scope:

Preface

Although there is little doubt that diet plays a role in the development of obesity, and experts frequently recommend a "healthy" diet for the prevention and treatment of overweight, there is remarkably little consensus regarding the definition of a healthy diet in general, and in particular the characteristics of a diet that would protect against excess weight gain. This debate is often derailed by a shift in focus to findings from weight loss studies that indicate that all sorts of diets can be effective for weight loss. Findings from weight loss studies are seductive, because dramatic results may be achieved over a relatively short period of time. It is easy to lose sight of the fact that very few of these diets are effective in the long term, seriously limiting any applicability to the prevention of obesity. Rather than weight loss, our greatest challenge - and our greatest opportunity - is prevention of excess weight gain.

Research has shown that in a 5-year period, up to 7% of the population may move into the overweight category. Stemming the obesity epidemic in the U.S. will require that many individuals slow their rate of weight gain or that substantial number of obese individuals lose weight. This former strategy has two advantages: improving the health of a greater segment of the population and providing sustainable change. Even a small decline in the number of new cases of obesity has the potential to dramatically shift the BMI distribution. If adults are able to maintain their current weights, and if children are able to maintain or slow their current rate of weight gain, society could reverse the obesity epidemic in just a few generations. Accordingly, this book shifts the focus of the obesity debate to prevention and therefore relies on studies that can evince a preventive approach.

It is particularly critical, at a time when the public is bombarded by nutrition advice from multiple sources, that nutrition experts, educators, and decision-makers in government, academia, clinical practice, and public health provide clear, actionable, and unequivocal dietary recommendations for the prevention of overweight. Messages such as "all foods can fit" and "no food is a bad food" are meaningless detractors that offer no compelling alternative to the latest nutrition fads and weight loss trends. In this manuscript, we therefore systematically review all of the literature regarding 26 different aspects of dietary intake including macronutrients, micronutrients, specific types of foods and beverages, meal and snack patterns, and feeding practices to arrive at 9 dietary recommendations most strongly supported by currently available evidence. These recommendations are intended to form the basis not merely for messages to the public but, more importantly, as the focus of interventions to improve the dietary environments where Americans work, live, and play so that "healthy eating" is convenient, enjoyable, and affordable. For these environmental interventions to be effective, they must have a clear and specific emphasis on the behaviors they are intended to support. Our aim is that this book provide the evidence base to define those foods and dietary behaviors that should be supported and encouraged as well as those that should be discouraged by the multiple sectors of society that are involved in the provision and promotion of foods and beverages.

Although the evidence presented here is extensive, it is by definition not conclusive. It is, however, certainly strong enough to merit action. Clearly, additional research is warranted. But the stakes are too high to await the results of decades of further study. Ultimately, the risk of inaction is greater than the risk of action.

The evidence presented in this book is the most comprehensive on the subject to date and provides what we anticipate will be a critical step forward in our quest to identify actionable strategies to prevent obesity.