Obesity is a lot more deadly than previously thought. Across recent decades, obesity accounted for 18 percent of deaths among Black and White Americans between the ages of 40 and 85, according to a study funded by the Robert Wood Johnson Foundation. This finding challenges the prevailing wisdom among scientists, which puts that portion at around 5%.

“Obesity has dramatically worse health consequences than some recent reports have led us to believe,” says first author Ryan Masters, PhD, who conducted the research as a Robert Wood Johnson Foundation Health & Society Scholar at Columbia University’s Mailman School of Public Health. “We expect that obesity will be responsible for an increasing share of deaths in the United States and perhaps even lead to declines in U.S. life expectancy.”

While there have been signs that obesity is in decline for some groups of young people, rates continue to be near historic highs. For the bulk of children and adults who are already obese, the condition will likely persist, wreaking damage over the course of their lives.

In older Americans, the rising toll of obesity is already evident. Dr. Masters and his colleagues documented its increasing effect on mortality in White men who died between the ages of 65 and 70 in the years 1986 to 2006. Grade one obesity (body mass index of 30 to less than 35) accounted for about 3.5% of deaths for those born between 1915 and 1919 - a grouping known as a birth cohort. For those born 10 years later, it accounted for about 5% of deaths. Another 10 years later, it killed off upwards of 7%.

When the obesity epidemic hit in the 1980s, it hit across all age groups, so older Americans have lived through it for a relatively short period of time. But younger age groups will be exposed to the full brunt for much longer periods.

“A 5-year-old growing up today is living in an environment where obesity is much more the norm than was the case for a 5-year-old a generation or two ago. Drink sizes are bigger, clothes are bigger, and greater numbers of a child’s peers are obese,” explains co-author Bruce Link, PhD, professor of epidemiology and sociomedical sciences at Columbia University’s Mailman School of Publ