William H. Dietz, M.D., Ph.D.
Director, Division of Nutrition and Physical Activity
National Center for Chronic Disease Prevention and Health Promotion, CDC
"A Public Health Approach to Childhood Obesity"
November 7, 2001

William Dietz: I’d like to start with a series of slides that show adult data from the Behavioral Factor Surveillance System, which is an annual telephone-based survey of states. The sample size is huge-- about 150,000 people per year. Obesity is defined here as a Body Mass Index of equal to or greater than 30 (which, for a 5’4’’ woman means she weights over 175 pounds, or for a 6’ man means he weights over 220 pounds). The data from 1991 to 2000 shows a very rapid increase in the prevalence of obesity. And, if anything, these are underestimates because they are self-reported heights and weights. People tend to over-record their height and under-record their weight. The interesting thing is that Colorado has not changed substantially, for reasons that I don’t yet understand.

We don’t have annual data for children, but we do have data from four national surveys, beginning in the 1960’s with the National Health Examination Survey and moving up through the National Health and Nutrition Examination Surveys in the 70’s.

The definition of obesity that I am using here is a BMI greater than the 95 percentile, which, in a young adult, corresponds to a BMI of 30. All the data from these surveys for children of different ages and different genders look the same. That is that the prevalence of obesity had the greatest increase in African American children in adolescence during the 60’s and early 70’s. The greatest increase in Caucasian’s occurred around 1980. In addition, you see this disparity between African American children and Caucasian children (which is replicated in the adult data)–there is far more obesity in African American women and Mexican American women than there is in Caucasian women. Just to give you a sense of the magnitude of the shift, between 2 tests, the prevalence of obesity in adults increased by 50% while during the same time period, the prevalence of obesity doubled in children and teenagers. If we annual data for children and teenagers from the last ten years, I think it would be even more dramatic than the shifts I just showed you with adults.

Charlottesville is fortunate to have a task force that supplied me with these data that look at a combination of overweight and obesity–which, defined here is a BMI greater than the 85^th percentile. This slide shows differences in city and county prevalence of obesity. Notice that over 40% of children and adolescents in the city are overweight or obese, while the county has a lower prevalence than the urban areas (and I understand that may well be both an ethnic and a socioeconomic difference). You see the same difference of prevalence among African American and Caucasian children. To give you a sense of the percentage of overweight and obese children by city/school, notice that there is almost a three-fold difference in prevalence between, what I understand, a predominately Caucasian and high SES school versus schools that are lower SES or more mixed ethnicity. As one can imagine from these slides, Charlottesville is not at all immune from this problem.

Right behind the epidemic of obesity is a second epidemic–diabetes. Although not as dramatic as the obesity epidemic, I think you will agree that this is also an epidemic. This epidemic of diabetes is driven, predominately, by the epidemic of obesity. Children, also, are not immune from Type II Diabetes (this used to be a rare disease). Now, in pediatric clinics around the country, Type II Diabetes in children accounts for almost 50% of new cases of diabetes. The associated cardiovascular disease risk factors are also quite prevalent.

I used to think that obesity in children was predominately a cosmetic problem which exerted its effects if those overweight children became overweight adults, but we have recently published data that has looked at lipid levels, blood pressure, and insulin levels in 5-10 year old overweight children. Over 60% of overweight children have at least one additional cardiovascular risk factor (such as elevated blood pressure, elevated lipid or insulin levels). 25% have two or more of these risk factors. These risk factors, as they endure throughout childhood adolescence and into adulthood, become the substantial diseases in adulthood–cardiovascular disease, stroke, gall bladder disease, cancer, et cetera.

Anne Wolf and Graham Colditt’s (?) published estimates in 1995 suggested that the direct costs of obesity already accounted for 5% of the National Health Care Budget. Those data probably do not reflect the rise in obesity and the impact that this is going to have on subsequent health care costs. Just as an example, Type II Diabetes accounts for over 25% of all the Medicare costs already. So, these costs are only going to increase further. I think that it is quite clear that this problem–the problem of obesity–is going to drive the Health Care Budget for certainly the next decade. If we are not active in reducing the prevalence of obesity, it is clearly going to effect the Health Care Budget through the next century. We are not going to have money to do much of anything else.

Fortunately, these uncommon complications in children are rare. One, however, that we have become particularly concerned about is Sleep Apnea. Last year, the CDC published data that indicated that there had been a 12% rise in mortality among young adults due to cardiovascular disease. A lot of that is probably driven by obesity. For instance, there was a recent death in Georgia of a 12 year-old girl who weighed 300 pounds. She died in her classroom, probably of respiratory problems and carbon dioxide retention, which eventually put her to sleep, led to a fall in oxygen and triggered a cardiac arrhythmia. These deaths are going to become increasingly common, and the 12% increase that we saw last year is probably just the forerunner of this.

How can we account for such rapid changes? Clearly, these changes are not genetically driven because the gene pool for the population did not change in the ten years between 1990 and the year 2000. Clearly these are environmentally driven. It is worthwhile to look at some of the factors that changed with the epidemic. I think that these can be broadly divided into "altered dietary intake," "decreased physical activity," and "increased inactivity." There have been substantial changes in food practices in the United States. Fast food consumption now accounts for 40% of the family’s budget spent on food. Children derive 25% of their calories, daily, from snacks. There is a reduced frequency of family meals. Preliminary data suggests that children who have family meals tend to have meals that are lower in fat, they tend to consume less fast food, less soda, and more fruits and vegetables. There is an increase in the frequency of restrained eating and meal skipping, particularly in girls.

Paradoxically, there are now several studies that suggest that, rather than controlling weight, these practices actually enhance the likelihood of weight gain. Consumption of soft drinks has increased dramatically and now counts for 6% of the child’s average daily caloric intake. There are an extraordinary number of products to which we are exposed, and there is good experimental data that suggests that the greater variety of foods which we are exposed to, the more likely we are to over-consume those foods. I need to stress that none of these have been linked as causes of this epidemic, but nonetheless I think they reflect a major shift in the food environment that is likely contributing to this problem.

The other problem is portion size. I think this is best represented by this new product which Coca Cola is bringing out–a 42 liter bottle of Coke, which is only available in Atlanta at the moment, but is coming here soon. We know that children increase food consumption in proportion to the portion size that they are offered. So, a portion size, which is substantially increased in restaurants around the country, may also be contributing to this problem.

Decreased physical activity, I think, is also a related concern. Part of that relates to the types of communities that we are building and in which we are living. In contrast to what is called a "connected network"–a community in which there are lots of ways to get from one place to another and there are centralized shopping facilities and schools that make it possible for people to walk as a part of everyday life. New communities, particularly those around Atlanta, are culdesac communities that often lack sidewalks and centralized schools, therefore causing people to drive to school and the store.

The two statistics that I think reflect the change in community design most strongly are that only a third of children who live within a mile of school walk to school. And although 25% of all the trips we make are less than a mile, 75% of those trips are by car.

The other disturbing development is that physical education programs in schools have declined. In 1991, 41% of all schools offered daily PE. By 1999, that number had declined to 27%. As a result, very few children and adolescents meet the health goals for various physical activity.

The final issue is increased inactivity. In populations, television viewing, which is the principle form of inactivity, has an independent effect on the prevalence of obesity from activity. There is data that shows substantial changes in the amount of television viewed in the 60’s to the 90’s. In the 1960’s, the median amount of television watched was about two hours per day. By 1990, the median was about 4.8 hours per day, and 35% of children were watching 5 or more hours of television a day. Only part of this has to do with lack of parental control of television. There is certainly anecdotal evidence that these children who are high television viewers have no alternative but to watch television, either because of a dangerous neighborhood, a single parent, or "latch-key" children. I used to think of this as a parent-child interaction problem, but now I see it as a much broader problem which reflects the availability of community resources to support children and parents, particularly in the after-school hours when television viewing is at its greatest among children.

We also know that there is a linear relationship between television viewing and obesity. Data from the National Health Examination Survey shows that the relationship between television viewing and obesity prevalence, by 1990, had become more malignant. Although we call this inactivity, recent data suggests that the most important effect of television viewing may be on food intake, rather than the displacement of more vigorous physical activity. Food ads account for 40% of all commercials, and about 25% of a child’s food intake occurs in front of a television set. In the studies that have been done, which look at the impact of reduced television viewing, it appears that activity does not substantially increase, but food intake may be significantly reduced (which accounts for the reduction in obesity as a result of reduced television viewing).

Let’s move from this to how we can think about preventing this. It is clear that this is going to take very substantial changes in the population. The first challenge is to identify science-based interventions that can be applied to the population. I believe that there are 3 of those. The strategies that I think are justified are increased breastfeeding, reduction in television viewing in children and adolescents, and increase in physical activity. The standards of evidence, here, are strongest for the increase in physical activity. There are a number of randomized control trials and several different types of trials that relate first, to breastfeeding, and second, to television viewing.

There have been three major studies that show an impact of ever breastfeeding and duration of breastfeeding on the subsequent prevalence of obesity among breastfed children. Notice that children who were ever breastfed have a reduction in prevalence that ranges from about 15% to 25%. Those who were breastfed for greater than 6 months may have a reduction in prevalence that ranges from 22% to even 43%. The challenge, here, is how to change the number of women who initiate breastfeeding and who maintain breastfeeding. I think that represents a very significant challenge that is essential to implement this policy. But, I think the data are there that warrant an emphasis on breastfeeding, as though we needed other rationales for breastfeeding.

Secondly, I’ll address reductions in television time. These are clinical data that show that, in a clinical setting–a focus that included diet, behavior modification, family involvement, and differed only in whether exercise was reinforced or reductions in sedentary behavior. The results show that the group reinforced for reduced television viewing had much more substantial weight losses initially than the group reinforced for exercise. Following the end of the intervention, I think you can see that the rates of re-gain were comparable in both these groups. But, these data plus some school-based studies provide a very strong rationale for a focus on television viewing. The challenge, here, is not only to provide children with alternatives, but to also understand what the incentives are for parents to turn off the television set. I think those are issues that we are addressing in primary prevention protocol that we are implementing in a number of pediatric practices.

The final issue is increased physical activity. I think that the emphasis on physical activity and the best data come from the recommendations from the National Heart and Lung Blood Institute regarding the assessment and treatment of adult obesity. Where it is quite clear that the implementation of physical activity in overweight people reduces many of the obesity-associated problems, it may not have a major impact on weight reduction. The other important caveat here is that we do not know the dose of physical activity necessary to prevent the development of obesity, and that is another challenge.

But, the strongest evidence exists for the following recommendations for the prevention obesity just published as a chapter in the Guide for Community Preventative Services, provided by the CDC. The first strategies that are effective are the informational strategies–community-wide education and point of decision prompts. There are three behavioral and social strategies recommended to increase physical activity–school-based PE, non-family social support and individually adapted behavior change. And finally, with the environmental and policy arena, enhance access to recreational facilities or parks where people can be physically active and encouraged to do so.

What we see here are evidence-based recommendations, and what we lack are examples of how to translate those in practice. The fact that we now have three strategies that we can focus on as strategies to address obesity within the communities moves us a long way down the line because now the issue is not what we do, but how we do it.

I am going to now move to a brief discussion on how we implement some other strategies and settings. But, before we do that, I just wanted to mention that we are not going to be talking about the major public health infrastructure that I think is necessary to prevent obesity. We are now finding 12 states to develop community-base programs aimed at the subsets of the population with a strong design and evaluation component to begin to understand how this works.

What I would like to leave you all with are some examples of effective strategies that implement not only some of these physical activity strategies, but begin to address how we implement obesity prevention and treatment in a variety of settings. The settings that I am going to focus on are going to be primarily school and community settings. I think the major challenge in medical settings is first, reimbursement for obesity treatment. Without the reimbursement for obesity treatment, there is no incentive for health care providers to deliver care despite the kind of impact that this has on costs. Secondly, we know what works in experimental settings, but we lack our effective therapies–things that can be widely implemented in primary care settings. From the research and strategic point of view, I think that those are the two most important challenges we face.

I would like to focus, in the time remaining, more on schools and community-based inventions. The first issue is why schools? Schools have the facilities to support, or at least they used to, physical activity in children. Furthermore, many schools offer children, and even feed children, one to three meals a day. Finally, schools provide a link for parents to the community–an opportunity to link school and community based approaches. There are a variety of strategies that can be implemented in schools that are consistent with the strategies that I outlined. I mentioned PE classes, there is a growing interest in media curricula and TV turnoffs that are school-based. I think the issue is how to translate those into the more sustainable programs. I would like to spend some time covering the topics of modifying food environment and comprehensive school-based interventions.

Schools are a fairly rich source of calories. The a la carte foods most often served in lunch lines are high-caloric density foods as are those foods stored in vending machines. Our lack of support of schools means that schools are increasingly reliant on sales of these products to fund other school programs. The best example of this is the contracts that soda companies have with the schools to fund them if they exclusively stock those products in the vending machines. In some schools there is a commission given depending on the number of sales of their product. So, we now have situations where the student is encouraged to come to class with a soft drink because that increases the sales margin. Many communities have begun to look very critically at these problems. Most recently in Sacramento, California voted down a very lucrative contract, and Senator Leahy may introduce it in this or next term, legislation that bans these contracts.

It is important to emphasize that this food environment reflects the food environment of the country. We actually don’t know that this is driving the epidemic, just the same way that we lack the dietary information. But, if we want to begin to address the epidemic, I think it is essential that we begin to address the food environment within the schools. That has been done in one comprehensive school-based intervention that is Planted Health. This was a program in Massachusetts that was a school-based intervention that focused on obesity. This was really the first study that showed that a school-based intervention could be effective in reducing the prevalence of obesity.

Planted Health had four strategies:

• Increase physical activity
• Reduce television time
• Reduce fat intake
• Increase fruit and vegetable intake

These were well integrated into the curriculum, and in girls there was a significant impact of this intervention–the prevalence of obesity as both a BMI (greater than the 85^th percentile) of about 33% (which is a very significant decrease for a school-based intervention ). In boys, interestingly enough, there was no difference (for reasons that are not clear). Nevertheless, the promise of this and other school-based interventions suggest that a focus on many of the strategies I have outlined as prevention strategies, may be a very effective way to address obesity at the community level.