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When we’re stressed out, many of us turn to junk food for comfort. But new research suggests this strategy may backfire. The study found that in animals, a high-fat diet influences brain chemicals in ways that fuel anxiety. “Everyone knows that these are not healthy foods, but we tend to think about them strictly in terms of a little weight gain,” said lead author Christopher Lowry. “If you understand that they also impact your brain in a way that can promote anxiety, that makes the threats even higher.”

In a previous study, the team found that rats fed a high-fat diet showed increases in neuroinflammation (神经炎症) and anxiety-like behavior.

To better understand what may be driving the fat-anxiety connection, Lowry’s team divided male adolescent rats into two groups: Half got a standard diet of about 11% fat for nine weeks; the others got a high-fat diet of 45% fat. Throughout the study, the researchers collected fecal (排泄物的) samples and assessed the animals’ gut (肠) bacteria. After nine weeks, the animals underwent behavioral tests.

When compared to the control group, the group eating a high-fat diet, not surprisingly, gained weight. But the animals also showed significantly less diversity of gut bacteria. The high-fat diet group also showed higher expression of three genes (tph2, htr1a, and slc6a4) involved in production and signaling of the neurotransmitter serotonin (神经递质血清素), which is associated with stress and anxiety.

Lowry stresses that not all fats are bad, and that healthy fats like those found in fish, olive oil, nuts and seeds can be good for the brain. But his research in animals suggests that exposure to an ultra-high-fat diet, particularly at a young age, could both boost anxiety in the short-term and make the brain more likely to suffer from it in the future.

1.What does the underlined word “backfire” mean?

A Cause something unpleasant to happen.

B Add more fuel to make a big fire.

C Have an unexpected and undesired effect.

D Walk backwards and make a fire.

解析：选C。C词义猜测题。根据划线单词前文意思：当我们感到压力时，许多人会转向垃圾食品寻求安慰。和后文意思：研究发现，在动物中，高脂肪饮食会影响大脑化学物质，从而加剧焦虑。由此可知，该句句意为“但新的研究表明，这种策略可能会适得其反”，即划线单词表示的意思为“事与愿违”。故选C。

2.What can we know about the study?

A The duration lasted for two months.

B Researchers measured rats’ behavior.

C The subjects were female adolescent rats.

D One third rats got a standard diet of 11% fat.

解析：选B。B细节理解题。根据第三段中的“After nine weeks, the animals underwent behavioral tests.”可知，九周后，研究人员对动物进行了行为测试。故选B。

3.What’s the result of the study?

A The group eating a low-fat diet lost weight.

B The high-fat diet group had lower tph2.

C Tph2, htr1a, and slc6a4 are associated with stress.

D The high-fat diet group gained weight.

解析：选D。D细节理解题。根据倒数第二段中的“the group eating a high-fat diet, not surprisingly, gained weight”可知，与对照组相比，高脂饮食组体重增加。故选D。

4.What’s the best title of the passage?

A Could Anxiety Increase the Risk of Disease?

B How a High-fat Diet Could Make You Anxious?

C The Surprising Link Between Foods and Stress.

D The Hidden Dangers of a High-Fat Diet.

解析：选B。B主旨大意题。根据全文内容，可知本文介绍了一项科学研究；结合文章最后一句“But his research in animals suggests that exposure to an ultra-high-fat diet, particularly at a young age, could both boost anxiety in the short-term and make the brain more likely to suffer from it in the future.”研究表明，接触超高脂肪的饮食，尤其是在年幼的时候，可能会在短期内增加焦虑，并使大脑在未来更容易受到焦虑的影响。研究表明，高脂饮食或加剧焦虑。故选B。