Obesity Changes The Brain.

According to a recent study, obesity may impair the brain’s capacity to perceive fullness and feel satiated after consuming fats and sweets.

„There was no sign of reversibility,“ said Dr. Caroline Apovian, a professor of medicine at Harvard Medical School and codirector of the Center for Weight Management and Wellness at Brigham and Women’s Hospital in Boston. „The brains of people with obesity continued to lack the chemical responses that tell the body, „OK, you ate enough.“

As defined medically, people with obesity have a body mass index, or BMI, of over 30, while normal weight is a BMI of between 18 and 25.

↓Get your Fitness on track here↓

„This study captures why obesity is a disease – there are actual changes to the brain,“ claimed Apovian, who was not involved in the research.

„The study is very rigorous and quite comprehensive,“ said Dr. I. Sadaf Farooqi, a professor of metabolism and medicine at the University of Cambridge in the UK who was not involved in the current investigation.

According to her, „the design of their study increases confidence in the findings, adding to earlier research that also found obesity causes some changes in the brain.“

———————————————————————

Nutrients delivered by feeding tube

The study, which was released on Monday in Nature Metabolism, involved a controlled clinical experiment in which 30 individuals who were deemed medically obese and 30 individuals of normal weight received either water (as a control), sugary carbs (glucose), fats (lipids), or water. On different days, a feeding tube was used to administer each set of nutrients straight into the stomach.

“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, professor of endocrinology at Yale School of Medicine in New Haven, Connecticut.

All 60 study participants ate the same dinner at home the evening before the test, and they did not eat again until the feeding tube was inserted the next morning. Researchers employed functional magnetic resonance imaging (fMRI) and single-photon emission computed tomography (SPECT) to record the brain's reaction over a 30-minute period while either sugars or fats entered the stomach via the tube.

“The MRI shows where neurons in the brain are using oxygen in reaction to the nutrient — that part of the brain lights up,” Farooqi said. “The other scan measures dopamine, a hormone that is part of the reward system, which is a signal for finding something pleasurable, rewarding and motivating and then wanting that thing.”

Researchers were interested in how different brain regions associated with the pleasurable features of eating might be activated individually by lipids and glucose. They were interested in finding out if that would be different in obese individuals compared to those who are of a healthy weight.

The study discovered that brain impulses in the striatum in people with normal weight slowed when either carbohydrates or fats were delivered into the digestive tract – proof that the brain understood the body had been nourished.

“This overall reduction in brain activity makes sense because once food is in your stomach, you don’t need to go and get more food,” Serlie explained.

In parallel, dopamine levels increased in people who were of normal weight, indicating that the brain's reward regions had also become active.

Different findings for medically obese

However, brain activity did not diminish and dopamine levels did not raise when the identical nutrients were ingested through feeding tubes by individuals who were deemed medically obese.

This was especially true when the food was lipids or fats. That finding was interesting, Farooqi said, because the higher the fat content, the more rewarding the food.

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, Serlie said.

Nothing changed; the brain continued to fail to register feelings of fullness or satisfaction, she claimed. "At this point, you can argue that three months is not long enough or that they did not drop enough weight.

The impact on the brain may not be as reversible as we would like it to be, which could help to explain why some who successfully lose weight subsequently gain it all back.

A 2018 meta-analysis of long-term weight loss clinical trials found 50% of a person’s original weight loss was regained after two years — by the fifth year, 80% of the weight was regained.

———————————————————————

↓Get your fitness on track here↓