Textbook of Obesity

Biological, Psychological and Cultural Influences

Sharon R. Akabas, Sally Ann Lederman, Barbara J. Moore, Sharon R. Akabas, Sally Ann Lederman, Barbara J. Moore

• Publisher: Wiley-Blackwell
• Year: 2012
• ISBN:
  9781118318386
• Edition: 1
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

Textbook of Obesity is designed to cover all of the essential elements concerning the etiology, prevention and treatment of obesity suitable for students in nutrition, dietetics and health science courses. Providing core knowledge for students is an essential and urgent requirement to ensure that those graduating will be properly equipped to deal with the high prevalence of overweight and obesity, currently affecting almost two-thirds of the population of the USA and with prevalence in much of the rest of the world rapidly catching up.

This landmark text is organized into 5 parts comprising 27 chapters, each carefully written in a user-friendly style by experts in the area. Part I helps the reader to understand the scope and complexity of the problem of obesity. Part II focuses on obesity etiology. Part III examines the health consequences of obesity for both children and adults. Part IV discusses the challenge of assessing obesity in humans and offers insights into community factors that influence the risk of obesity. Finally, Part V dedicates 13 chapters to a discussion of a wide variety of obesity prevention and treatment interventions that are currently in use.

Textbook of Obesity is an essential purchase for students and the many health professionals dealing with obesity on a day-to-day basis. A dedicated companion website features an extensive bank of questions and answers for readers to test their understanding, and all of the book's illustrations for instructors to download: www.wiley.com/go/akabas/obesity

Part I
Understanding the Scope

Introduction

Part I, Understanding the Scope, covers broad topics and includes the epidemiology, etiology, and consequences of obesity, as well as its cultural and psychodynamic perspectives. Currently, worldwide, there are about 1 billion overweight people, 300,000 of whom are obese, and more than two-thirds of the US population are now overweight or obese. Since obesity contributes to several chronic diseases, it has become a major public health problem. This first part will also consider what can be learned from other public health initiatives (e.g., smoking) to stem the tide of overweight and obesity.

Chapter 1, Epidemiology, Etiology, and Consequences of Obesity, an overview for the entire book, presents current definitions of obesity, epidemiological data on the growing prevalence of obesity and its consequences, and some of its putative causes. The chapter systematically explains the definition of overweight and obesity and the contribution of the amount and distribution of body fat to the development of type 2 diabetes, heart disease, and other chronic diseases related to obesity. A review of etiological factors reveals that many factors combine to create positive energy balance. Hence, it is difficult to measure the contribution of any one factor.

Chapter 2, Cultural Attitudes and Biases Toward the Obese, addresses the pervasive existence of weight bias in western cultures This bias is harmful to children and adults; for the rates of weight bias are similar to or higher than other forms of discrimination, such as racial discrimination. The consequences of weight bias can be severe and enduring; they include impaired mood, low self-esteem, and, in some cases, suicidal ideation. Though high to begin with, the rates of weight bias are increasing, and the chapter emphasizes the need for research to understand and reverse the trend.

Chapter 3, The Application of Public Health Lessons to Stemming the Obesity Epidemic, places obesity in the context of other major public health challenges. The goal of this chapter is to focus on successes achieved in these other spheres, including tobacco control, injury prevention, and underage alcohol use, and to apply the lessons learned to obesity prevention models. The chapter reviews models of health behavior and planning that diagnose problems, identify contributing factors, and develop interventions to solve the problem. Obesity prevention, especially childhood obesity prevention, views the individual in the larger context of the family, community, and society. This “ecologic framework” has proven utility in other public health interventions and will likely have utility in obesity prevention. The approach will lead to interventions that balance targeted approaches to individuals, and emphasis on changing the broader environment in which they live.

Chapter 4, Psychodynamic Approaches to the Treatment of Obesity, addresses the psychological impact of obesity in US society. Building on the phenomena described in Chapter 2, this chapter focuses on the impact of the puritanical roots in US society and the idea that with sufficient effort and focus, anything, including thinness, is achievable. With this framework, obesity is seen as a moral failure. Perhaps even more striking is the fact that obese people perceive themselves as a failure; this can begin in childhood and persist into adulthood. The chapter focuses on the psychological meaning of food, appetite, and weight. In addition, the psychological consequences of recidivism and weight regain are addressed.

Collectively, these four chapters set the stage for understanding the global trends in obesity, and its etiological, cultural, and psychological factors. It also creates a framework for thinking about how the obesity epidemic is both similar to, yet different from, other major public health challenges.

1

Epidemiology, etiology, and consequences of obesity

Barbara J. Moore and Xavier Pi-Sunyer

Learning Objectives

The reader will be able to:

• Define obesity in adults and children.
• Describe the estimated prevalence of obesity in adults and children in the United States and for adults, globally.
• Discuss how obesity prevalence is estimated in the United States.
• Discuss the health consequences of obesity with respect to diseases commonly associated with obesity, health-related quality of life, and premature death.
• Identify putative causal factors related to the development of obesity.

Introduction

“Last week, I met with the G. family in the—clinic at my hospital. One of the parents was overweight, and the other was obese. The five children were more severely obese and had numerous weight-related complications—one had evidence of fatty liver, one had high blood pressure, two had gastroesophageal reflux, two had orthopedic problems, three had marked insulin resistance, four had dyslipidemia, and all had emotional problems related to their weight.

Sadly, this family might be a microcosm of 21st-century America: if we don’t take steps to reverse course, the children of each successive generation seem destined to be fatter and sicker than their parents. How will obesity affect the physical and psychological well-being of children in coming decades? What effects will childhood obesity have on life expectancy, the national economy, and our society?”

D. Ludwig, New England Journal of Medicine, December 6, 2007 (1)

The above scenario typifies the great challenge of obesity in the 21st century—stemming the epidemic of obesity that threatens the health and quality of life of millions of people in all walks of life. Obesity is an increasingly important problem in world health: its prevalence has greatly risen around the world in the last two decades; and it is affecting people of all ages and ethnicities, but some groups more than others, as will be discussed below. The onset of obesity is occurring at increasingly younger ages and its negative consequences are occurring earlier in life—a scenario with profound economic consequences as obesity becomes commonplace among the workforce. Obesity is affecting individuals in all social strata and it is escalating in the industrialized world as well as in developing countries. As the economies of developing countries begin to shift, and as peoples all over the world become more urbanized and make the transition from hard physical labor to intensive use of labor-saving technology, the incidence of obesity increases. Also, as food production and distribution systems modernize and as people’s discretionary income increases, a wide variety of rich and highly palatable food is available to everyone. As a result, more people are overeating at a time when their energy expenditure is decreasing. Since fat storage occurs when the consumption of energy in food (i.e., calories, a measure of the chemical energy stored in food) exceeds energy expenditure (primarily, but not exclusively, through physical activity), these industrial, sociocultural, and economic changes are shifting the energy balance, with the result that people worldwide are gaining weight.

This chapter presents current definitions of obesity, epidemiological data on the growing prevalence of obesity and its consequences, and a brief presentation of some of the putative causes of obesity, many of which will be developed in subsequent chapters. This chapter concludes with a brief discussion of obesity prevention, which is treated in depth in Chapters 24, 26, and 27, and of issues that merit further attention from the research community.

Definitions and Assessment

The human body contains essential lipids, for example, constituents of cell membranes, and also nonessential lipids in the form of stored triglycerides. These molecules are commonly referred to as “fat” but are technically referred to as “triacylglycerols.” They are stored in specialized cells called adipocytes (see Chapter 7 for more information on adipocytes). Obesity is simplistically thought of as the excess accumulation of stored fat, but agreeing on how much is excessive from a health standpoint and measuring that excess is problematic. Rather than using direct measures of body fat in epidemiology and vital statistics, researchers have relied on simple measurements of weight and height, and the use of these measures to calculate a value known as the body mass index (BMI) to trace obesity prevalence. BMI is calculated as weight, expressed in kilograms, divided by the square of height, expressed in meters (kg/m²). Thus, BMI offers a measure of weight adjusted for height and this value correlates reasonably well with total body fat in the adult human (2). The assessment of obesity in children will be discussed in detail in Chapter 11 and more information about the measurement of human body composition is available in Chapter 13. Here we caution the reader that the body fat content associated with a given BMI depends critically on the sex, age, race, and developmental stage of the child, presenting difficulties in the use of BMI for assessment of pediatric populations, as will be discussed below.

For cost and other logistical reasons, many epidemiological surveys rely on self-reported (rather than measured) height and weight. This introduces error when BMI is calculated, since respondents often underestimate their weight and overestimate their height (3). Overestimation of height—which is a particular problem because height is squared when BMI is calculated—increases with age and differs by sex, with men overestimating height more than women (3). Underestimation of weight also differs by sex (women underestimate more than men), and by degree of obesity (overweight persons underestimate weight more than normal-weight persons), and there is also evidence that estimations may differ by ethnicity (4). Such self-reported data can nonetheless provide useful information about trends and regional information that might otherwise be too expensive to obtain. For the purpose of this chapter, we shall rely primarily on data collected through the National Health and Nutrition Examination Survey (NHANES), in which both height and weight are measured to yield a more accurate assessment of BMI.

The current classification of overweight and obesity using BMI is shown in Table 1-1. This classification has been adopted by both the National Institutes of Health (NIH) (5) and the Centers for Disease Control and Prevention (CDC) (6) in the US, and by the World Health Organization (WHO) (7). For adults, the BMI categories are age-independent and the same for both sexes. However, a given BMI value may not correspond to the same degree of fatness in all cases. For example, for two individuals with the same BMI, one male and one female, the female will have a greater fat content. Furthermore, a given BMI does not necessarily indicate the same level of disease risk in different ethnic populations (3). This is due, in part, to differing genetic susceptibility and variant fat distribution among ethnic groups.

Table 1-1 BMI-associated disease risk
The use of body mass index (BMI) has been proposed by the National Institutes of Health,^a the Centers for Disease Control and Prevention,^b and the World Health Organization^c as a method for defining overweight and obesity. This classification system is based on epidemiologic data indicating that the risk of morbidity and premature mortality usually begins to increase at a BMI of 25–29.9 kg/m², and increases further at a BMI of 30 kg/m². Other factors, such as waist circumference, weight gain since young adulthood, fitness level, and ethnic or racial background, also influence the relationship between BMI and overall disease risk

Classification	BMI (kg/m^2)	Risk
Underweight	<18.5	Increased
Normal	18.5–24.9	Normal
Overweight	25.0–29.9	Increased
Obese Class I	30.0–34.9	High
Obese Class II	35.0–39.9	Very high
Obese Class III	≥40	Extremely high

^a National Institutes of Health and National Heart, Lung, and Blood Institute. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults—the evidence report. Obes Res 1998; 6 (Suppl 2): 1S-209S.

^b Centers for Disease Control and Prevention. Overweight and Obesity: Defining Overweight and Obesity. www.cdc.gov/nccdphp/dnpa/obesity/defining.htm (accessed June 28, 2008).

^c World Health Organization. Obesity: Preventing and Managing the Global Epidemic. Report of a WHO Consultation on Obesity. Geneva: World Health Organization, Technical Report Series 2000; 894: 1–253.

An increase in central adiposity—the accumulation of body fat in the abdominal area—is associated with greater risk for diabetes and cardiovascular disease (8–9) and a...