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For further information, see CMDT Part 29-04: Obesity

Key Features

Essentials of Diagnosis

  • Excess adipose tissue; body mass index (BMI) ≥ 30

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

  • Many associated comorbid conditions, including diabetes mellitus, hypertension, hyperlipidemia, heart disease, stroke, and sleep apnea

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) have a greater risk of weight-related comorbid conditions and early death than patients with the same BMI and lower ratios

  • Upper body obesity (excess fat around the waist and flank) is a greater health hazard than lower body obesity (fat in the thighs and buttocks)

  • Visceral fat within the abdominal cavity is more hazardous to health than subcutaneous fat around the abdomen

Demographics

  • US survey data indicate that almost 40% of Americans have obesity

  • Both genetic and environmental factors contribute to the development of obesity

  • Twin studies have demonstrated that genetics account for 50–90% of the variation in BMI

  • Only a small percentage of human obesity is thought to be due to single gene mutations

  • Most human obesity develops from the interactions of multiple genes, environmental factors, and behaviors

  • The rapid increase in obesity in the last several decades points to major roles for environmental and behavioral factors in its development

Clinical Findings

  • Historical information about the following should be obtained:

    • Age at onset

    • Recent weight changes

    • Family history of obesity

    • Occupational history

    • Eating and exercise behavior

    • Cigarette and alcohol use

    • Previous weight loss experience

    • Psychosocial factors, including assessment for depression and eating disorders

  • Physical examination should assess the

    • BMI

    • Degree and distribution of body fat

    • Overall nutritional status

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

Diagnosis

  • Blood pressure

  • Waist circumference

  • Fasting serum glucose and hemoglobin A1c

  • Comprehensive metabolic profile

  • Lipid panel

Treatment

Medications

  • Can be considered in patients with a BMI ≥ 30 or a BMI ≥ 27 plus weight-related comorbidities

  • The most widely prescribed antiobesity medications approved by the FDA (Table 29–2) are

    • Phentermine

    • Orlistat

    • Phentermine/topiramate extended release (ER)

    • Lorcaserin

    • Naltrexone sustained release (SR)/bupropion SR

    • Liraglutide

Table 29–2.Medications tested in clinical trials for treatment of obesity.

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