If you really want to see that number on weight loss, what you put in your mouth matters most. People who simply cut calories to lose weight lose about 2 pounds a week, says a study in the International Journal of Obesity and Related Metabolic Disorders. At the same time, people who exercise but don't cut calories drop less than half a pound each week.
Why doesn't the physical activity produce the same pound-dropping results as calories cut? One thought is that though exercise burns calories, it doesn't increase your metabolism (新陈代谢), says a study in Obesity Reviews. It doesn't prevent your metabolism from slowing as you lose pounds. As you slim down - through any method - your metabolism slows with your weight loss and exercising doesn't keep that from happening. As you lose weight, you burn fewer calories through exercise. For example, a 150-pound person who exercises for 30 minutes burns about 306 calories. After losing 10 pounds, that person will burn about 286 calories doing the same exercise. So to burn 306 calories, you need to extend (扩大) your exercise.
A research shows people who diet and exercise for weight loss drop the same amount of weight as people who have a balanced diet. They are, however, more successful keeping the weight off than their counterparts (相当的人) who simply eat less.
What does the underlined sentence mean?

A．If you want to put on weight, you should eat more.

B．If you want to lose weight, you should eat more.

C．If you want to lose weight, you should have a balance diet.

D．If you want to lose weight, you should exercise more.

Why can't the physical activity help people lose the same weight as calories cut?

A．Because it doesn't increase metabolism.

B．Because it doesn't burn calories.

C．Because it bums less calories than calories cut.

D．Because calories cut slows metabolism.

What does the underlined word "it" refer to in this passage?

A．Diet.	B．Exercise.
C．The calorie.	D．Metabolism.

According to the passage, which of the following is TRUE?

A．The physical activity is the most useful to lose weight.

B．As you lose weight, you bum more calories through exercise.

C．Doing exercises has the same effect with diet.

D．People who exercise but don't cut calories will lose less weight.

What's the main idea of this passage?

A．How to lose weight.

B．How to diet.

C．People who like sports can easily lose weight.

D．People who have a balanced diet can lose weight easily.