学进去

It is widely accepted that being overweight definitely poses a danger to our health. According to a new study, obesity may even damage the brain’s ability to recognize the sensation of fullness and be satisfied after eating fats and sugars.

Further, those brain changes may last even after people considered medically obese lose a significant amount of weight — possibly explaining why many people often regain the pounds they lose.

The study, published Monday in Nature Metabolism, was a controlled clinical trial in which 30 people considered to be medically obese and 30 people of normal weight were fed sugar carbohydrates (glucose), fats (lipids) or water (as a control). Each group of nutrients was fed directly into the stomach via a feeding tube on separate days.

The night before the testing, all 60 study participants had the same meal for dinner at home and did not eat again until the feeding tube was in place the next morning. As either sugars or fats entered the stomach via the tube, researchers used functional magnetic resonance(磁共振) imaging and single-photon emission computed tomography(断层扫描技术) to capture the brain’s response over 30 minutes.

In people with normal weight, the study found brain signals in the striatum(纹状体) slowed when either sugars or fats were put into the digestive system — evidence that the brain recognized the body had been fed. At the same time, levels of dopamine rose in those at normal weight, signaling that the reward centers of the brain were also activated. However, when the same nutrients were given via feeding tube to people considered medically obese, brain activity did not slow, and dopamine levels did not rise.

Next, the study asked people with obesity to lose 10% of their body weight within three months — an amount of weight known to improve blood sugars, reset metabolism and boost overall health.

Tests were repeated as before — with surprising results. Losing weight did not reset the brain in people with obesity.

Much more research is needed to fully understand what obesity does to the brain, and if that is triggered by the fat tissue itself, the types of food eaten, or other environmental and genetic factors.

1．What aspects did the researchers mainly focus on in the research?

A．Blood sugars and metabolism.	B．Diet and environmental factors.
C．Nutrients and the digestive system.	D．Brain activities and dopamine levels.

2．What are the correct procedures of the study?
①Providing participants with the same nutrients separately.
②Classifying participants in different groups by weight.
③Repeating the test on those who lost required weight.
④Detecting the brain’s reaction of the participants.

A．①④③②	B．④①②③
C．②①④③	D．②①③④

3．What can be inferred about the study?

A．Weight loss had no impact on the brain’s response to food.

B．The level of dopamine was closely related to people’s brain activity.

C．Nutrients taken by participants affected their digestive system rather than brain activity.

D．The sum of dopamine released varied slightly among participants with different weights.

4．What is the most suitable title for the article?

A．Effective Strategies for Weight Loss in Obesity

B．The Persistent Effects of Obesity on the Brain

C．Exploring the Brain’s Response to Sugars and Fats

D．How Obesity Harms the Brain’s Fullness Sensation