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INTRODUCTION AND EPIDEMIOLOGY

Since 1980, worldwide obesity has more than doubled. In 2008, more than 1.4 billion adults, age 20 and older, were overweight. Of these, over 200 million men and nearly 300 million women were obese. Sixty-five percent of the world population resides in countries where overweight and obesity kill more people than underweight. In 2010, more than 40 million children under the age of 5 were overweight.1

In children, an age- and sex-specific percentile for body mass index (BMI) determines weight status rather than the BMI categories used for adults, because children’s body composition varies as they age and varies between boys and girls.

The Centers for Disease Control and Prevention uses a BMI threshold of above the 85th percentile to define overweight and above the 95th percentile to define obese, compared to children of the same age and sex.2 The World Health Organization defines overweight as a BMI ≥25 kg/m2, whereas obesity is defined as a BMI ≥30 kg/m2.1

Care for bariatric surgery patients is discussed in Chapter 87, “Complications of General Surgical Procedures.”

PATHOPHYSIOLOGY

Obesity is an independent risk factor for acute coronary syndrome, especially in those <40 years old.3,4 Atypical symptoms may pose a problem with acute coronary syndrome diagnosis.5,6 Approximately 11% of cases of congestive heart failure are attributable to obesity alone.7 The physical deconditioning of obesity manifests with orthopnea, dyspnea, and lower extremity swelling mimicking acute congestive heart failure. Plain chest radiograph findings of congestive heart failure may be obscured by redundant overlying soft tissue and hypoventilation artifact. Brain natriuretic peptide levels are lower in the obese patient than in the nonobese.8,9 Cardiomyopathy may affect up to 10% of patients with a BMI >40 kg/m2.10 Obesity is a risk factor for venous thromboembolism11 and its recurrence once anticoagulation therapy is withdrawn.12

The increased prevalence of type 2 diabetes is closely linked to the upsurge in obesity. Excess weight accounts for 90% of type 2 diabetes.13 Obesity is strongly associated with insulin resistance in normoglycemic persons and in individuals with type 2 diabetes.14

The accumulation of fat impairs the function of ventilation in obese children and adults.15-17 Reductions in forced expiratory volume in 1 second, forced vital capacity,15,16 total lung capacity, functional residual capacity, and expiratory reserve volume are associated with increasing BMI.18

Obesity is a well-recognized risk factor for obstructive sleep apnea. Forty percent of people who are obese have obstructive sleep apnea, and approximately 70% of people with obstructive sleep apnea are obese.19

Increased fat deposition in the pharyngeal area along with reduced operating lung volumes associated with obesity reduce upper airway caliber, modifying airway configuration, which in turn ...

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