A new study has found that obesity could possibly alter a person’s brain permanently. It does so by altering the brain’s ability to recognize the sensation of fullness. Furthermore, it may also cause the brain to be satisfied after eating sugars and fats.
Additionally, the brain changes may last after those suffering from obesity lose a significant amount of weight. This could possibly explain why many individuals often regain the weight they lost.
“There was no sign of reversibility — the brains of people with obesity continued to lack the chemical responses that tell the body, ‘OK, you ate enough,’ ” stated Dr. Caroline Apovian, co-director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital in Boston. Dr. Apovian is also a professor of medicine at Harvard Medical School.
Additionally, she was not part of the obesity study. However, she added, “This study captures why obesity is a disease — there are actual changes to the brain.”
Definition
Obesity and overweight are defined as excessive or abnormal fat accumulation that presents a risk to one’s health. Anyone who has a body mass index (BMI) that is over 25 is classified as overweight. Those with a BMI over 30 are considered obese.
Additionally, the rates of obesity and overweight continue to grow in children and adults worldwide. From 1975 to 2016, the rate of obese or overweight youth aged 5 to 19 increased from 4% to 18%.
Currently, there are more people obese than overweight in every region except Asia and sub-Saharan Africa. Obesity was once considered a problem that only existed in high-income countries. However, now it is on the rise in low- and middle-income counties. Particularly in urban settings.
Gut-Brain Connection
The authors of the recent study published their findings in “Nature Metabolism” on June 12. They used 60 individuals to conduct the study, half were considered obese while the other half were of normal weight.
Researchers fed each individual nutrients directly into their stomach through a feeding tube. The nutrients consisted of sugar carbohydrates (glucose), fats (lipids), or water (as a control). The group of nutrients was fed to the individuals on separate days.
“We wanted to bypass the mouth and focus on the gut-brain connection, to see how nutrients affect the brain independently from seeing, smelling or tasting food,” said lead study author Dr. Mireille Serlie. She is a professor of endocrinology at Yale School of Medicine in New Haven, Connecticut.
Conducting Research
The night prior to testing, all the participants ate the same meal at home. Furthermore, they were instructed to fast after that, until they placed the feeding tubes the next morning. Afterward, researchers monitored the sugars and fats through functional magnetic resonance imaging (fMRI). Additionally, they used single-photon emission computed tomography (SPECT) to capture the brain’s response. They gathered the SPECT images for over 30 minutes.
The MRI allowed the researchers to see the neurons using oxygen in reaction to the nutrient. Researchers saw that part of the brain light up in the MRI. The SPECT scan measured the hormone dopamine.
This hormone is part of the reward system signaler. It alerts the brain it has found something pleasurable. Dopamine is the thing that makes people want something.
How Glucose and Fats Trigger the Brain
Researchers were interested in knowing how glucose and fats triggered the brain. Furthermore, they were curious about whether obesity caused the brain to have different triggers than normal weight people.
In addition, the researchers were curious if the different nutrients caused people to search for sustenance. “We were especially interested in the striatum, the part of the brain involved in the motivation to actually go and look for food and eat it,” stated Dr. Serlie. The striatum is buried deep within the brain and plays a role in emotion and habit formation.
Those with normal weight showed rising levels of dopamine, with those suffering from obesity did not. In fact, their brains did not slow down and their dopamine levels stayed low. This is why some people prefer foods like burgers instead of vegetables.
Losing Weight
Next, the researchers asked those with obesity to lose 10% of their body fat within a three-month period. Theoretically, it should have reset metabolism and improved blood sugars while boosting a person’s overall health.
Then, they conducted the same testing. However, what they found surprised them. “Nothing changed — the brain still did not recognize fullness or feel satisfied,” said Dr. Serlie. Some people may say the obese individuals didn’t lose enough weight or that the researchers didn’t wait long enough, added Dr. Serlie.
But this finding might also explain why people lose weight successfully and then regain all the weight a few years later — the impact on the brain may not be as reversible as we would like it to be.
Further Research on Obesity
While the recent study concurred with previous ones done on obesity, further testing will be needed. There are so many factors that could be in play when it comes to why people become obese. Many people feel that if one just “stops eating” they’ll have normal weight. However, genetics, and now this study, could prove to be a debilitating factor in losing weight.
By Sheena Robertson
Sources:
CNN: Obesity changes how the brain views food, even after weight loss, study finds
Nature Metabolism: Brain responses to nutrients are severely impaired and not reversed by weight loss in humans with obesity: a randomized crossover study
WHO: Obesity
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Second Inset Image Courtesy of Sandra Cohen-Rose and Colin Rose‘s Flickr Page – Creative Commons License
