TUESDAY, Jan. 1 (HealthDay News) -- A new international analysis
reveals a surprising pattern: while obesity increases the risk of
dying early, being slightly overweight reduces it.
These studies included almost 3 million adults from around the
world, yet the results were remarkably consistent, the authors of
the analysis noted.
"For people with a medical condition, survival is slightly better for people who are slightly heavier," said study author Katherine Flegal, a senior research scientist at the U.S. Centers for Disease Control and Prevention's National Center for Health Statistics.
Several factors may account for this finding, Flegal added.
"Maybe heavier people present to the doctor earlier, or get screened more often," she said. "Heavier people may be more likely to be treated according to guidelines, or fat itself may be cardioprotective, or someone who is heavier might be more resilient and better able to stand a shock to their system."
The report was published Jan. 2 in the
Journal of the American Medical Association.
For the study, Flegal's team collected data on more than 2.88
million people included in 97 studies. These studies were done in
the United States, Canada, Europe, Australia, China, Taiwan, Japan,
Brazil, Israel, India and Mexico. The researchers looked at the
participants' body mass index, or BMI, which is a measurement of
body fat that takes into account a person's height and weight.
Pooling the data from all the studies, the researchers found
that compared with normal weight people, overweight people had a 6
percent lower risk of death. Obese people, however, had an 18
percent higher risk of death.
For those who were the least obese, the risk of death was 5
percent lower than for normal weight people, but for those who were
the most obese the risk of death was 29 percent higher, the
While the study found an association between weight and
premature death risk, it did not prove a cause-and-effect
Indeed, one expert cautioned that body weight alone cannot
predict health and the risk of death.
"There are other factors that play a role in overall health," said Dr. William Cefalu, chief and professor of the section of endocrinology, diabetes and metabolism at Louisiana State University and co-author of an accompanying journal editorial.
"Body mass index simply is a parameter; it doesn't take into consideration family history, it doesn't take into consideration smoking, fitness, cholesterol and other factors that should be considered beyond body mass index," he said.
Another expert agreed and added that the issues around body
weight are more complicated than this study suggests.
"This is a large, sophisticated and statistically powerful study that shows convincingly that more severe degrees of obesity increase the risk of premature death, while being merely overweight does not," said Dr. David Katz, the director of the Yale University Medical School Prevention Research Center.
"Like the study itself, the messages here are a bit complex," Katz added.
There is a case to be made that a body mass index in what is now
considered the overweight range might be redefined as normal, Katz
said. "If weight is not harmful to health, there is no reason to
suggest otherwise," he said.
This study, however, looks only at death, not chronic medical
conditions, Katz noted.
"It may well be being overweight does increase the risk of such conditions as type 2 diabetes, or medication use for cardiac risk factors, without increasing mortality. This study would be blind to such effects," he said.
Katz also noted the trends in obesity may be tipping the scale
toward increased risk of dying. "Rates of overweight and obesity
overall appear to be stabilizing, while rates of severe obesity are
rising briskly," he said.
This study suggests being overweight and remaining so might
offer health advantages, "but moving from overweight to obese, and
from obese to more obese, is a serious peril and many in the
population are doing exactly that," Katz pointed out.
"By clarifying the thresholds at which weight poses a threat of premature death, this study invites us to concentrate our efforts there," he said.
For more on obesity, visit the
U.S. National Library of Medicine.
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