A
(2020·江苏卷)For those who can stomach it，working out before breakfast may be more beneficial for health than eating first，according to a study of meal timing and physical activity.
Athletes and scientists have long known that meal timing affects performance.However，far less has been known about how meal timing and exercise might affect general health.
To find out，British scientists conducted a study.They first found 10 overweight and inactive but otherwise healthy young men，whose lifestyles are，for better and worse，representative of those of most of us.They tested the men's fitness and resting metabolic (新陈代谢的) rates and took samples (样品) of their blood and fat tissue.
Then，on two separate morning visits to the scientists' lab，each man walked for an hour at an average speed that，in theory，should allow his body to rely mainly on fat for fuel.Before one of these workouts，the men skipped breakfast，meaning that they exercised on a completely empty stomach after a long overnight fast(禁食)．On the other occasion，they ate a rich morning meal about two hours before they started walking.
Just before and an hour after each workout，the scientists took additional samples of the men's blood and fat tissue.
Then they compared the samples.There were considerable differences.Most obviously，the men displayed lower blood sugar levels at the start of their workouts when they had skipped breakfast than when they had eaten.As a result，they burned more fat during walks on an empty stomach than when they had eaten first.On the other hand，they burned slightly more calories (卡路里)，on average，during the workout after breakfast than after fasting.
But it was the effects deep within the fat cells that may have been the most significant，the researchers found.Multiple genes behaved differently，depending on whether someone had eaten or not before walking.Many of these genes produce proteins (蛋白质) that can improve blood sugar regulation and insulin (胰岛素) levels throughout the body and so are associated with improved metabolic health.These genes were much more active when the men had fasted before exercise than when they had breakfasted.
The implication of these results is that to gain the greatest health benefits from exercise，it may be wise to skip eating first.
【语篇解读】 本文主要说明了早饭前锻炼比早饭后锻炼给身体带来的好处更多。
1．The underlined expression “stomach it” in Paragraph 1 most probably means “ ”．
A．digest the meal easily
B．manage without breakfast
C．decide wisely what to eat
D．eat whatever is offered
B [词义猜测题。此处考查stomach的熟词生义，该词在本句中意为“忍受”；另外，结合常识可以判断，有的人锻炼前不吃早饭是受不了的，所以此处意为“如果可以忍受空腹的话，在吃早餐前去锻炼比吃过早餐后去锻炼好处更多”，故B项正确。]
2．Why were the 10 people chosen for the experiment?
A．Their lifestyles were typical of ordinary people.
B．Their lack of exercise led to overweight.
C．They could walk at an average speed.
D．They had slow metabolic rates.
A [细节理解题。根据第三段中的“10 overweight and inactive but otherwise healthy young men，whose lifestyles are，for better and worse，representative of those of most of us”可知，选中的这十个人就是大众的代表，故A项正确。]
3．What happened to those who ate breakfast before exercise?
A．They successfully lost weight.
B．They consumed a bit more calories.
C．They burned more fat on average.
D．They displayed higher insulin levels.
B [推理判断题。根据第六段中的“On the other hand，they burned slightly more calories (卡路里)，on average，during the workout after breakfast than after fasting.”可知，锻炼前吃早餐的人相对而言在锻炼时燃烧的卡路里稍多一些，故B项正确。]
4．What could be learned from the research?
A．A workout after breakfast improves gene performances.
B．Too many workouts often slow metabolic rates.
C．Lifestyle is not as important as morning exercise.
D．Physical exercise before breakfast is better for health.
D [推理判断题。根据最后一段中的“to gain the greatest health benefits from exercise，it may be wise to skip eating first”可知，早饭前锻炼给身体带来的健康方面的好处更多，故选D。]
