Chapter 10: Obesity and Related Disorders

INTRODUCTION

Obesity is an increasingly common condition in childhood and adolescence and 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 comorbidities prior to adulthood. The profound personal and economic impacts of childhood obesity require a thorough examination of this complex topic as well as serious efforts toward prevention and early intervention.

OBESITY

Definitions of Overweight and Obesity in Children

Discussion of childhood obesity requires a consensus regarding the definition of overweight and obesity in the pediatric population. Multiple different indices and techniques have been used to estimate the degree of adiposity. The generally accepted measure for clinical screening of overweight or obesity in children and adolescents is age- and sex-adjusted body mass index (BMI), defined as kilograms (kg) of body weight per height in square meters (m²), plotted on US Centers for Disease Control and Prevention (CDC) growth charts.^1-3 Adults are defined as overweight if their BMI is 25.0 to 29.9 kg/m² and obese if BMI is greater than 30.0 kg/m². This index of adiposity, however, is inaccurate in children who have not yet achieved full adult height and underestimates obesity when applied to youth. The CDC therefore define youth as overweight if the BMI is greater than 85th percentile, obesity as BMI for-age/sex more than or equal to 95th percentile but less than 120% of the 95th percentile (Class I obesity), and severe obesity is defined as either (1) BMI-for-age/sex more than or equal to 120% of the 95th percentile (Class II) or (2) BMI-for-age/sex more than or equal to 140% of the 95th percentile (Class III).^4,5 The BMI percentile graphs only include youth older than 2 years. For children younger than 2 years, standard weight-for-length curves can be used to assess body mass (Figure 10-1).

Prevalence of Overweight and Obesity in Children

Multiple national surveys have indicated a significant increase in the frequency of youth with overweight over the past 30 years. With a current prevalence of youth with overweight and obesity 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.⁶ Although there was a significant increase in the prevalence of obesity in the 1980s and 1990s, continued large increases were not seen in the NHANES data ...