If the nation's weight gain continues on the same track, 86 percent of all American adults will be overweight or obese by 2030 - the percentage reaching 100 percent of the general population by 2048, the study found.
"The potential for all American adults to become overweight or obese is a reality," said Dr. Youfa Wang, an epidemiologist with the Johns Hopkins University Bloomberg School of Public Health who led the study that included researchers from AHRQ and the University of Pennsylvania School of Medicine.
"Our analyses clearly show an alarming picture of the future obesity epidemic and related challenges," he said.
Certain segments of the population are particularly at risk.
The findings also predicted that 97 percent of black women and 91 percent of Mexican-American men will be overweight in just more than two decades. In addition, 100 percent of black women will be overweight or obese by 2034 - 14 years earlier than the overall population.
Among white women, 88 percent were projected to be overweight or obese by 2030, along with 73 percent of black men and 88 percent of white men. Among Mexican-American women, the figure was 87 percent.
Black men statistically emerged as the leanest group. The study predicted that 100 percent of their population would not be overweight or obese until the year 2095 - compared with the year 2049 for white men.
The study, which was supported by grants from the National Institutes of Health and the Department of Agriculture, deemed the obesity trend "a public health crisis." It also predicted that objectives set by the federal Centers for Disease Control and Prevention's "Healthy People 2010" program - which aims to reduce obesity by 15 percent among adults - would not be met.
The consortium of researchers based its conclusions on decades of national health and nutrition data collected between 1971 and 2004 by the Department of Health and Human Services, the CDC and the U.S. Census Bureau.
The group predicted that the government could stagger under the financial burden of obesity-associated health problems, including diabetes, stroke, heart disease, osteoarthritis, sleep apnea, breast cancer and some other cancers. Health care costs associated with an overweight population will rise accordingly.
"Our projections indicate that direct health costs attributable to obesity and overweight will more than double every decade," Dr. Wang said.
One out of every $6 spent on the overall health for the nation will go toward obesity-related ills, he said, ultimately reaching $957 billion by 2030, or close to 18 percent of total U.S. health care costs.
"These are projected for 2030 only and are not cumulative numbers. They are based on what is currently spent that is attributable to obesity and then projected forward in time given the change in obesity prevalence," said May A. Beydoun, co-author of the study.
"These figures are likely to be an underestimation of the true impact," Dr. Wang said.
Why are Americans getting so chubby?
The reasons are complex, and the source of endless speculation in the medical community.
Earlier this year, research from the University of Southern California found that people gain weight because of genetic factors, suggesting that people are essentially "hardwired" to eat more from the start. In 2007, British researchers announced they had found an "obesity gene."
Some blame the culture.
"We live in an obesogenic environment that relies heavily on fast food, automobiles and remote controls, all which can be labeled as 'toxic' to maintaining a healthy body weight," said Brown University psychiatrist Rena Wing.
She presented her strategies to counter such influences on a global basis to the American Association for the Advancement of Science in February - emphasizing the grim factors of "globesity." Worldwide, 1 billion adults are overweight, according to the World Health Organization, which also labeled the phenomenon an "epidemic."
Some researchers contend that doctors are not prepared for the challenges.
According to University of Alberta research, 83 percent of family physicians "were less likely to perform physical examinations on reluctant obese patients," while one-fourth doubted their own competency in treating the ailments of overweight people.
Dr. Wang recommended immediate "creative initiatives" in the public and private sectors to counter the obesity trend, calling for input from educators, food producers, urban planners, transportation analysts, parents and the general public. He wants changes in health care systems and training to "face the rising burden of obesity-related health consequences."
Still, his findings are not necessarily written in stone.
"Future policy, environmental and behavioral changes may prove the assumptions wrong," Dr. Wang said. "It is our hope that the predicted grim future of the obesity epidemic will not turn into the actual scenario in the U.S. or any other countries."
The analysis was published in the Obesity Journal, an academic publication.