单选题 In the United States, 30 percent of the adult population has a "weight problem". To many people, the cause is obvious: they eat too much. But scientific evidence does little to support this idea. Going back to the America of the 1910s, we find that people were thinner than today, yet they ate more food. In those days people worked harder physically, walked more, used machines much less and didn"t watch television.
Several modern studies, moreover, have shown that fatter people do not eat more on the average than thinner people. In fact, some investigations, such as the study of 3545 London office workers, report that, on balance, fat people eat less than slimmer people.
Studies show that slim people are more active than fat people. A study by a research group at Stanford University School of Medicine found the following interesting facts :
The more the men ran the more body fat they lost. The more they ran the greater amount of food they ate. Thus, those who ran the most ate the most, yet lost the greatest amount of body fat.

单选题 The physical problem that many adult Americans have is that ______.

单选题 According to the article, given 500 adult Americans, ______ people will have a "weight problem".

单选题 Is there any scientific evidence to support that eating too much is the cause of a "weight problem" ?

单选题 In comparison with the adult American population today, the Americans of ______ the 1910s

单选题 Modern scientific researches have reported to us that ______.