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- Excess adipose tissue, typically quantified in adults by body mass index (BMI) ([kg] / [m2]), ≥30 kg/m2
- Obesity categorized into 3 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, musculoskeletal, dermatologic, mental health
- Synonym(s): overweight; adiposity
Underweight BMI (≤18) is also associated with an increased risk of mortality.
- Predominant age: Incidence rises in the early 20s.
- Predominant sex: female > male
- 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.
- Parental obesity
- Sedentary lifestyle
- Consumption of calorie-dense food
- Low socioeconomic status
- Stress and mental illness
- 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.