Chapter 9

### INTRODUCTION

Obesity is an increasingly common condition in childhood and adolescence, and it has emerged as one of the most serious public health concerns in the 21st century. The growing prevalence of childhood obesity has brought with it an increase in the incidence of obesity-related comorbid disease prior to adulthood. The profound personal and economic impacts of childhood obesity require a thorough examination of this complex topic leading to serious efforts toward prevention and early intervention.

### OBESITY

#### Definitions of Overweight and Obesity in Children

Discussion of this topic must begin with a consensus as to how overweight and obesity are to be defined in the pediatric population. Multiple different indices and techniques can be used to estimate the degree of adiposity. The most commonly used measure is body mass index (BMI), defined as kilograms (kg) of body weight per height in square meters (m2). Adults are defined as overweight if their BMI is 25.0 to 29.9 kg/m2 and obese if it is greater than 30.0 kg/m2. This index of adiposity, however, is less accurate in children that have not yet achieved full adult height. The number of children defined as obese using the adult criteria would be greatly underestimated. Therefore, the BMI percentile is a more accurate index of body mass in the pediatric age group. BMI percentile curves have been generated using data from the 2000 National Health and Nutrition Examination Survey (NHANES) and take into account both age and gender (Figures 9-1A and 9-1B). The Centers for Disease Control and Prevention (CDC) define children as overweight if the BMI is greater than 95th percentile and, at risk for overweight, if it is between the 85th and 95th percentile. The BMI percentile graphs only include children older than 2 years. For children younger than 2 years, standard weight-for-length curves can be used to assess body mass.

###### Figure 9-1

BMI percentile curves. Age- and gender-specific curves generated using data from the National Health and Nutrition Examination Survey (NHANES). (Source: National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.) A = boys and B = girls. (http://www.cdc.gov/growthcharts.)

#### Prevalence of Overweight and Obesity in Children

Multiple national surveys have indicated a significant increase in the frequency of overweight children over the past 30 years. With current prevalence of overweight and obese children ranging from 12% to 30% in developed nations and from 2% to 12% in the developing world, overnutrition is now one of the most common health problems in childhood.1 The most recent NHANES data indicate that 31.8% of American children and adolescents aged 2 ...

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