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Study Shows Obesity Risks May Have Been Overstated

Posted on: Thursday, 21 April 2005, 06:00 CDT

Obesity is less deadly now than in years past, and carrying a few extra pounds doesn't appear to increase mortality at all, a study in today's edition of the Journal of the American Medical Association showed.

The Centers for Disease Control and Prevention analysis also showed its own earlier estimates were overstated. Excess weight killed about 25,000 people in 2000, a dramatic drop from 365,000 deaths the CDC reported in January when the agency said excess weight and sedentary lifestyles may catch smoking as the leading cause of preventable death in the United States.

In fact, people who are overweight have a lower risk of death than those of normal weight, federal researchers are reporting in an unexpected outcome to the newest and most comprehensive study of the effect of obesity.

The researchers, statisticians and epidemiologists from the Centers for Disease Control and the National Cancer Institute, also found that the increased risk of death from obesity was not apparent until people became extremely heavy, a group that constitutes only 8 percent of Americans.

Being very thin - even though the thinness was longstanding and unlikely to be caused by disease - caused a slight increase in the risk of death, the researchers report.

The new study, considered by many to be the most rigorous yet, took into account such factors as smoking, age, race and alcohol consumption in a sophisticated analysis derived from a well-known method that has been used to predict cancer risk.

It used the federal government's own definitions of weight categories, which measure fatness according to body mass index, an estimate based on weight and height. For example, people 5 feet, 8 inches tall and weighing less than 122 pounds are considered underweight. If they weighed from 122 to 164 pounds their weight would be normal. They would be overweight if their weight was 165 to 196. And if they weighed 197 or more, they would be obese.

In the study, nearly all the death risk from obesity occurred in the heaviest of the obese, such as a 5-8 person weighing more than 230 pounds.

The findings are unexpected, and researchers have a full gamut of responses. Some see the report as a long-needed reality check on what they see as the nation's near-hysteria over fat.

"I love it," said Dr. Steven Blair, who is president and chief executive of the Cooper Institute, a non-profit research and educational organization in Dallas that focuses on preventive medicine. "There are people who have made up their minds that obesity and overweight are the biggest public health problem that we have to face," he said. "These numbers show that maybe it's not that big."

Others simply did not believe the findings.

Dr. Joann Manson, the chief of preventive medicine at Harvard's Brigham and Women's Hospital, pointed to her own study of nurses that found mortality risks in being overweight and even greater risks in being obese. Her study involved mostly white professional women and used different statistical methods.

"We can't afford to be complacent about the epidemic of obesity," she said.

Dr. Mark Mattson, a researcher at the National Institute on Aging who studies caloric restriction as a means to prolong life, said it is not clear that eating fewer calories means weighing significantly less since some people eat very little and never get very thin. Caloric restriction might extend life, he said, but he added, "there's certainly a point where you can overdo it with caloric restriction and we don't know what that point is."

In fact, the new study only addressed risk of death and not disability or disease. As weight increases from overweight to obese to super obese, people are more and more likely to have diabetes, high blood pressure and high cholesterol levels. But the investigators said it also is possible that being fat is less of a health risk than it used to be.

In a paper also published today in the Journal of the American Medical Association, Dr. Edward Gregg, Dr. David Williamson and their colleagues report that high blood pressure and high cholesterol levels are less prevalent now than 30 or 40 years ago, and fatter people made the greatest improvements in controlling these conditions that can lead to heart disease. People also are smoking less. Diabetes remains the same, however, afflicting about 4 percent of people of normal weight, 6 percent of those who are overweight and 14 percent of the obese.

Other statisticians and epidemiologists said the study's methods and data were exemplary. They also said the study's authors, Dr. Katherine Flegal and Williamson of the CDC and Dr. Barry Graubard and Dr. Mitchell Gail of the cancer institute, were highly regarded and experienced scientists.

"This is a well-known group and I thought their analysis and their statistical approaches were very good," said Dr. Barbara Hulka, an emerita professor of epidemiology at the University of North Carolina.

The study did not explain why overweight appears best as far as mortality is concerned, but Williamson said it may be that most people die when they are old, over 70, and having a bit of extra fat in old age appears to be protective, giving rise to more muscle and more bone.

"It's called the obesity paradox," he said, adding that while the paradox is real, the reasons are speculative. "It's raw conjecture," he said.

For now, said Dr. Dixie Snider, the CDC's chief science officer, said the agency is not going to take a position on what is the true number of deaths from obesity and overweight. "We're too early in the science," he said.

This report includes information from The New York Times and Bloomberg News.

A FEW EXTRA POUNDS MAY NOT HURT

People who are overweight but not obese have a lower risk of death thatn those at a normal weight, according to a new study. Those who are very thin or obese, however, are at a higher risk of death. %% Deaths by body type as compared to normal body 2000

Underweight Normal weight Over weight Obese Extremely obese

Body Mass Index 0-18.4 18.5-24.9 25-29.9 30- 34.9 35+

Deaths 33,746 --- 86,094 29,843 82,066

more fewer more more %%

Source: Seattle Post - Intelligencer

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