By Becky Ham, Staff Writer
Health Behavior News Service
Severe obesity can take up to 20 years off a young man’s life, a new study suggests. Women and men between ages 20 and 30 with a body mass index higher than 45 had the greatest reduction in their lifespans, say study authors David B. Allison, Ph.D., of the University of Alabama and colleagues.
Body mass index, or BMI, assesses obesity by measuring an individual’s weight relative to height. Individuals with a BMI higher than 45 are considered severely obese under guidelines issued by the National Heart, Lung and Blood Institute.
Young white men with a BMI higher than 45 lost an average of 13 years off their lives, while young white women lost eight years, the study reports. Severely obese black men and women in the same 20-30 age group can lose up to 20 and five years, respectively.
The shortened lifespan can be significant, the researchers note.
“When one considers that a 20-year-old white male is expected to live another 58 years, a 13-year reduction due to obesity actually represents a 22 percent reduction in remaining years of life,” Allison says. The 20 years of life lost for severely obese black men corresponds to a 40 percent reduction in remaining years of life.
Using information available in public databases, the researchers combined estimates of BMI for certain age groups and the odds of death at specific ages and BMI ranges. Allison and colleagues calculated years of life lost to obesity by subtracting the average age of death for individuals with high BMI from the average age of death for similar individuals with a BMI of 24, considered the upper limit of normal weight.
Being overweight took a greater toll on the lifespans of younger adults, those approximately 20 to 30 years old, compared to older adults, approximately 60 to 70 years old, regardless of how overweight an individual was.
White men and women lose years at a lower BMI than black men and women, according to the study. White men show a drop-off in life expectancy at an approximate BMI of 31, while life expectancy declines for young white women at an approximate BMI of 32. According to the study findings, obesity does not consistently steal years away from black men and women until they reach a BMI of 32 to 33 and 37 to 38, respectively.
These differences between blacks and whites may be due to different obesity-related causes of death, such as cardiovascular disease or diabetes, between the two groups. Other independent causes of death that differ between blacks and whites, such as the high homicide rate among young black males, may also play a role, say the study authors.
The researchers hope their study findings can be expanded to look at other ethnic and racial groups, including Mexican Americans and Pacific Islanders, who have a high prevalence of obesity.
“Our estimates of years of life lost due to obesity strongly support the public health recommendation for adults to avoid obesity,” Allison says.
The study is published in the Jan. 8 issue of the Journal of the American Medical Association, and was supported in part by the National Institutes of Health and the Arthritis Foundation.
The National Heart, Lung and Blood Institute has a BMI calculator and tables at http://nhlbisupport.com/bmi/bmicalc.htm.