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Key Features

Essentials of Diagnosis

  • Excess adipose tissue; body mass index (BMI) = weight (in kg)/height (in m2) > 30

  • Associated with health consequences, including diabetes mellitus, hypertension, and hyperlipidemia

  • Upper body obesity (abdomen and flank) of greater health consequence than lower body obesity (buttocks and thighs)

General Considerations

  • Quantitative evaluation involves determination of BMI

  • BMI accurately reflects the presence of excess adipose tissue; it is calculated by dividing measured body weight in kilograms by the height in meters squared

    • Normal: BMI = 18.5–24.9

    • Overweight: BMI = 25–29.9

    • Class I obesity: BMI = 30–34.9

    • Class II obesity: BMI = 35–39.9

    • Class III (extreme) obesity: BMI > 40

  • Increased abdominal circumference (> 102 cm in men and > 88 cm in women) or high waist/hip ratios (> 1.0 in men and > 0.85 in women) confers greater risk of

    • Diabetes mellitus

    • Stroke

    • Coronary artery disease

    • Early death

  • Associated with significant increases in morbidity and mortality

  • Surgical and obstetric risks greater

  • The relative risk associated with obesity decreases with age, and excess weight is no longer a risk factor in adults aged > 75


  • 68% of Americans are overweight

  • 33.8% of Americans are obese

  • Approximately 60% of individuals with obesity in the United States have the metabolic syndrome

  • As much as 40–70% of obesity may be explained by genetic influences

Clinical Findings

Symptoms and Signs

  • Assess body mass index

  • Assess degree and distribution of body fat

  • Assess overall nutritional status

  • Signs of secondary causes of obesity (hypothyroidism and Cushing syndrome) are found in < 1%

Differential Diagnosis

  • Increased caloric intake

  • Fluid retention: heart failure, cirrhosis, nephrotic syndrome

  • Cushing syndrome

  • Hypothyroidism

  • Diabetes mellitus (type 2)

  • Drugs, eg, antipsychotics, antidepressants, corticosteroids

  • Insulinoma

  • Depression

  • Binge eating disorder


Laboratory Tests

  • Endocrinologic evaluation, including serum thyroid-stimulating hormone and dexamethasone suppression test in obese patients with unexplained recent weight gain or clinical features of endocrinopathy, or both

  • Assessment for medical consequences and metabolic syndrome

    • Blood pressure

    • Fasting glucose

    • Low-density (LDL) and high-density cholesterol (HDL)

    • Triglyceride levels

Diagnostic Procedures

  • Calculation of BMI

  • Measurement of waist circumference



  • Catecholaminergic or serotonergic medications

    • Sometimes used in patients with BMI > 30 or patients with BMI > 27 who have obesity-related health risks

    • Average weight loss approximately 3–5 kg more than placebo

    • No evidence of long-term benefit

  • Catecholaminergic medications

    • Amphetamines (high abuse potential)

    • Nonamphetamine schedule IV appetite suppressants (phentermine, diethylpropion, benzaphetamine, and phendimetrazine) are approved for short-term use only and have limited utility

  • Orlistat, 120 mg orally three times daily with meals

    • Reduces fat absorption in the gastrointestinal tract by inhibiting intestinal lipase

    • Side effects include diarrhea, gas, and cramping and perhaps reduced absorption ...

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