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Source: Chen JT, Sheehan AH, Yanovski JA, and Calis KA. Obesity. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. Accessed July 29, 2012.

  • State of excess body fat as determined by measures of adiposity
    • Imbalance between energy intake and energy expenditure over time, resulting in increased energy storage
  • Overweight: body mass index (BMI) 25–29.9
  • Obese: BMI 30–39.9
  • Severely obese: BMI 40 and over

  • Specific etiology of obesity unknown, but multifactorial and related to varying contributions from genetic, environmental, and physiologic factors.

  • Many neurotransmitters and neuropeptides stimulate or depress brain’s appetite network, impacting total calorie intake.
  • Net balance of energy ingested relative to energy expended over time determines degree of obesity.
    • Metabolic rate largest determinant of energy expenditure.
    • Amount of physical activity contributing factor.
  • Adrenergic stimulation activates lipolysis in fat cells and increases energy expenditure in adipose tissue and skeletal muscle.
    • Major types of adipose tissue
      • White, which manufactures, stores, and releases lipid
      • Brown, which dissipates energy via uncoupled mitochondrial respiration

  • Prevalence
    • Varies by sex among racial and ethnic minorities in United States.
    • Increases with age until eighth decade
    • Increased with lower socioeconomic class and educational achievement

  • Increased level of physical activity
  • Decreased caloric intake relative to physical activity

  • Sedentary lifestyle
  • Association with other obese individuals
  • Lower socioeconomic status
  • Lower educational achievement

  • Amount of excess fat and its distribution regionally in body important clinically.
    • Central obesity reflects high levels of intra-abdominal or visceral fat associated with development of hypertension, dyslipidemia, type 2 diabetes, and cardiovascular disease.

Signs and Symptoms

  • BMI >25, calculated as weight (kg) divided by square of height (m2).
  • Waist circumference (WC) >40 inches (102 cm) for men and >35 inches (89 cm) for women (narrowest circumference between the last rib and top of iliac crest)
  • Both of above are independent predictors of disease risk (Table 1).

Table 1. Classification of Overweight and Obesity by Body Mass Index (BMI), Waist Circumference, and Associated Disease Risk

Means ...

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