Chapter 298: The Patient With Morbid Obesity

INTRODUCTION AND EPIDEMIOLOGY

Since 1980, worldwide obesity has more than doubled. In 2008, more than 1.4 billion adults, 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 defines overweight as a BMI at or above the 85th percentile and lower than the 95th percentile for children of the same age and sex.² Obesity is a BMI at or above the 95th percentile for children of the same age and sex.² The World Health Organization definition is as follows: a BMI ≥25 is overweight, whereas a BMI ≥30 is obesity.¹

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 About 11% of cases of congestive heart failure are attribuTable to obesity alone.⁷ The physical deconditioning of obesity manifest by orthopnea, dyspnea, and lower extremity swelling is very similar to symptoms of acute congestive heart failure, making diagnosis problematic. Plain chest x-ray findings of congestive heart failure may be obscured by redundant overlying soft tissue and hypoventilation. 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 and those with a long duration of significant obesity.¹⁰ Obesity is a risk factor for venous thromboembolism¹¹ and its recurrence once anticoagulation therapy is withdrawn.¹²

The increase in the prevalence of type 2 diabetes is closely linked to the upsurge in obesity. About 90% of type 2 diabetes is attribuTable to excess weight.¹³ Obesity has been 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.^15,16,17 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 ...