CNN
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obesity A new study finds that it can damage the brain’s ability to perceive satiety and feel satisfied after eating fats and sugars.
Moreover, these brain changes can persist even after people who are considered medically obese lose weight. a considerable amount Weight — Maybe it explains why so many people carry weight get back often of Pounds they lose.
“There was no sign of recovery,” said Harvard Medical School professor and co-director Caroline Apobian, Ph.D. ‘ said. Doctor of Weight Management and Wellness Center at Brigham and Women’s Hospital in Boston.
Obese people, as medically defined, have the following characteristics: body mass index, or BMIover 30, while normal weight has a BMI between 18 and 25.
“This study reveals why obesity is a disease “We’re seeing real changes in the brain,” said Apobian, who was not involved in the study.
“This study is very rigorous and very comprehensive,” said Dr. I. Sadaf Farooqi, Professor of Metabolism and Medicine at the University of Cambridge, UK, who was not involved in the new study.
“The way they designed the study gave us even more confidence in the results, Previous research We also found that obesity causes some changes in the brain,” she said.
the study, published on monday In a controlled clinical trial published in Nature Metabolism, 30 people considered medically obese and 30 people of normal weight were given sugar, carbohydrates (glucose), fat (lipids), or water (as a control). . Nutrients for each group were fed directly into the stomach via feeding tubes on separate days.
“We wanted to bypass the mouth and focus on the gut-brain connection to see how nutrients affect the brain apart from seeing, smelling and tasting food. “That’s right,” said lead study author Mireille Celery, Ph.D., professor of endocrinology at Yale University School of Medicine. Located in New Haven, Connecticut.
The night before testing, all 60 study participants ate the same meal for dinner at home and did not eat again until the next morning when a feeding tube was inserted. After sugar or fat enters the stomach through a tube, the researchers used functional magnetic resonance imaging (fMRI) and single-photon emission computed tomography (SPECT) to monitor the brain’s response over 30 minutes. Recorded.
“The MRI shows where neurons in the brain are using oxygen in response to nutrients, and that part of the brain lights up,” Faroochi said. “The other scan measures dopamine, a hormone that’s part of the reward system. Dopamine signals that you’ve found something fun, challenging, and motivating and you want it. is.”
Researchers were interested in how fat and glucose individually cause v.different areas of the brain It leads to rewarding food. They wanted to know if it was different in obese people compared to normal weight people.
“We were particularly interested in the striatum, which is the part of the brain involved in the motivation to actually go in search of food and eat it,” Celery said. Embedded deep in the brain, the striatum is also involved in shaping emotions and habits.
The study found that in normal-weight people, throwing sugar or fat into the digestive system slowed brain signals in the striatum, suggesting that the brain was nourishing the body. It is said to be evidence of recognition of
“It makes sense for brain activity to drop overall, because once food is in the stomach, there’s no need to fetch more food,” Surley explained.
At the same time, normal-weight individuals showed increased dopamine levels and activation of the brain’s reward center.
But when people who were medically considered obese were given the same nutrients via feeding tubes, brain activity did not decrease and dopamine levels did not rise.
This is especially true if the food is lipid or fatty. Faroochi said the finding was interesting because the higher the fat content, the more rewarding the food. “That’s why you really want to eat hamburgers instead of broccoli. The fat in hamburgers biologically gives a better response in the brain.”
Next, the study asked obese people to lose 10% of their body weight within three months. This weight is an amount known to improve blood sugar levels, reset metabolism, and boost overall health, Celery said.
The tests were repeated as before with amazing results.didn’t lose weight reset the brain It’s more common in obese people, Celery says.
“Nothing changed. The brain still wasn’t recognizing fullness or satisfaction,” she said. “Well, you might say that three months isn’t enough or you didn’t lose enough weight.
“But the findings may also explain why people lose weight so successfully that they regain it after a few years. The effects on the brain may not be reversible as much as we would like. ”
a 2018 meta-analysis A long-term weight loss clinical trial found that 50% of the original weight loss was recovered after 2 years and 80% of the body weight was recovered by the 5th year.
There are many unknowns, so caution is needed in interpreting the results of the study, Surley said. When does the brain get out of alignment and start losing its ability to perceive?”
Obesity has a genetic component, and although the study sought to control for it by excluding people with childhood-onset obesity, it is possible that “genes influence the brain’s response to certain nutrients.” Sex is still there, Farooqi said. He spent years studying the role of genes on body weight.
More research is needed to fully understand the effects of obesity on the brain, and whether it is driven by the adipose tissue itself, the type of food eaten, and other environmental and genetic factors.
“Does anything change in people as they gain weight? Or is there something they were eating as they gained weight? ultra processed foods, Did it change the brain? All of these things are possible, but we don’t really know which one,” Farooqi said.
Until science answers these questions, this study once again emphasizes: weight stigma That’s irrelevant to the fight against obesity, Surley said.
“The idea that weight gain can be fixed by simply eating less and exercising more, and not doing so is a lack of willpower, is too simplistic to be true,” she says.
“I think it’s important for obese people to know that their struggle with food intake can be due to brain dysfunction,” says Celery. “And I hope this information will increase empathy for that struggle.”
