For every excess pound piled on the body, the brain gets a little bit smaller.
That's the message from new research that found that elderly individuals who were obese or overweight had significantly less brain tissue than individuals of normal weight.
"The brains of obese people looked 16 years older than their healthy counterparts while [those of] overweight people looked 8 years older," said UCLA neuroscientist Paul Thompson, senior author of a study published online in Human Brain Mapping.
Much of the lost tissue was in the frontal and temporal lobe regions of the brain, the seat of decision-making and memory, among other things.
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The findings could have serious implications for aging, overweight or obese individuals, including a heightened risk of Alzheimer's, the researchers said.
"We're all trying to protect our bodies and our brains from aging and this is just one factor that's accelerating that on top of all the other factors such as pollution, smoking, alcohol. We all lose some tissue as we get older and they're saying this is being accelerated," said Paul Sanberg, distinguished professor of neurosurgery and director of the University of South Florida Center for Aging and Brain Repair in Tampa.
According to the U.S. National Center for Health Statistics, 30 percent of American adults 20 years and older -- more than 60 million people -- are now obese, while another 36 percent are considered overweight. Either condition puts you at a much higher risk for type 2 diabetes, cancer and heart disease, as well as cognitive problems.
The findings seem to explain why heavier people are more prone to such cognitive conditions. "This is the first study to show physical evidence in the brain that connects overweight and obesity and cognitive decline," said Thompson, who is professor of neurology at UCLA and a member of the UCLA Laboratory of Neuro Imaging.
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The researchers studied brain images of 94 people in their 70s who had participated in an earlier study looking at cardiovascular health and cognition. None of the participants had dementia or other cognitive impairments. They were followed for five years, and any volunteers who developed cognitive symptoms were excluded from the study.
Clinically obese people had 8 percent less brain tissue, while the overweight had 4 percent less brain tissue compared to normal-weight individuals.
Dr. Jonathan Friedman, an associate professor of surgery and neuroscience and experimental therapeutics at the Texas A&M Health Science Center College of Medicine noted that the causal relationship here is not clear. Theoretically, he said, a smaller brain might mean appetite and weight-control centers of the brain are actually propelling the weight-gain process.
Thompson believes it may be a vicious cycle. "Each one is contributing to the other," he said. A person's genetics may be contributing to overeating and weight gain, which leads to less activity, which leads to a shortfall in the oxygen and nutrients that the brain needs to thrive and grow.
Overall, though, the findings really weren't surprising, added Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York City.
"Obesity affects every system in your body. The body can't be splintered. It's completely linked. We are what we eat and we eat too much," he said. "The bottom line is that an obese, sedentary person is going to have a breakdown of every organ system, and that includes a greater chance of impotence and infertility and other things that people don't generally think are directly related to obesity."