More than 45 million Americans now belong to a health club. We spend some $19 billion a year on gym memberships. Of course, some people join and never go. According to a survey, the number of people who said they【C1】______regular exercise, has been rising. And yet obesity【C2】______have risen significantly: a third of Americans are obese, and another third【C3】______as overweight by the Federal Government's【C4】______. Yes, it's entirely possible that those of us who regularly go to the gym would weigh even more if we exercised【C5】______. But like many other people, I get hungry after I exercise,【C6】______I often eat more on the days I work out than on the days I don't. Could exercise actually be keeping me from losing weight? The【C7】______wisdom that exercise is essential for shedding pounds is actually fairly【C8】______. As recently as the 1960s, doctors routinely advised against【C9】______exercise, particularly for older adults who could【C10】______themselves. Today doctors encourage even their oldest patients to exercise, which is sound advice for many reasons: People who regularly exercise are at significantly lower risk for all manner of【C11】______—those of the heart in particular. They less often develop cancer, diabetes and many other illnesses. But the past few years of obesity research show that the role of exercise in weight loss has been wildly【C12】______. "In general, for weight loss, exercise is pretty【C13】______," says Eric Ravussin, chair in diabetes and metabolism at Louisiana State University and a prominent exercise researcher. Many recent studies have found that exercise isn't as important【C14】______helping people lose weight as you hear so regularly in gym advertisements or on【C15】______like The Biggest Loser. The basic problem is that【C16】______it's true that exercise burns calories and that you must burn calories to lose weight, exercise has another effect: it can【C17】______hunger. That causes us to eat more, which【C18】______can deny the weight-loss benefits we just【C19】______. Exercise, in other words, isn't necessarily helping us lose weight. It may even be making it【C20】______.
【答案解析】解析：下句说到运动对帮助人们减肥没有人们听说的那么重要(exercise isn't as important)以及末段倒数第二句提到运动未必有益于减肥(isn't necessarily helping us lose weight)，因此推断此处应填入有否定意义的词，故选B项useless“无用的；无效的”。