Recent remarkable trends and discoveries regarding obesity and health

Tim Byers MD MPH
Professor of Preventive Medicine
University of Colorado School of Medicine

27 February, 2002

We have known for many years that obesity increases risk for many different diseases, and that it is healthier to avoid becoming overweight. What, then, is so remarkable about recent trends and discoveries? The past 10 years have produced some surprises in the trends and implications of obesity in the United States.

Trends in obesity
The accelerating increase in obesity in the United States has been rightfully labeled as an "epidemic" by public health leaders.1 That obesity has been increasing throughout the 20th Century has been widely known, but the steepness of the rate of increase in obesity over the past 20 years has been quite surprising. The figures below show the dramatic recent increases in obesity among US adults and children. Obesity among US adults has increased almost 2-fold only in the past decade, while obesity among children and adolescents has increased more than 2-fold in the past 20 years. The definitions of obesity used for adults differs from that used for children, so the absolute prevalences are not directly comparable, but both for adults and children obesity as defined here is not only modest overweight, but levels of overweight that are quite extreme and clearly associated with increased risk of death and disability from many causes.

Trends in diabetes
One of the diseases most tightly linked to obesity is diabetes. Diabetes rates have been increasing sharply in the past 20 years, coincident with the obesity epidemic. In the past decade alone the incidence of diabetes has increased 30% among those ages 50-59, 40% among those ages 40-49, and 70% among those ages 30-39.2 Even more shocking has been the rapid appearance in children over the past decade of the type of diabetes we used to think only occurred in adults. This condition, previously referred to as "adult onset diabetes", has now begun to become increasingly common among children.3

Increasing recognition of the importance of obesity in cancer
In the past decade there has been an increased understanding of the relationships between obesity and various cancers. In a report soon to be released by the International Agency for Cancer Research, a WHO agency, obesity and physical inactivity will be concluded to be major causes of several cancers.4 The American Cancer Society will also soon publish its new guidelines for cancer prevention.5 Those new guidelines will recognize the growing understanding of the importance of obesity and physical activity in cancer, and will for the first time make specific recommendations for community action to reduce obesity and increase physical activity.

Increased understanding of the health risks of obesity in children
In the past decade research on several fronts has improved our understanding of the potentially serious consequences of childhood obesity.6 We now know that the more extreme forms of obesity track from childhood to adulthood, and that the trends in obesity are due to the combined effects of increased caloric intake by children, especially from food high in fats and sugars, and decreasing physical activity at home and at school. The tracking of obesity between childhood and adulthood is not perfect, of course, as many people who were overweight as kids are not now overweight as adults (and many of us have also changed in the other direction), but it is now clear that obese adolescents are likely to be obese adults, and that the chronic disease process caused by obesity begins in childhood.

Implications of obesity trends in adults and children
The relationships between obesity and heart disease, diabetes, and several cancers are now firmly enough established that we can predict the obesity epidemic will have substantial adverse effects on the future health of Americans. Even though heart disease deaths and cancer death rates are declining now (due to combined peffects of positive changes in tobacco control, blood pressure treatment, cholesterol reduction, early detection, and improved treatments), it is clear that the progress we have made in the past decade would have been more without the obesity epidemic, and that the future gains we can make in these chronic diseases will be substantially blunted by the ongoing obesity epidemic.

Conclusions
In the past 20 years there has been a quite remarkable set of observations and discoveries about obesity in America. Obesity is increasing much faster than ever before, both in adults and in children. We are now seeing rising rates of diabetes in obese children of the type formerly thought to occur only in adults. Coincident with these tends, there has been a growing consensus about the health risks of obesity in children and the importance of obesity and physical inactivity as factors causing cancer, heart disease, and diabetes.

Dr David Satcher, Surgeon General of the US, has said:
"Left unabated, overweight and obesity may soon cause as much preventable disease and death as cigarette smoking……Many people believe that dealing with overweight and obesity is a personal responsibility. To some degree they are right, but it is also a community responsibility. When there are no safe, accessible places for children to play or adults to walk, jog, or ride a bike, that is a community responsibility. When school lunchrooms or office cafeterias do not provide healthy and appealing food choices, that is a community responsibility."1

Public health experts at the School of Public Health in Berkeley have warned that:
"..overweight could emerge as a major public health problem in California in the next century". 7

The future burden of chronic diseases that our children will bear early in adulthood should be a particularly sobering challenge to our responsibilities as adults. As we contemplate the future, we need to seriously consider how we can improve personal, family, and community support for healthy eating and physical activity for all, especially for our children. A real question we now must answer for the future of our children is: "Do we want that super-sized?"

References
1. US Department of Health and Human Services. The Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity. DHHS, Office of the Surgeon General, Rockville, MD, 2001.

2. Mokdad A, Ford E, Bowman B, et al. Diabetes trends in the US: 1990-1998. Diabetes Care 2000;23:1278-1283.

3. Fagot-Campagna A, Pettit D, et al. Type 2 diabetes among North American children and adolescents: An epidemiologic review and public health perspective. Journal of Pediatrics 2000;136:664-72.

4. International Agency for Cancer Research. IARC Handbook of Cancer Prevention: Weight control and physical activity. IARC, Lyon, France (report to be published March, 2002.

5. American Cancer Society. Guidelines for nutrition and physical activity and cancer prevention. ACS, Atlanta, Georgia. (Report to be published March, 2002).

6. Goran M. Metabolic precursors and effects of obesity in children: a decade of progress, 1990-1999. American Journal of Clinical Nutrition 2110;73:158-71.

7. Ragland D, Buffler P, Reingold A, Syme L, Buffler M. Disease and injury in Califronia with projections to the Year 2007: Implications for medical education. Western Journal of Medicine 1998;168:378-399.