• A serious, progressive, and chronic disease characterized by excess adipose tissue, typically quantified in adults by body mass index (BMI) (kg/m2), ≥30 kg/m2
  • Overweight: BMI 25.0 to 29.9 kg/m2
  • Obesity is categorized into three classes:
    • Class 1 obesity is BMI 30.0 to 34.9 kg/m2.
    • Class 2 obesity is BMI 35.0 to 39.9 kg/m2.
    • Class 3 obesity (also called severe obesity) is BMI ≥40 kg/m2.
  • Obesity is associated with negative health outcomes. Abdominal obesity increases the risk of morbidity and mortality.

Geriatric Considerations
Aging is associated with changes in body composition including sarcopenia, decreased bone mineral density, and accumulation of visceral fat.


Predominant age: Incidence rises in the early 20s and peaks at middle-aged adults 40 to 59 years old.


  • 42% of U.S. adults classify as obese, and 68.5% classify as overweight or obese (1).
  • 17% of children and adolescents (2 to 19 years old) in the United States are obese, and 32% classify as overweight or obese.

Pediatric Considerations

  • The U.S. Preventive Services Task Force (USPSTF) recommends screening for obesity in children and adolescents ≥6 years old and refer them to comprehensive, intensive behavioral interventions (grade B recommendation).
  • Pediatric classifications by age- and sex-specific WHO or CDC growth curves:
    • Overweight: BMI ≥85th to 94th percentile
    • Obesity (class I): BMI ≥95th percentile
    • Severe obesity:
      • Class II: BMI ≥120th percentile of the 95th percentile
      • Class III: BMI ≥140th percentile of the 95th percentile
  • Obesity during adolescence is strongly associated with obesity in adulthood.
  • Obesity in children is associated with mental health and psychological issues, low self-esteem, and impaired quality of life (2).

Etiology and Pathophysiology

  • Multifactorial process where genetic, environmental, behavioral, and psychosocial issues lead to an imbalance between energy intake and expenditure
  • After obesity has developed, an individual’s neuronal signaling is altered to decrease satiety (3).
  • Adipocytes (fat cells) produce peptides called adiponectin and leptin. Adiponectin improves insulin sensitivity and the absence of leptin has been associated with severe obesity.


  • Genetic syndromes such as Prader-Willi and Bardet-Biedl are found in a minority of people with obesity.
  • Multiple genes are implicated in obesity and certain genotypes may account for differences in weight loss response following dietary changes (4).

Risk Factors

  • Parental obesity
  • Sedentary lifestyle and lack of regular physical activity
  • Poor nutrition, especially consumption of calorie-dense food, and limited access to fresh produce/foods
  • Stress and mental illness

General Prevention

  • Encourage regular physical activity with a goal of at least 150 minutes of moderate activity per week (e.g., 30 minutes of exercise, 5 days per week), and a well-balanced diet with appropriate portion sizes.
  • Avoid calorie-dense and nutrient-poor foods such as sugar-sweetened beverages and processed foods.
  • Early preventive counseling, especially in children and young adults

Commonly Associated Conditions

  • Type 2 diabetes, HTN, hyperlipidemia
  • Coronary artery disease (CAD), congestive heart failure
  • Obstructive sleep apnea
  • Osteoarthritis
  • Nonalcoholic fatty liver disease
  • Mood disorders: anxiety, depression
  • Polycystic ovarian syndrome

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