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Introduction and Overview |
National Dairy Council, Rosemont, Illinois
Address reprint requests to: Gregory D. Miller, PhD, FACN, National Dairy Council, 10255 W. Higgins Road, Suite 900, Rosemont, IL 60018-5616. gregorym{at}rosedmi.com
Multiple disease outcomes are related to poor nutrition and sedentary lifestyle, but obesity, as evidenced by the epidemic we face, is a sensitive and pervasive indicator of these behaviors. Prevalence in both adults and children has increased in the past decades to an extent that the health of millions of Americans is impacted [1]. Overweight and obesity is the topic of one of the ten Leading Health Indicators which Healthy People 2010 introduces to serve as a barometer of the nation’s health. For the first time, the prevalence of overweight among children will be tracked with Healthy People 2010 [2].
Persons who are overweight or obese are at increased risk for high blood pressure, type 2 diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea, respiratory problems and some types of cancer. Direct and indirect costs attributable to obesity in the United States have been estimated at $99.2 billion 1995 U.S. dollars [1]. These figures can only increase given the fact that the number of overweight children 6 to 17 years of age has doubled within three decades and that overweight during childhood is associated with overweight in adulthood [3,4]. The striking recent increase in type II diabetes in children and adolescents is also emerging as a likely consequence of the present obesity epidemic [1,5]. As with perturbed endocrine function, impaired cardiovascular function is now being reported in studies of obese adolescents [6,7].
Poor eating habits and inactivity are typically identified as the root causes of overweight and obesity for both children and adults, but children in particular are vulnerable to environments that present barriers to healthier behaviors. The overall nutrient intake of children is eroding due to many factors, including changing lifestyles that demand more convenience foods and foods eaten away from home. A recent USDA study, indicates that only 2% of children are meeting the minimum number of servings from all five food groups in the Food Guide Pyramid. The percentages of children meeting the recommended number of food group servings are 14% for fruit, 17% for meat, 20% for vegetables, 23% for grains and only 30% for dairy [8,9]. The number of schools requiring physical education has declined. Children and adolescents spend more time now watching television, using computers and watching video games than in the past [10,11]. It is critical to understand the barriers and forces that prevent the development of healthy eating and activity habits in children.
To date, efforts from the nutrition research and public health communities have been devoted to defining the scope of the problem and understanding the etiology and nature of the disease. Epidemiological studies have focused on identifying determinants of obesity while basic science and clinical intervention trials provide further insight into physiological mechanisms and cause and effect relationships. One conclusive statement based on summation of all the research is that multiple etiologies work in concert to result in obesity [1,12]. Environmental factors such as diet (composition, eating patterns, caloric density and the like) and physical activity and their associated metabolic consequences cannot be separated from predisposing genetic factors but clearly play a significant role for many individuals who become overweight [13].
Just as environmental factors contribute to obesity, they also provide the means by which the individual can alter conditions to promote weight loss. Prevention of obesity is frequently attempted through educational approaches aimed at improving knowledge and motivation with consequent presumed impact on individual lifestyle choices [14]. The real challenge lies in motivating consumers to change dietary patterns and physical activity levels. Unfortunately, behavioral and education-based interventions have been minimally effective at getting people to make sustained changes to achieve appropriate body weight [14]. The health community recognizes the critical need for innovative approaches to develop effective strategies and approaches to assist people in managing weight.
Part of the challenge to developing effective interventions lies in the fact that overweight is not a "sudden onset" condition, but one that occurs gradually over time for most people. Small differences in energy balance, for example, an excess of 10 kcal/day, will result in a one pound weight gain over the course of a year [15]. Conversely, if people can achieve a small shift to a negative energy balance, they will lose excess body weight and fat over time. Interventions to induce negative energy balance may focus on energy intake (diet) or energy expenditure (exercise) or a combination of these elements. Physical activity is clearly a key determinant of success [16]. However, every person has to consume food and will consume food. Every person should exercise, but not every person will exercise or increase physical activity. Therefore, nutrition should be a primary consideration in approaches to dealing with obesity.
Significant literature has emerged over the past few years and has identified previously unexplored concepts in diet and metabolic outcome. Application of these concepts may assist in altering metabolic efficiency and energy balance to result in weight maintenance and/or weight and fat loss. These include modulation of energy density of foods, eating patterns and glycemic index [16,17,18], as well as the emerging concept that increasing dairy product intake may protect against excess adiposity while low dairy and calcium intakes increase the risk of obesity [19,20,21]. Notably, there appear to be sharp differences between the effects of calcium and the effects of dairy products, with dairy foods proving to have markedly greater effects in protecting against excess adiposity. Consequently, the suboptimal calcium and dairy intakes of American youth may contribute to the obesity epidemic. For example, low calcium intakes have been identified as a serious public health concern, especially for teenage girls [22], and more than 80% females between 9 and 19 years of age do not meet the recommended intake of calcium. Moreover, only 30% of children consume the recommended number of milk group servings each day [23].
Improving the calcium intake of the U.S. population has the potential to effect a substantial reduction in the prevalence of obesity. Recognizing that calcium intake accounts for approximately 3% of the variability in Body Mass Index, it is important to remember that even small shifts in the mean of a population are widely recognized as important for any number of variables [24]. Children, in particular, should be a target focus of this effort, given the additional health benefits of consuming recommended levels of calcium and dairy products [25]. This population warrants special attention, considering the multitude of medical as well as social complications that overweight children experience and the reality that obesity prevention is likely to be the most effective strategy in reversing the epidemic. Of course, the overall diet must be considered in this context as well. Studies indicate that the strategy of lowering dietary fat as a way to promote negative energy balance has likely led us to underestimate the potential role of dietary composition with regard to reducing energy intake and subsequently enhancing weight loss. For example, dietary fat, fiber and glycemic index appear to be influential in energy regulation and could be significant factors in the development and treatment of obesity [16,17,18].
In the interest of addressing the following related objectives, a symposium titled "New Frontiers in Weight Management" was held at the annual meeting of the American College of Nutrition:
Received December 17, 2001. REFERENCES
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