As American waistlines expand, obesity-related healthcare costs are rising. But U.S. officials underestimate the long-term costs of the obesity epidemic, according to a report published in March by the nonprofit Campaign to End Obesity.

As the obesity rate increases, healthcare costs from chronic conditions such as diabetes, hypertension and heart disease have jumped.

Obesity-related healthcare costs $147 billion in 2008, 10 percent of all medical expenses, according to the report. The cost nearly doubles to $300 billion when lost productivity and absenteeism from obesity-related problems are figured into the costs, according to the authors.

The Congressional Budget Office estimates national costs, including costs related to obesity, in a 10-year budget window, inadequate for assessing obesity challenges that could take 25 years to become apparent, researchers said. The U.S. estimates are too narrow and don't focus on complications from obesity that may take longer than 10 years to show, the authors noted.

Ten years is adequate for food stamps and aircraft carriers, but there are certain policy areas where we know the disease has a 20- to 25-year progression, Michael O'Grady, co-author of the report and senior health care researcher at the National Opinion Research Center at the University of Chicago, told HealthDay.

You need the flexibility to go beyond 10 years. We probably want to modify the status quo of how we measure these things in order to capture the full value of that.

Well-informed policy making is one of the best weapons against obesity, the authors concluded. Congress should be projecting what could happen in 25 years if obesity is left uncheck to make smarter decisions aimed at curbing the growing epidemic as well as increase short-term spending to avoid higher costs in the future, the authors wrote.

Obesity is not just about added costs to our already-straining health budgets, as problematic as that is in itself, Tevi Troy, former deputy secretary of U.S Department of Health and Human Services, wrote in the report's foreword. Obesity also creates real challenges to our overall economy, to the public health and to our national security.

Obesity has steadily increased since the 1980s, according to the Centers for Disease Control and Prevention. In 1985, no state had an obesity rate above 14 percent. In 2010, the last year for which data is available, no state has an obesity rate under 20 percent.