14．Many of us start exercising in the hope of losing unwanted pounds.Unquestionably，aiming to be more active is a good thing.But if the main reason is to lose weight，your resolution could very well come to nothing.
For starters，exercise is typically
futile for weight loss.Take walking for example.A 150-pound person who walks for 30 minutes will burn，on average，around 140 calories.That's equal to one can of soda — not exactly a great return on your investment of time and effort.It's much easier just to skip the soda.
When exercise is added to a diet，the results are equally unimpressive.Researchers found that a combination of dieting and exercising brought no greater weight loss than dieting alone after six months.At 12 months，the diet-and-exercise combination showed an advantage，but it was slight — about 4 pounds.
In studies where exercise has produced meaningful weight loss，participants burned at least 400 to 500 calories per session on five or more days a week.To achieve that，a 150-pound person would need to walk a minimum of 90 minutes or run 30 minutes per day.In short，sessions need to go well beyond what most of us are willing or able to do.And even if we manage to make that much effort，our bodies often compensate （抵消） by eagerness for more food and slowing down metabolism （新陳代謝），effects that over time limit how many pounds we lose.
When exercise fails to meet our weight-loss expectations，we often stop working out.Perhaps the biggest problem with exercising to drop pounds is that it turns physical activity into punishment — a price we have to pay for a slimmer body.How many times have you heard someone say "I'll need to do extra exercise" after eating too much？We treat exercise as a form of self-punishment for being "bad." In this case，we' re unlikely to keep doing it for very long.
The conclusion is that we're more likely to treat exercise positively and actually do it when we focus on our well-being rather than our weight.
（1）What does the underlined word "futile" in paragraph 2 mean？
A．necessary.
B．popular.
C．dangerous.
D．useless.
（2）What happens when you run 30 minutes on a daily basis？
A．You will burn 140 calories every day.
B．You will lose 4 pounds in a month.
C．You might have a higher metabolic rate.
D．You might eat more than usual.
（3）Why do people who want to lose weight through exercise often give up？
A．They are unlikely to really enjoy it.
B．They find it too challenging physically.
C．They have difficulty resisting （抵抗） delicious food.
D．They turn their attention to their well-being.
（4）What can be the best title for the text？
A．How long should you exercise a day to lose weight？
B．What are the best exercises for losing weight？
C．Weight loss：why exercise is the wrong path
D．Exercise and weight loss：a pair of brothers
