[单项选择]In the United States, 30 percent of the adult (成年人) population has a "weight problem". To many people, the cause is clear: we eat too much. But scientific evidence (科学证明) 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 (体力地), walked more, used machines much less, and didn’t watch television. Several modern studies, moreover (此外), have shown that fatter people don’t eat more on average (平均) than thinner people. In fact, some investigations, such as a 1970 study of 3,545 London office workers, report that, on balance, fat people eat less than slimmer (苗条) 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 greater loss (失去) of body fat. The more they ran, the greater their increase (增加) in food int
A. they are too slim
B. they work too hard
C. they are too fat
D. they lose too much body fat