Older women with a “normal” body mass index (BMI) are still at high risk of early death if they carry extra fat around their bellies, according to a study published online this week in JAMA Network Open.
Specifically, the study found that women aged 50 and older who were considered of normal weight (a BMI of 18.4 to 24.9) but who also had central obesity (a waist circumference of more than 34.6 inches) were a third more likely to die within a two-decade period than normal-weight women without central obesity.
That raised risk was almost identical to what was observed among women who had both obesity (a BMI of 30 or higher) and central obesity — the group considered at highest risk.
Those results underscore that waist size is too often overlooked when determining weight-related health risks, the study’s authors say.
As an editorial that accompanies the study points out, this is not a new finding. “As far back as 1947, French physician Jean Vague, MD, suggested that obesity in the upper half of the body was associated with cardiovascular disease and diabetes, an association he did not find in individuals with more fat in the lower half of the body,” the authors of the editorial write.
How the study was done
For the current study, a team of researchers led by Dr. Wei Bao, a molecular epidemiologist at the University of Iowa, analyzed two decades of data collected from more than 156,624 participants in the Women’s Health Initiative, an ongoing national health study that was launched in the early 1990s. All the women were between the ages of 50 and 79 when they entered the study.
During the 20 years that the women were followed, 43,838 of them died, including about 30 percent from cardiovascular disease and 27 percent from cancer. The researchers adjusted that mortality data to account for factors known to be related to early death, such as smoking, lack of physical activity, education level, annual income, race/ethnicity and the use of hormone therapy (for menopause). They then looked to see if they could find an association between the deaths and the participants’ BMI and/or central obesity.
They could. Not surprisingly, they found that women who had both obesity (as determined by BMI) and central obesity were 30 percent more likely to have died within the 20 years than normal-weight women without central obesity.
But the analysis also revealed that the increased risk for normal-weight women with central obesity in the study was almost identical — 31 percent.
Furthermore, women who were obese or overweight but who weren’t carrying excess fat around their middles were slightly lesslikely to have died during the 20 years.
Limitations and implications
This is the largest study so far to find that normal-weight people with central obesity are at increased risk of early death, according to its authors. It’s an observational study, however, so it can’t prove that body shape is a direct cause of that increased risk.
The study also included only older women, and so its findings may not be applicable to younger women or to men.
In addition, the relatively small number of women in the study with a normal BMI and central obesity (1,390, or 0.9 percent) or with an obese BMI and no central obesity (4,957, or 3.2 percent) means the findings regarding those groups need to interpreted with caution.
Still, the findings are in line with other research that has shown a link between excess abdominal fat in normal-weight people and an increased risk of chronic disease. Earlier this month, for example, another group of researchers reported that apple-shaped older women may be at an increased risk of a heart attack and stroke, even if their BMI indicates they are not overweight. (That study also used data from the Women’s Health Initiative.)
“Our results highlight the inability of BMI alone to distinguish body shape or body fat distribution… and the importance of measuring central obesity even among people with normal weight,” Bao and his colleagues conclude in their paper.
FMI: You can read the study in full on the JAMA Network Open website.