Obesity is a topic covered in the 5-Minute Clinical Consult.

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  • Excess adipose tissue, typically quantified in adults by body mass index (BMI) ([kg] / [m2]), ≥30 kg/m2
  • Obesity categorized into three classes:
    • Class 1 obesity is BMI 30 to 34.9 kg/m2.
    • Class 2 obesity is BMI 35 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.
  • System(s) affected: endocrine/metabolic, cardiac, respiratory, gastrointestinal (GI), musculoskeletal, dermatologic, mental health
  • Synonym(s): overweight; adiposity

Geriatric Considerations
Underweight BMI (≤18) is also associated with an increased risk of mortality.


  • Predominant age: Incidence rises in the early 20s.
  • Predominant sex: female > male

  • 35% of U.S. adults are obese (1,2).
  • 40% of men and 25% of women are overweight.
Pediatric Considerations
  • The USPSTF recommends that clinicians screen for obesity in children and adolescents ≥6 years and refer them to comprehensive, intensive behavioral interventions to promote improvements in weight status (grade B recommendation).
  • Pediatric obesity is defined as a BMI ≥95th percentile, by age- and sex-specific WHO or CDC growth curves.
  • Obesity during adolescence and young adulthood is strongly associated with obesity in adulthood.

Etiology and Pathophysiology

  • Obesity is caused by an imbalance between food intake, absorption, and energy expenditure.
  • Underlying organic causes include psychiatric disturbances, hypothyroidism, hypothalamic disorders, insulinoma, and Cushing syndrome. It is likely that an individual’s gut microbiome may cause obesity and/or make it difficult to lose weight.
  • Medications that contribute to obesity include corticosteroids, neuroleptics (particularly atypical antipsychotics), and antidepressants.

  • Genetic syndromes such as Prader-Willi and Bardet-Biedl are found in a minority of people with obesity.
  • Multiple genes are implicated in obesity.

Risk Factors

  • Parental obesity
  • Sedentary lifestyle
  • Consumption of calorie-dense food
  • Low socioeconomic status
  • Stress and mental illness
  • Medications

General Prevention

  • Encourage at least 1 hour of daily exercise, limited television viewing, and moderation in portion size.
  • Avoid calorie-dense and nutrient-poor foods such as sugar-sweetened beverages and processed foods.

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