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 type 2 diabetes mellitus, hypertension, hyperlipidemia, heart disease, stroke, and obstructive 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

  • 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 A_1c

• 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