A recent study has discovered that obesity can impair the ability of a person’s brain to recognize when they are full and satisfied after having fatty and sugary foods.
Moreover, these changes in the brain may persist even after individuals who were medically classified as obese manage to shed a substantial amount of weight. This finding may provide an explanation as to why many people often regain the weight they previously lost.
Dr. Caroline Apovian, a professor of medicine at Harvard Medical School and co-director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital in Boston, stated that there were no indications of the brain’s ability to reverse the effects caused by obesity.
People with obesity still experience a deficiency in the chemical reactions that send signals to the body, indicating that they have consumed an adequate amount of food.
Monitoring the brain’s response with fMRI and SPECT
The trial involved 30 individuals classified as medically obese and 30 individuals with normal weight. The participants were given sugar, carbohydrates (glucose), fats (lipids), or water (as a control) through a feeding tube that directly delivered the nutrients to their stomachs.
This approach was taken to bypass the influence of the mouth and focus on understanding how nutrients affect the brain independently from the sensory experience of seeing, smelling, or tasting food.
Dr. Mireille Serlie, the lead author of the study and a professor of endocrinology at Yale School of Medicine in New Haven, Connecticut, explained the rationale behind the research.
#Obesity changes the #brain’s ability to recognize fullness and feel satisfied by #fats and #sugars – and losing #weight doesn’t reverse the change, according to @YalePsych’s Ralph DiLeone, PhD, @YaleIMed’s Mireille Serlie, MD, PhD, and colleagues. https://t.co/B6SAhWzqxD pic.twitter.com/nRzqphAC8E
— Yale School of Medicine (@YaleMed) June 12, 2023
The night before the experiment, all 60 participants had the same dinner at home and refrained from eating until the following morning when the feeding tube was inserted.
The researchers then utilized functional magnetic resonance imaging (fMRI) and single-photon emission computed tomography (SPECT) to observe the brain’s response to the nutrients over a period of 30 minutes.
Results of fMRI scans
Dr. Serlie emphasized their particular interest in the striatum, a region of the brain responsible for the motivation to seek out and consume food. Located deep within the brain, the striatum also plays a role in emotions and the formation of habits.
The study discovered that in individuals with normal weight, the brain signals in the striatum slowed down when either sugars or fats entered the digestive system. This showed that the brain recognized the body had been adequately nourished.
However, when the same nutrients were administered via a feeding tube to individuals classified as medically obese, their brain activity did not show a decrease, and there was no rise in dopamine levels.
It helps explain why a person may desire a burger over broccoli, as the fat in the burger elicits a stronger biological response in the brain, explained Dr. I. Sadaf Farooqi, a professor of metabolism and medicine at the University of Cambridge in the UK, who was not involved in the research.