四级冲刺练习阅读（113）

　　Eat more, Play more Weigh Less

　　In the United States, 20 to 40 percent of the adult population has a weight problem. To many people, the cause seems obvious; we eat too much. But scientific evidence does little to support this idea. Going back to the America of 1910, we find that people were leaner than today, yet they consumed more food. In those days people worked harder physically, walked more, used machines much less, didnt watch television.

　　Several modern studies, moreover ? have shown that fatter people do not eat more on average than thinner people. In fact, some investigations, such as a 1979 study of 3454 London office workers, reveal that, on balance, fat people eat less than slimmer people.

　　Studies show that slim people are more active than fat people. Measurement of calorie intake in slim, active populations compared with moderately overweight, inactive groups routinely shows striking differences. A study by my research group at Stanford University School of Medicine found that among slim, tennis-playing women average daily calorie intake was 2417, while among sedentary , moderately overweight women of the same age it was 1490. Here were slim women remaining slim on 62 percent more calories than overweight women. The critical difference; physical activity.

　　In another Stanford study, 48 sedentary men ages 30 to 55 started on a one-year jogging program. We observed these changes after the training period:

　　The more the men ran, the greater their loss of body fat.

　　The more they ran, the greater their increase in food intake.

　　Thus, those who ran the most ate the most, yet lost the greatest amount of body fat!

　　I believe that this illustrates the evolution of moderately overweight people to relatively slim individuals via a progressive program of regular exercise. The crucial ingredient is regular, enjoyable activity.

　　Use of energy by the body falls into two categories. The first is energy used for essential bodily functions digestion, heart beat, breathing and is known as the basal metabolic rate, or BMR. In an average-sized adult, BMR requires about 1400 calories per day.

　　The second category is energy used for physical activity standing, walking and all other movements. Together with the BMR, it makes up total calorie use, which should be balanced by food intake for weight to remain stable.