改错：Exercise is one of the few factors with a positive role in long term maintenance of body weight. Exercise is one of the few factors with a positive role in long term maintenance of body weight. Unfortunately, that message has not gotten through to the average American, that would rather try __1__switching to "light" beer and low-calorie bread than increase physical exertion. The Centers for Disease Control, for example, found that fewer than one-fourth of overweight adults were trying to shed __2__pounds said they were combining exercise with their diet. In rejecting exercise, some people may be discouraged too much by calorie-expending charts; for example, one would have to __3__briskly walk three miles just to work the 275 calories in one __4__delicious Danish pastry. Even exercise professionals concede half a point here. "Exercise in itself is a very tough way to lose weight," __5__says York Onnen, the program director of the President's Council on __6__Physical Fitness and Sports. Therefore, exercise's supporting role in weight reduction is vital. __7__A study at the Boston University Medical Center of overweight police officers and other public employees confirmed that those who diet __8__without exercise regained almost all their old weight, while those who worked exercise into their daily routine maintained their new weight. If you decide to start walking one mile a day, the added exercise could burn an extra 100 calories daily. In a year's time, assumed no __9__increase in food takein, you could lose ten pounds. By increasing the __10__distance of your walks gradually and making other dietary adjustments,you may lose even more weight.