Special Issue on Obesity, Lifestyle, and Weight Management

Abstract

The International Life Sciences Institute (ILSI) Committee on Lifestyle and Weight Management initiated a project in 2002 to review and evaluate various components of lifestyle, principally diet and physical activity, as they relate to body weight management. The rationale for investigating these issues rested principally on the alarming increases in the prevalence of obesity during the last 15 years of the 20th century in most countries, as well as the adverse health effects associated with obesity. My colleagues have presented excellent scholarly reviews of current studies related to lifestyle and obesity. In this issue of Obesity Research, Jeffery and Utter provide descriptive data on trends in environmental exposures and body weight, as well as data from randomized trials focusing on the influence of environmental factors and body weight change. In his article on self-regulation of energy and intake, Lowe evaluates evidence that weight-control interventions focusing on the availability, types, composition, and portion sizes of foods improve long-term weight control. Baranowski et al. review health behavior models used to identify the mechanisms, resources, processes, and procedures necessary for promoting change, and they suggest areas of research needed to integrate behavioral and biological approaches to understanding eating and physical activity behaviors. Wing discusses the progress in behavioral interventions related to the prevention and treatment of obesity. In his article on the challenges faced in combating obesity, Peters comments on the environmental, social, and economic forces that need to be addressed in order to have meaningful dialogue on obesity's threat to public health. It is clear that the rapidly increasing rates of obesity are due to lifestyles that too often result in positive caloric balances in too many individuals. Human evolution has prepared our species to survive famines and to flourish when adequate food supplies are available. However, our evolutionary experience has not equipped us to adapt to the current situation—one that humans have never before experienced—in which we require extremely low levels of daily energy expenditure for our occupations and lifestyles and food is abundant and inexpensive. The specific causes of the recent obesity epidemic are obscure. We do not have adequate data for representative population samples to clearly specify the individual contributions of caloric intake and caloric expenditure. This leaves me, and you, to speculate on the issue. My own view is illustrated in Figure 1. Energy requirements declined beginning with the Industrial Revolution, and they continued to decline during the first half of the 20th century. It seems likely that this downward trend in energy requirements was accelerated during the post-World War II economic expansion, which increased the amount of mechanization used in the home and on the job. During these periods, however, obesity rates remained low and stable, indicating that the majority of individuals were in energy balance. I speculate that the computer and telecommunications revolution in the last 20 or so years of the 20th century further reduced the average daily energy demand for ever larger numbers of individuals. At these low levels of energy turnover, food-intake regulatory mechanisms, particularly the classical physiological controls, but also psychological and cognitive controls, were unable to adapt sufficiently to keep many individuals in energy balance. The result of large numbers of individuals in positive caloric balance was an inevitable increase in obesity at the population level. Hypothetical model for the cause of the obesity epidemic of the late 20th century. As described by the authors of the reports in this supplement of Obesity Research, a complex mix of biological susceptibility and social, environmental, and economic factors have caused the high obesity rates currently seen in many countries. Any solution to the problem will likewise be complex and will require development, implementation, and evaluation of lifestyle-intervention programs that address these key factors. In addition, initiatives on factors such as creating an environment more conducive to promoting daily physical activity must be developed and tested. The development of such initiatives will require extensive and unprecedented cooperation and collaboration among public, private, and scientific organizations. Simplistic solutions not based on sound science, such as the current “rush to judgment” to remove vending machines from schools, are likely to fail. Some of these approaches are probably worth trying, but they should be carefully evaluated before widespread implementation. The danger of broadly based, but untested, interventions is that we will have an illusion of progress, while the real problems continue unabated. The need for thoughtful and informed action is great, and the time to begin is now. My work is supported, in part, by grants from NIH (AG06945, HL66262, and HL62508). I thank members of the International Life Sciences Institute Committee on Lifestyle and Weight Management for helpful and thoughtful comments on an early draft of the manuscript.