Author’s Note: My report of the following findings should not lead anyone to believe that I think obese people are “stupid,” or that I am in any way “targeting” them.” I am not making an argument that thin people are smarter than overweight people. My mother is obese, and she is a brilliant and highly educated woman. However, I do think obesity is a health risk and believe in proper fitness and nutrition, though I am no “health nut.” I think the research that has been done over the past few years on obesity and the brain is very interesting, and I believe it’s something we should all take a closer look at, regardless of our size.
ADDITIONAL Author's Note: Yes, the sample sizes in these studies are small. No, correlation does not have to imply causation. Yes, there could be all sorts of other factors contributing to test results. I am posting some findings I find interesting. Pretty simple, pretty benign. Chill, people.
It has already been documented that obesity is linked with brain atrophy (PDF), though the findings have proven controversial. A review, for those who may not have read it, of a previous study from 2009:
A new brain-imaging study by researchers at UCLA and the University of Pittsburgh finds that the brains of overweight and obese subjects were on average 4% and 8% smaller, respectively, than the brains of those who were at a healthy weight--evidence, according to UCLA neurology professor and study author Paul Thompson, of "severe brain degeneration."
For the obese--those with a BMI over 30--the news is particularly bad: the areas of significant observed shrinkage were the frontal temporal lobes, the seat of higher-order reasoning and judgment; the anterior cingulate gyrus, key to attention and decision-making as well; the hippocampus, where long-term memories are processed, and the basal ganglia, from which smooth movement is initiated.
Overweight people--those with a BMI over 25--also had shrinkage in the basal ganglia, as well as in the parietal lobe, where we integrate sensory input and position ourselves in space, and in the brain's white matter, which helps speed messages among regions of the brain that must work together for us to function properly.
After virtually weighing and measuring the brains of 94 subjects over age 70, the study authors concluded that the brains of the overweight appeared, on average, eight years older than those of subjects at healthy weight. Brains of the obese appeared 16 years older. While the subjects scanned in the study showed no outward signs of cognitive impairment at the time of the study, the study's authors predicted the premature aging and loss of brain volume they observed would put heavier subjects at greater risk of Alzheimer's disease and other degenerative brain diseases.
Some images from that study, which is available free online (PDF):
Scores on the tests were assessed against those of people in the Brain Resource International Database, a large multicenter project with data on very healthy people. Obese individuals in the new study initially performed on the low end of the normal range for healthy individuals from the database on average, Gunstad says, although nearly one-quarter of the obese participants’ scores on memory and learning actually fell within what researchers consider the impaired range.
Tested again 12 weeks after bariatric surgery — when most had shed some 50 pounds — the lighter but still heavy patients scored substantially better. Most now performed “within the average or greater-than-average range for all cognitive tests,” the researchers report online in Surgery for Obesity and Related Diseases.
Study participants who didn’t have surgery — or lose weight — performed worse on the second test. “That was a bit surprising,” Gunstad says.
Neurologist Stefan Knecht of the University of Münster in Germany, who is not involved in the new research, says he is not surprised that the untreated participants experienced rapid, continuing drops in cognitive performance. Among the morbidly obese, he says, “You can actually watch them getting worse from one three-month period to the next if you have sufficiently sensitive measures, which [Gunstad’s group] did.”
Another study used magnetic resonance imaging (MRI) to examine the wiring connecting nerve cells which allow signals and information to travel through the brain. In some obese individuals (BMI 30+), the white matter that protects this wiring appears damaged, as compared with normal-weight and overweight individuals. It should be noted that the damage being described is to the protective sheath, not to the nerve fibers themselves.
Both studies were done with a relatively low number of subjects, particularly the second. Further research into the mechanisms behind the possible link between brain deterioration and obesity is still needed.