University of Washington: Obesity Linked to Brain Damage
May 11, 2012
Researchers are beginning to understand why lasting weight loss is so
hard. They believe it has to do with damage to the part of the brain
that’s involved in weight control.
If obese people stop overeating, switch to a healthful diet and start
exercising, they lose weight. However, they may quickly gain it back
again. The reason, say researchers, is not a lack of willpower but
injury to brain cells, or neurons, in the hypothalamus - a structure
deep in the brain that helps control a number of body functions
including appetite and weight.
The notion that brain damage might play a role in body weight is not a
new one, according to Michael Schwartz of the Diabetes and Obesity
Center at the University of Washington in Seattle.
Scientists have known for about five years that the hypothalamus of
overweight animals - including humans - displays inflammation, a typical
reaction to injury.
But researchers, led by Schwartz, wanted to determine the role
hypothalamus injury plays in obesity, and they had several questions
they wanted to answer:
“Is it simply a consequence of becoming obese or does it occur before
the obesity occurs?" says Schwartz. "And what could be driving that
response? What is causing the inflammatory response and could that have
something to do with the obesity itself?”
Schwartz’s team put laboratory mice and rats on a high-fat diet to make
them gain weight. When they looked for evidence of inflammation in their
brains, they made a startling discovery.
“We were frankly shocked to realize the inflammation became apparent
within 24 hours of the switch in diet,” says Schwartz.
researchers also saw evidence of a strong and rapid neuro-protective
response, as cells were activated to repair the damaged neurons. But the
animals were kept on the high-fat diet for nine months and the
inflammation eventually returned.
The key message, according to Schwartz, is that it’s not the fault of
people who try and fail repeatedly to lose weight through dieting.
“Our data would point to a more structural, biological basis for why it
is difficult to keep weight off," he says. "It has to do with damage to
the brain area that is responsible for controlling body weight.”
Schwartz says that also explains why drugs are not effective at helping
people achieve lasting weight loss. The compounds currently available do
not target what appears to be the underlying cause of obesity.