We all know that America is in the throes of an obesity epidemic. Over two-thirds of Americans are officially overweight or obese; obesity in children is on the rise; and type II diabetes (almost always associated with obesity) is being seen in great numbers, including in young Americans for the first time. And it's something you can see with your own eyes: anyone who has traveled to Europe in the past few years can tell you how striking a contrast it is to see large numbers of trim people.
There's no question that obesity greatly increases one's risk of developing diabetes and cardiovascular disease. Obesity is not a problem to be ignored.
Yet, we are increasingly hearing the faint sound of dissenting voices: Obesity is a growing medical problem, but really, how significant is it? They point out the following:
- At least a substantial part of the obesity epidemic can be accounted for by a change in the definition of "obesity." When the CDC changed the definition in 1997, 30 million Americans who had been of normal weight now found themselves to be obese, all without gaining a pound.
- A 2007 report in the Journal of the American Medical Association showed that one's level of physical fitness correlated with long-term survival better than one's level of obesity. That is, overweight people who were fit had a lower risk of death than non-overweight people who were sedentary. Read more here about being "fat and fit."
- While Americans are fatter, they have made other changes in health behavior -- chiefly, smoking reduction and better management of cholesterol and hypertension -- that have more than offset the health risk incurred by the increase in population obesity, according to a 2007 National Bureau of Economic Research report.
- A 2006 report in The Lancet suggested that individuals who were overweight but not obese (BMI of 25 to 29.9), actually had a slightly lower risk of dying than patients who were of "normal" weight (BMI 20 to 24.9).
- A 2009 review paper in the Journal of the American College of Cardiology describes a somewhat puzzling relationship between obesity and heart disease that is now emerging: While obesity increases the risk for heart disease, obese patients who develop heart failure or coronary artery disease may actually have better survival than thin people who develop the same cardiac conditions. Do overweight people develop less severe forms of heart disease than thin people, or does fat tissue somehow mitigate the severity of heart conditions once they develop? Nobody knows.
So far, the backlash to the anti-obesity movement is fairly muted, but it promises to become louder. As the obesity controversy begins to spread, here are three things you should keep in mind to avoid becoming confused by the hyperbole that is sure to arise from both sides:
1) Being very obese (BMI 30 or greater) is very bad for you, as it tremendously increases your risk of cardiovascular disease. No controversy here whatsoever.
2) On a population basis, being merely overweight (BMI between 25 and 29.9) is also associated with increased risk. But on an individual basis, the level of risk really does depend on several other factors, including your fitness levels, the amount of "excess" weight accounted for by muscle mass rather than fat, and your waist-to-hip ratio. (Your waist size should be less than your hip size.)
3) If you are overweight and sedentary, you need to exercise. For one thing, it is difficult to achieve sustained weight loss without regular exercise. But more importantly, even if you do not get down to your ideal weight, the increase in fitness will offset -- at least partially -- the increase in risk posed by the excess pounds.
Sources:
Cutler DM, Glaeser EL, Rosen AB. Is the US Population Behaving Healthier? NBER Working Paper No. 13013. April, 2007. http://www.nber.org/digest/dec07/w13013.html
Sui X, LaMonte MJ, Laditka JN, et al. Cardiorespiratory fitness and adiposity as mortality predictors in older adults. JAMA 2007; 298:2507-2516.
Lavie CJ, Milani RV, Ventura HO. Obesity and cardiovascular disease. Risk factor, paradox, and impact of weight loss. J Am Coll Cardiol 2009;53:1925-1932.
0 komentar:
Posting Komentar