If it seems like your clothes are shrinking, it could be that you’ve gained weight and your clothes aren’t really shrinking. But researchers have found that something even more important may be shrinking due to excess body fat – your brain.
It seems that having excessive body fat around the middle can lead to brain shrinkage, according to recent research. Specifically, shrunken gray matter volume. Gray matter contains the brain’s 100 billion nerve cells. The brain’s white matter contains the nerve fibers necessary for connecting brain regions.
Study author Mark Hamer, a professor of exercise as medicine at Loughborough University in England, said the findings support those of previous studies.
“Previous studies have shown associations between gray matter atrophy and risk of developing dementia.”
For the study, published in the journal Neurology, Hamer and his colleagues measured the body mass index (BMI) and waist-to-hip ratio of 9,652 middle-aged adults in the U.K. A BMI score between 18.5 and 24.9 is considered healthy, while a score above 30 is considered obese. A waist-to-hip ratio above 0.90 for men and above 0.85 for women indicates that a person has a bigger belly than hips.
Nearly 1 in 5 of the participants were found to be obese.
The team also used MRI scans to look at the participants’ brain volume. They factored in age, physical activity, smoking, and high blood pressure, all of which can shrink brain volume.
The study revealed that people with both a higher BMI and waist-to-hip ratio had the lowest gray matter volume.
“The reductions in brain size increase in a linear fashion as fat around the middle grew larger.”
By comparison, excessive body weight appeared to make no difference in white matter volume. However, fat around the middle did shrink other regions of the brain, including the pallidum, nucleus accumbens, putamen (linked only to a higher BMI), and caudate (linked only to a higher waist-to-hip ratio). These brain regions are associated with motivation and reward.
But which comes first? Brain shrinkage or obesity?
“It’s unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain.”
It’s possible that brain shrinkage actually causes obesity, but there is evidence to suggest it’s the other way around. Fat around the mid-section, called visceral fat, is linked to a number of health problems: 
- Heart attacks
- Heart disease
- Type 2 diabetes
- High blood pressure
- Breast and colorectal cancer
- Alzheimer’s disease
Harvard Health explains that fat cells – primarily abdominal fat cells – are biologically-active and should be thought of as organs. This is because visceral fat produces hormones and other substances that can have a negative impact on your health. Immune system chemicals that promote cardiovascular disease called cytokines are produced by fat cells. Cytokines and other biochemicals “are thought to have deleterious effects on cells’ sensitivity to insulin, blood pressure, and blood clotting.” 
Visceral fat is not the flab you can grab with your hands around your mid-section. Rather, it refers to fat that builds up around the body’s organs.
In addition, due to the location of visceral fat near the portal vein, which carries blood from the intestinal area to the liver, substances released by the fat can enter the portal vein and travel to the liver, where they can affect the production of blood lipids. This is why excessive fat around the middle is linked with higher total cholesterol and LDL “bad” cholesterol, lower HDL “good” cholesterol, and insulin resistance.
In the recent study, the researchers hypothesized that excessive visceral fat may cause brain shrinkage by producing inflammatory substances that may play a role in brain atrophy. 
Dr. Gayatri Devi, a neurologist at Lenox Hill Hospital in New York, who was not involved with the study, said:
“Brain gray matter shrinkage … seems to be associated with obesity and with increased visceral fat. All this goes to show that good general health is very important for good brain health.”
 Live Science