Chapter 21

### INTRODUCTION

One in 6 children in the United States is obese.1 While previous studies in adults have demonstrated obesity as an important comorbid condition that can complicate care, obesity is often underrecognized and consequently overlooked as a comorbidity in children.2 An understanding of how obesity affects children and their care in the pediatric intensive care unit (PICU) is essential.

The chapter starts with obesity definitions and epidemiology. Key physiologic changes seen in obesity that may affect the critically ill pediatric patient are reviewed. Comorbidities seen in obese patients are discussed, and a focused section on the challenges of caring for these patients in the PICU is included. The chapter ends with considerations for nutrition care for the critically ill obese pediatric patient.

### DEFINITIONS

Obesity is defined as excess body fat. Body mass index (BMI) is a readily available proxy for body fatness, based on body weight adjusted for height. The formula is weight in kilograms divided by the square of height in meters: BMI=weight (kg)/(height (m))2. Body mass index is not a direct measure of body fat, but it correlates strongly with percent body fat in adults; the correlation is somewhat less strong in children.3

Because of the impact of growth and changing body composition in children, the Centers for Disease Control and Prevention (CDC) define obesity differently for adults and children. Obesity in adults is defined as a BMI greater than 30 kg/m2, whereas obesity in a patient 2 years to 19 years is defined as a BMI at the 95th percentile or higher, adjusted for age and gender. Of note, there are older adolescent patients where the 95th percentile BMI is greater than a BMI of 30 kg/m2, so obesity for the older adolescent is defined as a BMI at or above the 95th percentile or a BMI ≥30 kg/m2, whichever is lower.3 Of particular relevance to the discussion in this chapter is the issue of severe obesity. Using the BMI cutoff of 95th percentile does not distinguish degree of severity, yet children with BMI Z-score 3 and above have been shown to have strikingly greater risk for cardiovascular and metabolic comorbidities.4 The Expert Committee thus advocated for a category of “severe obesity” to designate children with BMI ≥99th percentile for age. For children under the age of 2, normative values for BMI have not been established. Weight-for-length values above the 95th percentile are used to define overweight in this age group; the term obesity is not used.3, 5

### EPIDEMIOLOGY

In the United States, the prevalence of overweight for infants and toddlers from birth to 2 years of age is 9.7%.1 The prevalence of obesity for children in the United States has increased dramatically in the past 40 years. However, the most recent study in ...

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