Obesity

Key Features

Essentials of Diagnosis

• Disorder of energy homeostasis; body mass index (BMI) ≥ 30

• Central obesity (abdomen and flank) is a greater health risk than excess weight in the lower body (buttocks and thighs)

• Over 200 health conditions are more prevalent in patients with obesity; associated comorbidities include

  • Diabetes mellitus

  • Hypertension

  • Hyperlipidemia

  • Heart disease

  • Stroke

  • Sleep apnea

  • Many cancers

  • Major depression and binge eating disorder

General Considerations

• Quantitative evaluation involves determination of BMI

• BMI accurately reflects the presence of excess adipose tissue but does not reflect body composition; it is calculated by dividing measured body weight in kilograms by 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

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

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

Demographics

• Over 40% of Americans have obesity

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

• Twin studies demonstrate that genetics account for 40–90% of variation in BMI

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

• Most 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

• Medical history should determine the following:

  • Age at onset of weight gain

  • 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 mood and eating disorders

• Physical examination should assess

  • BMI

  • Degree and distribution of body fat

  • Overall nutritional status

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

Diagnosis

• Blood pressure

• Waist circumference

• Fasting serum glucose and hemoglobin A_1c

• Comprehensive metabolic profile

• Lipid panel

Treatment

Medications

• Medications approved for weight management should be viewed as additions to diet and exercise for patients who have been unsuccessful with lifestyle changes alone

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

• The ...