Researchers predict a decline in life expectancy in the United States due to rising obesity levels.

The team said based on currently obesity levels reduces life expectancy by approximately four to nine months.

But they warn that if obesity levels continue to rise so rapidly life spans could be reduced by two to five years in the next 50 years.

The team, lead by Professor Jay Olshansky of the University of Illinois, have published their findings in the recent issue of the New England Journal of Medicine.

It warns that unless effective interventions are developed to reduce obesity, children today may live less healthy and shorter lives than their parents and will be more at risk of dying early from heart disease, cancer, diabetes and kidney failure.

To estimate the current impact of obesity on life expectancy, the researchers calculated how much longer people would live if obesity did not exist.

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.

They say 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, 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. "Cutbacks in funding for regular, mandatory PE classes and limited insurance reimbursement for obesity prevention and treatment are also contributory."

"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."