Jan. 15--For people with Type 2 diabetes who had hoped that their love handles
might serve some purpose by reducing their risk of premature death, Harvard
researchers have some bad news: The "obesity paradox" does not exist.
"We found no evidence of lower mortality among patients with diabetes who were
overweight or obese at diagnosis, as compared with their normal-weight
counterparts, or of an obesity paradox," the research team reported in a study
that appears in Thursday's edition of the New England Journal of Medicine.
What they did find will be pretty disheartening to those with a body mass index
outside the 22.5-to-24.9 range, which is considered the higher end of "normal"
Compared with people in this index group, people with a BMI between 30 and 34.99
(considered "obese") were 24% more likely to die during the course of the study,
and people with a BMI above 35 (considered "severely obese") were 33% more
likely to die. People whose BMIs in the 25-to-29.99 range who were merely
"overweight" also had higher rates of premature death, though the difference
wasn't large enough to be statistically significant.
The data also offer sobering news for diabetes patients on the lower end of the
normal range. Compared with people in the index group, those with a BMI between
18.5 and 22.4 were 29% more likely to die of any cause during the study period.
These findings are in line with some previous studies, but they contradict
several other reports that identified a surprising relationship that came to be
known as the obesity paradox. In these studies, people who were obese were less
likely to die than people with a "healthy" weight. Examples of the obesity
paradox have been seen among people with diabetes, people with various kinds of
heart disease and people on dialysis.
Considering that excess weight is widely recognized by medical experts as a risk
factor for early death due to ailments like cardiovascular disease and cancer,
the team from the Harvard School of Public Health, Harvard Medical School, and
Brigham and Women's Hospital decided to take a detailed look at the issue.
They suspected that previous studies failed to take smoking into account, which
is a problem because smokers are more likely to have lower BMIs and to die
prematurely. They also figured the results could be skewed because people who
are frail or suffer from chronic diseases can also have lower weight and a
higher risk of premature death.
So they turned to two large long-term studies that tracked thousands of people
in copious detail: The Nurses Health Study and the Health Professionals
Follow-up Study. Together, these studies provided the researchers with data on
11,427 people who were diagnosed with diabetes before 2010. The study subjects
were tracked for an average of 15.8 years. During that time, 3,083 of the people
The researchers found that the lowest risk of death from any cause was among
people with a BMI between 22.5 and 24.9. After adjusting for factors like
smoking history, alcohol consumption, exercise habits, diet quality and
demographic factors like age, race and marital status, they discovered that the
severely obese had the highest risk of premature death, followed by those on the
low end of normal weight and those who were obese. They described the results as
a "J-shaped" association.
Among the subset of diabetes patients who had never smoked, the increased risk
of death was large enough to be statistically significant only in people who
were obese (36% higher odds) or severely obese (56% higher odds).
But among smokers, the greatest risk of premature death was seen among people
with BMIs in the low-health range (32% higher odds).
More than 90% of the people included in the analysis were white, and the
researchers cautioned that their results might not apply to people of "other
racial and ethnic groups."
Why did these results contradict studies that found an obesity paradox? The
researchers raised several possibilities.
One problem may be that the earlier studies followed volunteers for a shorter
period of time and recorded fewer deaths, making the true signal harder to find.
Also, some of the studies did not take account of smoking behavior or
undiagnosed chronic diseases, which could also skew the results. In one case, a
study that reported an obesity paradox separated study subjects into only two
BMI groups -- those above and below 25.
"The maintenance of a healthy body weight should remain the cornerstone of
diabetes management," they concluded.
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