • Small for gestational age
  • Large for gestational age
  • Prematurity
• Rapid weight gain in first 6 months of life
• Behavioral factors
  • Excess calorie intake
  • Limited physical activity
  • Increased screen time or other sedentary activities
• Genetics
  • Syndromes in which obesity is a primary manifestation: Bardet-Biedl syndrome, Beckwith-Wiedemann Syndrome, Cohen syndrome, Prader-Willi syndrome
• Endocrine
  • Obesity with poor linear growth: Cushing syndrome, hypothyroidism, growth hormone deficiency, pseudohypoparathyroidism type Ia

GENERAL PREVENTION

• Encourage exclusive breastfeeding and support breastfeeding throughout the 1st year of life.
• In formula-fed infants, watch for signs of overfeeding and rapid weight gain in 1st year of life. Educate families on the difference between hunger and oral suck reflex. Avoid rice cereal in the bottle.
• Recognize parental obesity as a significant risk.
• Incorporate early nutrition and activity counseling including supervised tummy time for infants.
• Careful attention to BMI (and weight-for-length for children aged <2 years) with intensive counseling for children crossing percentiles
• Stress importance of portion size and nutrient-rich foods (fruits and vegetables) as infants transition to a solid diet.
• Limit sugar-sweetened beverage intake and avoid fruit juice for infants aged <1 year.
• Daily physical activity; limit screen time.

PATHOPHYSIOLOGY

Complex interaction between genetics, hormones, environment, and behavior

• Short-term energy regulation: adaptation of meal size in response to energy needs; hypothalamic neurons modulate sensitivity of nucleus tractus solitarius (NTS) neurons to satiety signals adjusting for changes in body fat mass.
• Long-term energy regulation: Hypothalamus senses and integrates energy balance signals including hormones such as insulin, leptin, ghrelin, and nutrients such as fatty acids, amino acids, and glucose.
  • Leptin
    • A negative feedback regulator—plays an important role in energy homeostasis
    • Communicates to hypothalamus changes in energy balance and fuel stored as fat
    • Increased fat mass results in increased leptin signaling which limits energy intake and supports energy expenditure.
    • Decreased leptin promotes increased food intake, positive energy balance, and fat accumulation.
  • Ghrelin
    • Derived from the stomach, it is the only known peripherally acting orexigenic hormone. It stimulates appetite.
    • All other gut-derived hormones are anorectic and limit food, optimize digestion and absorption, and avoid overfeeding.
  • Adiponectin
    • Insulin sensitizing, anti-inflammatory, and antiatherogenic
    • Increased visceral fat results in reduced levels of adiponectin and increased proinflammatory milieu leading to insulin resistance and endothelial dysfunction. This predisposes to metabolic syndrome, diabetes, and atherosclerosis.

COMMONLY ASSOCIATED CONDITIONS

• Endocrine: type 2 diabetes mellitus, metabolic syndrome, polycystic ovarian syndrome (PCOS), low vitamin D level
• Cardiovascular: hypertension, dyslipidemia
• Respiratory: sleep apnea, asthma
• Gastrointestinal: nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), cholelithiasis (gallstones),gastroesophageal reflux (GER)
• Orthopedic: slipped capital femoral epiphysis (SCFE), Blount disease (tibial bowing)
• Dermatologic: acanthosis nigricans, hirsutism
• Neurologic: pseudotumor cerebri
• Psychiatric: Binge eating disorder, mood disorder (anxiety and depression), low self-esteem