In the United States, 30 percent of adult population
has a "weight problem". Because they eat too much. Going back to America of
1910, we find that people were leaner (较瘦) than today, yet they ate more food.
In those days people worked harder physically (体力上), walked more, used machine
much less, and they didn’t watch television. Several modern
studies, moreover, have shown that fatter people do not eat more on average (平均)
than thinner people. A 1979 study of 3, 545 London office workers showed that
fat people ate less than slim (苗条) people. Studies also show
that slim people are more active and have more physical activities than fat
people. A study by a research group at Stanford University found the following
interesting fact: The more the man ran, the greater loss (损耗)
of body fat. The more the man ran, the greater more food he
needed. So those who ran the most ate the most, yet lost
greater amount (数量) of body fat. According to the passage, how many people in 900 adult Americans have a
"weight problem"