Looking at data on 1,528 people with a normal body mass index (BMI) - a measure of weight in relation to height - researchers found one in five men and nearly one in three women had a body fat percentage above what is considered healthy.
"Just because someone has a normal BMI does not necessarily mean they are metabolically normal," said lead researcher Dr. John Batsis, a geriatrician at Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, referring to the body's ability to process fats and sugars.
The researchers analyzed data from national nutrition surveys, looking specifically at normal-weight adults who were 70 years old, on average.
A total of 902 of the participants died during the following13 years, including 419 of cardiovascular disease.
Batsis and his colleagues did not find any differences in how often people with high and normal body fat levels died of any cause. High body fat was defined as levels above 25 percent for men and above 35 percent among women.
However, women in the study with excess body fat had a 57 percent higher chance of dying from heart-related causes within 11 years of their assessments, compared to women with a healthy amount of body fat.
Men with extra fat faced a greater risk of heart-related death after the 11-year mark, according to findings published in The American Journal of Cardiology.
Batsis told Reuters Health more research is needed to understand what could explain the differences between men and women.
His team found survey participants with the highest body fat percentages were most likely to have high blood pressure and metabolic syndrome, a cluster of risk factors that together can signal heart troubles and diabetes down the line.
BMI measurements have come under fire in the past as inaccurate gauges of body fat. But doctors and health clinics continue to use them because they are easy, practical and affordable.
More high-tech options exist for measuring body fat levels. For example, a dual-energy x-ray absorptiometry (DEXA) scan - also used for osteoporosis detection - can measure fat levels inside the body. But this is "currently clinically impractical," Batsis said, due to costs. A DEXA scan runs for about $300.
Dr. Javier Salvador, an endocrinologist at the University Clinic of Navarra in Pamplona, Spain, who was not involved with the study, agreed that expensive scans would take the guesswork out of fat measurements.
As a cheaper alternative, health workers could gather nutrition information from older patients in addition to their BMI, Salvador wrote in an email to Reuters Health.
"These data, along with those found by our group, indicate again that BMI, the most widely used method to diagnose obesity, is not precise enough to infer body fat content and associated metabolic abnormalities," Salvador said.
For now, BMI numbers from older patients should be interpreted cautiously, Batsis said, adding that older adults lose muscle mass in the aging process anyway.
"Doctors can help their older patients change their health behavior, such as controlling high blood pressure, losing weight or addressing elevated cholesterol," Batsis said.
SOURCE: bit.ly/1etzmbq The American Journal of Cardiology, online August 29, 2013.