Tuesday, January 02, 2007

Fat is where it's at?

The New Republic:Weighting Game
As we have seen, most of the people the government and the health establishment claim are too fat--those categorized as "overweight" or "mildly obese"--do not in fact suffer from worse health than supposedly "ideal-weight" individuals. It is true that some groups of fat people--generally those with BMI figures well above 30--are less healthy than average, although not nearly to the extent the anti-fat warriors would have you believe. (Large-scale mortality studies indicate that women who are 50 or even 75 pounds "overweight" will on average still have longer life expectancies than those who are 10 to 15 pounds "underweight," a.k.a. fashionably thin.) Yet there is considerable evidence that even substantially obese people are not less healthy because they're fat. Rather, other factors are causing them to be both fat and unhealthy. Chief among these factors are sedentary lifestyle and diet-driven weight fluctuation.

The most comprehensive work regarding the dangers of sedentary lifestyle has been done at the Cooper Institute in Dallas. The institute's director of research, Steven Blair, is probably the world's leading expert on the relationship between activity levels and overall health. For the past 20 years, the Cooper Institute has maintained a database that has tracked the health, weight, and basic fitness levels of tens of thousands of individuals. What Blair and his colleagues have discovered turns the conventional wisdom about the relationship between fat and fitness on its head. Quite simply, when researchers factor in the activity levels of the people being studied, body mass appears to have no relevance to health whatsoever--even among people who are substantially "obese." It turns out that "obese" people who engage in moderate levels of physical activity have radically lower rates of premature death than sedentary people who maintain supposedly "ideal-weight" levels.

For example, a 1999 Cooper Institute study found the highest death rate to be among sedentary men with waist measurements under 34 inches and the lowest death rate to be among physically fit men with waist measurements of 40 inches or more. And these results do not change when the researchers control for body-fat percentage, thus dispensing with the claim that such percentages, rather than body mass itself, are the crucial variables when measuring the health effects of weight. Fat people might be less healthy if they're fat because of a sedentary lifestyle. But, if they're fat and active, they have nothing to worry about.

Still, even if it's clear that it's better to be fat and active than fat and sedentary--or even thin and sedentary--isn't it the case that being thin and active is the best combination of all? Not according to Blair's research: His numerous studies of the question have found no difference in mortality rates between fit people who are fat and those who are thin.

Of course, in a culture as anti-fat as ours, the whole notion of people who are both fat and fit seems contradictory. Yet the research done by Blair and others indicates that our belief that fatness and fitness are in fundamental tension is based on myths, not science. "Fitness" in Blair's work isn't defined by weight or body-fat percentage but rather by cardiovascular and aerobic endurance, as measured by treadmill stress tests. And he has found that people don't need to be marathon runners to garner the immense health benefits that follow from maintaining good fitness levels. Blair's research shows that to move into the fitness category that offers most of the health benefits of being active, people need merely to engage in some combination of daily activities equivalent to going for a brisk half-hour walk. To move into the top fitness category requires a bit more--the daily equivalent of jogging for perhaps 25 minutes or walking briskly for close to an hour. (Our true public health scandal has nothing to do with fat and everything to do with the fact that 80 percent of the population is so inactive that it doesn't even achieve the former modest fitness standard.)

Other researchers have reached similar conclusions. For instance, the Harvard Alumni Study, which has tracked the health of Harvard graduates for many decades, has found the lowest mortality rates among those graduates who have gained the most weight since college while also expending at least 2,000 calories per week in physical activities. Such work suggests strongly that when obesity researchers have described the supposed health risks of fat, what they have actually been doing is using fat as a proxy--and a poor one at that--for a factor that actually does have a significant effect on health and mortality: cardiovascular and metabolic fitness. As Blair himself has put it, Americans have a "misdirected obsession with weight and weight loss. The focus is all wrong. It's fitness that is the key."

So I suppose losing fat is not as important as getting fit. Of course I'm sure you can read ten different well researched, well written articles and find ten different prescriptions for what your body should be like.

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