That prediction, which is based on the dramatic rise in obesity, especially among young people and minorities, is from a special report appearing in the March 17 issue in the New England Journal of Medicine.
The study determines that obesity currently reduces life expectancy by approximately four to nine months.
"The magnitude of that effect may sound trivial to some, but in fact it's greater than the negative effect of all accidental mortality, such as car accidents, suicides and homicides combined," said Olshansky, who is professor of epidemiology in the UIC School of Public Health.
The researchers also predict that the rapid rise in obesity among children and teenagers in the past 30 years will have life-shortening effects in the future -- perhaps enough to offset any improvements in longevity from anticipated advances in biomedical technology.
Researchers also believe the life-shortening effect of obesity could rise so rapidly in the United States -- from two to five years in the next 50 years -- that it may eventually exceed the current life-shortening effects of cancer or ischemic heart disease.
The findings are contrary to what some scientists predict about human life expectancy, which assumes that past increases will continue indefinitely. Most forecasts of life expectancy are based on historical trends, but the authors conclude that such estimates fail to consider the obesity epidemic.
Olshansky and colleagues argue that current extrapolation models used to predict life expectancy do not take into consideration the health status of people currently alive.
Longevity predictions are crucial for health policy and for economic policy as well.
"One of the consequences of our prediction is that Social Security does not app ear to be in nearly as bad a shape as we think," Olshansky said.
"The obese may be inadvertently 'saving' Social Security, but the obese themselves and the health care system that cares for them will pay a very heavy price in terms of higher death rates and escalating health care costs."
To estimate the current impact of obesity on life expectancy, the researchers calculated how much longer people would live if obesity did not exist. To do this, they used recently published health statistics and assumed that everyone who is currently obese acquired the body mass index of people who have the lowest risk of death.
By calculating years-of-life-lost due to obesity and combining that with estimates of the prevalence of obesity in younger generations, the authors were able to illustrate that in the coming decades the risk of death from obesity-related causes is about to rise. The hardest hit will be minorities, because of limited access to health care and because they have experienced the most rapid increases in obesity in recent years, according to the authors.
It is well documented that obesity is associated with an increased risk of diabetes, heart disease, cancer and other complications. Obesity and overweight are the second leading cause of preventable death in the United States. And the largest increases in obesity have occurred among children and minorities.
Body weight is affected by many genetic, psychological and environmental factors that influence diet or physical activity levels, says Dr. David Ludwig, associate professor and director of the Obesity Program at Children's Hospital Boston and a co-author of the study. For children in particular, fast food, sugar-sweetened beverages and other high-calorie/low-quality junk foods are major contributors to obesity.
"These adverse changes in diet have been driven by a multi-billion dollar marketing campaign by the food industry aimed at young children," said Ludwig. "C utbacks in funding for regular, mandatory PE classes and limited insurance reimbursement for obesity prevention and treatment are also contributory."
The researchers predict that unless effective interventions are developed to reduce obesity, children today may live less healthy and shorter lives than their parents.
"In addition to the enormous economic costs of obesity, the personal toll is incalculable," Ludwig said. "The rapidly escalating prevalence of childhood obesity and its most feared complication, Type 2 diabetes, raises the prospect of heart attack becoming a common condition of young adulthood."
The authors expect that this study will raise awareness of the importance of increased funding for obesity research and treatment, especially in children. They also point out that new investment into the Social Security system, while at the same time under-funding obesity prevention and treatment, is not sound economic or public health policy.
"Some may view this as pessimistic," Olshansky said. "But in fact, it is a realistic assessment of where we are today and where we appear to be headed in the future. It is a problem that can be fixed.
"One of the reasons that we've done this is to alert the public to the serious health and life-shortening effects of obesity, to find ways to treat it more effectively and to prevent it. If we succeed in our efforts, our predictions will be wrong. And that's what we hope."
The full text of the article is available free on the journal's web site at http://www.nejm.org.
Olshansky will also present the results of the paper at the Second International Conference on Healthy Ageing and Longevity in Brisbane, Australia on March 20.