A large study finds that obese people may show signs of shrinkage in their brain in as early as middle age.
Researchers looked at the brain scans of thousands of adults in the UK and found that those who had higher body-fat levels showed differences in their brain structure when compared with those who were thin. The differences included a reduced volume of gray matter in the brain.
The human brain consists of gray matter and white matter. Gray matter contains the nerve cells, while white matter contains the fibers, which connect different parts of the brain.
The findings were published Tuesday in the journal Radiology.
The findings are based on MRI scans of the brain of over 12,000 British adults, between 45 and 76 years of age. In general, the researchers found that the more the body fat people had, the lower the volume of gray matter is, at least in certain areas of the brain.
Earlier this year, another study found that middle-aged people with abdominal obesity had less gray matter volume than those who had normal weight.
So, what does it all mean?
Previous studies have linked obesity to a greater risk of dementia in the elderly. In the meantime, studies have linked gray matter shrinkage to dementia risk. So, there is a possibility that the current findings are somehow connected to previous studies.
Experts were quick to point out the limitations of the new study. They said the study did not assess the memory or other mental skills of the participants, so it is not clear what the differences in the scans mean.
Lead researcher Dr. Ilona Dekkers of Leiden University Medical Center said, “It’s not even clear that extra body fat is the reason for the brain differences.”
Dr. Dekkers said, “One possibility is that ‘non-optimal’ brain structure comes before the excessive weight gain. The lower tissue volume was seen, in part, in the brain’s ‘reward’ circuitry and areas related to movement.”
She explained that there is also a possibility that the differences could be due to other things associated with obesity, such as sedentary lifestyle or poor dietary habits.
The lead researcher mentioned, “Recent studies are showing that being obese has a substantial impact on our hormonal and immune systems, which has been shown to lead to inflammatory reactions that also affect brain tissue.”
Dr. Harold Bays, a U.S. endocrinologist, who was not involved in the study, said, “Is it possible that unhealthy nutrition and physical inactivity could be partly responsible, and it’s not just the body fat itself? Yes.” However, he agreed that “dysfunctional fat tissue” might directly affect the brain. “In reality, fat is ‘active’ tissue. And when fat cells become excessively large – and accumulate around the heart, intestines and other organs – they become dysfunctional,” explained Dr. Bays. “Basically, your body fat gets sick. It churns out hormones and inflammatory substances — a process that contributes to conditions such as diabetes, high blood pressure and fatty liver disease.”