Cut the growth in rates of obesity by just 1 percent a year over the next two decades, and you’ll slice health care costs by $85 billion.

Keep obesity rates at their current levels – which is well below a 33 percent increase being projected — and you’ll save nearly $550 billion during the same time frame.

Those are the attention-grabbing conclusions of a new paper being released this morning at the “Weight of the Nation” conference in Washington, D.C., sponsored by the U.S. Centers for Disease Control and Prevention. Researchers from Duke University, RTI International and CDC prepared the study, published in the American Journal of Preventive Medicine.

It’s the latest effort to document medical costs associated with obesity and the severe financial consequence of failing to address this epidemic.

In the new study, researchers estimate that obesity will continue to expand and will affect 42 percent of adults by 2030.  (Obesity represents a body mass index score, a ratio of weight to height, of 30 or higher.  Separate estimates for children aren’t calculated.)

That projection takes account of recent evidence that obesity has leveled off among some groups, and as a result it’s lower than an earlier estimate that just over half of the nation’s adults would be obese by 2030.  It also factors in conditions in the states that can affect the prevalence of obesity, such as unemployment, the availability of fast food, and price differences between healthy and less healthy food items.

But while increases in obesity may have moderated, the trends laid out in this study still point upward – especially for people who are roughly 100 pounds overweight, with body mass index scores of 40 or higher.

That rapidly-growing group of severely obese people, who have the most medical problems and incur the highest health care costs, will rise from about 5 percent of the population in 2010 to 11 percent by 2030, researchers suggest.

The findings are meant to be a call to action as experts gathering at the CDC conference consider intensified strategies to combat obesity, a public health problem that affects about 78 million adults and 12.5 million children and adolescents.  Tuesday morning, the Institute of Medicine, an arm of the National Academies of Science, will release a new report examining ways to accelerate progress against obesity – an objective that has proved elusive to date, with a few, limited exceptions.

Proven interventions are now available. “We know more than ever about the most successful strategies that will help Americans live healthier, more active lives and reduce obesity rates and medical costs,” said Dr. William H. Dietz, director of the CDC’s division of nutrition, physical activity and obesity, in a prepared statement.

But adopting new policies will cost money. The new study from Duke, RTI and CDC suggests even small dents in obesity rates can prove cost efficient.

Still, projections included in the report could prove overly aggressive if effective strategies to lower obesity rates are adopted, researchers note.

Earlier this year, a separate report underscored the enormous cost of obesity by calculating that $190.2 billion, or one in every five dollars spent annually on health care in the U.S., was associated with obesity-related expenditures. That is double the amount previously estimated.