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 85–94%: overweight
  • BMI 95–98% or BMI ≥30 kg/m²: obese
  • BMI ≥99%: severe obesity. Severe obesity has also been defined as BMI ≥120% of the 95th%.
• BMI reference standards are not available for children <2 years of age. In this age group, overweight is defined as weight-for-length ≥95% for age and sex.

EPIDEMIOLOGY

RISK-FACTORS

• Obesity is most often a multifactorial condition with several risk factors:
  • Parental obesity
  • Maternal obesity in pregnancy
  • Maternal history of gestational diabetes
  • Intrauterine growth retardation
  • Rapid weight gain in first 6 months of life
  • Low socioeconomic status
• Genetics
  • Obesity with developmental delay and/or dysmorphic features: Bardet- Biedl syndrome, Cohen syndrome, Prader-Willi syndrome
• Endocrine
  • Obesity with poor linear growth: Cushing syndrome, hypothyroidism

GENERAL-PREVENTION

• Encourage exclusive breastfeeding at prenatal visit 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.
• Careful attention to BMI (and weight-for-length for children <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
• 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.

ETIOLOGY

Energy imbalance

• Excessive caloric intake: calorie-rich foods and beverages consumed preferentially over nutrient-rich foods. Portion size is inappropriately large for age.
• Low-caloric expenditure: excessive sedentary time with TV, computers, video games, and handheld devices; limited daily physical activity

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)
  • Gallstones
  • Gastroesophageal reflux (GER)
• Orthopedic
  • Slipped capital femoral epiphysis (SCFE)
  • Blount disease (tibial bowing)
• Skin conditions
  • Acanthosis nigricans
  • Hirsutism
• CNS: pseudotumor cerebri
• Psychiatric
  • Binge-eating disorder
  • Mood disorder: anxiety and depression
  • Low self-esteem