Calculating obesity's toll is more than a number

Washington -- Although its 400,000 tally was probably a bit too high, officials at the Centers for Disease Control and Prevention are still certain that poor diet and physical inactivity do lead to nearly that many deaths each year in the United States.

CDC experts admitted last month that they made a computational error in coming up with the 400,000 figure for an article on actual causes of death that appeared in the March 10 Journal of the American Medical Association.

A new figure has been sent to JAMA and is being scrutinized there, said the CDC's Chief Science Officer Dixie E. Snider, MD, MPH. But until it is published, CDC officials are mum on the subject.

However, they did say that poor diet and physical inactivity, which are factors that lead to obesity, would almost certainly retain the No. 2 spot in actual causes of death in the nation.

The latest data from the CDC's 1999-2000 National Health and Nutrition Examination Survey show that nearly one-third of all adults are classified as obese and the number of overweight children continues to increase.

Obesity's impact on health was also the focus of a recent summit meeting convened by the AMA. "It's a very rare part of medicine that is not impacted by obesity," said Melvyn Sterling, MD, summit moderator and chair of the AMA's Council on Scientific Affairs.

Among its recommendations are that doctors become role models for physical activity and healthy eating and that body mass index be promoted as the fifth vital sign in physical exams.

All the recommendations were to be presented at the AMA's Interim Meeting held this month in Atlanta.

The March JAMA study, which made a splash when it was published, found that tobacco use caused 435,000 deaths each year and that poor diet and physical inactivity were in second place, causing 400,000 deaths per year. Alcohol consumption finished a distant third at 85,000.

Difficult math

But calculating the role obesity plays as a cause of death is no easy matter. "When you talk about how many people die from heart attacks, that's one thing," said Dr. Snider. "But when you step back and start looking at risk factors, it starts getting very complicated."

For one thing, there are several methods in use that attempt to determine the role obesity plays in mortality. "It's not as though there is some magic method that everybody has agreed to," said Dr. Snider. In an attempt to sort through the methods, the CDC asked the Institute of Medicine to meet this month to help with this task.

And although the focus of the JAMA study was on causes of death, there are other poor health outcomes associated with being overweight, he noted, just as there are other health outcomes from other risky behaviors.

For example, certain sexually transmitted diseases like HIV can be fatal but others, such as Chlamydia or gonorrhea, cause a lot of morbidity. "Obesity results in things other than heart disease or diabetes. It can cause arthritis, which is disabling," said Dr. Snider.

The CDC is now establishing health impact goals, he noted, and the paper on causes of death will provide just one piece of information to use in setting those goals.

"We'll look at this, we'll look at disability, we'll look at hospitalizations, we'll look at morbidity. It's only by doing all of those things that you can get a good handle on how much of an impact any risk factor has -- whether it's tobacco use, or obesity, or risky sex behavior -- and, therefore, how much attention we should give it as a nation."