by Robert M. Otto

According to the World Health Organization health is defined as "a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity". Since the inception of this definition in 1948, our perspective on health has evolved to include individual responsibility for our well being through the practice of health-promoting lifestyle behaviors. These behaviors are directed toward an improvement in quality of life and the reduction in the risk of premature disease. Obviously health is far from elusive, but it is labile. The interdependence of mental, physical and social components of health is depicted as a continuum with positive lifestyle habits contributing to optimal health on one end and premature death or the absence of health on the other extreme. Premature death is often preceded by a prolonged duration of negative lifestyle habits.

Although Americans are living longer, we still rank twenty-fifth in life expectancy around the world. The world leader in life expectancy is Japan. Most European countries also surpass the life expectancy of people in the United States. Longevity is merely one measure of life. More importantly, we should be concerned with the proportion of quality life versus unhealthy life. Currently Americans enjoy approximately 83% or 64.2 years of life in a healthy state. The remaining 17% are spent in less than optimal health because of chronic or acute disease and illness. It is estimated that more than 70% of all premature deaths as well as the decline in one's own health are attributed to individual health behaviors and environmental factors.

Research indicates that one effective intervention for developing and maintaining health is a chronic engagement in physical activity and/or exercise. Ample data support the impact of exercise on quality of life by enhanced glucose control, reduced blood pressure, attenuated osteopenia and osteoporosis, enhanced body composition and a lowered risk of cardiovascular disease. In an analysis of the relative risk of all-cause-mortality, a low fitness level (sedentary lifestyle) is of greater risk than cigarette smoking, high blood pressure, high cholesterol, or obesity. One who expends less than 1000 kcalories per week in physical exertion beyond their normal resting metabolic rate is considered sedentary. Currently, approximately 40% of Americans engage in no leisure physical activity and another 20% move sparingly. Hence, over 60% of the United States population is classified as sedentary. This number parallels the 61% prevalence of overweight and obesity in American adults. It can be argued that Americans are the heaviest people in the world. Over the past thirty years adults in the US have increased their overweight/obesity prevalence almost 28%, while the youth of America has increased more than 200%. The statistics with children are alarming because the percentage of obese preschool, school-age, and adolescents who become obese adults are 33%, 50%, and 80%, respectively.
The trends show no signs of abatement.

Americans are acutely aware of overweight/obesity since at any one time approximately 40% report being on a diet. Although the incidence of overweight and obesity is often noted due to physical appearance, the danger is far greater than expected with a high risk of hypertension, hyperlipdemia, gallstones, ostoeathritus, diabetes, metabolic syndrome, cancer, and premature death.

The cause of this epidemic involves cultural, lifestyle, environmental, and genetic factors. Despite all of these factors, experts agree that a caloric consumption in excess of caloric expenditure is the simple equation leading to the epidemic. The popularity of fast foods and the marketing of "super size" portions has increased caloric intake of a typical fast food meal by more than 150% in the past thirty years. Additionally, convenient foods often contain portions of high density calories. Conversely, energy expenditure has decreased dramatically. As a mode of transportation, walking trips have decreased from 9.3% to 5.5%, while automobile trips have increased from 84% to 89% since 1977. Sedentary leisure activities such as computer use and television viewing now occupy almost four hours of a typical American's day. In children, the prevalence of obesity is 12% if watching less than two hours of television per day, but rises to 34% for children viewing five or more hours per day. In adults, the risk of type 2 diabetes is proportional to the amount of television watching with a two-fold increase in risk for the individual watching 3-6 hours/day versus the individual viewing one hour or less/day.

The results of physical inactivity are exemplified in the application to the overweight/obesity epidemic. However, the role of physical activity is more far reaching than this. Physical activity is inversely associated with the risk of all-cause and cause-specific mortality, as well as the incidence and severity of several chronic morbidities. The quantity and quality of the physical activity is still under investigation. In our Human Performance Laboratory, we are directly involved with the role of physical activity and exercise on the health continuum. This leads to diverse research studies that over the past year include the evaluation of bone density and body composition as related to exercise, the energy cost of specific exercise activities (vinyasa yoga and salsa aerobics), the training of senior citizens to enhance balance, and a twelve week training study to compare the impact of Pilates versus resistance exercise on conditioned females. Data from our laboratory, in conjunction with studies from a global network of exercise science laboratories contribute to the development of public health recommendations for physical activity and exercise. As associate editor of the American College of Sports Medicine's Guidelines for Exercise Testing and Prescription, 7th edition (in press), I can assure you that a new recommendation for adequate physical activity will be an expenditure of 2000 kcalories/week. Are you moving in the direction of enhancing your health?