CLEVELAND, Ohio -- Researchers had a hunch that the way previous studies measured the impact of obesity grossly underestimated the problem. So they decided to do their own analysis.

What they found was that in the 20-year period ending in 2006, obesity contributed to the premature deaths of more people than previously thought: nearly 20 percent of all deaths in people between ages 40 and 85 – almost four times more than the prevailing wisdom of 5 percent.

It’s the first time that a study accounts for differences in age, birth cohort, sex, and race in analyzing Americans’ risk for death from obesity, the researchers said.

"We believe we have a clearer picture of how obesity is impacting the [United States] population," said Ryan Masters, lead author of the study. Not only is the problem more serious than previously thought, it is destined to get worse as younger generations move into adulthood, he said. "It's quite worrisome."

The study, which was paid for by the Robert Wood Johnson Foundation – of which Masters was a Health & Society Scholar at Columbia University at the time of the study -- appears online Thursday in the American Journal of Public Health.

The message of obesity’s devastating effect on the country’s health is not a new one, said Masters, assistant professor of sociology at the University of Colorado at Boulder, Department of Sociology.

He drew from previous studies – including the work of his co-authors that looked at obesity’s effects on different generations over time -- and took it one step further by approaching the data in a different way.

The researchers analyzed data from 19 survey years of the National Health Interview Survey, a yearly household survey of roughly 40,000 households. That data was linked to individual National Death Index mortality records.

Their conclusions:

• The estimated percentage of adult deaths associated with overweight and obesity was 5 percent for black men; 15 percent for white men; 26.8 percent for black women; and 21.7 percent for white women.

“The prevalence for obesity between men and women and race ethnic groups is vastly different,” Masters said. “We found it was worthwhile to explore that.”

Not enough data was available to make estimates for Asians, Hispanics, and other groups.

• There exists a much stronger association between aging and mortality risk than stated in previous research, which asserts that the risk of dying from obesity weakens as one gets older.

The absence of evidence of the obesity effect in older people is likely because obese people are more likely to experience early death, or they have serious health complications that would reduce their participation in health surveys, Masters said.

• As successive generations, or “birth cohorts,” emerged over time, the percentage of deaths from obesity grew. For example, estimates suggest that obesity accounted for about 3.4 percent of deaths at age 66 for white men who were born between 1915 and 1919. By the time a white man born between 1935 to 1939 died at age 66, obesity accounted for about 5.8 percent of deaths in that group.

Masters said he hopes he analysis will provide researchers and the general public with a better understanding of the toll obesity has taken.

The findings are a testament to ongoing initiatives aimed at preventing and reducing obesity in children, Masters said. “It coincides nicely with our findings. It’s those younger generations that are at most risk.

“Barring any revolutionary breakthrough to lessen the prevalence, we’re likely to see that obesity is going to account for a larger share [of deaths] in the future,” he said.