Obesity

Dietary and Developmental Influences

Gail Woodward-Lopez, Lorrene Davis Ritchie, Dana E. Gerstein, Patricia B. Crawford

• Publisher: CRC Press
• Year: 2006
• ISBN:
  9781000654509
• Edition: 1
• Topic: Medicine
• Subtopic: Endocrinology & Metabolism

Focusing on prevention rather than treatment, Obesity: Dietary and Developmental Influences reviews and evaluates the determinants of obesity. The book uses evidence-based research as a basis to define foods and dietary behaviors that should be supported and encouraged as well as those that should be discouraged. This comprehensive review re

1 Introduction

The Obesity Epidemic

The World Health Organization has referred to the trends in body weight currently observed worldwide as a “global epidemic of obesity” (Sorensen, 2000). National survey data show significant increases in mean body mass index (BMI) and the prevalence of overweight and obesity for adults and children in the United States (Flegal and Troiano, 2002). Obesity represents a significant risk factor for type 2 diabetes, cardiovascular disease, and other morbidities. The causes of overweight and obesity are complex, with genetic and environmental risks. However, given the likelihood that the underlying genetic makeup of the population hasn’t altered in the past 30 years, most of the recent dramatic change in the distribution of childhood and adult overweight and obesity surveyed in recent decades by the National Health and Nutrition Examination Survey (NHANES) I, II, III, and 1999–2002 is likely attributable to change in environmental factors. Our focus on dietary determinants of energy imbalance is a response to the necessity of synthesizing the current research on potential modifiable risk factors for obesity. While a focus on physical activity is similarly key to our understanding of the determinants of energy imbalance, it is outside the area covered by this review.

The Obesity Prevention Network Determinants of Energy Imbalance Workgroup

The Obesity Prevention Network (OPN) was first organized by the Centers for Disease Control and Prevention (CDC) Division of Physical Activity and Nutrition for the purpose of helping to identify effective strategies for the prevention of obesity. Members include (1) the CDC, (2) seven Prevention Research Centers at Universities across the nation [University of New Mexico (Coordinating Center), University of California-Berkeley, Harvard University, University of North Carolina, University of Oklahoma, University of South Carolina, and University of Washington], and (3) twelve State Departments of Health (California, Colorado, Connecticut, Florida, Massachusetts, Michigan, Montana, North Carolina, Pennsylvania, Rhode Island, Texas, and Washington). The CDC funded two OPN workgroups, one to evaluate methods of obesity surveillance in the United States and the other to identify factors and circumstances that contribute to obesity. The present literature review is the culmination of part of the work conducted by the latter. The emphasis of this review, coordinated by the Center for Weight and Health at the University of California, Berkeley, is on dietary determinants. The group chose to focus on the dietary determinants because of the lack of scientific consensus on the role of specific nutrients, foods, and dietary behaviors in the development of obesity. The group selected for review those dietary determinants that have been implicated in the literature as probable contributors to obesity and for which there was a sufficient body of evidence to consider. The group also reviewed the role of television viewing in the development of obesity; however, this topic is covered in a separate document. A review of physical activity as a determinant of energy imbalance was coordinated by the University of Oklahoma and will also be presented elsewhere.

A Focus on Prevention

It is important to keep in mind that this document focuses exclusively on energy balance and the prevention of overweight and obesity. Therefore, weight loss studies are not reviewed or discussed in any depth (see page 6 for the rationale for excluding weight loss studies). The workgroup chose to focus on prevention of overweight and obesity, as opposed to weight loss, for a variety of reasons:

• Weight loss programs are rarely successful with maintenance of weight loss. Although many Americans have had some success at losing weight, very few are successful in the long run. It has been documented that 95–97% of persons losing weight by dietary restriction and exercise regain this weight within 5 years (Barner, 1991). Although a return to the preweight-loss lifestyle may be to blame in part, some evidence suggest that metabolic responses to weight loss may be largely responsible for weight regain (Liebel, 1995). Therefore, sustained weight loss may not be a realistic goal for many people.
• Most “diets” are unsustainable. Most diets severely restrict the variety and quantity of foods the dieter can consume. Some diets are so restrictive they even fail to provide the recommended levels of required nutrients. It also appears unrealistic to expect individuals to conform to a diet that requires reduced intakes of the most convenient, affordable, and commonly consumed foods in their homes and communities. Unless the whole community commits to similar dietary adjustments and corresponding changes in the availability of foods and beverages, it is unlikely that overweight individuals will be able to depend upon self-control alone to lose weight and maintain the loss.
• The majority of the U.S. population is “at risk.” Almost two thirds of the current adult population is overweight or obese. Treatment for such a large portion of the population is untenable and, therefore, prevention of excess weight gain appears to be the only viable option.
• Prevention is probably less costly in the long run. The cost of providing weight management programs to a majority of the U.S. population is not financially feasible; societal changes that make healthy eating and active living easier are likely to have a more enduring and sustainable impact.
• Healthy lifestyles provide added benefits. The promotion of healthy eating and active living is associated with lower morbidity and mortality even in the absence of weight loss. Although sustained weight loss may not be realistic for many individuals, all individuals can benefit from healthier lifestyles.

Defining Target Behaviors: A First Step

Before answering the question as to “how” and in what venues to improve eating to facilitate energy balance, one must first define “which” behaviors to target. Given this review’s focus on the dietary side of the energy balance equation, the goal is to define what dietary composition and behaviors are most likely to facilitate energy balance.

TABLE 1.1
Research Questions

What	How	Where
What types of physical activity and how much Which changes in what and how we eat ^* Other lifestyle changes	Environment Media/Marketing Education	School Community Workplace

^* The question of interest for this review

When planning an intervention program, the conclusions of this review provide a basis for choosing target behaviors. Other considerations include resource availability, other efforts currently underway, other health outcomes of interest, and the particular needs and priorities of the target population. This review, therefore, assists the reader in identifying which behaviors to target but does not provide information regarding how best to affect the targeted behavior changes. Specifically, these target behaviors are not synonymous with messages that should be directed to the public. Tailoring of messages that would be effective in producing the targeted behavior changes would require formative research with the target population.

2 Methodology

Search Process and Criteria

A systematic search process was undertaken of dietary factors in relation to a measure of adiposity. Searches of the PubMed database were conducted using the search terms listed in Table 2.1. The following limits were applied to all searches: publication date from January 1992 through March 2003, English, and human. The additional limits, “randomized controlled” or “clinical trial,” were applied to the searches for prevention trials using the terms “overweight prevention OR obesity prevention.” However, not all trials identified were randomized and/or controlled; studies did not have to be randomized, controlled trials to be included. Abstract lists generated by the searches were reviewed by at least one, and not more than three, reviewers (OPN members) to determine which studies would be included. Additional studies on children were obtained from a previously conducted review (Ritchie et al., 2001). Articles identified through the formal search process were also supplemented with studies referenced in the other articles or previously known to the reviewers. Previously unpublished data for secular trends were obtained directly from the source. Data regarding food supply trends were obtained from the United States Department of Agriculture (USDA) web site. Data from the National Food Consumption Survey/Continuing Survey of Food Intake by Individuals (NFCS/CSFII) were obtained directly from USDA, and food intake data from NHANES were obtained directly from CDC. In all cases, these data were nationally representative. Obesity prevention trials were also identified by Yale’s SIP-08 project: Evidence-Based Guidelines for Obesity Prevention and Control. Regardless of the source of studies, the same inclusion and exclusion criteria were applied in selecting articles for review.

Inclusion criteria included the following:

• Studies reporting on secular trends with regard to the dietary factor of interest covering at least a six-year time period since 1975.
• Experimental and other types of studies designed to elucidate the relationship between the dietary factor of interest and adiposity.
• Observational studies that examined the relationship between the dietary factor of interest and some measure of adiposity.
• Intervention trials that aimed to modify at least one of the dietary factors of interest with the aim of preventing weight gain, improving health, or preventing chronic disease, but not designed to promote weight loss.
• Intervention trials whose primary outcome was a change in a health index other than adiposity (e.g., blood pressure, total cholesterol) were included as long as adiposity was also measured and examined in the analysis.
• Reviews that covered the types of studies listed above.

Exclusion criteria included the following:

• Weight loss studies — studies that examined weight loss interventions, studies t...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Preface
• Acknowledgments
• About the Authors
• Contributers
• Obesity Prevention Network Determinants of Energy Balance Workgroup Members
• Abstract
• Table of Contents
• Chapter 1 Introduction
• Chapter 2 Methodology
• Chapter 3 Critical Periods
• Chapter 4 Dietary Influences on Energy Balance
• Chapter 5 Conclusions
• References
• Index