If health advice were a symphony, everybody from the horn section to the violins would be playing the same note, and “obesity” would be its name.
The symphony reached a crescendo last summer, when the U.S. Obesity Prevention Act of 2008 was introduced with alarm bells. Announcement of the initiative included words like “hurricane,” “emergency,” “havoc” and “dire.” The epidemic would doom the nation’s children and kill the rest of us while soaking up more resources than the health care system has to offer. But lately, another quiet little melody has been playing. This tune goes like this: Why don’t you stop sitting around calculating your BMI—body mass index—and go take a nice long walk?
The BMI is a calculation of body fat based on height and weight. To calculate your BMI, you can go to a handy online calculator devised by the National Institutes of Health. Any number below 25 is “normal,” “overweight” is 25-30 and “obese” is over 30. The number is supposed to tell us our fate. For most of us, the message has become dire and overly simplistic: Lose weight or die.
Even before last summer’s pronouncement of an obesity emergency, researchers had reported different findings in a study published in December 2007 in the Journal of the American Medical Association (JAMA). The study found that fitness—in this case the ability to walk quickly on a treadmill for a few minutes or longer—was a better predictor of who would die, and when, than BMI.
The study followed 2,600 adults over age 60 for 12 years. Participants were asked to walk on a treadmill at a quick walking pace, with a gradually increasing incline. Based on the results of the treadmill test, they were then put in five fitness categories, from least to most fit.
Researchers found that the least fit, regardless of BMI, were four times more likely to die during the course of the study than the most fit. But the most surprising difference in mortality was between the least fit group and the one just above that, who were half as likely to die during the study. In other words, just a little fitness could be twice as good as no fitness at all.
When the results were adjusted for other factors, such as smoking and age, fitness still mattered most.
So is it fitness, rather than fatness, that really counts? “That’s what we keep finding,” says Steven N. Blair, a coauthor of the JAMA study, and professor of exercise science and of epidemiology and biostatistics at the Arnold School of Public Health at the University of South Carolina. Clinical trials under way on the benefits of fitness will likely show that physical activity preserves brain health, too, Blair adds, meaning fitness may also lower the risk of dementia.
To be sure, nobody is saying that obesity is desirable. Overweight and obese individuals may have a harder time moving around, face all kinds of bias and discrimination, and are more likely to have risk factors for cardiovascular and other diseases. But being fat isn’t the same thing as being unhealthy, and it doesn’t have to mean early death.
Another study of 5,400 adults, published in August 2008 in the Archives of Internal Medicine, found that fully half of overweight and one-third of obese participants were “metabolically healthy,” meaning they had few, if any, risk factors for heart disease, such as high blood pressure or low levels of “good” cholesterol. On the other hand, about a quarter of “normal”-weight people were metabolically unhealthy and exhibited cardiovascular risk factors. This study did not measure the fitness levels of the participants.