六级冲刺练习：阅读（113）_大学英语阅读

六级冲刺练习：阅读（113）

　　Use of energy by the body falls into two categories. The first is energy used for essential bodily functionsdigestion, heart beat, breathingand 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 activitystanding, 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.

　　An inactive person might add only 300 calories a day to his BMR, for an average total of 1700. But a marathon runner might add 2300, for a total of 3700. For endurance athletes in training, 4000- to 5000-calorie intakes are not uncommon.

　　We can see from such figures that the sedentary person has a BMR-dominated total calorie expenditure, so that anything he does to increase his BMR will help burn fat, whereas anything he does to decrease his BMR will compound his overweight problem.

　　For years now, we have known that dietingespecially severe dietingdecreases BMR. This is the bodys defense mechanism to conserve energy when food supply is reduced. Unfortunately, it tends to undermine the diets effects by enabling the body to get by on fewer calories. For this reason, I believe that severe dieting should be used sparingly, and all dieting should be seen as a temporary measure.

　　A fascinating concept that has emerged in recent years has been the apparent effect of vigorous exercise in temporarily increasing BMR. A jogger returning from a five-mile run may have a higher BMR. While this effect probably lasts only a few hours, the jogger who runs every day should maintain an increased BMR.