RTI International - News Release - 8.26.2009

Study: Severe Obesity Greatly Reduces Life Expectancy; Overweight, Moderate Obesity Do Not

RESEARCH TRIANGLE PARK, N.C.—Severe obesity can have a significant impact on reduced life expectancy, but being overweight or moderately obese appears to have little, if any, effect, according to a new study by researchers at RTI International.

The study, published online in Obesity, looked at effects of overweight and three categories of obesity on life expectancy across sex, race and smoking strata, based on life expectancy tables and National Health Interview Survey data linked to death certificates.

The results showed that life expectancy for those who are overweight (body mass index 25-30) or moderately obese (BMI 30-35) was similar to that of normal weight adults. However, life expectancy was greatly reduced for those with a BMI over 35, and even more so for those with a BMI over 40.

The results showed that for 18 year olds with a BMI above 35, life expectancy was reduced by five to 12 years depending on race, sex, and whether or not the person smoked. The largest reduction in life expectancy occurred for white male smokers.

"An 18-year-old white male who is normal weight and does not smoke can expect to live to age 81," said Derek Brown, Ph.D., a research health economist at RTI and the study's co-author. "However, were he to smoke and have a BMI above 40, his life expectancy would be only 60, a difference of 21 years."

In aggregate, excess weight is responsible for roughly 95 million years of life lost.

"The prevalence of severe obesity has been increasing at an alarming rate," Brown said. "Unless something is done to reverse this trend, it’s going to have an impact on the life expectancy of U.S. adults."

The results suggest that the impact of obesity on mortality may be greater for men than for women and greater for whites than for blacks.