Excess weight won't decrease life-expectancy

The study made waves across the country because its findings contradict what Americans have been told for the last 30 years about the health risks of excess weight. It, no doubt, made a lot of people very happy. Looking solely at mortality in a representative sample of Americans, government researchers reported that more deaths appeared at the two extremes. It's bad to be too thin, and it's bad to be extremely obese. What's more, people who are overweight but not obese have a lower risk of death than those of normal weight.

The news brings a certain amount of clarity to the conflicting public health messages aimed at Americans for decades. The country is experiencing an "epidemic of obesity" that began around 1980, yet more and more Americans are living to an advanced age. If obesity, or any amount of excess weight, is as bad for the heart as virtually every public health campaign contends, then why has the heart disease death rate decreased steadily over the last 40 years? And here's another contradiction. America is also in the midst of an epidemic of diabetes 2, the greatest risk of which is cardiac death.

The risk of an early demise due to excess weight appears to have been greatly exaggerated.

The new study was conducted by researchers at the National Cancer Institute and the Centers for Disease Control and Prevention (JAMA, 4/20/05). Dr. Katherine M. Flegal and colleagues based their conclusions on a national survey that is conducted periodically and is broadly representative of the U.S. population. The participants offer a wide range of information about themselves, including weight, smoking, age, race, and alcohol consumption. All of the data for these surveys were collected by the National Center for Health Statistics, Centers for Disease Control (CDC) and Prevention.

After this study got considerable media attention last month, the nation's pundits went into full gear, gloating over the fact that the "food police" can now get off our backs and let us return to the pleasure of eating whatever we want. So what if I'm overweight--now it's healthy!

That's exactly the take-home message that disturbs Marion Nestle, PhD, the Paulette Goddard Professor of Nutrition and Food Studies at New York University and author of Food Politics (University of California Press). "I'm floored that the CDC could put out a paper like this without putting it in context for the public," she said in a telephone interview. "People think it's healthy to be overweight, yet there is nothing in this [study] about illness," explained Dr. Nestle. "It's about excess deaths."

Dr. Flegal, the lead author of the new study, was asked in a telephone interview whether she had any trouble with people concluding that it is healthy to be overweight. "We prefer to be cautious about our findings and just say that we found no excess risk of death associated with overweight," she responded., "We did not look at health conditions associated with excess weight." When asked whether it is correct to conclude that people who are overweight but not obese are better off than the people of normal weight, Dr. Flegal said, "It's not unreasonable in terms of mortality," she said. "Overweight people did have fewer deaths than people of normal weight and the differences were statistically significant."

There is a reason that Dr. Flegal speaks in terms of excess risk of death and fewer deaths. The study did not look at causes. Participants were divided into groups according to age and body weights and then compared in terms of mortality. They had provided personal information to the National Health and Nutrition Examination Surveys which were conducted several times from the early 1970s through 2000. Four measures of body mass index, or BMI were used in this survey: underweight (under 18.5), normal (18.5 to 24.9), overweight (25 to 30), obesity (30 to 35), and extremely obese (35 plus).

As for the counterintuitive finding that obesity is associated with only a modestly increased relative risk of mortality, Dr. Flegal and colleagues speculate, within the conclusion of their study, that this could be due to improvements in medical care. As for the excess deaths among the very thin, the researchers were able to rule out illness-induced weight loss as a factor, but offered no speculation about this finding. "The majority of deaths occur among the very old, and it's pretty well established [in other studies] that most people will weigh less as they age beyond 80 years," Dr. Flegal explained. [However,] "our data showed that 50% of the people over 80 were overweight."

Some obesity researchers believe that we have yet to see the full effects of the massive increase in the percentage of Americans, including children, who are diagnosed with type 2 diabetes. The expected increase in heart-related deaths may very well be years away. The first thing people diagnosed with this condition are told to do is to lose weight. Dr. Nestle, the N.Y. University professor, is concerned that people will not take diabetes 2 seriously as a result of this study. "Overweight is a problem," she said, "Maybe it's not a huge problem, but how risky it is depends on other factors," she said, referring to metabolic response and body shape (an excess of abdominal fat). "Not everyone who is overweight will go on to develop diabetes 2, but the risk for this illness is higher among people who are," she cautioned. "Of the people who get diabetes 2, 85% are overweight."