EXTREME OBESITY MAY SHORTEN LIFE EXPECTANCY UP TO 14 YEARS
Adults with extreme
obesity have increased risks of dying at a young age from cancer and many other
causes including heart disease, stroke, diabetes, and kidney and liver
diseases, according to results of an analysis of data pooled from 20 large
studies of people from three countries. The study, led by researchers from the
National Cancer Institute (NCI), part of the National Institutes of Health,
found that people with class III (or extreme) obesity had a dramatic reduction
in life expectancy compared with people of normal weight.
The findings
appeared July 8, 2014, in PLOS Medicine.
"While once a
relatively uncommon condition, the prevalence of class III, or extreme, obesity
is on the rise. In the United States, for example, six percent of adults are now
classified as extremely obese, which, for a person of average height, is more
than 100 pounds over the recommended range for normal weight," said Cari
Kitahara, Ph.D., Division of Cancer Epidemiology and Genetics, NCI, and lead
author of the study. "Prior to our study, little had been known about the
risk of premature death associated with extreme obesity."
In the study,
researchers classified participants according to their body mass index (BMI),
which is a measure of total body fat and is calculated by dividing a person's
weight in kilograms by their height in meters squared. BMI classifications
(kilogram/meter-squared) are:
·
Normal weight: 18.5-24.9
·
Overweight: 25.0- 29.9
·
Class I obesity: 30.0-34.9
·
Class II obesity: 35.0-39.9
·
Class III obesity: 40.0 or higher
The 20 studies that
were analyzed included adults from the United States, Sweden and Australia.
These groups form a major part of the NCI Cohort Consortium, which is a
large-scale partnership that identifies risk factors for cancer death. After
excluding individuals who had ever smoked or had a history of certain diseases,
the researchers evaluated the risk of premature death overall and the risk of
premature death from specific causes in more than 9,500 individuals who were
class III obese and 304,000 others who were classified as normal weight.
The researchers
found that the risk of dying overall and from most major health causes rose
continuously with increasing BMI within the class III obesity group.
Statistical analyses of the pooled data indicated that the excess numbers of
deaths in the class III obesity group were mostly due to heart disease, cancer
and diabetes. Years of life lost ranged from 6.5 years for participants with a
BMI of 40-44.9 to 13.7 years for a BMI of 55-59.9. To provide context, the
researchers found that the number of years of life lost for class III obesity
was equal or higher than that of current (versus never) cigarette smokers among
normal-weight participants in the same study.
The accuracy of the
study findings is limited by the use of mostly self-reported height and weight
measurements and by the use of BMI as the sole measure of obesity.
Nevertheless, the researchers noted, the results highlight the need to develop
more effective interventions to combat the growing public health problem of
extreme obesity.
"Given our
findings, it appears that class III obesity is increasing and may soon emerge
as a major cause of early death in this and other countries worldwide,"
said Patricia Hartge, Sc.D., Division of Cancer Epidemiology and Genetics, and
senior author of the study.
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