【导读】

我们真的需要每天努力走上一万步或者喝足两升水吗？本文介绍了一些广为接受的关于饮食和健康的观念以及目前科学的研究发现，了解了这些，您就可以开始做出明智的健康决策了。

Should we really be aiming to walk 10,000 steps a day, or drink two litres of water?

我们真的应该每天努力走一万步或者喝两升水吗？

By Joel Snape

刘立军 选编

Here are some widely held dietary and health-based beliefs and what science says now - so you can start making informed health decisions this year.

1. ‘Lifting weights will give you big muscles’

This obviously isn’t true. To understand the scietnce, though, you have to realise that there are two main ways to get strong: increasing the size of individual muscle fibres or coaxing more of them into firing at the same time.

Bodybuilders aim to do the first, by doing many repetitions in each set of exercises, lifting until their muscles fail. Athletes, who generally have smaller shoulders than bodybuilders, aim to do the second, by lifting heavier weights for fewer reps, and avoiding muscular failure.

2. ‘Breakfast is the most important meal of the day’

This is a tricky one. Although there is nothing about the first meal of the day that makes it especially magical, the timing of meals is increasingly recognised as an important factor in weight loss. One study found that those who ate a large breakfast saw greater weight loss than another group who had a low-calorie breakfast and larger dinner.

“This might be because skipping breakfast leads to increased hunger levels later in the day, resulting in people overeating,” says Brady Holmer, a researcher in nutrition.

3. ‘You should walk 10,000 steps a day’

This number wasn’t based on any science when it was first used in the 1960s, but it might be good advice. A study released in 2022 found that walking may reduce the risk of premature death from cardiovascular disease and cancer. Another study found similar results for dementia, with as little as 3,800 steps a day proving effective. But it’s also worth stepping up the pace, as the dementia study saw a power-walker’s pace showing benefits above and beyond the number of steps walked.

4. ‘You need eight hours of sleep’

It’s easy to think of sleep as an individual thing: some people need eight hours, while others can get by on seven. But in one of the largest ever sleep studies, launched in 2017, participants who reported sleeping seven to eight hours performed better cognitively than those who slept more or less than that, regardless of age. Those who slept four hours or less performed as if they were almost nine years older.

5. ‘You should aim to eat five portions of fruit and veg a day’

“Many studies have found that roughly this number is associated with improved health, but there is also evidence that up to 10 servings per day of these foods can be beneficial,” says Holmer. In general, those who consume more fruits and vegetables have lower risks for cognitive decline and dementia, and diabetes, and may even experience decreased levels of stress.

6. ‘You need to drink two litres of water a day’

Staying hydrated is important, but the recommendation to drink two litres of water a day, while reasonable advice, is not based on hard science. In 1974, a book by leading US nutritionist Dr. Frederick J. Stare stated: “How much water each day? For the average adult, somewhere around six to eight glasses, and this can be in the form of coffee, tea, milk, soft drinks, beer, etc. Fruits and vegetables are also good sources of water.” The bit about getting your hydration from lattes, celery or Fanta often gets lost – which is a shame because it’s still valid.

7. ‘A daily glass of wine is better than abstinence’

This one is a classic of the “correlation is not causation” genre. The old recommendation to have a glass each night is based on observational evidence that people who classify themselves as “moderate drinkers” (roughly 1-2 units a day) seem to have a lower risk for some diseases. However, recent research suggests that regular, small-scale drinking is far from ideal: one study found that even one or two drinks a day might decrease the chance of healthy ageing and reduce the size of your brain.

That said, there are well-known health benefits that come from a lively social life – so if you are drinking the occasional wine with friends, it might be doing you more good than harm.

8. ‘Abdominal exercises will give you a six-pack’

“It makes a sort of sense that if you want to build your abs, you would do typical abdominal exercises like sit-ups,” says Emma Storey-Gordon, a personal trainer and sports scientist. “But the truth is that whether you have visible abs or not has far more to do with your body fat levels and where you are predisposed to store fat than the number of sit-ups you do.” Many resources will tell you that you need to be around the 10-15 per cent body fat range to start seeing the outline of your abs if you’re male, or 15-20 per cent if you’re female. In reality, it’s a bit more complicated. “A lot of women need to go below a healthy body fat range for abs; those with longer torsos, who don’t store fat around their midsection, may not.”

9. ‘Dieting will slow your metabolism’

It’s a common belief that eating a very low-calorie diet, or even fasting, will trigger “starvation mode”, where the body slows metabolism as a way to keep you from losing any more weight. “While there’s no such thing as ‘starvation mode’, there may be small changes to someone’s metabolic rate when they lose weight or go on a diet,” says Holmer. “It’s called adaptive thermogenesis - a process during which the body reduces its production of heat in order to conserve energy.” This might explain why some people have a hard time keeping weight off, or even regain weight after dieting. To lessen the chances of your metabolism slowing down due to dieting or weight loss, you should avoid rapid weight loss: gradual is better.

10. ‘Red meat is bad for you’

Red meat was often advised against because it contains a lot of saturated fat - but it’s not as simple as that. Several studies have shown an association between a higher intake of red meat and an increased risk of prostate cancer and heart disease, but it is now widely believed that the associations between red meat and disease risk might be proved wrong, because many studies don’t distinguish between processed (bacon, sausages, burgers, etc.) and unprocessed red meat intake.

“Several recent studies have found that eating unprocessed red meat may not actually increase the risk for heart disease or cancer,” says Holmer. “And major health organisations have recommended that people can continue to eat unprocessed red meat.”

Adapted from https://www.theguardian.com/lifeandstyle/2023/jan/04/truth-behind-10-of-the-biggest-health-beliefs

【词汇】

1. coax vt. to persuade sb to do sth by talking to them in a kind and gentle way 哄劝；劝诱 例如：It took almost an hour to coax the cat down from the tree. 花了近一个小时才把那只猫从树上哄下来。

2. premature adj. happening before the normal or expected time 未成熟的；过早的；提前的 例如：his premature death at the age of 37他37岁时早逝

3. cognitive adj. connected with mental processes of understanding 认知的；感知的；认识的 例如：a child's cognitive development儿童的认知开发

4. correlation n. a connection between two things in which one thing changes as the other does 相互关系；关联 例如：the correlation of social power with wealth社会权力与财富的相关性

5. genre n. (formal) a particular type or style of literature, art, film or music that you can recognize because of its special features （文学、艺术、电影或音乐的）体裁，类型

6. metabolism n. (biology 生) the chemical processes in living things that change food, etc. into energy and materials for growth 新陈代谢 例如：The body's metabolism is slowed down by extreme cold. 严寒可以使身体新陈代谢的速度下降。

7. saturated fat （来自肉类和乳类的）饱和脂肪

【练习与参考答案】

Choose the best answer.

1. What is the difference between the way bodybuilders and athletes lift weights?

A. Bodybuilders lift heavier weights for fewer reps.

B. Athletes lift until their muscles fail.

C. Bodybuilders aim to increase the size of individual muscle fibers.

D. Athletes focus on increasing the number of muscle fibers that fire at the same time.

【答案】D

【解析】Athletes focus on increasing the number of muscle fibers that fire at the same time, while bodybuilders aim to increase the size of individual muscle fibers.

2. What is the author’s view on the statement “Breakfast is the most important meal of the day”?

A. The author believes it is true.

B. The author believes it is false.

C. The author is undecided.

D. The author does not address it.

【答案】B

【解析】The passage explains that although breakfast is often touted as the most important meal of the day, the timing of meals is increasingly recognized as an important factor in weight loss. The study cited in the passage suggests that eating a larger breakfast can lead to greater weight loss, but this does not necessarily mean that breakfast is the most important meal of the day. The author’s view is that the statement is false.

3. According to the passage, why is it recommended to walk 10,000 steps a day?

A. It is based on scientific research.

B. It reduces the risk of premature death.

C. It prevents cardiovascular disease and cancer.

D. It prevents dementia with a power-walker’s pace.

【答案】B

【解析】While the number of 10,000 steps per day was not based on scientific research, a study released in 2022 found that walking can reduce the risk of premature death from cardiovascular disease and cancer. Therefore, it is recommended to walk 10,000 steps a day to reduce this risk.

4. What is the main finding of the sleep study according to the passage?

A. Sleeping for eight hours is essential for good health.

B. Different people require different amounts of sleep.

C. Sleeping for seven to eight hours a day is the best for cognitive performance.

D. Sleeping less than four hours a day is equivalent to aging by nine years.

【答案】C

【解析】The passage states that in one of the largest ever sleep studies, participants who reported sleeping seven to eight hours performed better cognitively than those who slept more or less than that, regardless of age. Therefore, option C. is the correct answer. Option A. and B. are not supported by the passage, while option D. is true, but not the main finding of the study mentioned in the passage.

5. According to the text, how many portions of fruit and vegetable should one aim to eat per day?

A. Five.

B. Ten.

C. Twenty.

D. It varies from person to person.

【答案】A

【解析】The text states that “You should aim to eat five portions of fruit and veg a day” and goes on to say that “Many studies have found that roughly this number is associated with improved health.” While there is evidence that up to 10 servings per day can be beneficial, the text does not suggest that one should aim for this higher number. Therefore, the correct answer is A. Five.

6. According to the article, the recommendation to drink two litres of water a day ___________.

A. is based on hard science

B. is unreasonable advice

C. was first made in 1974 by Dr. Frederick J. Stare

D. is the only way to stay hydrated

【答案】C

【解析】The article states that the recommendation to drink two litres of water a day is not based on hard science, and that Dr. Frederick J. Stare first made the recommendation of “somewhere around six to eight glasses” in 1974. Therefore, option C is the correct answer.

7. What is the author’s attitude towards the idea that a daily glass of wine is better than abstinence?

A. The author believes that a daily glass of wine is better for health than abstinence.

B. The author believes that there is no scientific evidence to support the claim that a daily glass of wine is better than abstinence.

C. The author believes that a daily glass of wine is acceptable as long as it is consumed in moderation.

D. The author believes that the health benefits of a daily glass of wine are outweighed by the risks.

【答案】B

【解析】The passage states that the idea that a daily glass of wine is better than abstinence is a “classic of the ‘correlation is not causation’ genre” and that recent research suggests that even one or two drinks a day might decrease the chance of healthy aging and reduce brain size. Therefore, the author’s attitude towards this idea is that there is no scientific evidence to support it.

8. What does Emma Storey-Gordon say about building visible abs?

A. It is only possible through typical abdominal exercises.

B. It depends on the number of sit-ups you do.

C. It is more related to body fat levels and predisposition to store fat.

D. It is easier for women with longer torsos.

【答案】C

【解析】Emma Storey-Gordon, a personal trainer and sports scientist, says that whether you have visible abs or not has far more to do with your body fat levels and where you are predisposed to store fat than the number of sit-ups you do. Therefore, the correct answer is C.

9. What is “adaptive thermogenesis” according to the passage?

A. A process where the body increases heat production to burn more calories.

B. A process where the body slows down metabolism to conserve energy.

C. A process where the body burns fat instead of glucose for energy.

D. A process where the body increases appetite to compensate for weight loss.

【答案】B

【解析】The passage explains that “adaptive thermogenesis” is a process where the body reduces its production of heat in order to conserve energy, resulting in small changes to someone’s metabolic rate when they lose weight or go on a diet.

10. What is the common belief about red meat?

A. It contains too much protein.

B. It is hard to digest.

C. It is high in calories.

D. It is unhealthy due to high saturated fat.

【答案】D

【解析】The passage mentions that red meat was often advised against because it contains a lot of saturated fat. The belief is that it increases the risk of prostate cancer and heart disease. However, recent studies have shown that eating unprocessed red meat may not actually increase the risk for these diseases.

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