Last year, University of North Carolina at Chapel Hill scientist Dr. June Stevens published a study in the New England Journal of Medicine showing that excess weight boosted the risk of dying prematurely at least until age 75.
"We found no differences in ideal body weight before that age," said Stevens, associate professor of nutrition and epidemiology at the UNC-CH schools of public health and medicine. "In other words, optimal weight was the same for a 60-year-old as it is for a 30-year-old."
Now, the nutrition expert has a new study of more than 300,000 people pinpointing just how dangerous carrying around extra weight can be.
"Among men and women aged 40 to 50 years, being obese increases the risk of death to that of a person who is 5.9 years older if you are a man and 6.4 years older if you are a women," Stevens said.
"If you are a man in his 70s, and you are obese, you are taking on the death rate of men who are 3.5 years older than you are," she said. "An obese woman in her 70s boosts her risk of premature death by 1.7 years."
A report on the new findings appears in the Aug. 15 issue of the American Journal of Epidemiology. Besides Stevens, UNC-CH authors are Dr. Jianwen Cai, assistant professor of biostatistics, statistician Joy L. Wood and postdoctoral fellow Dr. Juhaeri (Note: he does not use a first name); Dr. Michael J. Thun of the American Cancer Society; and Dr. David F. Williamson of the National Center for Chronic Disease Prevention and Health Promotion.
Calculations assumed a body mass index (BMI) -- a measure of weight for height -- of 30 and above as compared to 18.5 to 25, Stevens said. Determined by dividing one's weight in kilograms by one's height in meters squared, a BMI between 18.5 and 25 is considered ideal. A typical female fashion model has a BMI of about 18.
Years of life lost attributable to obesity tended to increase over time but declined slightly for those in their 70s, she said.
"Obviously, the more obese a person is, the more years he or she artificially adds to his or her real age and the greater the chance of dying in any given year," Stevens said.
Researchers analyzed deaths among healthy white women and men who participated in the American Cancer Society's Cancer Prevention Study-I, conducted from 1960 to 1972. A strength of the analysis was the large number of subjects. A weakness was that more recent data would have been preferable.
None of the more than 62,000 men and 262,000 women subjects had ever smoked, was sick or had a history of heart disease, stroke, cancer or recent unintentional weight loss. Those who died in the first year of data collection were excluded, and researchers controlled for age, education, physical activity and alcohol use.
The question of the effect of weight on health among the very oldest people remains difficult to answer, Stevens said. That is because being thin in late life may be a result of and a sometimes subtle sign of declining health. A little extra weight might indicate otherwise good health.
In general, optimal weight for a 5-foot-4-inch woman is between 111 and 128 pounds and for a five-foot-10-inch man, between 133 and 153 pounds, she said. A 5-foot-10-inch man between ages 30 and 44 faces a 20 percent higher risk of death if he weighs 166 pounds than if he is 20 pounds lighter.
Note: Stevens' office numbers are (919) 962-2756 and 966-1065, home is 967-3609.
E-mail: June_Stevens@unc.edu
Contact: David Williamson, (919) 962-8596.
Journal
American Journal of Epidemiology