Another wrinkle has been added to the debate over whether obesity is a major cause of early death. New research suggests that it is, but only in people who also have diabetes.
People with diabetes were three times as likely as those without it to develop life-threatening critical illness and die prematurely, shows a newly published study. But obese people who did not have diabetes had the same risk of death or organ failure as normal-weight people without the disease.
Being obese is a huge risk factor for type 2 diabetes. Nine out of 10 people with newly diagnosed type 2-diabetes are overweight or obese, according to the American Diabetes Association.
But most previous studies that have linked obesity to early death have not considered the independent impact of diabetes, researcher David M. Mannino, MD, tells WebMD.
“What this paper shows pretty clearly is that diabetes is really the driving factor in early death from critical illness among people who are overweight or obese,” Mannino says.
Mannino and colleagues from the University of Kentucky Chandler Hospital and Atlanta’s Emory University School of Medicine analyzed data from 15,408 people. The study was conducted in the mid- to late 1980s, and the participants were between the ages of 44 and 66 at enrollment.
Obesity was measured by calculating body mass index (BMI), and hospital records were examined to determine if the participants experienced either acute organ failure (critical illness) or death from organ failure during the critical-illness hospitalization or within three years after the acute organ failure.
In the absence of diabetes, obese people in the study were not found to have an increased risk for either organ failure or early death.
But obese study participants -- those with BMIs over 30 -- were four times as likely to have diabetes as those who were normal weight.
The study appears in today’s issue of the journal Critical Care.
“Our results do not support the contention that obesity itself is a risk factor for increased mortality in patients with acute organ failure,” the researchers wrote. “It brings up a new perspective on this still controversial subject of obesity, critical illness, and mortality.”
The new findings are not likely to end the medical debate about whether obesity is a direct or indirect cause of early death.
The issue made headlines a year ago last spring, when CDC researchers reported that the risk of obesity-related death was much lower than had been previously believed.
Researchers also reported no increase in death risk among people who were overweight but not obese.
The report was widely criticized, and a reanalysis of the same data by researchers from the Harvard School of Public Health showed a strong association between obesity and early mortality.
Just last month, two new studies were published which seemed to further confuse the issue.
In one, researchers from the Mayo Clinic concluded that obesity, as measured by BMI, was a poor predictor of death from heart disease.
The other, conducted by researchers from the National Cancer Institute, suggested that being even slightly overweight in middle age is a risk factor for early death.
Cardiologist Richard A. Stein, MD, says the new study may give physicians a more nuanced understanding of the role of obesity and obesity-related conditions like diabetes in early death.
Stein is director of cardiology at Beth Israel Medical Center in New York City. He is also a spokesman for the American Heart Association.
“It has become a mantra in the U.S. that being overweight will kill you,” he tells WebMD. “This study suggests that it is not obesity per se, but the company it keeps that is to blame.”
The distinction is important, he says, because even if someone can’t manage to lose weight they can take steps to keep obesity-related diseases under control.
“Telling an overweight person that they either need to lose weight or they will die is the wrong message,” he says. “There is increasing evidence that aggressively treating diabetes and other risk factors that go along with obesity, like cholesterol and high blood pressure, is even more important than losing weight.”
But JoAnn Manson, MD, of the Harvard School of Public Health in Boston, doesn’t buy the idea that diabetes alone is responsible for the increased risk of early death in people who are obese. Manson led the team which reanalyzed the CDC data.
She tells WebMD that there is plenty of good evidence implicating obesity in death from cardiovascular disease and several types of cancer, as well as diabetes.
“There are clearly pathways through which obesity increases the risk of death that do not involve type 2 diabetes,” she says.
By Salynn Boyles, reviewed by Louise Chang, MD
SOURCES: Slynkova, K. Critical Care, Sept. 25, 2005; online edition. David M Mannino, MD, division of pulmonary and critical care medicine, University of Kentucky Medical Center, Lexington. Richard A. Stein, director of preventive cardiology, Beth Israel Medical Center, New York; director, Beth Israel Hospital-Long Island College Hospital Cardiology Fellowship Training Program. JoAnn Manson, MD, DrPh, professor of epidemiology, Harvard School of Public Health, Boston. WebMD Medical News: “Risk of Death for Obese May Be Declining.” WebMD Medical News: “Panel: CDC Study Wrong on Obesity Risk.” WebMD Medical News: “BMI a Bust for Predicting Heart Death.” WebMD Medical News: “Overweight Boomers Risk Early Death.”